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# RFC index
Generated by `pnpm run gen-rfc-index` from the RFC tree — never edit by hand; `verify-rfc-classification` fails when this file is stale. The curated front door — layout, classification, when to write one, and the in-file format — is [README.md](README.md).
## Proposed
### Feature
| Title | First proposed |
|---|---|
| [Pre-tool input rewrite — a consistent design](proposed/feature/2026-06-30-pre-tool-input-rewrite.md) | 2026-06-30 |
| [Claude Code and Codex subagent backends (out-of-process delegation to external coding agents)](proposed/feature/2026-07-07-claude-code-and-codex-subagent-backends.md) | 2026-07-07 |
### Simplification
| Title | First proposed |
|---|---|
| [Unify the agent id and the session id](proposed/simplification/2026-06-20-unify-agent-and-session-id.md) | 2026-06-20 |
| [Prune dead core-spine surface — `SurfaceManager.invalidate()`, the loop-internal exports, `ToolExecutionResult.callId`](proposed/simplification/2026-07-04-prune-dead-core-spine-surface.md) | 2026-07-04 |
### Architecture
| Title | First proposed |
|---|---|
| [Runtime schemas for the event vocabulary (Zod vs the merge-extensible-map pattern)](proposed/architecture/2026-06-16-typed-event-schemas.md) | 2026-06-16 |
| [Extract a generic long-running tool runtime](proposed/architecture/2026-06-20-generic-long-running-tool-runtime.md) | 2026-06-20 |
### Process
| Title | First proposed |
|---|---|
| [API extractor reports](proposed/process/2026-06-11-api-extractor-reports.md) | 2026-06-11 |
| [Architectural conformance — dependency rules and the adapter kit](proposed/process/2026-06-11-architectural-conformance.md) | 2026-06-11 |
| [Supply chain checks and vendor drift verification](proposed/process/2026-06-11-supply-chain-and-vendor-drift.md) | 2026-06-11 |
| [Discover package inventories instead of maintaining static lists](proposed/process/2026-06-20-discover-package-inventory.md) | 2026-06-20 |
### Testing
| Title | First proposed |
|---|---|
| [Deterministic tests, the replay invariant fixture, and race stress](proposed/testing/2026-06-11-deterministic-and-stress-testing.md) | 2026-06-11 |
| [Mutation testing as the coverage counterweight](proposed/testing/2026-06-11-mutation-testing.md) | 2026-06-11 |
## Implemented
### Feature
| Title | First proposed |
|---|---|
| [Agent Client Protocol (ACP) support — drive the coding agent from external editors](implemented/feature/2026-06-14-acp-agent-client-protocol.md) | 2026-06-14 |
| [Multiplex concurrent ACP sessions over one connection](implemented/feature/2026-06-14-acp-multi-session.md) | 2026-06-14 |
| [Code Mode — the model writes TypeScript against the tool registry](implemented/feature/2026-06-15-code-mode.md) | 2026-06-15 |
| [Filesystem tool schemas — model-facing read/write/edit shapes](implemented/feature/2026-06-17-filesystem-tool-schemas.md) | 2026-06-17 |
| [Rich ACP bash rendering — the terminal card via the `_meta` convention](implemented/feature/2026-06-18-acp-terminal-and-tool-rendering.md) | 2026-06-18 |
| [Compaction as a capability seam (abstract contract + basic backend)](implemented/feature/2026-06-18-compaction-capability-seam.md) | 2026-06-18 |
| [Subagent capability seam](implemented/feature/2026-06-21-subagent-capability-seam.md) | 2026-06-21 |
| [ACP subagent backend (out-of-process delegation)](implemented/feature/2026-06-22-acp-subagent-backend.md) | 2026-06-22 |
| [Ask-user question capability](implemented/feature/2026-06-25-ask-user-question.md) | 2026-06-25 |
| [The `todo_write` tool — model task list as event-sourced session state](implemented/feature/2026-06-29-todo-write-tool.md) | 2026-06-29 |
| [dsh-hooks-claude + dsh-hooks-codex — the Claude Code / Codex hook bridges](implemented/feature/2026-06-30-hook-bridges.md) | 2026-06-30 |
| [dsh-hook-protocol — the shared Claude Code / Codex hook wire-protocol core](implemented/feature/2026-06-30-hook-protocol-lib.md) | 2026-06-30 |
| [Interception seams — the typed-Decision surface a hook programs against](implemented/feature/2026-06-30-interception-seams.md) | 2026-06-30 |
| [SessionStore fork API](implemented/feature/2026-06-30-session-store-fork-api.md) | 2026-06-30 |
| [Subagent lifecycle enrichment — lastAssistantMessage (observe-only)](implemented/feature/2026-06-30-subagent-observe-enrich.md) | 2026-06-30 |
| [Dynamic workflows — a script-driven multi-agent orchestration seam](implemented/feature/2026-07-05-dynamic-workflows.md) | 2026-07-05 |
| [Skill system — progressive disclosure instructions for agents](implemented/feature/2026-07-05-skill-system.md) | 2026-07-05 |
| [The approval seam — one-shot permission decisions over a waterfall of answerers](implemented/feature/2026-07-06-approval-seam.md) | 2026-07-06 |
| [Explicit model-facing tool order](implemented/feature/2026-07-06-explicit-tool-order.md) | 2026-07-06 |
| [The subprocess sandbox — confinement seam, native runners, escalation, and per-session modes](implemented/feature/2026-07-06-sandbox.md) | 2026-07-06 |
| [The session prefix — request-only messages in front of the derived history](implemented/feature/2026-07-07-session-prefix.md) | 2026-07-07 |
| [Repeat-tool-call guard plugin](implemented/feature/2026-07-08-repeat-tool-guard.md) | 2026-07-08 |
| [The self-referential cordis toolset](implemented/feature/2026-07-08-self-referential-cordis-toolset.md) | 2026-07-08 |
### Simplification
| Title | First proposed |
|---|---|
| [Drop the mutable session summary](implemented/simplification/2026-06-19-drop-mutable-session-summary.md) | 2026-06-19 |
| [Fold trace-only session facts into load-bearing events](implemented/simplification/2026-06-20-collapse-trace-only-session-events.md) | 2026-06-20 |
| [Drop the unconsumed `llm/adapter-change` event](implemented/simplification/2026-06-20-drop-unconsumed-llm-adapter-change-event.md) | 2026-06-20 |
| [Drop unconsumed assembled LLM convenience surfaces](implemented/simplification/2026-06-20-drop-unconsumed-llm-assembled-surfaces.md) | 2026-06-20 |
| [Prune dead methods from the persistence seam](implemented/simplification/2026-06-20-prune-dead-seam-methods.md) | 2026-06-20 |
| [Keep one public stop primitive](implemented/simplification/2026-06-20-public-agent-stop-surface.md) | 2026-06-20 |
| [Stop mirroring durable boundaries as agent events](implemented/simplification/2026-06-20-remove-agent-boundary-mirror-events.md) | 2026-06-20 |
| [Split the filesystem seam — provider text mutations plus the `dsh-fs-policy` plugin](implemented/simplification/2026-06-26-fsspec-style-fs-seam.md) | 2026-06-26 |
| [Stop mirroring the token stream as an agent event](implemented/simplification/2026-07-02-remove-stream-chunk-mirror.md) | 2026-07-02 |
| [Drop the `image` content block until a path can honor it](implemented/simplification/2026-07-04-drop-image-content-block.md) | 2026-07-04 |
| [Drop `GenerateOptions.prefill` and `ToolSchema.strict` — request knobs with no working end-to-end path](implemented/simplification/2026-07-04-drop-inert-request-knobs.md) | 2026-07-04 |
| [Drop the unconsumed web observation surface — the `providers-change` event and the status methods](implemented/simplification/2026-07-04-drop-unconsumed-web-observation-surface.md) | 2026-07-04 |
| [Fold the stdio UI helper into the stdio app](implemented/simplification/2026-07-04-fold-stdio-ui-helper.md) | 2026-07-04 |
| [Prune producer-less vocabulary variants (block cache hints, the `agent` message source, the `continuation` turn trigger)](implemented/simplification/2026-07-04-prune-producerless-vocabulary-variants.md) | 2026-07-04 |
| [Prune write-only fields and a dead routing knob from the fs seam](implemented/simplification/2026-07-04-prune-write-only-fs-surface.md) | 2026-07-04 |
| [Remove the `agent/steering` mirror emit](implemented/simplification/2026-07-04-remove-agent-steering-mirror.md) | 2026-07-04 |
| [Share the app bins' boot glue instead of maintaining twin copies](implemented/simplification/2026-07-04-share-app-bin-boot-glue.md) | 2026-07-04 |
| [Tighten the hook-protocol contract — dialect, discarded fields, double defaults, and lib-owned `hook/result` semantics](implemented/simplification/2026-07-04-tighten-hook-protocol-contract.md) | 2026-07-04 |
| [Trim unreachable ACP bridge surface — the branding knobs and the kind-sniffing fallback](implemented/simplification/2026-07-04-trim-acp-bridge-unreachable-surface.md) | 2026-07-04 |
### Architecture
| Title | First proposed |
|---|---|
| [Provider-neutral content-block vocabulary owned by dsh-llm](implemented/architecture/2026-06-11-content-block-vocabulary.md) | 2026-06-11 |
| [Custom typed tool-schema DSL instead of schemastery](implemented/architecture/2026-06-11-custom-schema-dsl.md) | 2026-06-11 |
| [Dev-mode invariants over compile-time deep-readonly](implemented/architecture/2026-06-11-dev-invariants-over-deep-readonly.md) | 2026-06-11 |
| [Event-sourced sessions with derived message history](implemented/architecture/2026-06-11-event-sourced-sessions.md) | 2026-06-11 |
| [Microkernel — extension via Cordis event taxonomy, one concrete loop](implemented/architecture/2026-06-11-microkernel-event-taxonomy.md) | 2026-06-11 |
| [Runtime arg validation at the model boundary](implemented/architecture/2026-06-11-runtime-arg-validation.md) | 2026-06-11 |
| [Structured error taxonomy](implemented/architecture/2026-06-11-structured-error-taxonomy.md) | 2026-06-11 |
| [Tool schemas are part of the system-prompt assembly](implemented/architecture/2026-06-11-tool-schemas-in-prompt-assembly.md) | 2026-06-11 |
| [Capability seams — interface / implementation / consumer split](implemented/architecture/2026-06-13-capability-seams.md) | 2026-06-13 |
| [Two LLM adapters as a design-verification twin](implemented/architecture/2026-06-13-twin-llm-adapters.md) | 2026-06-13 |
| [Session persistence as an abstract service over the existing `SessionEvent`](implemented/architecture/2026-06-14-session-persistence.md) | 2026-06-14 |
| [Every session event is enclosed in a turn](implemented/architecture/2026-06-15-turn-enclosure-invariant.md) | 2026-06-15 |
| [Filesystem capability seam — ctx.fs, local backend, and model-facing filesystem tools](implemented/architecture/2026-06-17-filesystem-capability-seam.md) | 2026-06-17 |
| [Agent lifecycle and ownership seams](implemented/architecture/2026-06-18-agent-lifecycle-and-ownership-seams.md) | 2026-06-18 |
| [Session surface — a linked list over the event log for LLM message derivation](implemented/architecture/2026-06-18-session-surface.md) | 2026-06-18 |
| [Shared persistence write coordinator](implemented/architecture/2026-06-18-shared-persistence-write-coordinator.md) | 2026-06-18 |
| [Branded IDs everywhere they belong](implemented/architecture/2026-06-20-branded-ids.md) | 2026-06-20 |
| [Extract example apps into packages](implemented/architecture/2026-06-20-extract-example-app-packages.md) | 2026-06-20 |
| [Reorganize packages into a modular hierarchy](implemented/architecture/2026-06-20-package-hierarchy.md) | 2026-06-20 |
| [Mandatory `User-Agent` attribution for provider requests](implemented/architecture/2026-06-21-mandatory-app-attribution-headers.md) | 2026-06-21 |
| [Web capability seam - stable tools over multiple providers](implemented/architecture/2026-06-24-web-capability-seam.md) | 2026-06-24 |
| [Make `dsh-fs-policy` an event-gate plugin, not a method interface](implemented/architecture/2026-06-26-file-context-as-event-gate.md) | 2026-06-26 |
| [stdin + extra env on the bash seam](implemented/architecture/2026-06-30-bash-stdin-env-trusted-plugin-surface.md) | 2026-06-30 |
| [Event-domain semantics — session is the fact log, agent is the live surface](implemented/architecture/2026-06-30-event-domain-semantics.md) | 2026-06-30 |
| [Resolve filesystem paths against the caller's session cwd](implemented/architecture/2026-07-02-fs-per-session-cwd.md) | 2026-07-02 |
| [Result-time applied-hunk diffs for file mutations](implemented/architecture/2026-07-02-result-time-applied-hunk-diffs.md) | 2026-07-02 |
| [Tagged render-intent union for tool-call presentation](implemented/architecture/2026-07-02-tool-render-intent-union.md) | 2026-07-02 |
| [Add direct directory listing to the filesystem seam](implemented/architecture/2026-07-03-filesystem-directory-listing-seam.md) | 2026-07-03 |
| [Prompt variables and tool-guidance ownership](implemented/architecture/2026-07-05-prompt-variables-and-tool-guidance-ownership.md) | 2026-07-05 |
| [Every LLM request is reconstructable from the session log](implemented/architecture/2026-07-05-reconstructable-requests.md) | 2026-07-05 |
| [Subagent provider-lifecycle events — `subagent/provider-added` / `subagent/provider-removed`](implemented/architecture/2026-07-05-subagent-provider-lifecycle-events.md) | 2026-07-05 |
| [A shared timeout/deadline primitive, with hard-kill left to each capability](implemented/architecture/2026-07-06-timeout-deadline-library.md) | 2026-07-06 |
| [Tool-call timeout policy as a plugin](implemented/architecture/2026-07-07-tool-call-timeout-policy.md) | 2026-07-07 |
### Process
| Title | First proposed |
|---|---|
| [Doc-sync enforcement](implemented/process/2026-06-11-doc-sync-enforcement.md) | 2026-06-11 |
| [Mechanical quality gates over prose guidelines](implemented/process/2026-06-11-quality-gates.md) | 2026-06-11 |
| [tsdown for JS bundling instead of dumble](implemented/process/2026-06-11-tsdown-over-dumble.md) | 2026-06-11 |
| [Vendor Cordis as source, not npm dependencies](implemented/process/2026-06-11-vendor-cordis-as-source.md) | 2026-06-11 |
| [pnpm as the package manager instead of Yarn 4](implemented/process/2026-06-16-pnpm-over-yarn.md) | 2026-06-16 |
| [TSC-first build and one tsconfig](implemented/process/2026-06-17-ts-build-config.md) | 2026-06-17 |
| [Markdown cross-link validity linting](implemented/process/2026-06-18-markdown-cross-link-lint.md) | 2026-06-18 |
| [Core-data-structures catalog and the `ts type-equiv` drift gate](implemented/process/2026-06-20-core-data-structures-catalog.md) | 2026-06-20 |
| [Generated cordis events + services catalog](implemented/process/2026-06-20-generated-cordis-catalog.md) | 2026-06-20 |
| [Classify RFCs by kind via path-encoded subdirectories](implemented/process/2026-06-20-rfc-classification.md) | 2026-06-20 |
| [Bilingual documentation via paired sibling files and a pairing gate](implemented/process/2026-07-02-bilingual-docs-and-pairing-gate.md) | 2026-07-02 |
| [Generated tool-schema catalog (boot-and-harvest)](implemented/process/2026-07-02-tool-schema-catalog.md) | 2026-07-02 |
| [Documentation graph index for maintainers and SDK users](implemented/process/2026-07-03-documentation-graph-atlas.md) | 2026-07-03 |
| [JSDoc completeness gate for the cordis surface](implemented/process/2026-07-04-cordis-jsdoc-completeness-gate.md) | 2026-07-04 |
| [Documentation tiers, budgets, and the ceiling gate](implemented/process/2026-07-04-doc-tiers-and-budgets.md) | 2026-07-04 |
| [Generate the RFC index tables](implemented/process/2026-07-04-generate-rfc-index-tables.md) | 2026-07-04 |
| [Generated persistence log event catalog](implemented/process/2026-07-04-persistence-log-catalog.md) | 2026-07-04 |
| [One gated in-file format for RFCs](implemented/process/2026-07-05-uniform-rfc-format.md) | 2026-07-05 |
| [Export-surface JSDoc gate](implemented/process/2026-07-06-export-surface-jsdoc-gate.md) | 2026-07-06 |
| [Generated plugin config catalog](implemented/process/2026-07-06-generated-config-catalog.md) | 2026-07-06 |
| [Raise the Node LTS engine floor to 22.19](implemented/process/2026-07-06-node-engine-floor.md) | 2026-07-06 |
| [Parallel GitHub CI gates](implemented/process/2026-07-06-parallel-github-ci-gates.md) | 2026-07-06 |
| [Parallel pre-push gates](implemented/process/2026-07-06-parallel-pre-push-gates.md) | 2026-07-06 |
### Testing
| Title | First proposed |
|---|---|
| [Property-based testing for protocol-shaped code](implemented/testing/2026-06-11-property-based-testing.md) | 2026-06-11 |
| [ACP snapshot tests — record-once / replay-deterministic](implemented/testing/2026-06-19-acp-snapshot-tests.md) | 2026-06-19 |
| [Real-API e2e in CI against the external DeepSeek API](implemented/testing/2026-06-19-real-api-e2e-ci.md) | 2026-06-19 |
| [Use `session.jsonl` as the only snapshot session-log artifact](implemented/testing/2026-06-20-remove-redundant-snapshot-log-goldens.md) | 2026-06-20 |
| [Persist the seed boundary so fork-child replay routes correctly](implemented/testing/2026-06-22-fork-child-replay-seed-boundary.md) | 2026-06-22 |
| [Record fork and mixed spawn+fork snapshot scenarios](implemented/testing/2026-06-22-fork-snapshot-scenarios.md) | 2026-06-22 |
| [Per-session snapshot replay for nested agents](implemented/testing/2026-06-22-subagent-snapshot-replay.md) | 2026-06-22 |
| [Hook snapshot matrix — end-to-end goldens for both bridges](implemented/testing/2026-07-04-hook-snapshot-matrix.md) | 2026-07-04 |
| [Single-source the acp-agent replay config](implemented/testing/2026-07-04-single-source-acp-replay-config.md) | 2026-07-04 |
| [Pin request-header content in one snapshot scenario](implemented/testing/2026-07-06-pin-request-header-content-in-one-scenario.md) | 2026-07-06 |
| [Extract the ACP snapshot suite into a support package](implemented/testing/2026-07-08-shared-acp-snapshot-package.md) | 2026-07-08 |
## Rejected
### Simplification
| Title | First proposed |
|---|---|
| [Persist assembled assistant messages, not stream chunks](rejected/simplification/2026-06-20-assembled-assistant-messages-only.md) | 2026-06-20 |
| [Drop ACP session/load until resume has a product shape](rejected/simplification/2026-06-20-drop-acp-session-load.md) | 2026-06-20 |
| [Drop ACP terminal `_meta` rendering](rejected/simplification/2026-06-20-drop-acp-terminal-meta.md) | 2026-06-20 |
| [Drop bash full-output spill files](rejected/simplification/2026-06-20-drop-bash-output-spill-files.md) | 2026-06-20 |
| [Drop durable step boundary events](rejected/simplification/2026-06-20-drop-durable-step-boundaries.md) | 2026-06-20 |
| [Drop unused session lineage metadata](rejected/simplification/2026-06-20-drop-unused-session-lineage.md) | 2026-06-20 |
| [Fold the persistence interface into dsh-session](rejected/simplification/2026-06-20-fold-session-persistence-interface.md) | 2026-06-20 |
| [Collapse tool-owned UI presentation](rejected/simplification/2026-06-20-generic-tool-rendering.md) | 2026-06-20 |
| [Retire mid-turn steering](rejected/simplification/2026-06-20-retire-mid-turn-steering.md) | 2026-06-20 |
| [Return the ACP bridge to one live session per connection](rejected/simplification/2026-06-20-single-session-acp-bridge.md) | 2026-06-20 |
| [Truncate interrupted final turns on load](rejected/simplification/2026-06-20-truncate-interrupted-turns.md) | 2026-06-20 |
| [Prune the unimplemented subagent seam vocabulary](rejected/simplification/2026-07-04-prune-unimplemented-subagent-vocabulary.md) | 2026-07-04 |
### Architecture
| Title | First proposed |
|---|---|
| [Deep-readonly public surfaces](rejected/architecture/2026-06-11-immutable-public-surfaces.md) | 2026-06-11 |
| [Make the shared example base providerless](rejected/architecture/2026-06-20-providerless-example-base.md) | 2026-06-20 |

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@@ -1,6 +1,6 @@
# RFCs
One kind of design doc lives here. An **RFC** records a decision or proposal that shapes this codebase — the *why* and *what we gave up*, the parts code and docs can't carry.
One kind of design doc lives here. An **RFC** records a decision or proposal that shapes this codebase — the *why* and *what we gave up*, the parts code and docs can't carry. The full list is the generated [INDEX.md](INDEX.md); this file is the contract — where RFCs live, when to write one, and [the in-file format](#the-file-format).
## Layout and naming
@@ -16,7 +16,7 @@ The date in the filename is when the topic was **first proposed** (per git histo
## Classification
Each RFC is filed under exactly one **class** — the kind of decision it records. The class is encoded in the path (the folder *is* the label, so a file's location declares its class) and the set is **closed**: `scripts/verify-rfc-classification.ts` rejects any folder outside the set and asserts this index lists every RFC under the heading matching its path. Adding a new class means amending that gate and this section, not just dropping a new folder. See [the classification RFC](implemented/process/2026-06-20-rfc-classification.md) for why the taxonomy is path-encoded and gated.
Each RFC is filed under exactly one **class** — the kind of decision it records. The class is encoded in the path (the folder *is* the label, so a file's location declares its class) and the set is **closed**: `scripts/rfc-index.ts` owns the canonical set, `scripts/verify-rfc-classification.ts` rejects any folder outside it, and [INDEX.md](INDEX.md) is **generated** from the tree in full (`pnpm run gen-rfc-index` rewrites it from each RFC's path, H1 title, and filename date; the gate fails when it is stale, and rejects an index-shaped row in this file). Adding a new class means amending that `const` and this section, not just dropping a new folder. See [the classification RFC](implemented/process/2026-06-20-rfc-classification.md) for why the taxonomy is path-encoded and gated, and [the index-generation RFC](implemented/process/2026-07-04-generate-rfc-index-tables.md) for why the index is generated while this prose stays curated.
| Class | What it covers |
|---|---|
@@ -35,176 +35,75 @@ Write an RFC when a decision is **durable** (it shapes the codebase beyond a sin
Do NOT write one for a mechanical or local choice (a variable name, a one-file refactor), for anything already enforced and explained by a gate or a convention in AGENTS.md, or for a still-provisional decision tagged `TODO(...)` in the code — record those as TODOs and promote to an RFC only once they settle. An RFC is never edited into a *different decision*: supersede it with a new one and cross-link. (Editing an `implemented/` RFC to track where its already-made decision now *lives* — a moved file, a renamed package — is not a different decision and is required, not forbidden; see [implemented/AGENTS.md](implemented/AGENTS.md).)
## Proposed
## The file format
### Feature
Every RFC follows one in-file format, enforced by `pnpm run verify-rfc-format` ([scripts/verify-rfc-format.ts](../../scripts/verify-rfc-format.ts), part of `doc-sync`); the rationale for the format — and the alternatives it rejected — is [the uniform-format RFC](implemented/process/2026-07-05-uniform-rfc-format.md).
| Title | First proposed |
|---|---|
| [Agent Client Protocol (ACP) support for external editors](proposed/feature/2026-06-14-acp-agent-client-protocol.md) | 2026-06-14 |
| [Multiplex concurrent ACP sessions over one connection](proposed/feature/2026-06-14-acp-multi-session.md) | 2026-06-14 |
| [Optional Code Mode — model writes TypeScript against an SDK of all tools](proposed/feature/2026-06-15-optional-code-mode.md) | 2026-06-15 |
| [Pre-tool input rewrite — a consistent design](proposed/feature/2026-06-30-pre-tool-input-rewrite.md) | 2026-06-30 |
### The header block
### Simplification
The first three lines of every RFC are exactly:
| Title | First proposed |
|---|---|
| [Unify the agent id and the session id](proposed/simplification/2026-06-20-unify-agent-and-session-id.md) | 2026-06-20 |
| [Prune producer-less vocabulary variants (block cache hints, the `agent` message source, the `continuation` turn trigger)](proposed/simplification/2026-07-04-prune-producerless-vocabulary-variants.md) | 2026-07-04 |
| [Drop `GenerateOptions.prefill` and `ToolSchema.strict` — request knobs with no working end-to-end path](proposed/simplification/2026-07-04-drop-inert-request-knobs.md) | 2026-07-04 |
| [Drop the unconsumed web observation surface — the `providers-change` event and the status methods](proposed/simplification/2026-07-04-drop-unconsumed-web-observation-surface.md) | 2026-07-04 |
| [Drop the `image` content block until a path can honor it](proposed/simplification/2026-07-04-drop-image-content-block.md) | 2026-07-04 |
| [Prune write-only fields and a dead routing knob from the fs seam](proposed/simplification/2026-07-04-prune-write-only-fs-surface.md) | 2026-07-04 |
| [Trim unreachable ACP bridge surface — the branding knobs and the kind-sniffing fallback](proposed/simplification/2026-07-04-trim-acp-bridge-unreachable-surface.md) | 2026-07-04 |
| [Prune dead core-spine surface — `SurfaceManager.invalidate()`, the loop-internal exports, `ToolExecutionResult.callId`](proposed/simplification/2026-07-04-prune-dead-core-spine-surface.md) | 2026-07-04 |
| [Share the app bins' boot glue instead of maintaining twin copies](proposed/simplification/2026-07-04-share-app-bin-boot-glue.md) | 2026-07-04 |
| [Remove the `agent/steering` mirror emit](proposed/simplification/2026-07-04-remove-agent-steering-mirror.md) | 2026-07-04 |
| [Tighten the hook-protocol contract — dialect, discarded fields, double defaults, and lib-owned `hook/result` semantics](proposed/simplification/2026-07-04-tighten-hook-protocol-contract.md) | 2026-07-04 |
| [Fold the stdio UI helper into the stdio app](proposed/simplification/2026-07-04-fold-stdio-ui-helper.md) | 2026-07-04 |
```markdown
# RFC: <title>
### Architecture
Status: <status>
```
| Title | First proposed |
|---|---|
| [Runtime schemas for the event vocabulary (Zod vs the merge-extensible-map pattern)](proposed/architecture/2026-06-16-typed-event-schemas.md) | 2026-06-16 |
| [Extract a generic long-running tool runtime](proposed/architecture/2026-06-20-generic-long-running-tool-runtime.md) | 2026-06-20 |
followed by a blank line. The `Status:` value is one of three forms, and must agree with the lifecycle folder the file sits in — the gate cross-checks them:
### Process
- `Status: proposed`
- `Status: implemented`
- `Status: rejected — <why, in one line>`
| Title | First proposed |
|---|---|
| [Architectural conformance — dependency rules and the adapter kit](proposed/process/2026-06-11-architectural-conformance.md) | 2026-06-11 |
| [API extractor reports](proposed/process/2026-06-11-api-extractor-reports.md) | 2026-06-11 |
| [Supply chain checks and vendor drift verification](proposed/process/2026-06-11-supply-chain-and-vendor-drift.md) | 2026-06-11 |
| [Discover package inventories instead of maintaining static lists](proposed/process/2026-06-20-discover-package-inventory.md) | 2026-06-20 |
| [Generate the RFC index tables](proposed/process/2026-07-04-generate-rfc-index-tables.md) | 2026-07-04 |
The status carries no dates and no parentheticals: the filename holds the first-proposed date, git holds everything else, and an "accepted in amended form" note is body content (state the amendment where the decision is stated). The rejection reason is the one status with content, because a rejected RFC's verdict is the fact readers come for.
### Testing
### The body skeleton
| Title | First proposed |
|---|---|
| [Mutation testing as the coverage counterweight](proposed/testing/2026-06-11-mutation-testing.md) | 2026-06-11 |
| [Deterministic tests, the replay invariant fixture, and race stress](proposed/testing/2026-06-11-deterministic-and-stress-testing.md) | 2026-06-11 |
| [Single-source the acp-agent replay config](proposed/testing/2026-07-04-single-source-acp-replay-config.md) | 2026-07-04 |
Every RFC opens its body with `## Problem` — the motivation, written to stand without the solution. What follows depends on the lifecycle; recurring sections use these canonical names and nothing else, while genuinely bespoke technical sections (package topology, wire contracts, schemas) remain free-form between the required ones.
## Implemented
#### `proposed/`
### Feature
```markdown
## Problem
## Proposal
…bespoke sections…
## Alternatives considered
## Acceptance criteria
## Risks
```
| Title | First proposed |
|---|---|
| [Filesystem tool schemas — model-facing read/write/edit shapes](implemented/feature/2026-06-17-filesystem-tool-schemas.md) | 2026-06-17 |
| [Rich ACP bash rendering — the terminal card (`_meta`) and command classification](implemented/feature/2026-06-18-acp-terminal-and-tool-rendering.md) | 2026-06-18 |
| [Compaction as a capability seam (abstract contract + basic backend)](implemented/feature/2026-06-18-compaction-capability-seam.md) | 2026-06-18 |
| [Subagent capability seam](implemented/feature/2026-06-21-subagent-capability-seam.md) | 2026-06-21 |
| [ACP subagent backend (out-of-process delegation)](implemented/feature/2026-06-22-acp-subagent-backend.md) | 2026-06-22 |
| [The `todo_write` tool — model task list as event-sourced session state](implemented/feature/2026-06-29-todo-write-tool.md) | 2026-06-29 |
| [Interception seams — the typed-Decision surface a hook programs against](implemented/feature/2026-06-30-interception-seams.md) | 2026-06-30 |
| [Subagent lifecycle enrichment — lastAssistantMessage (observe-only)](implemented/feature/2026-06-30-subagent-observe-enrich.md) | 2026-06-30 |
| [dsh-hook-protocol — the shared Claude Code / Codex hook wire-protocol core](implemented/feature/2026-06-30-hook-protocol-lib.md) | 2026-06-30 |
| [dsh-hooks-claude + dsh-hooks-codex — the Claude Code / Codex hook bridges](implemented/feature/2026-06-30-hook-bridges.md) | 2026-06-30 |
`## Proposal` is the intended change and may legitimately speak in the future tense — plans, migration steps, and open questions belong here while the work is unbuilt. `## Acceptance criteria` says what observable state means done. `## Risks` covers both what could go wrong and what the change knowingly gives up.
### Simplification
#### `implemented/`
| Title | First proposed |
|---|---|
| [Drop the mutable session summary](implemented/simplification/2026-06-19-drop-mutable-session-summary.md) | 2026-06-19 |
| [Drop unconsumed assembled LLM convenience surfaces](implemented/simplification/2026-06-20-drop-unconsumed-llm-assembled-surfaces.md) | 2026-06-20 |
| [Drop the unconsumed `llm/adapter-change` event](implemented/simplification/2026-06-20-drop-unconsumed-llm-adapter-change-event.md) | 2026-06-20 |
| [Prune dead methods from the persistence seam](implemented/simplification/2026-06-20-prune-dead-seam-methods.md) | 2026-06-20 |
| [Keep one public stop primitive](implemented/simplification/2026-06-20-public-agent-stop-surface.md) | 2026-06-20 |
| [Fold trace-only session facts into load-bearing events](implemented/simplification/2026-06-20-collapse-trace-only-session-events.md) | 2026-06-20 |
| [Stop mirroring durable boundaries as agent events](implemented/simplification/2026-06-20-remove-agent-boundary-mirror-events.md) | 2026-06-20 |
| [Split the filesystem seam — provider text mutations plus the `dsh-fs-policy` plugin](implemented/simplification/2026-06-26-fsspec-style-fs-seam.md) | 2026-06-26 |
| [Stop mirroring the token stream as an agent event](implemented/simplification/2026-07-02-remove-stream-chunk-mirror.md) | 2026-07-02 |
```markdown
## Problem
## Decision
…bespoke sections…
## Alternatives considered
## Consequences
```
### Architecture
`## Decision` describes shipped reality in the present tense, and the whole file is kept current with it per [implemented/AGENTS.md](implemented/AGENTS.md). `## Consequences` records what the trade-off cost **and** bought. Proposal-era headings are spec-speak here and the gate rejects them: `## Proposal`, `## Plan`, `## Migration plan`, and `## Acceptance criteria` may not appear in an implemented RFC (the [slop checklist](../AGENTS.md) names why). A `## Testing`, `## Deferred`, or `## Related` section is fine where it states present-tense fact.
| Title | First proposed |
|---|---|
| [Microkernel: extension via Cordis event taxonomy, one concrete loop](implemented/architecture/2026-06-11-microkernel-event-taxonomy.md) | 2026-06-11 |
| [Event-sourced sessions with derived message history](implemented/architecture/2026-06-11-event-sourced-sessions.md) | 2026-06-11 |
| [Provider-neutral content-block vocabulary owned by dsh-llm](implemented/architecture/2026-06-11-content-block-vocabulary.md) | 2026-06-11 |
| [Custom typed tool-schema DSL instead of schemastery](implemented/architecture/2026-06-11-custom-schema-dsl.md) | 2026-06-11 |
| [Tool schemas are part of the system-prompt assembly](implemented/architecture/2026-06-11-tool-schemas-in-prompt-assembly.md) | 2026-06-11 |
| [Runtime arg validation at the model boundary](implemented/architecture/2026-06-11-runtime-arg-validation.md) | 2026-06-11 |
| [Dev-mode invariants over compile-time deep-readonly](implemented/architecture/2026-06-11-dev-invariants-over-deep-readonly.md) | 2026-06-11 |
| [Structured error taxonomy](implemented/architecture/2026-06-11-structured-error-taxonomy.md) | 2026-06-11 |
| [Capability seams — interface / implementation / consumer split](implemented/architecture/2026-06-13-capability-seams.md) | 2026-06-13 |
| [Two LLM adapters as a design-verification twin](implemented/architecture/2026-06-13-twin-llm-adapters.md) | 2026-06-13 |
| [Session persistence as an abstract service over `SessionEvent`](implemented/architecture/2026-06-14-session-persistence.md) | 2026-06-14 |
| [Every session event is enclosed in a turn](implemented/architecture/2026-06-15-turn-enclosure-invariant.md) | 2026-06-15 |
| [Filesystem capability seam — ctx.fs, local backend, and model-facing filesystem tools](implemented/architecture/2026-06-17-filesystem-capability-seam.md) | 2026-06-17 |
| [Shared persistence write coordinator](implemented/architecture/2026-06-18-shared-persistence-write-coordinator.md) | 2026-06-18 |
| [Agent lifecycle and ownership seams](implemented/architecture/2026-06-18-agent-lifecycle-and-ownership-seams.md) | 2026-06-18 |
| [Session surface — a linked list over the event log for LLM message derivation](implemented/architecture/2026-06-18-session-surface.md) | 2026-06-18 |
| [Reorganize packages into a modular hierarchy](implemented/architecture/2026-06-20-package-hierarchy.md) | 2026-06-20 |
| [Branded IDs everywhere they belong](implemented/architecture/2026-06-20-branded-ids.md) | 2026-06-20 |
| [Extract example apps into packages](implemented/architecture/2026-06-20-extract-example-app-packages.md) | 2026-06-20 |
| [Web capability seam — provider registry and model-facing web tools](implemented/architecture/2026-06-24-web-capability-seam.md) | 2026-06-24 |
| [Make `dsh-fs-policy` an event-gate plugin, not a method interface](implemented/architecture/2026-06-26-file-context-as-event-gate.md) | 2026-06-26 |
| [Event-domain semantics — session is the fact log, agent is the live surface](implemented/architecture/2026-06-30-event-domain-semantics.md) | 2026-06-30 |
| [stdin + extra env on the bash seam](implemented/architecture/2026-06-30-bash-stdin-env-trusted-plugin-surface.md) | 2026-06-30 |
| [Resolve filesystem paths against the caller's session cwd](implemented/architecture/2026-07-02-fs-per-session-cwd.md) | 2026-07-02 |
| [Tagged render-intent union for tool-call presentation](implemented/architecture/2026-07-02-tool-render-intent-union.md) | 2026-07-02 |
| [Result-time applied-hunk diffs for file mutations](implemented/architecture/2026-07-02-result-time-applied-hunk-diffs.md) | 2026-07-02 |
| [Add direct directory listing to the filesystem seam](implemented/architecture/2026-07-03-filesystem-directory-listing-seam.md) | 2026-07-03 |
#### `rejected/`
### Process
A rejected RFC is the proposal, frozen: it keeps whatever proposal-time sections it had (including `## Acceptance criteria` or `## Plan`), and the verdict lives on the `Status:` line. Only the header block, the `## Problem` opener, a `## Proposal` section, and the Alternatives-considered mandate below apply.
| Title | First proposed |
|---|---|
| [Vendor Cordis as source, not npm dependencies](implemented/process/2026-06-11-vendor-cordis-as-source.md) | 2026-06-11 |
| [Mechanical quality gates over prose guidelines](implemented/process/2026-06-11-quality-gates.md) | 2026-06-11 |
| [tsdown for JS bundling instead of dumble](implemented/process/2026-06-11-tsdown-over-dumble.md) | 2026-06-11 |
| [Doc-sync enforcement](implemented/process/2026-06-11-doc-sync-enforcement.md) | 2026-06-11 |
| [pnpm as the package manager instead of Yarn 4](implemented/process/2026-06-16-pnpm-over-yarn.md) | 2026-06-16 |
| [TSC-first build and one tsconfig](implemented/process/2026-06-17-ts-build-config.md) | 2026-06-17 |
| [Markdown cross-link validity linting](implemented/process/2026-06-18-markdown-cross-link-lint.md) | 2026-06-18 |
| [Core-data-structures catalog and the `ts type-equiv` drift gate](implemented/process/2026-06-20-core-data-structures-catalog.md) | 2026-06-20 |
| [Generated cordis events + services catalog](implemented/process/2026-06-20-generated-cordis-catalog.md) | 2026-06-20 |
| [Classify RFCs by kind via path-encoded subdirectories](implemented/process/2026-06-20-rfc-classification.md) | 2026-06-20 |
| [Generated tool-schema catalog (boot-and-harvest)](implemented/process/2026-07-02-tool-schema-catalog.md) | 2026-07-02 |
| [Bilingual documentation via paired sibling files and a pairing gate](implemented/process/2026-07-02-bilingual-docs-and-pairing-gate.md) | 2026-07-02 |
| [Documentation tiers, budgets, and the ceiling gate](implemented/process/2026-07-04-doc-tiers-and-budgets.md) | 2026-07-04 |
| [JSDoc completeness gate for the cordis surface](implemented/process/2026-07-04-cordis-jsdoc-completeness-gate.md) | 2026-07-04 |
### Alternatives considered — mandatory
### Testing
Every RFC carries an `## Alternatives considered` section: each genuine alternative and why it lost, one bold-led paragraph per alternative or a `### Why not <X>?` subsection per contested one. A decision recorded without what it beat invites re-litigation — the failure RFCs exist to prevent.
| Title | First proposed |
|---|---|
| [Property-based testing for protocol-shaped code](implemented/testing/2026-06-11-property-based-testing.md) | 2026-06-11 |
| [ACP snapshot tests — record-once / replay-deterministic](implemented/testing/2026-06-19-acp-snapshot-tests.md) | 2026-06-19 |
| [Real-API e2e in CI against the external DeepSeek API](implemented/testing/2026-06-19-real-api-e2e-ci.md) | 2026-06-19 |
| [Use `session.jsonl` as the only snapshot session-log artifact](implemented/testing/2026-06-20-remove-redundant-snapshot-log-goldens.md) | 2026-06-20 |
| [Per-session snapshot replay for nested agents](implemented/testing/2026-06-22-subagent-snapshot-replay.md) | 2026-06-22 |
| [Persist the seed boundary so fork-child replay routes correctly](implemented/testing/2026-06-22-fork-child-replay-seed-boundary.md) | 2026-06-22 |
| [Record fork and mixed spawn+fork snapshot scenarios](implemented/testing/2026-06-22-fork-snapshot-scenarios.md) | 2026-06-22 |
| [Hook snapshot matrix — end-to-end goldens for both bridges](implemented/testing/2026-07-04-hook-snapshot-matrix.md) | 2026-07-04 |
Alternatives are recorded, never invented. An RFC dated before 2026-07-05 whose alternatives are not reconstructible from the record carries this exact comment in place of the section, which the gate accepts for pre-format files only:
## Rejected
```markdown
<!-- rfc-format: alternatives-not-recorded (pre-format RFC) -->
```
### Simplification
### Moving between lifecycles
| Title | First proposed |
|---|---|
| [Persist assembled assistant messages, not stream chunks](rejected/simplification/2026-06-20-assembled-assistant-messages-only.md) | 2026-06-20 |
| [Drop ACP session/load until resume has a product shape](rejected/simplification/2026-06-20-drop-acp-session-load.md) | 2026-06-20 |
| [Drop ACP terminal `_meta` rendering](rejected/simplification/2026-06-20-drop-acp-terminal-meta.md) | 2026-06-20 |
| [Drop bash full-output spill files](rejected/simplification/2026-06-20-drop-bash-output-spill-files.md) | 2026-06-20 |
| [Drop durable step boundary events](rejected/simplification/2026-06-20-drop-durable-step-boundaries.md) | 2026-06-20 |
| [Drop unused session lineage metadata](rejected/simplification/2026-06-20-drop-unused-session-lineage.md) | 2026-06-20 |
| [Fold the persistence interface into dsh-session](rejected/simplification/2026-06-20-fold-session-persistence-interface.md) | 2026-06-20 |
| [Collapse tool-owned UI presentation](rejected/simplification/2026-06-20-generic-tool-rendering.md) | 2026-06-20 |
| [Retire mid-turn steering](rejected/simplification/2026-06-20-retire-mid-turn-steering.md) | 2026-06-20 |
| [Return the ACP bridge to one live session per connection](rejected/simplification/2026-06-20-single-session-acp-bridge.md) | 2026-06-20 |
| [Truncate interrupted final turns on load](rejected/simplification/2026-06-20-truncate-interrupted-turns.md) | 2026-06-20 |
| [Prune the unimplemented subagent seam vocabulary](rejected/simplification/2026-07-04-prune-unimplemented-subagent-vocabulary.md) | 2026-07-04 |
Moving a file between lifecycle folders means updating the `Status:` line and re-satisfying that folder's skeleton in the same change — the gate fails the move otherwise. Concretely, `proposed/` → `implemented/` rewrites `## Proposal` into a present-tense `## Decision`, folds `## Acceptance criteria` and `## Risks` into `## Consequences` (or a present-tense `## Testing`/`## Verification` section for what now pins the behavior), and drops plans in favor of what shipped — the rewrite [implemented/AGENTS.md](implemented/AGENTS.md) requires, made mechanical. `proposed/` → `rejected/` only adds the reason to the `Status:` line and freezes the file.
### Architecture
### Chinese counterparts
| Title | First proposed |
|---|---|
| [Deep-readonly public surfaces](rejected/architecture/2026-06-11-immutable-public-surfaces.md) | 2026-06-11 |
| [Make the shared example base providerless](rejected/architecture/2026-06-20-providerless-example-base.md) | 2026-06-20 |
A `.zh.md` counterpart mirrors its English sibling's structure section-for-section under the [i18n contract](../i18n/README.md); the machine-checked header tokens (`# RFC: ` and the `Status:` line) stay in English verbatim. The format gate skips `.zh.md` files — the pairing gate owns their consistency.

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@@ -1,6 +1,6 @@
# AGENTS.md — Implemented RFCs
These are RFCs whose decision has **shipped**. The repo-wide and docs-wide rules still apply ([root AGENTS.md](../../../AGENTS.md) § "Type safety and documentation", [docs/AGENTS.md](../../AGENTS.md)); this file adds one rule specific to this folder.
These are RFCs whose decision has **shipped**. The repo-wide and docs-wide rules still apply ([root AGENTS.md](../../../AGENTS.md) § "Type safety and documentation", [docs/AGENTS.md](../../AGENTS.md)), and the in-file skeleton — including the proposal→implemented rewrite a lifecycle move owes — is [README.md § The file format](../README.md#the-file-format), gated by `verify-rfc-format`; this file adds one rule specific to this folder.
## Keep an implemented RFC current with what actually shipped

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@@ -1,21 +1,24 @@
# RFC: Provider-neutral content-block vocabulary owned by dsh-llm
Status: implemented (accepted 2026-06-11)
Status: implemented
<!-- XXX: legacy ADR/RFC body format, not yet normalized to a unified RFC template. -->
## Problem
## Context
The harness needs one internal language for messages that the loop, session log, and all plugins speak. Options: mirror the DeepSeek/OpenAI chat-completions shape (zero mapping for the first provider, awkward for rich content), adopt Anthropic's Messages block structure verbatim (battle-tested, but our canonical types would mirror a third-party API we don't target first), or own a vocabulary.
The harness needs one internal language for messages that the loop, session log, and all plugins speak.
## Decision
Own it: messages are arrays of typed content blocks (`text`, `reasoning`, `tool-call`, `tool-result`, `image`), with the union derived from the merge-extensible `ContentBlockMap` so plugins add block types via declaration merging. The same merge-extensible-map pattern types every "stringly" field (`MessageSource`, `FinishReason`, `TurnTrigger`, `TurnEndReason`). Streaming is a raw chunk protocol; `BlockAssembler` is the single shared assembly implementation. Adapters translate to provider wire formats — mapping cost lives in adapters, where it belongs.
Own the vocabulary: messages are arrays of typed content blocks (`text`, `reasoning`, `tool-call`, `tool-result`), with the union derived from the merge-extensible `ContentBlockMap` so plugins add block types via declaration merging. The same merge-extensible-map pattern types every "stringly" field (`MessageSource`, `FinishReason`, `TurnTrigger`, `TurnEndReason`). Streaming is a raw chunk protocol; `BlockAssembler` is the single shared assembly implementation. Adapters translate to provider wire formats — mapping cost lives in adapters, where it belongs.
In-session context injection (`context/message`, `steering/message`) renders as tagged user-role envelopes (the system-reminder pattern) rather than a new role, so adapters carry zero burden. Live-adapter review has since validated the tagged-envelope rendering against current DeepSeek behavior; a future provider-specific mismatch should be handled in that adapter rather than by adding a new role to the canonical content vocabulary.
## Alternatives considered
- **Mirror the DeepSeek/OpenAI chat-completions shape** — zero mapping cost for the first provider, but awkward for rich content (reasoning, tool results as structured blocks).
- **Adopt Anthropic's Messages block structure verbatim** — battle-tested, but the canonical types would mirror a third-party API the harness does not target first.
## Consequences
- Reasoning, prefill, cache hints, and multimodal content all have a home without provider contortions.
- Reasoning has a home without provider contortions. Multimodal content deliberately has NO core block type: the core set is limited to blocks every shipping path honors, and a multimodal feature adds its block type through the merge-extensible map in the same coordinated change that maps it in the adapters, surfaces it in the UI bridges, and prices it in compaction — see [the drop-image RFC](../simplification/2026-07-04-drop-image-content-block.md). Block cache hints likewise have no core field: DeepSeek prompt caching is automatic, so no shipping adapter can transmit a hint; a caching feature adds a `cache` field together with the adapter that honors it — see [the producer-less-variants RFC](../simplification/2026-07-04-prune-producerless-vocabulary-variants.md). Assistant-prefix continuation (prefill) likewise has no request field: DeepSeek's chat-prefix completion is a Beta feature on a base URL neither shipping adapter targets, so a prefill feature adds `GenerateOptions.prefill` together with the adapter that honors it — see [the inert-request-knobs RFC](../simplification/2026-07-04-drop-inert-request-knobs.md).
- Every adapter pays a translation cost; the first real adapters have since validated the streaming protocol, and new adapters should continue proving their provider-specific mapping in adapter-local tests.
- IDs that cross package boundaries are branded (`CallId`, `SessionId`, `AgentId`) — nominal typing at zero runtime cost.

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@@ -1,10 +1,8 @@
# RFC: Custom typed tool-schema DSL instead of schemastery
Status: implemented (accepted 2026-06-11)
Status: implemented
<!-- XXX: legacy ADR/RFC body format, not yet normalized to a unified RFC template. -->
## Context
## Problem
Tool parameters must reach the model as standard JSON Schema (the wire format), and tool authors deserve typed `execute(args)` without casts. The repo already vendors schemastery (used for plugin Config), so reusing it was the obvious candidate. The user also explicitly preferred per-property `required: true` booleans over JSON Schema's separate `required` array.
@@ -12,7 +10,9 @@ Tool parameters must reach the model as standard JSON Schema (the wire format),
A small custom DSL in dsh-tools: `SchemaSpec` (per-property specs with `required: true` booleans), type-level `InferArgs<S>` mapping a spec to the argument type (required keys non-optional, others genuinely optional via `?`), a runtime `schemaSpecToJsonSchema()` converter, and `defineTool()` tying them together. Raw JSON-Schema `ToolDefinition`s remain accepted by `ToolRegistry.register()` — that's how MCP-sourced tools arrive.
Schemastery was evaluated and rejected for this use: it targets validation / transformation against StandardSchema, not JSON Schema *generation*, so it would add indirection without producing the wire format cleanly.
## Alternatives considered
**Schemastery** (already vendored, used for plugin Config) was evaluated and rejected for this use: it targets validation / transformation against StandardSchema, not JSON Schema *generation*, so it would add indirection without producing the wire format cleanly.
## Consequences

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@@ -1,10 +1,8 @@
# RFC: Dev-mode invariants over compile-time deep-readonly
Status: implemented (accepted 2026-06-13)
Status: implemented
<!-- XXX: legacy ADR/RFC body format, not yet normalized to a unified RFC template. -->
## Context
## Problem
The session log is append-only by contract, but the types don't enforce it: `session.events` returns `readonly SessionEvent[]` whose *elements* are mutable, and `deriveMessages()` handed the logged `content` arrays/blocks out by reference. The loop then passes those derived messages into the `agent/request` waterfall and on to adapters, where mutating the request is sanctioned — so a request middleware could reach back and rewrite history, silently breaking replay equivalence and the derived-history guarantee. Separately, the event taxonomy (turn/step nesting, seq monotonicity, tool-call/result pairing, legal status transitions) was asserted only where individual tests happened to look.
@@ -19,7 +17,9 @@ Reject the pervasive `DeepReadonly<T>` type flip. Instead:
The invariants encode the *real* contract, not an idealized one: a `tool/call` may have no `tool/result` (a thrown tool-execution pipeline step ends the turn), and both `idle→disposed` and `running→disposed` are legal.
`DeepReadonly` was rejected because it is compile-time only (a plugin casts straight through it), high type-noise across every log/message consumer and adapter, and would force readonly types through code where mutation is the sanctioned API. The clone draws the mutable/immutable boundary exactly at "logged vs in-flight" without any of that noise.
## Alternatives considered
**The pervasive `DeepReadonly<T>` type flip** ([the rejected proposal](../../rejected/architecture/2026-06-11-immutable-public-surfaces.md)) — compile-time only (a plugin casts straight through it), high type-noise across every log/message consumer and adapter, and it would force readonly types through code where mutation is the sanctioned API. The clone draws the mutable/immutable boundary exactly at "logged vs in-flight" without any of that noise.
## Consequences

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@@ -1,12 +1,10 @@
# RFC: Event-sourced sessions with derived message history
Status: implemented (accepted 2026-06-11)
Status: implemented
<!-- XXX: legacy ADR/RFC body format, not yet normalized to a unified RFC template. -->
## Problem
## Context
The MVP requires strict event-based tracing with fully replayable sessions (严格的基于事件的trace、logging系统,session完全可回放). Two models were considered: a mutable message array with events fired as notifications (simpler, but state and log can diverge), or event-sourcing where the log IS the state.
The MVP requires strict event-based tracing with fully replayable sessions (严格的基于事件的trace、logging系统,session完全可回放).
## Decision
@@ -16,9 +14,13 @@ Appends are synchronous (the hot path never blocks on I/O); `session/event` is a
Ordering contract: the loop appends to the session *before* emitting the corresponding Cordis event, and the `agent/step-result` waterfall runs before the `assistant/message` append so the log records what tool dispatch actually used (post-review fix; regression-tested).
## Alternatives considered
**A mutable message array with events fired as notifications** — simpler, but state and log can diverge; with event-sourcing the log IS the state, so divergence is structurally impossible.
## Consequences
- Replay, trace, and telemetry are structurally guaranteed, not bolted on.
- Persistence stays a plugin concern; the in-memory store ships in dsh-session.
- The event vocabulary is merge-extensible (plugins add e.g. compaction events); it carries a TODO(review) marker until the first persistence plugin and real adapter exercise it.
- The event vocabulary is merge-extensible (plugins add e.g. compaction events); [session persistence](2026-06-14-session-persistence.md) froze its shape once the log became durable.
- Derivation cost grows with log length — compaction (future plugin) is the intended mitigation, not log mutation.

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@@ -1,12 +1,10 @@
# RFC: Microkernel — extension via Cordis event taxonomy, one concrete loop
Status: implemented (accepted 2026-06-11)
Status: implemented
<!-- XXX: legacy ADR/RFC body format, not yet normalized to a unified RFC template. -->
## Problem
## Context
The product principle (see the 微内核Harness实现思路 design doc) is "everything is a plugin": hooks, /goal, /loop, dynamic workflows, compaction, sandboxing, permissions, UI, persistence, MCP, skills must all be writable as plugins without modifying the core. Candidate mechanisms considered: a purpose-built middleware stack (koa-compose style), an explicit phase state machine plugins can insert into, or Cordis's native event system.
The product principle is "everything is a plugin": hooks, /goal, /loop, dynamic workflows, compaction, sandboxing, permissions, UI, persistence, MCP, skills must all be writable as plugins without modifying the core.
## Decision
@@ -18,6 +16,10 @@ Pure Cordis event taxonomy. The loop's extension seams are typed events with del
The event vocabulary lives in interface packages (dsh-agent declares the agent/* events); `@deepseek-ai/dsh-agent-loop` is the only concrete loop plugin and is itself swappable — nothing outside it may depend on it.
## Alternatives considered
**A purpose-built middleware stack (koa-compose style)** and **an explicit phase state machine plugins insert into** — both would re-implement dispatch, disposal, and reload semantics that Cordis's native event system already provides; as Cordis effects, listeners get HMR and disposal for free.
## Consequences
- Every MVP feature maps to a listener (the [feature → mechanism map](../../../cookbook/extension-cookbook.md#the-feature--mechanism-map) is the proof obligation, kept current).

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@@ -1,10 +1,8 @@
# RFC: Runtime arg validation at the model boundary
Status: implemented (accepted 2026-06-13)
Status: implemented
<!-- XXX: legacy ADR/RFC body format, not yet normalized to a unified RFC template. -->
## Context
## Problem
`defineTool` ([the custom schema DSL](2026-06-11-custom-schema-dsl.md)) gives tool authors a typed `execute(args)` via the `InferArgs<S>` mapping. But that type is a compile-time claim about a value that arrives at runtime as model-generated JSON: nothing forced the model to honor the schema, so a malformed call — missing a required key, a string where a number was declared, an enum value outside the set — reached `execute` typed-in-name-only. The tool body then either crashed on the bad shape (a generic stack trace the model can't act on) or, worse, silently misbehaved. Meanwhile the converter already encodes the exact structure a validator would need to walk.
@@ -17,6 +15,8 @@ The validator mirrors `schemaSpecToJsonSchema` semantics exactly — same struct
## Consequences
- The model gets actionable feedback on its own malformed calls instead of an opaque crash, closing the gap between `InferArgs`'s promise and runtime reality.
- The validator and `InferArgs` must stay in agreement; that drift risk is to be closed by a property test ([property-based testing](../testing/2026-06-11-property-based-testing.md), not yet landed) generating args that satisfy `InferArgs` and asserting they pass `validateArgs`. Until then the agreement rests on the example tests and the shared converter structure.
- The validator and `InferArgs` must stay in agreement; [a property test](../testing/2026-06-11-property-based-testing.md) generates args satisfying a spec and asserts they pass `validateArgs` (with targeted corruptions rejected), closing that drift risk mechanically.
- `ToolArgsError` is a plain `Error` with a `code` field for now; if a harness-wide error taxonomy lands it becomes a subclass without changing callers that read `.message`.
- Validation cost is negligible next to a model call.
<!-- rfc-format: alternatives-not-recorded (pre-format RFC) -->

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@@ -1,10 +1,8 @@
# RFC: Structured error taxonomy
Status: implemented (accepted 2026-06-14)
Status: implemented
<!-- XXX: legacy ADR/RFC body format, not yet normalized to a unified RFC template. -->
## Context
## Problem
Failures crossed seams as bare strings. A tool error flattened to a text block — name, code, and stack lost — so a future sandbox/retry plugin couldn't tell ENOENT from EACCES, and the model got less actionable feedback than it could. A non-Error throw degraded further: the loop wrapped it in `new Error(String(x))`, dropping any code. And `LlmError` was the only typed error in the system, with no shared base, so there was nothing for a consumer to `instanceof` against generically.
@@ -24,3 +22,5 @@ A single `HarnessError extends Error` base in `dsh-llm` (the leaf package every
- One base class is imported widely, but it lives in the package everyone already depends on, so the cost is a single import, not a new edge.
- `deriveMessages` does not surface `error` into model history — the model still sees the text block; the structured field is for code and replay.
- Reverting this PR returns the earlier errors to plain `Error`+`code` form; nothing else in the stack depends on the shared base.
<!-- rfc-format: alternatives-not-recorded (pre-format RFC) -->

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@@ -1,17 +1,19 @@
# RFC: Tool schemas are part of the system-prompt assembly
Status: implemented (accepted 2026-06-11)
Status: implemented
<!-- XXX: legacy ADR/RFC body format, not yet normalized to a unified RFC template. -->
## Problem
## Context
On the wire, tool schemas travel in a dedicated `tools` field of the model request, not in prompt text. Architecturally, though, "what the model is told it can do" is one coherent concern: prompt sections and the tool list are assembled from the same plugin contributions and consumed at the same moment. The alternative — the loop querying the tool registry separately from the prompt service — splits one concern across two seams.
On the wire, tool schemas travel in a dedicated `tools` field of the model request, not in prompt text. Architecturally, though, "what the model is told it can do" is one coherent concern: prompt sections and the tool list are assembled from the same plugin contributions and consumed at the same moment.
## Decision
`PromptAssembly { sections, tools }`: the system-prompt service collects ordered text sections AND tool schemas (the tool registry auto-contributes a provider). The loop consumes one assembly per step; adapters map `sections` to the provider's system slot and `tools` to the wire `tools` field. The `system-prompt/assemble` waterfall is therefore a single interception point for everything the model is told up front — tool filtering (ToolSearch / progressive disclosure) is an assembly rewrite, same as prompt edits.
## Alternatives considered
**The loop queries the tool registry separately from the prompt service** — splits one coherent concern across two seams, and every interception that wants to shape "what the model is told" (tool filtering, plan mode) would need two listeners on two surfaces instead of one assembly rewrite.
## Consequences
- One waterfall governs the model's standing context; plugins like plan mode can swap prompt text and visible tools in one listener.

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@@ -1,10 +1,8 @@
# RFC: Capability seams — interface / implementation / consumer split
Status: implemented (accepted 2026-06-13)
Status: implemented
<!-- XXX: legacy ADR/RFC body format, not yet normalized to a unified RFC template. -->
## Context
## Problem
The harness has swappable capabilities — bash execution today, sandboxed/remote executors and alternative model providers tomorrow. A capability has three concerns that change at different rates and for different reasons: the *contract* (what the capability is), the *implementation* (how it runs), and the *consumer surface* (what the model and other plugins program against). Bundling them in one package couples those rates of change — swapping a local executor for a sandboxed one would churn the tool schemas the model sees, even though the model-facing contract never changed.
@@ -20,10 +18,13 @@ A swappable capability is **three packages**:
Implementation and consumer then evolve independently: a sandboxed executor replaces `dsh-bash-local` without touching a tool schema.
Alternatives considered: **one combined package** — rejected because it recouples the three rates of change the split exists to separate (the whole point). **`@cordisjs/plugin-capability`** — a different axis entirely: it is a permission/capability-*security* service (named permissions with inheritance, tested against a session via `ctx.capability.test`), a candidate for the deferred permissions/sandbox work on the `tools/pre-execute` deny/ask seam, NOT a mechanism for swapping implementations. Confusing the two ("capability") is the trap this RFC names.
The split is not mandatory when the parts are genuinely one concern: the LLM seam folds interface + consumer into `dsh-llm` (the consumer is the loop itself, not a swappable schema surface) with adapters as the implementation packages. Don't split preemptively — a capability with one conceivable implementation and one consumer stays one package until a second appears.
## Alternatives considered
- **One combined package** — rejected because it recouples the three rates of change the split exists to separate (the whole point).
- **`@cordisjs/plugin-capability`** — a different axis entirely: it is a permission/capability-*security* service (named permissions with inheritance, tested against a session via `ctx.capability.test`), a candidate for the deferred permissions/sandbox work on the `tools/pre-execute` deny/ask seam, NOT a mechanism for swapping implementations. Confusing the two ("capability") is the trap this RFC names.
## Consequences
More packages and more boilerplate per capability (a `package.json`/`tsconfig`/README trio, the inject wiring). Bought: implementations and consumers ship and version independently, and a new backend never risks the model-facing contract. The rule is documented in [AGENTS.md](../../../../AGENTS.md) § Conventions ("Capability seams are three packages") and [architecture.md](../../../architecture.md) § "Capability seams"; the bash trio is the reference template. When to fold vs. split is a judgment call the architecture doc spells out — this RFC records *why* the default is to split.

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@@ -1,10 +1,8 @@
# RFC: Two LLM adapters as a design-verification twin
Status: implemented (accepted 2026-06-13)
Status: implemented
<!-- XXX: legacy ADR/RFC body format, not yet normalized to a unified RFC template. -->
## Context
## Problem
`dsh-llm` owns a provider-neutral streaming vocabulary — the `StreamChunk` protocol (`block-start`, `text-delta`, `reasoning-delta`, `tool-call-delta`, `block-end`, `usage`, `finish`) and the content-block types ([the content-block vocabulary](2026-06-11-content-block-vocabulary.md)). A vocabulary defined against a single adapter risks baking that adapter's quirks into the "neutral" contract: anything the one implementation happens to do becomes the de-facto spec, and the abstraction is unverified until a second provider arrives — by which point the leak is expensive to fix.
@@ -17,7 +15,10 @@ Ship **two** adapters against the one contract from the start, deliberately buil
The rule they enforce: **anything the StreamChunk vocabulary cannot express for BOTH implementations is a core-vocabulary bug**, caught immediately rather than at the next provider. The pair pinned down conventions now documented on `StreamChunk` in `dsh-llm/src/types.ts`: usage emitted before finish, nothing after finish, tool-call `arguments` as raw JSON strings end-to-end, and the two sanctioned error paths (throw from `stream()` *or* end with `finish {kind:'error'|'aborted'}`) that a consumer must handle on both sides — a divergence the library-backed adapter surfaced that a single hand-rolled adapter would have hidden.
Alternatives considered: **a single adapter** — less code and half the e2e cost, but leaves the "provider-neutral" claim unverified; the vocabulary would encode DeepSeek-via-fetch assumptions silently. **A mock second adapter** — cheaper but doesn't exercise a real provider's wire quirks, so it proves little. The twin is real-on-real.
## Alternatives considered
- **A single adapter** — less code and half the e2e cost, but leaves the "provider-neutral" claim unverified; the vocabulary would encode DeepSeek-via-fetch assumptions silently.
- **A mock second adapter** — cheaper but doesn't exercise a real provider's wire quirks, so it proves little. The twin is real-on-real.
## Consequences

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@@ -1,14 +1,12 @@
# RFC: Session persistence as an abstract service over the existing `SessionEvent`
Status: implemented (proposed 2026-06-14, accepted 2026-06-15)
<!-- XXX: legacy ADR/RFC body format, not yet normalized to a unified RFC template. -->
Status: implemented
> Merges the original proposal and the decision record for one topic. The proposal's full method-surface and write-path detail lives in git history; this records the decision and the durable, contested choices.
## Context
## Problem
Sessions lived only in memory. The example `session-jsonl.ts` plugin (duplicated byte-for-byte in both examples) was write-only telemetry: it buffered `session/event` and appended JSON lines, with no read/replay path, no crash-safety (no fsync, no atomic write, a fire-and-forget dispose drain), no listing, and no format versioning. Nothing could rehydrate a past session from disk into a live agent, so durable resume ("continue yesterday's task"), durable forking, and the ACP `session/load` method ([ACP support](../../proposed/feature/2026-06-14-acp-agent-client-protocol.md)) were all impossible.
Sessions lived only in memory. The example `session-jsonl.ts` plugin (duplicated byte-for-byte in both examples) was write-only telemetry: it buffered `session/event` and appended JSON lines, with no read/replay path, no crash-safety (no fsync, no atomic write, a fire-and-forget dispose drain), no listing, and no format versioning. Nothing could rehydrate a past session from disk into a live agent, so durable resume ("continue yesterday's task"), durable forking, and the ACP `session/load` method ([ACP support](../../implemented/feature/2026-06-14-acp-agent-client-protocol.md)) were all impossible.
The [event-sourced model](2026-06-11-event-sourced-sessions.md) makes the append-only log the single source of truth and derives LLM history from it. Persistence had to stay faithful to that: persist the existing `SessionEvent` directly, with no parallel "persisted message" type that the log is converted to and from. The backend also had to be swappable — a file store now, a database store later — behind one interface.
@@ -27,8 +25,12 @@ Key choices recorded here because they are durable, contested, and surprising:
- **Metadata is out-of-log.** Format version, cwd, and lineage are storage concerns, not replayable conversation state, so they live in a `SessionHeader` owned by `dsh-session` and attached to a `Session` via a new readonly `session.header` — never in `SessionEventMap`, never reaching `deriveMessages()`. The alternative (a merge-extensible `session/meta` event as log line 0) was rejected: an in-log event would ride along with a seeded/forked session for free, but metadata is not replayable state, so the explicit out-of-log header seam is the cleaner cost. (The header was originally split into an immutable `SessionHeader` plus a mutable `SessionSummary` whose union was `SessionMeta`; the mutable summary was later removed as dead state — see [Drop the mutable session summary](../simplification/2026-06-19-drop-mutable-session-summary.md).)
- **Resume is an async factory, not a change to synchronous create.** `ctx.agents.resume({ resumeSessionId })` awaits `ctx.sessionPersistence.load`, recreates the live session with the loaded events (so `lastTurnNumber`/`deriveMessages` continue), and starts a fresh agent on the resumed id (NOT `${agentId}-session`). The agent-loop does NOT hard-inject `sessionPersistence` (that would pend non-persistent demos forever); `resume` rejects with a clear error when it is absent.
## Alternatives considered
Each key choice above records its rejected alternative where the choice is stated: a **chunk-filtered canonical log** (Codex's `policy.rs` shape) — breaks the contiguous-seq contract; **truncating a crashed turn** — silently destroys a long autonomous run's real work; an **in-log `session/meta` event as line 0** — metadata is not replayable state; **hard-injecting `sessionPersistence` into the loop** — would pend non-persistent demos forever.
Format versioning: the header carries a `version`; `load` rejects any non-current version (no migration — the pre-release session format is pinned at `SESSION_FORMAT_VERSION = 0` and absorbs shape churn, per the AGENTS.md pre-release stance). Stated honestly: append-only + flush is robust to partial trailing writes (tolerated on load) but not to fsync-less power loss mid-line; a DB/WAL backend is the stronger option later.
## Consequences
Two new packages and the metadata seam in `dsh-session` (`session.header`, the `create(id?, options?)` signature). Bought: durable resume/fork, a read/replay path, crash tolerance, and the foundation the ACP `session/load` ([ACP support](../../proposed/feature/2026-06-14-acp-agent-client-protocol.md)) needs — all over the existing event-sourced log, with the backend swappable behind one interface. The reusable `runPersistenceContract` suite holds every backend to the same append-only / contiguous-seq / lazy-materialization / serializability semantics. This completes [event-sourced sessions](2026-06-11-event-sourced-sessions.md)'s deferred "real persistence backend" and resolves its `TODO(review)` on the event vocabulary: persisting the log freezes its shape, and the `assistant/chunk` fidelity question is answered above (persist verbatim).
Two new packages and the metadata seam in `dsh-session` (`session.header`, the `create(id?, options?)` signature). Bought: durable resume/fork, a read/replay path, crash tolerance, and the foundation the ACP `session/load` ([ACP support](../../implemented/feature/2026-06-14-acp-agent-client-protocol.md)) needs — all over the existing event-sourced log, with the backend swappable behind one interface. The reusable `runPersistenceContract` suite holds every backend to the same append-only / contiguous-seq / lazy-materialization / serializability semantics. This completes [event-sourced sessions](2026-06-11-event-sourced-sessions.md)'s deferred "real persistence backend" and resolves its `TODO(review)` on the event vocabulary: persisting the log freezes its shape, and the `assistant/chunk` fidelity question is answered above (persist verbatim).

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@@ -1,10 +1,8 @@
# RFC: Every session event is enclosed in a turn
Status: implemented (accepted 2026-06-15)
Status: implemented
<!-- XXX: legacy ADR/RFC body format, not yet normalized to a unified RFC template. -->
## Context
## Problem
A durable session-persistence backend (added in a companion change) uses the **turn** as its crash-recovery boundary: a crash can leave an unclosed final turn, which `load` closes with a synthetic `turn/end {kind:'interrupted'}` while preserving the turn's real events (see [session persistence](2026-06-14-session-persistence.md)). This recovery is only well-defined if nothing *legitimately* durable sits OUTSIDE a turn — between the last `turn/end` and the next `turn/start` — since such an event would be swept into the next turn's interrupted close.
@@ -15,8 +13,6 @@ That assumption did not hold. Two paths recorded events outside any turn:
In case 2, if the injected `context/message` is the last event before a flush/dispose (no later turn appends a `turn/end`), `scanLog` treats it as crash debris and **drops it on resume** — the injected context is durably on disk but silently lost on reload. Case 1 was benign in isolation (a `user/message` is always followed by the turn it triggered) but made the "what may appear outside a turn" rule fuzzy.
Two ways to fix it: relax the *reader* (let `scanLog` commit events that sit outside an open turn), or constrain the *producer* (make every event turn-enclosed so the reader's simple "last `turn/end`" rule is both correct and complete). We chose the producer-side invariant: a single, checkable rule beats a more permissive boundary scan that has to reason about partial turns *and* loose between-turn events.
## Decision
**Every session event lives inside a turn** — between a `turn/start` and its matching `turn/end`. Concretely:
@@ -29,6 +25,10 @@ Two ways to fix it: relax the *reader* (let `scanLog` commit events that sit out
The serializability invariant is enforced at the same source boundary (`Session.append` throws on non-JSON-serializable data), so "what may enter the log" is now governed in one place rather than discovered downstream by whichever backend happens to be watching.
## Alternatives considered
**Relax the reader instead of constraining the producer** — let `scanLog` commit events that sit outside an open turn. Rejected: a single, checkable producer-side rule beats a more permissive boundary scan that has to reason about partial turns *and* loose between-turn events.
## Consequences
The turn is now the *single* durability/replay boundary, so [session persistence](2026-06-14-session-persistence.md)'s crash-recovery rule is complete, not merely sufficient: an interrupted final turn is closed (with a synthetic `turn/end {interrupted}`) and its real events preserved, with zero risk of conflating between-turn context into it, because there is no between-turn context. `scanLog` stays simple (one possibly-open final turn, never a loose between-turn event), and an idle background-task notice survives persist + resume.

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@@ -16,9 +16,9 @@ Without a `ctx.fs` interface, swapping local filesystem access for a sandboxed o
We need the filesystem tools to land in the same capability-seam shape as bash before they become a public package surface.
## Proposal
## Decision
Introduce filesystem access as a first-class capability seam following [the capability-seam RFC](../../implemented/architecture/2026-06-13-capability-seams.md):
Filesystem access is a first-class capability seam following [the capability-seam RFC](../../implemented/architecture/2026-06-13-capability-seams.md):
1. `@deepseek-ai/dsh-fs` (`packages/fs/fs`) owns the abstract `ctx.fs` service, the filesystem vocabulary types, and the `fs/*` policy event vocabulary.
2. `@deepseek-ai/dsh-fs-local` (`packages/fs/fs-local`) provides the first implementation, backed by the local filesystem.
@@ -26,7 +26,7 @@ Introduce filesystem access as a first-class capability seam following [the capa
The consumer package depends only on the interface package, never on `dsh-fs-local`. A deployment that wants a different backend loads a different provider for `ctx.fs` without changing the tool schemas or model-facing prompt guidance.
The read-before-write/edit and observed-state policy is a fourth package, `@deepseek-ai/dsh-fs-policy` (`packages/fs/fs-policy`), contributed through the `fs/*` event gate rather than living on `ctx.fs`. This RFC established the three-package seam; the split of policy off the provider base class is decided by [the split-fs-seam RFC](../simplification/2026-06-26-fsspec-style-fs-seam.md), and its realization as an event-gate plugin (not a method service) by [the event-gate RFC](2026-06-26-file-context-as-event-gate.md). This document is updated to describe that landed four-package shape.
The read-before-write/edit and observed-state policy is a fourth package, `@deepseek-ai/dsh-fs-policy` (`packages/fs/fs-policy`), contributed through the `fs/*` event gate rather than living on `ctx.fs`; a deployment loading `dsh-tool-fs` also loads `dsh-fs-policy` to get read-before-write/edit. This RFC established the three-package seam; the split of policy off the provider base class is decided by [the split-fs-seam RFC](../simplification/2026-06-26-fsspec-style-fs-seam.md), and its realization as an event-gate plugin (not a method service) by [the event-gate RFC](2026-06-26-file-context-as-event-gate.md). This document is updated to describe that landed four-package shape.
The first backend is deliberately local-only: `dsh-fs-local` implements `ctx.fs` against the host filesystem. Future sibling backends can provide sandboxed, remote, virtual, or project-scoped filesystems behind the same interface.
@@ -57,7 +57,7 @@ The root `tool-fs` plugin registers the full filesystem tool suite (`read`, `wri
`@deepseek-ai/dsh-fs` owns a semantic filesystem service. It is higher-level than `readFile` / `writeFile` so `tool-fs` does not reimplement path resolution, versioning, text decoding, binary rejection, pagination, atomic replacement, symlink behavior, or literal edit semantics.
The exact TypeScript signatures are implementation details for the PR, but the interface must cover four semantic operations:
The interface covers these semantic operations:
- Resolve a model/plugin-supplied path into a backend-defined target.
- Stat target metadata without reading file contents.
@@ -73,7 +73,7 @@ The provider seam also carries the freshness hooks that policy builds on — but
Authorization is version freshness, not a full/partial view distinction: any read records the target's version, and a later write/edit is authorized as long as the file is still at that version — so a windowed read of lines 100-150 authorizes an edit of line 120. The observed-state store is a `WeakMap<owner, Map<targetKey, version>>` inside `dsh-fs-policy`; `dsh-fs` holds none of it and treats the actor as opaque. (This RFC first modeled a `FileState` cache with `full`/`partial` views on `ctx.fs`; the split-fs-seam and event-gate RFCs replaced that with the freshness-based policy plugin described here.)
Path resolution should be explicit and allowed to be async. Local resolution may only normalize a path, but sandboxed/remote/project-scoped backends may need I/O to resolve a user-supplied path into a stable target identity.
Path resolution is explicit and allowed to be async. Local resolution may only normalize a path, but sandboxed/remote/project-scoped backends may need I/O to resolve a user-supplied path into a stable target identity.
Resolved targets must expose at least three concepts:
@@ -81,7 +81,7 @@ Resolved targets must expose at least three concepts:
- An opaque `targetKey`, used for stale guards and file-state lookup. The local backend might use a realpath-like key; a remote backend might use a workspace URI or file id. Consumers must not parse or assume this is a local absolute path.
- A `displayPath`, used for model/UI-facing output. It may be a local absolute path, workspace-relative path, or remote URI depending on the backend.
Read and mutation results must include an opaque file `version`. A local backend can use mtime/size or a hash-like token; a remote backend can use a revision id. `ctx.fs` records versions in its file-state store for stale checks; consumers may display related metadata but must not interpret the version token.
Read and mutation results must include an opaque file `version`. A local backend can use mtime/size or a hash-like token; a remote backend can use a revision id. The `dsh-fs-policy` plugin records versions for stale checks; consumers may display related metadata but must not interpret the version token.
The provider hands back decoded text: `readText` returns a whole regular text file, `streamText` streams the same text semantics for large files. Both own regular-file checks, bounded line/output handling is NOT theirs — line windowing, numbered-line rendering, and total-line accounting live in the executor (`dsh-tool-fs`), which reads through `ctx.fs` and renders the model-facing window. The provider owns UTF-8 decoding and binary/NUL rejection; it does not know about line windows or views.
@@ -89,7 +89,7 @@ Observed-state recording is not on `ctx.fs`: after a successful read the executo
Full-file writes create or replace UTF-8 text files. Backends may create parent directories when that behavior is supported and documented. Existing non-regular targets are rejected. `writeText` takes an optional expectation: `createIfAbsent` creates a missing target and rejects an existing one with `FS_NOT_OBSERVED` (the path the policy uses for an unobserved owner); `replaceIfVersion` replaces only when the target exists at the observed version, else `FS_STALE_VERSION`; omitting the expectation is the unconditional bare-provider create-or-overwrite. The policy plugin chooses which expectation to supply from the owner's observed state.
Literal edit is a provider primitive (`editText`), not composed in `tool-fs` from a read plus write. Literal matching, duplicate-match rejection, CRLF preservation, binary rejection, optional stale-version checking, and atomic read-modify-write must stay together inside the backend's mutation critical section. `editText` takes the same optional version expectation; the stale check runs before literal matching so an edit against an old read reports `FS_STALE_VERSION`. A remote backend may implement edit as a native compare-and-edit operation; the consumer should not force local-style composition.
Literal edit is a provider primitive (`editText`), not composed in `tool-fs` from a read plus write. Literal matching, duplicate-match rejection, CRLF preservation, binary rejection, optional stale-version checking, and atomic read-modify-write must stay together inside the backend's mutation critical section. `editText` takes the same optional version expectation; the stale check runs before literal matching so an edit against an old read reports `FS_STALE_VERSION`. A remote backend may implement edit as a native compare-and-edit operation; the consumer does not force local-style composition.
The policy plugin, not `ctx.fs`, gates on prior observation: an `edit` requires a prior observation by the owner (else `FS_NOT_OBSERVED`), and the recorded version is passed to `editText` as the CAS basis. With the policy plugin absent, `ctx.fs` alone is a complete unconstrained seam (unconditional write/edit); the tool is never method-coupled to the policy.
@@ -114,56 +114,30 @@ Each tool follows the same execution shape:
The package registers prompt guidance through `ctx.systemPrompt.section(...)` and registers schemas through `ctx.tools.register(...)`. Tool schemas still flow into the normal prompt assembly path via `SystemPrompt.assemble()` and `ToolRegistry.schemas()`; no agent-loop changes are required.
The tool package must keep model-facing contracts stable when backends change. A local backend and a remote backend may resolve paths differently internally, but the `read` / `write` / `edit` schemas should not change solely because the backend changes.
The tool package keeps model-facing contracts stable when backends change: a local backend and a remote backend may resolve paths differently internally, but the `read` / `write` / `edit` schemas do not change solely because the backend changes.
The default deployment requires a prior `read` before updating an existing file with `write` or `edit`. `tool-fs` does not implement this by checking whether a tool named `read` ran: it dispatches the `fs/write-intent`/`fs/edit-intent` events (passing the execution context as the opaque actor), and the `dsh-fs-policy` plugin derives the owner, gates on prior observation, and supplies the version expectation. Any windowed read authorizes a later write/edit as long as the file is unchanged. Creating a new file with `write` does not require prior observation.
The root plugin registers the full suite by composing the per-tool registration helpers. It injects `fs`, `tools`, and `systemPrompt`.
## Migration plan
## Testing
This RFC starts from `origin/master`, where no filesystem tool package exists yet. The landed implementation adds the new three-package topology directly:
Tests follow the package boundary, not only the user-visible tools: the service seam in `dsh-fs`; real filesystem behavior through the `ctx.fs` interface in `dsh-fs-local` (resolution, symlinks, streaming, binary/UTF-8 rejection, unconditional and version-guarded writes, literal-edit semantics, line-ending preservation, structured `FsError` codes); the consumer surface in `dsh-tool-fs` against the real local provider (mock only the model/clock, never the collaborator); and integration through `ctx.tools.execute()` with and without `dsh-fs-policy`, world-verified by reading files back from disk rather than trusting the returned `ContentBlock[]`. The observed-state/owner-derivation policy is tested in `dsh-fs-policy`, not here.
1. Add `packages/fs/fs` with the `ctx.fs` abstract service and vocabulary types.
2. Add `packages/fs/fs-local` with the local backend implementation and backend-level tests.
3. Add `packages/fs/tool-fs` with the model-facing `read`, `write`, and `edit` tools over `ctx.fs`.
4. Update `docs/architecture.md`, `packages/README.md`, package READMEs, build/typecheck config, and aggregate maintenance scripts such as `scripts/publint-all.ts`.
The defensive-pattern classes this repo has been bitten by are pinned directly:
This RFC's first landing kept the observed-state store behind `ctx.fs`. The split-fs-seam and event-gate RFCs then moved it into the standalone `@deepseek-ai/dsh-fs-policy` plugin on the `fs/*` event gate, which is the shipped shape; a deployment loading `dsh-tool-fs` also loads `dsh-fs-policy` to get read-before-write/edit.
- **Atomic-write temp-file safety.** Write/edit stage through a private random `0700` directory next to the target with an exclusive owner-only (`'wx'`, `0o600`) temp file, cleanup on failure, and a final atomic rename — mirroring the bash spill-file rules, because predictable world-readable temp paths invite symlink races and disclosure. Tests assert the permissions and that a pre-existing temp path is not clobbered; this primitive is a standing requirement of the seam.
- **`targetKey` identity through symlinks.** Two input paths resolving to the same realpath share one observed-state entry: a `read` via path A satisfies the read-before-edit guard for an `edit` via symlink path B, and a stale write through one path is detected through the other.
- **Concurrency / stale races.** Two concurrent write/edit operations against the same target settle deterministically — one succeeds, the other is rejected with `FS_STALE_VERSION` — and a successful edit refreshes recorded state so the same owner's next edit proceeds.
- **HMR safety and disposal.** Disposing the backend's fiber withdraws the `ctx.fs` provider; a later provider starts with no inherited state.
Example leaf configs stay bash-only in this landing. Wiring `examples/coding-agent` or `examples/acp-agent` to `dsh-fs-local` + `dsh-tool-fs` changes the model prompt, visible tool schemas, and ACP snapshot transcript, so it should land as a follow-up UX/example change with prompt and snapshot updates in the same PR.
## Alternatives considered
If this work is split into multiple PRs, they should follow the seam order:
- **Model-facing tools directly over `node:fs`** — the tool package would own execution policy, path resolution, atomic writes, text decoding, and edit semantics at once, coupling the three independently-changing concerns the Problem names and churning schemas on any backend swap.
- **One combined `dsh-fs-tools` package** — the pre-seam shape; rejected for the same interface/implementation/consumer split as bash, and the combined name never became public surface.
- **Observed-state on `ctx.fs`** — the shape this RFC first landed; superseded by [the split-fs-seam RFC](../simplification/2026-06-26-fsspec-style-fs-seam.md) and [the event-gate RFC](2026-06-26-file-context-as-event-gate.md): a sandboxed/remote backend must not inherit model-facing observation policy, so the provider keeps only the version token and the optional version-guarded mutation.
1. Interface PR: `dsh-fs` only, with service registration and contract tests.
2. Implementation PR: `dsh-fs-local`, with real filesystem behavior tests.
3. Consumer PR: `dsh-tool-fs`, docs, and integration tests; example wiring follows in a separate prompt/snapshot PR.
The earlier combined package name `@deepseek-ai/dsh-fs-tools` should not become part of the new public surface.
## Tests
Tests should follow the package boundary, not only the user-visible tools.
`dsh-fs` tests cover the service seam itself: a provider registers `ctx.fs`, duplicate providers follow Cordis service behavior, disposal removes the service, and any shared contract helpers or type-level utilities behave as documented.
`dsh-fs-local` tests cover real filesystem behavior through the `ctx.fs` interface, not through model tools. They should include path resolution, absolute paths, `..` segments, symlinks inside and outside the configured base directory, reading small and large text files, streaming, binary-file rejection, invalid-UTF-8 rejection, abort handling, unconditional and version-guarded full-file writes, `createIfAbsent`/`replaceIfVersion` semantics, parent-directory creation, non-regular target rejection, literal edit success/failure, unique-match enforcement, replace-all behavior, line-ending preservation, stale-version rejection (guarded edit against an old version), and structured `FsError` codes. The observed-state/owner-derivation policy is NOT here — it lives in `dsh-fs-policy` and is tested there.
Beyond the happy/sad paths above, `dsh-fs-local` tests must cover the defensive-pattern classes this repo has been bitten by:
- **Atomic-write temp-file safety**, not just cleanup. The atomic replace must write its temp file into a private (`0700`) directory, with a random name and an exclusive owner-only (`'wx'`, `0o600`) open, mirroring the bash spill-file rules — predictable world-readable temp paths invite symlink races and disclosure. Assert the temp file's permissions and that a pre-existing temp path does not get clobbered, alongside the existing cleanup-on-failure path.
- **Implementation requirement:** `dsh-fs-local` write/edit use the same private-temp primitive: a random `0700` staging directory next to the target, an exclusive `0o600` temp file, cleanup on failure, and a final atomic rename. Do not move this RFC to `implemented/` if that primitive regresses or is deliberately revised.
- **`targetKey` identity through symlinks.** Two different input paths that resolve to the same realpath must share one file-state entry: a `read` via path A must satisfy the read-before-edit guard for an `edit` via symlink path B, and a stale write through one path must be detected through the other. This is the contract that makes the stale guard correct, so test it directly.
- **Concurrency / stale races.** The RFC names edit as race-prone (see Risks). Test that two concurrent write/edit operations against the same target settle deterministically: one succeeds and the other is rejected with `FS_STALE_VERSION` rather than silently overwriting, and that a successful edit refreshes recorded state so an immediately-following edit by the same owner proceeds.
- **HMR safety and disposal.** `dsh-fs-local` registers `ctx.fs` and owns the in-memory file-state store, so it needs its own HMR-safety test (register the backend on a fiber, dispose it, assert the `ctx.fs` provider is withdrawn and the file-state store is released — a later provider starts with no inherited state).
`dsh-tool-fs` tests cover the consumer surface against the real `dsh-fs-local` provider (mock only the model/clock, not the collaborator). They should verify tool schemas, argument validation, prompt-section registration, formatting of successful results, propagation of backend `FsError` codes into `isError` tool results through `ctx.tools.execute()`, that read/write/edit dispatch the `fs/*` events (passing the execution context as the actor), root-plugin suite registration, and HMR cleanup of both tool schemas and prompt sections.
Integration tests should load `dsh-fs-local` plus `dsh-tool-fs` (and, for the default deployment, `dsh-fs-policy`) and execute `read`, `write`, and `edit` through `ctx.tools.execute()` to prove the packages work together without bypassing the tool registry — including a bare-provider path (no `dsh-fs-policy`) where an unread edit/overwrite succeeds. They must verify the world, not the tool's self-report: after a `write`/`edit`, read the file back from disk and assert byte-identical content (and that untouched files are unchanged), rather than trusting the returned `ContentBlock[]`. Each integration/e2e test owns its resources — create the harness in the test, run against a per-test temporary directory, and dispose the harness and remove the directory in `afterEach` even on failure or timeout.
Repo gates for the implementation include the focused vitest suites, `pnpm run typecheck`, `pnpm run test:coverage` for runtime code, and build/publint coverage after adding package entrypoints.
## Risks
## Consequences
**`cwd` can be mistaken for a sandbox.** The local backend's base directory is a resolution default, not automatically a containment boundary. If containment is required, it must be enforced by the backend contract or by a permission/sandbox plugin on `tools/execute`.
@@ -171,14 +145,14 @@ Repo gates for the implementation include the focused vitest suites, `pnpm run t
**The interface can become too thin.** If `ctx.fs` only mirrors `node:fs` primitives, `tool-fs` will reimplement binary detection, pagination, atomic writes, and edit semantics. That recreates the coupling this RFC is trying to avoid.
**Edit semantics are race-prone.** Literal edit is a read-modify-write operation. Without a stale-content guard or backend-level atomic edit primitive, concurrent edits can overwrite each other. The first implementation should document its guarantees clearly; stronger compare-and-swap semantics can be added later if needed.
**Edit semantics are race-prone by nature.** Literal edit is a read-modify-write operation; the guard is the backend's atomic mutation critical section plus the optional version expectation, so concurrent edits settle deterministically — one wins, the other gets `FS_STALE_VERSION`.
**Observed state does not belong on `ctx.fs`.** Recording what an execution context has seen is workflow policy, not raw filesystem I/O. This RFC first placed it inside the filesystem seam; the split-fs-seam RFC then established that a sandboxed/remote backend should not inherit model-facing observation policy, and moved it into the `dsh-fs-policy` plugin. The provider seam keeps only what write/edit safety genuinely needs at the storage layer — a backend-minted version token and an optional version-guarded mutation — while the policy plugin owns owner derivation, observed-state, and read-before-edit gating over the `fs/*` events.
**The `resolve`-then-operate shape costs an extra round-trip per call.** Each tool may resolve a path to an `FsTarget` and then issue the read/write/edit as a separate `ctx.fs` call. For the local backend this is negligible (resolution is in-memory path normalization), but a remote/sandboxed backend may turn each step into its own request, so a single `read` can become two network round-trips. Backends where the round-trip matters can cache or fold resolution internally while preserving the observable contract.
**File-state persistence is deferred.** The first implementation can keep file state in memory. Resumed sessions should conservatively require files to be read again before write/edit tools accept updates until a future session-event or persistence mechanism makes file state replayable.
**Observed-state persistence is deferred.** Observed state lives in memory (the `WeakMap` inside `dsh-fs-policy`), so a resumed session conservatively requires files to be read again before write/edit until a future session-event or persistence mechanism makes observation replayable.
**Error codes become part of the seam.** `FsError` codes make stale-version and observation failures machine-routable through the existing structured error taxonomy. The cost is that `dsh-fs` imports the shared `HarnessError` base from `dsh-llm`; that dependency is intentional and should stay limited to the error vocabulary.
**Error codes become part of the seam.** `FsError` codes make stale-version and observation failures machine-routable through the existing structured error taxonomy. The cost is that `dsh-fs` imports the shared `HarnessError` base from `dsh-llm`; that dependency is intentional and stays limited to the error vocabulary.
**Package churn is front-loaded.** The three-package split adds boilerplate before there is more than one backend. This is intentional: filesystem access is a likely sandbox/remote boundary, and changing the package surface after shipping model-facing tools would be more expensive.

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@@ -6,9 +6,9 @@ Status: implemented
Several ACP and tool-bash limitations were symptoms of the same missing seam: plugins could create or resume agents through `ctx.agents`, but they could not own and dispose one agent independently, and long-running bash tasks carried no stable owner in the executor itself. ACP aborted and awaited agents on disconnect but could not unregister just that session's agent; `session/cancel` could not cancel queued-but-not-yet-started work; and `tool-bash` kept task ownership in a plugin-local `Map`, so an HMR reload could make an old task look unowned.
## What was implemented
## Decision
The three seams shipped across a stacked chain of PRs (the queue-aware cancel, the `AgentHandle` disposer, and the bash owner token), each converged independently.
Three seams: the queue-aware cancel, the `AgentHandle` disposer, and the bash owner token.
### 1. Queue-aware `Agent.cancel(reason?)`
@@ -24,7 +24,9 @@ A new `cancel()` verb on the `Agent` interface — the single public stop primit
Background-task ownership moved from a `tool-bash` plugin-local `Map<string, Agent>` into the executor. `BashExecRequest` gains an optional `owner?: string`; the resolved `BashExecSpec` carries it as required-but-nullable `owner: string | undefined` (a forgotten owner is a visible `undefined`, never a silently-absent property). The executor stores the token on its task and exposes it via a new `BashExecutor.ownerOf(id): string | undefined` seam (NOT on the public `BashTask` — one read path, no redundant API). `tool-bash` deletes its `Map` entirely: it stamps `exec.agent?.session.header.id` as the owner at `start`, and `bash_output`/`bash_kill` compare `ctx.bash.ownerOf(id)` to the caller's token with `!== undefined` semantics (an empty-string token is still a real owner). The completion notice finds the live agent by scanning `ctx.get('agents')?.list()` for `agent.session.header.id === ownerToken` (read via `ctx.get` — `onTaskDone` runs on the bash fiber, a foreign fiber, where the `ctx.agents` proxy would throw). Because ownership now lives on the task in the executor (disposed with the `dsh-bash` fiber), it SURVIVES a `tool-bash` HMR reload — closing the old `XXX(tool-bash-owner-hmr)` gap. (The `onTaskDone` listener is still effect-scoped to `tool-bash`'s `apply`, so a completion landing during the reload gap still drops its one notice — the pre-existing reload-gap drop — but the ownership fence itself is HMR-proof.)
## Acceptance Criteria (met)
## Verification
These invariants hold and are pinned by tests:
- ACP disconnect/session close leaves no registered agent AND no session-store entry for that session, even when `session/load` races teardown.
- `session/cancel` before a queued prompt starts prevents that prompt from running and cannot batch the next prompt into the cancelled turn.
@@ -37,6 +39,12 @@ The bash owner-token comparison relies on `session.header.id` being unique among
The planned resolution is to remove the precondition by construction — see [unify the agent id and the session id](../../proposed/simplification/2026-06-20-unify-agent-and-session-id.md): once an agent IS its session (one id), the registry's existing unique-`agentId` check is a unique-session-id guarantee and no two live agents can share a session token.
## Notes
## Alternatives considered
- **A public `BashTask.owner` field** instead of the `BashExecutor.ownerOf(id)` seam — rejected: one read path, no redundant API.
- **Sibling cordis effects for the agent's session lifecycle** — rejected: a fiber unload disposes sibling effects concurrently (`Promise.all`), racing the session's `onAppend` detach against the loop's closing `session/flush`; the single composite effect's ordered LIFO chain is what captures the closing `turn/end` on both disposal paths.
- **A separate step-only `abort()` beside `cancel()`** — shipped originally, then removed as unused; `cancel()` is the single public stop primitive ([the public-stop-surface RFC](../simplification/2026-06-20-public-agent-stop-surface.md)).
## Consequences
This touched public interfaces (`Agent`, `AgentFactory`, the bash seam) deliberately, not as a local ACP patch. The simple synchronous `Agent.send()` ergonomics were preserved; the async lifecycle path is additive, for owners that need it.

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@@ -1,8 +1,8 @@
# RFC: Session surface — a linked list over the event log for LLM message derivation
Status: implemented (accepted 2026-06-18)
Status: implemented
## Context
## Problem
The `Session` event log is the single source of truth ([event-sourced sessions](2026-06-11-event-sourced-sessions.md)), but the only view over it was `deriveMessages()` — a linear scan that filtered and transformed raw events into `Message[]`. This creates problems for session-history-manipulating plugins (compaction, tool-call result pruning, etc.). Without a central mechanism, each plugin would need to wrap `agent/request` to rewrite the message list — a pattern that suffers from listener-ordering fragility, provides no durable record of what was changed, and forces repeated changes to the core `deriveMessages()` whenever a new manipulation is added. A central hub in the `session` package, with a provenance-recording mechanism and enough flexibility for future plugins to manipulate session history through a stable API, lays a solid foundation for plugin development.
@@ -29,13 +29,11 @@ export type SurfaceOp =
2. **Replace** — remove nodes from `start` through `end` (both inclusive) and insert a new node in their place. Both `start` and `end` must be valid surface node seqs in the current surface; `start === end` replaces a single node. The node's `sourceEventSeqs` must contain every shadowed surface node. The shadowed events remain in the log but are no longer on the surface.
The both-ends-inclusive design was chosen over half-open `[start, endExclusive)` because the surface is a doubly-linked list — both ends are naturally named by node seqs, and single-node replacement (`start === end`) is a common case that reads naturally with inclusive semantics.
### SurfaceManager: delta-based, not full rebuild
A `SurfaceManager` class (private to `Session`) maintains the cached linked list. It tracks `_lastProcessedSeq` and processes only the **delta** (new events since the last access) rather than rescanning the entire log. Because the log is append-only, prior events never change — full rebuild is only needed after a wholesale log replacement (e.g., seeding).
Why delta processing? The naive approach (a dirty flag + full rebuild on every access) would be O(N²) over a session's lifetime — every single-event append triggers a complete scan of all prior events. Delta processing is O(1) when no new events and O(new events) when new events arrive.
Delta processing is O(1) when no new events and O(new events) when new events arrive.
`deriveMessages()` uses the surface when surface markers exist, falling back to the existing linear scan for sessions without markers (backward compatibility).
@@ -53,6 +51,12 @@ The dev-mode invariants plugin validates: `sourceEventSeqs` references (non-empt
Because the surface is the SOLE derivation path, a surface-eligible event that carries no `surfaceOp` marker is invisible to `deriveMessages()` — it would land in the log yet silently drop from history on resume/fork. `append`'s typed overload makes the marker mandatory for `SurfaceEventType` events at compile time, but only when the type argument is a SPECIFIC literal; when it widens to the `SessionEventType` union (a caller iterating raw events, e.g. `for (const e of log) append(e.type, e.data)`) the conditional rest collapses to optional and the compiler stops enforcing it. The marker requirement is therefore ALSO checked at runtime in two places: `append` itself throws on a marker-less surface-eligible event (covering the union-widening loophole), and the `Session` seed constructor re-checks the same invariant (alongside its seq-contiguity and JSON-serializability checks) so a seed/load/fork — which arrives as raw `SessionEvent[]`, bypassing `append` — is REJECTED rather than constructing a session that resumes with missing history. (No backward-compat path for surface-less logs: per the pre-release stance there is no persisted user data to preserve, so such a log is rejected, not upgraded.)
## Alternatives considered
- **Per-plugin `agent/request` wrapping** (the pre-surface pattern for history manipulation) — listener-ordering fragility, no durable record of what was changed, and every new manipulation forces another change to core `deriveMessages()`.
- **Half-open `[start, endExclusive)` replace ranges** — rejected: the surface is a doubly-linked list whose ends are naturally named by node seqs, and single-node replacement (`start === end`) reads naturally with inclusive semantics.
- **Full rebuild behind a dirty flag** instead of delta processing — O(N²) over a session's lifetime: every single-event append would rescan all prior events.
## Consequences
- **`packages/core/session`**: New `surface.ts` (`SurfaceManager`), new types (`SurfaceOp`, `SurfaceIntent`), new fields on `SessionEvent`, modified `append()` (third required `SurfaceIntent` param), refactored `deriveMessages()` (walks the surface as the sole derivation path), surface-aware `repair.ts`. The seed constructor rejects a surface-eligible seed event missing its `surfaceOp` marker (see § Invariants).

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@@ -1,6 +1,6 @@
# RFC: Shared persistence write coordinator
Status: implemented (proposed and accepted 2026-06-18, implemented 2026-06-20)
Status: implemented
## Problem
@@ -32,6 +32,11 @@ The single design choice that keeps the seam clean: the crash-repair "where is t
The shared `runPersistenceContract` (public-API contract) keeps running for every backend. A new `runCoordinatorContract` (`tests/coordinator-contract.ts`) holds the write-path orchestration — adoption, HMR, collision, dispose-drain, crash-tail repair — and runs once per backend through a `CoordinatorFixture` (an in-memory reference + jsonl + sqlite). The per-backend specs shrank to storage mechanics only (JSONL: path safety, fsync rollback, bucket listing; SQLite: schema version, `scanRows`, transaction rollback). A through-coordinator torn-tail→load→`commitRepair` test per real backend (via a `corruptTail` fixture hook) keeps the coordinator's torn-marker repair branch covered under the 100% per-file gate — the contract crash test only produces synthetic closers, never a torn marker, so it could not reach that branch.
## Risks and what we gave up
## Alternatives considered
- **A base class the backends extend** — rejected for composition: a backend exposes only the hooks, cannot reach the coordinator's private orchestration state, and a third-party backend may still implement the abstract service directly without the coordinator at all.
- **A wider hook surface** — each candidate hook folded away: there is no separate `materialize` hook (the materialize-write must commit atomically with the first event batch inside `appendBatch`), no separate create-collision probe (it is `loadStored(id) !== undefined`), and no coordinator pass-through for `list()` (listing needs none of the orchestration).
## Consequences
The pre-extraction duplication was verbose but explicit — each backend read top-to-bottom. The coordinator adds one indirection (the hook seam) and one new concept (the opaque torn marker). This clears the bar because the centralized logic is the correctness-heavy part that was already being fixed twice, and the hook set is narrow (six methods, no inheritance). The hook surface was deliberately held to the minimum: the create-collision probe is NOT a separate hook — it folds into `loadStored(id) !== undefined`; there is no separate `materialize` hook (folded into `appendBatch` for atomicity); `list()` stays a backend method with no coordinator pass-through (listing needs none of the orchestration). The net effect is a reduction: one orchestration copy instead of two, the backends shrank by ~1200 lines of duplicated churn, and a future backend implements a handful of small primitives instead of copying the entire `session/event` → buffer → flush machinery.

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@@ -1,6 +1,6 @@
# RFC: Branded IDs everywhere they belong
Status: implemented (proposed and accepted 2026-06-20)
Status: implemented
## Problem
@@ -12,7 +12,7 @@ The bash **owner token** is the related sub-case: `BashExecRequest.owner?: strin
**Gap 2 — brand erosion at the seams of the *already-branded* IDs.** Even `CallId`/`SessionId`/`AgentId` decay back to bare `string` at exactly the places confusion is most likely: the registry/store `Map` key types and most public method params. Representative sites: `SessionStore.store = new Map<string, Session>()` and `create`/`prepare(id?: string)`/`get(id: string)` (`packages/core/session/src/index.ts`); `AgentRegistry.store = new Map<string, Agent>()` and `register`/`get(id: string)` (`packages/core/agent/src/index.ts`); `ToolPresenter.pending = new Map<string, …>()` keyed by call id and `call(callId: string)`/`result(callId: string)` (`packages/ui/acp/src/index.ts`); the ACP session-id surface beyond the store map — `SessionRecord.sessionId: string`, `bySession = new WeakMap<Agent, string>()`, `loadingIds = new Set<string>()`, `requireSession(sessionId: string)`, and the exported `streamSessionEventUpdate(sessionId: string, …)` (`packages/ui/acp/src/index.ts`); and the persistence coordinator's `Map<string, …>` keyed by session id (`packages/session-persistence/session-persistence/src/coordinator.ts`). A brand that is dropped at the `Map` key buys nothing on lookups — the value of the existing brands is partly unrealized.
## Proposal
## Decision
A type-only change. Brands are zero-cost casts; nothing about runtime behavior, serialization, comparison, or the wire format changes. The work is in three parts, all honoring the existing "not every string" policy.
@@ -40,7 +40,9 @@ export function OwnerToken(id: string): OwnerToken {
}
```
## Why a distinct OwnerToken brand (not SessionId)
## Alternatives considered
### Why not typing `owner` as `SessionId`?
The obvious shortcut is to type `owner` as `SessionId` directly — it always *is* one. We reject that. The bash executor seam is a capability seam (interface `dsh-bash`, implementation `dsh-bash-local`, consumer `dsh-tool-bash`) and its owner token is *documented as deliberately opaque*: the executor "never interprets it (no access policy lives in the seam — that is the consumer's job)" (`packages/bash/bash/src/types.ts`). Typing the seam's field as `SessionId` would import `dsh-session`'s vocabulary into a package that must not know what an owner token *means* — it would couple a generic execution backend to the session model and contradict the opaque-token design. A sandboxed or remote executor that replaces `dsh-bash-local` should not inherit a session dependency. The distinct `OwnerToken` brand keeps the seam decoupled: `dsh-bash` knows only "an owner is some opaque branded token," and the `dsh-tool-bash` consumer — which already decides the access policy — is the single boundary that casts its `SessionId` into an `OwnerToken`. The brand still delivers the safety win (you cannot pass a `BashTaskId` or a raw string where an owner is expected) without the coupling.
@@ -54,15 +56,12 @@ Kept deliberately narrow per the "not every string needs a brand" policy. Each o
- **Numeric ordinals** — turn number, step number, and the event `seq` are `number`, not `string`, so `Branded<string>` does not apply; a parallel `number & { readonly [BRAND]: B }` variant could brand them, but they are positional ordinals rarely passed across boundaries, so the payoff is low.
- **Validated construction** — the brand factories are pure casts with no runtime check, and every boundary (ACP `sessionId`, provider-issued `call.id`, the empty-string fallback in `dsh-llm-deepseek`) trusts the raw string today. A `SessionId.parse()` / `isValid()` companion that throws on malformed input at boundaries is a genuine gap, but it is a *runtime-behavior* change with its own design (what is "malformed"? what do we do on failure?) and belongs in its own RFC, not bundled into this type-only pass.
## Acceptance criteria
## Verification
- `BashTaskId` and `OwnerToken` are defined in `dsh-bash` and threaded end-to-end: the executor seam, the `dsh-bash-local` generation site, and the `dsh-tool-bash` model-facing surface all speak the brands; `dsh-bash` gains no dependency on `dsh-session`.
- No collection keyed by an in-scope branded id (`CallId`/`SessionId`/`AgentId`/`BashTaskId`) is keyed by bare `string` — this covers `Map`, `WeakMap` value slots, and `Set` membership (e.g. the ACP `bySession`/`loadingIds`), not just `Map<string, …>`; the corresponding public method params and exported function signatures (e.g. `streamSessionEventUpdate`) take the brand, not `string`.
- Brands are constructed via the cast factory at each boundary where a raw string enters (provider call id, ACP session id, model-supplied `task_id`); no `as` casts scattered at call sites.
- `pnpm run typecheck` and `pnpm run doc-sync` are green; the change is observably type-only (no snapshot, no e2e behavioral diff).
The landed invariants: `BashTaskId` and `OwnerToken` are defined in `dsh-bash` and threaded end-to-end (executor seam, the `dsh-bash-local` generation site, the `dsh-tool-bash` model-facing surface) with no `dsh-bash` dependency on `dsh-session`; no collection keyed by an in-scope branded id (`CallId`/`SessionId`/`AgentId`/`BashTaskId`) is keyed by bare `string` — `Map` keys, `WeakMap` value slots, `Set` membership (the ACP `bySession`/`loadingIds`), public method params, and exported signatures (`streamSessionEventUpdate`) all take the brand; and brands are constructed via the cast factory at each boundary where a raw string enters (provider call id, ACP session id, model-supplied `task_id`), never as scattered `as` casts.
## Risks / what we give up
## Consequences
- **Mechanical churn across two surfaces.** Propagating brands touches the bash seam (interface + impl + consumer) and the ACP session-id surface plus the persistence coordinator. The risk is broad but low-severity: a missed site is a compile error, not a silent bug. It ships as its own PR, converged with Codex, and stacks naturally near the [unify-the-agent-id-and-the-session-id](../../proposed/simplification/2026-06-20-unify-agent-and-session-id.md) work (both touch the session-id / owner-token boundary; if that proposal lands first, `OwnerToken` still stays distinct from the unified id for the decoupling reason above).
- **Mechanical churn across two surfaces.** Propagating brands touches the bash seam (interface + impl + consumer) and the ACP session-id surface plus the persistence coordinator. The churn is broad but low-severity: a missed site is a compile error, not a silent bug. The change is observably type-only — no snapshot or e2e behavioral diff. It sits next to the [unify-the-agent-id-and-the-session-id](../../proposed/simplification/2026-06-20-unify-agent-and-session-id.md) proposal (both touch the session-id / owner-token boundary); if that proposal lands, `OwnerToken` still stays distinct from the unified id for the decoupling reason above.
- **Brands do not validate.** A brand is a confusability guard, not a correctness proof: a *wrong* session id that is still a well-formed string passes the type checker exactly as before. This RFC does not close that gap (see Out of scope) — it only stops the *category* error of passing the wrong *kind* of id.
- **The "where to stop" line stays a judgment call.** Branding `BashTaskId` but not `ToolName`, `OwnerToken` but not `ModelId`, is a taste call about which strings "could plausibly be confused." Reasonable reviewers may want more or fewer; the policy in `brand.ts` is the tie-breaker, and this RFC errs toward the ids that are model-facing or used for access control.

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@@ -8,13 +8,13 @@ An example folder is supposed to be *thin* — the variable wiring of a demo, no
The deeper problem was a **coupled front-door cluster** that lived at the leaf with nothing enforcing it. Choosing the ACP bridge over `ui-stdio` was not one swappable line: an ACP server must **drop the stdout console logger** (stdout is the JSON-RPC channel — a stray log corrupts the frames) and pre-create **no** agents (ACP `session/new` creates them on demand), whereas the stdio app needs a console logger and a pre-created `main`. (`timer` is the one infra plugin common to both — it writes nothing to stdout — so it belongs in the shared spine, not the cluster.) That coupling was enforced only by prose warnings in the leaf YAML. A leaf that wired a console logger into the ACP config was a one-line, comment-only mistake away — exactly the [stdout-purity footgun](../feature/2026-06-18-acp-terminal-and-tool-rendering.md) the examples guarded by hand. The three `start.ts` files also duplicated the Loader-boot tail, the `.env` loader, and (for ACP) snapshot-mode branching and the stdin-dispose lifecycle.
## What shipped
## Decision
Each example is now **mostly an invocation of an app package**, splitting the wiring along the existing [interface / implementation / consumer seam](2026-06-13-capability-seams.md): the **app package owns the composition**, the leaf `cordis.yml` owns only the **swappable choices** (which LLM adapter, which bash executor, model, prompt, persistence root).
- **`@deepseek-ai/dsh-agent-core`** ([packages/core/agent-core](../../../../packages/core/agent-core)) — a Cordis bundle plugin for the providerless, executor-less, UI-less spine: `timer` + `llm` + sessions + system-prompt + tools + agents + invariants + `tool-bash` + `agent-loop`, mounted as child plugins inside its `apply(ctx)` via `ctx.plugin(...)`. This is the old `base-core.yml` **minus** `bash-local`, **plus** `timer` and the loop, as code instead of a YAML include. The bundle **forwards** `agent-loop`'s `agents` list as its own config (`export const Config = AgentLoop.Config`, default `[]`, the existing `AgentLoop.Config` shape in [packages/core/agent-loop/src/index.ts](../../../../packages/core/agent-loop/src/index.ts)) — so each app supplies its own pre-created agents. This is precisely the reason the old `base-core.yml` gave for keeping `agent-loop` *out* of the shared core ("the examples disagree — stdio needs a pre-created `main`, acp needs none"); forwarding the config dissolves that objection — the loop is shared, the agents list is per-app. The bundle children register into the root service store, so a leaf-mounted sibling (the adapter, the executor) sees them exactly as a nested `plugin-include` subtree's services were seen before. Depending on the CONCRETE `dsh-agent-loop` (not just the `dsh-agent` interface) is deliberate and is the sanctioned exception to the "extension plugins depend on interfaces, never on the concrete loop" rule (packages/README.md, docs/architecture.md § Layering): the rule constrains plugins that EXTEND the system, whereas this bundle's whole job is to COMPOSE the concrete spine. Swapping the loop means publishing a different bundle, not rewiring every extension.
- **`@deepseek-ai/dsh-agent-core`** ([packages/core/agent-core](../../../../packages/core/agent-core)) — a Cordis bundle plugin for the providerless, executor-less, UI-less spine: `timer` + `llm` + sessions + system-prompt + tools + agents + invariants + `tool-bash` + `agent-loop`, mounted as child plugins inside its `apply(ctx)` via `ctx.plugin(...)`. This is the old `base-core.yml` **minus** `bash-local`, **plus** `timer` and the loop, as code instead of a YAML include. The bundle **forwards** `agent-loop`'s `agents` list as its own config (`export const Config = AgentLoop.Config`, default `[]`, the existing `AgentLoop.Config` shape in [packages/core/agent-loop/src/index.ts](../../../../packages/core/agent-loop/src/index.ts)) — so each app supplies its own pre-created agents. This is precisely the reason the old `base-core.yml` gave for keeping `agent-loop` *out* of the shared core ("the examples disagree — stdio needs a pre-created `main`, acp needs none"); forwarding the config dissolves that objection — the loop is shared, the agents list is per-app. The bundle children register into the root service store, so a leaf-mounted sibling (the adapter, the executor) sees them exactly as a nested `plugin-include` subtree's services were seen before. Depending on the CONCRETE `dsh-agent-loop` (not just the `dsh-agent` interface) is deliberate and is the sanctioned exception to the "extension plugins depend on interfaces, never on the concrete loop" rule (packages/README.md, docs/architecture.md § Service map): the rule constrains plugins that EXTEND the system, whereas this bundle's whole job is to COMPOSE the concrete spine. Swapping the loop means publishing a different bundle, not rewiring every extension.
- **`@deepseek-ai/dsh-stdio-agent`** ([packages/ui/stdio-agent](../../../../packages/ui/stdio-agent)) and **`@deepseek-ai/dsh-acp-agent`** ([packages/ui/acp-agent](../../../../packages/ui/acp-agent)) — app packages, each consuming `dsh-agent-core` and **baking in its coupled front-door cluster**: stdio = `ui-stdio` + console logger + a pre-created `main`; acp = the `acp` bridge + JSONL persistence + **no stdout logger** + no pre-created agents. The leaf no longer carries the cluster, so it has no logger entry to copy wrong by default — the common stdout-purity mistake loses its foothold. (A leaf can still *add* a sibling logger entry — a package cannot forbid what a leaf author writes — so the rule "never add a stdout logger to an ACP leaf" stays documented at the leaf; what changed is that the default leaf has nothing to get wrong.) They land under the existing `ui` group alongside `acp`, so no new package group (and no `tsconfig`/`packages/README` group plumbing) was needed.
- **`start.ts` is gone.** Each app package exposes a `bin` (`dsh-stdio-agent` / `dsh-acp-agent`); the `demo:*` scripts invoke it (e.g. `dsh-stdio-agent ./cordis.yml`). The Loader-boot tail, `.env` loading, snapshot-mode selection, and stdin-dispose lifecycle moved into that bin, owned by the app. The `bin.ts` files are coverage-excluded (a self-executing CLI entry, like the old `start.ts`) and driven by the keyless Loader-path tests.
- **`start.ts` is gone.** Each app package exposes a `bin` (`dsh-stdio-agent` / `dsh-acp-agent`); the `demo:*` scripts invoke it (e.g. `dsh-stdio-agent ./cordis.yml`). The Loader-boot tail, `.env` loading, and fail-loud guards live in the shared [`@deepseek-ai/dsh-app-boot`](../../../../packages/ui/app-boot) package (unit-tested under the per-file coverage gate — see [share the app bins' boot glue](../simplification/2026-07-04-share-app-bin-boot-glue.md)); each bin is a thin self-executing composition over those helpers plus its app-specific lifecycle (the ACP bin: snapshot-mode selection and stdin-dispose). The `bin.ts` files themselves stay coverage-excluded (self-executing CLI entries, like the old `start.ts`) and are driven by the keyless Loader-path tests.
- **Each leaf `cordis.yml` collapses** to backends + config: the LLM adapter (`llm-deepseek` with apiKey/models, or `llm-replay`), the bash executor (`bash-local`), `hmr` for the stdio demos (see the amendment below), and one app entry carrying the app's config (model, system prompt, persistence root — surfaced as the app package's own `Config`, which routes each value to wherever the app wires it: stdio onto its pre-created agent, acp onto the bridge plugin).
- **echo-agent folds onto `dsh-stdio-agent`**, swapping the LLM backend to the local `mock-llm` and adding the local `echo-tool` (plus `bash-local`, which the spine's `tool-bash` injects) at the leaf — the clean demonstration of "swap the backend, keep the app". `mock-llm.ts` / `echo-tool.ts` stay as example-local teaching plugins.
- **`base.yml`, `base-core.yml`, and `acp-agent/acp-tail.yml` are retired** — the spine they shared now lives in `dsh-agent-core`.
@@ -30,7 +30,9 @@ The proposal listed `hmr` among the stdio app's baked-in front-door cluster. Val
Crucially, `hmr` is **not** a stdout-purity footgun the way the console logger is — a stray `hmr` in the ACP config would not corrupt the JSON-RPC frames — so leaving it at the leaf costs none of the safety the coupling argument is about. The **logger** (the real coupling) stays baked in: the stdio app includes it, the ACP app omits it.
## Why not keep the wiring in shared YAML includes?
## Alternatives considered
### Why not keep the wiring in shared YAML includes?
The old `base*.yml`/`acp-tail.yml` includes already deduped the *config*, but a YAML include cannot **encapsulate** the front-door coupling — it can only describe it in a comment and trust every leaf to obey. It also cannot own a `bin`, so the boot glue stayed copied across three `start.ts` files. A package turns "the ACP app never logs to stdout" from a prose warning into a property of the artifact: there is no logger entry in the leaf to get wrong.
@@ -41,7 +43,7 @@ The old `base*.yml`/`acp-tail.yml` includes already deduped the *config*, but a
- The new packages carry the per-file 100% coverage gate and a README like every `@deepseek-ai/dsh-*`. Each app package has a keyless **real-load-path** smoke that boots it through its `bin` + the cordis Loader (not a hand-built `ctx.plugin({...})` mount), guarding the `unwrapExports` export-shape bug class ([postmortem 0001](../../../postmortem/0001-acp-default-export-drops-inject.md)).
- The ACP snapshot **replay** transcript is unchanged: the boot restructuring preserved the plugin set + load order, so `pnpm run test:snapshot` stays green against the committed goldens with no re-record.
## What we give up
## Consequences
- **The bare-plugin-tree pedagogy.** echo-agent's inlined `cordis.yml` showed every plugin at once; the spine now lives behind a bundle, so seeing the whole tree means opening `dsh-agent-core`. The app package's README carries that teaching weight.
- **A layer of indirection.** "What does this demo load?" becomes a package read, not a single YAML scan.

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@@ -8,7 +8,7 @@ Status: implemented
This was not just cosmetic. Because every top-level package looked like part of the same public surface, future removal was harder, and publish/lint/doc scripts had to encode intent through comments or hand-maintained static lists rather than reading it off the layout.
## What landed
## Decision
Packages are grouped by modular role at a uniform `packages/<group>/<pkg>/` depth. Group directories are pure containers (no `package.json`); every package keeps its `@deepseek-ai/dsh-<pkg>` name — this is repo structure and maintenance policy, not package renaming.
@@ -62,6 +62,12 @@ Two doc-sync/hygiene gates keep the structure and its references honest, so the
- `scripts/verify-package-paths.ts` flags a `packages/<path>` reference (in Markdown or a `.ts` comment/string) that does not resolve **and** names a real package in a segment — i.e. a stale path to a moved package. A path naming a package that exists nowhere (a forward-looking proposal) is left alone, so the gate applies uniformly across proposed/implemented/rejected.
- `scripts/check-workspace-constraints.ts` asserts the `packages/<group>/<pkg>` shape: group dirs carry no `package.json`, and no package sits flat at the root or nests deeper. Group names stay open — a new group may be added without editing the gate; only the depth-2 shape is fixed.
## What we gave up
## Alternatives considered
- **A third tier (`adapters/` / `impls/` under each family)** — rejected: uniform depth 2 keeps the workspace glob a clean `packages/*/*` and lets one `@deepseek-ai/dsh-*` tsconfig wildcard resolve every package.
- **Nesting persistence under `core/session/`** — rejected: the storage backends form a parallel capability family mirroring `llm/` and `bash/`, while the session log itself stays core product API.
- **`ui-stdio` under `ui/`** — rejected: it is example-coupled dev support, not a product surface; `acp` is the only `ui/` member because an editor actually drives it.
## Consequences
The restructure churned imports, workspace globs, doc links, build references, and package paths in one coordinated move. That churn is acceptable pre-release (per the AGENTS.md foundation-over-blast-radius stance) because it stops the flat layout from fossilizing support packages as product contracts, and it is a one-time cost: the wildcard `paths`, the glob-derived publint list, and the shape gate mean a new package needs no further structural edits.

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@@ -0,0 +1,82 @@
# RFC: Mandatory `User-Agent` attribution for provider requests
Status: implemented
## Problem
LLM provider requests should identify the product making them. That is useful for provider-side support, abuse investigation, compatibility debugging, and traffic analytics. Before this RFC the harness only partially did this: the hand-rolled DeepSeek adapter sent a hand-copied `User-Agent` constant (`packages/llm/llm-deepseek/src/adapter.ts`), while the pi-ai-backed twin sent no harness-owned headers at all (`packages/llm/llm-pi-ai/src/adapter.ts`). New adapters could therefore omit attribution silently, and a library-backed adapter could drift from the hand-rolled adapter even though [the twin-adapter RFC](2026-06-13-twin-llm-adapters.md) exists to keep the provider seam honest across both implementations.
The immediate prompt came from OpenRouter's [App Attribution](https://openrouter.ai/docs/app-attribution) docs. OpenRouter creates app pages and rankings from `HTTP-Referer` plus display/category headers. That is valuable, but it is not the HTTP standard for application identity. The risk is adopting OpenRouter's exact header set as if it were universal, then leaking provider-specific headers to direct DeepSeek requests, future OpenAI/Anthropic/Vertex adapters, test servers, or proxies that log unknown fields indefinitely.
## Investigation
- **OpenRouter's mechanism is provider-specific.** Their current docs say app attribution is tracked through `HTTP-Referer` (required), `X-OpenRouter-Title`, and `X-OpenRouter-Categories`; `X-Title` is only accepted for backward compatibility. Their API reference calls the headers optional and says they make the app discoverable on OpenRouter. This is a concrete OpenRouter contract, not an IETF or OpenAI-compatible API standard.
- **In agent tooling, `HTTP-Referer` is an OpenRouter-aware convention, not a general agent convention.** It is common enough that OpenRouter SDKs and OpenRouter examples expose it directly, and frameworks that target OpenRouter usually need a way to pass it through. But agent protocols such as ACP negotiate names, versions, and capabilities in their own initialize messages, while model-provider requests still need HTTP-level identity. "Accepted in the agent world" therefore means "recognized by OpenRouter integrations," not "portable across agent runtimes or providers."
- **Observed coding agents use product/version `User-Agent` strings, sometimes with environment context.** A non-exhaustive public-code survey found OpenAI Codex building `{originator}/{version} ({os} {os_version}; {arch}) ...` and carrying an `originator` header; Google Gemini CLI sending `GeminiCLI[-clientName]/{version}/{model} ({platform}; {arch}; {surface})` or a Cloud Code VS Code variant; Cline's Codex backend client sending `cline/{version} ({platform} {release}; {arch}) node/{nodeVersion}` plus `originator: cline`; SWE-agent setting `swe-agent/{version}` unless the user already supplied a header; Continue setting `Continue/{version}` for its ClawRouter provider plus `X-Continue-Provider`. Aider also appends `Aider/{version} +{website}` to browser-like user agents for web scraping, but that is not a model-provider request path. The pattern is not one exact format; it is product identity in `User-Agent`, with provider-specific side headers only where a provider/backend asks for them.
- **The standards-track general client identity header is `User-Agent`.** RFC 9110 section 10.1.5 defines `User-Agent` as the user-agent software identity, says it is used for interoperability reports and analytics, and says a user agent SHOULD send it on each request unless configured not to. This is the only standard header that directly matches "what product is making this HTTP request."
- **`Referer` is standard, but OpenRouter's `HTTP-Referer` is not the standard field.** RFC 9110 section 10.1.3 defines `Referer` as the URI from which the target URI was obtained and spends significant text on privacy restrictions. OpenRouter instead asks for `HTTP-Referer`, using it as an app URL identifier. That name and meaning are OpenRouter-specific even though it resembles the CGI environment variable form of the standard `Referer` header.
- **`From` is standard but not suitable as a mandatory default.** RFC 9110 section 10.1.2 defines `From` as an email address for the human responsible for a user agent. Robotic agents SHOULD send it so servers can contact an operator, but non-robotic agents should not send it without explicit user configuration because of privacy and security policy concerns. The harness can support an operator contact later, but must not invent one or require it globally.
- **Request-body `user` or `metadata` fields are not app attribution.** Some model APIs expose a stable end-user identifier, request metadata, labels, or project/account headers. Those are useful for abuse monitoring, internal billing, dashboards, or trace correlation, but they either identify the end user rather than the product, are provider-specific body schema, or are not guaranteed to be forwarded through OpenAI-compatible gateways. They are not a substitute for a static application identity header.
- **SDK telemetry headers identify the SDK, not the app.** Official and third-party SDKs often send library/version headers. Those help the SDK maintainer debug their client, but they do not identify the harness as the application unless the application explicitly supplies a product attribution layer.
- **pi-ai has a first-class header hook.** `@earendil-works/pi-ai`'s `StreamOptions.headers` merges caller headers last over provider defaults, so a library-backed adapter can satisfy the same wire contract as the hand-rolled one without wrapping or upstream work. The mock-server suites assert arrival on the wire for both adapters.
## Decision
Provider request attribution is mandatory at the LLM adapter boundary, using the standard `User-Agent` header only. The rule: every product LLM adapter sends a static, non-secret application identity on every provider HTTP request, and every adapter has tests proving that `User-Agent` reaches the wire (a mock server asserting received headers; for a library-backed adapter, the library's header hook feeding the same mock-server assertion).
Do **not** implement OpenRouter app attribution in this RFC. `HTTP-Referer`, `X-OpenRouter-Title`, `X-Title`, and `X-OpenRouter-Categories` are OpenRouter-specific product-surface headers, not provider-neutral model-request attribution. They can be proposed later by an OpenRouter adapter or explicit OpenRouter mode, with its own privacy/product decision, tests, and docs. Until then, even requests pointed at OpenRouter send only the shared `User-Agent` attribution from this RFC.
The provider-neutral identity is owned by `dsh-llm` (`packages/llm/llm/src/attribution.ts`), not by individual adapters. `AppIdentity` contains only public product facts needed to build `User-Agent`, and the default `APP_IDENTITY` settles the values the proposal left open:
- product token for `User-Agent`: `deepseek-harness` (continuity with the pre-RFC wire value and the repo/org identity)
- version: read from the owning package's manifest via `createRequire`, never a hand-copied constant
- app URL: `https://github.com/deepseek-ai/deepseek-harness-sdk` - the planned public home; a `FIXME` in `attribution.ts` blocks release until that repository actually exists
The default is mandatory and non-empty. White-label deployments pass their own `AppIdentity` to `attributionHeaders(identity)` - the override seam is the function parameter, with no deployment config plumbing until a consumer needs it - and omission falls back to the harness default rather than suppressing attribution. There is no per-request API for the model, user prompt, session id, cwd, user email, API key owner, or local machine identity to influence these fields.
Wire mapping (`attributionHeaders`; header names lowercase in code - HTTP field names are case-insensitive on the wire):
| Target | Mapping |
|---|---|
| All HTTP-based adapters | `User-Agent: {product}/{version} (+{url})` - the parenthesized `+url` comment stays within RFC 9110's conservative product/comment syntax. |
| Direct DeepSeek endpoint | `User-Agent`; do not send OpenRouter-only headers unless DeepSeek documents an equivalent contract. |
| OpenRouter endpoints | `User-Agent` only for now. Do not send `HTTP-Referer`, `X-OpenRouter-Title`, `X-Title`, or `X-OpenRouter-Categories` under this RFC. |
| Future providers | `User-Agent` only unless a later provider-specific RFC accepts additional headers. Do not reuse `HTTP-Referer` by analogy. |
Endpoint detection is not part of this RFC because no endpoint-specific mapping is accepted here. If OpenRouter support lands later, detection must be explicit: either a dedicated OpenRouter provider package or an explicit `provider: 'openrouter'` / `attributionTarget: 'openrouter'` config, not arbitrary path fragments or model names.
## Verification
The landed contract:
- `dsh-llm` documents the mandatory `User-Agent` attribution contract for `LlmAdapter` authors (`LlmAdapter` JSDoc, package README, and the adapter-contract section of `docs/core-data-structures/llm-streaming.md`).
- A shared helper (`attributionHeaders` / `userAgent`) constructs the app identity and the standard `User-Agent` value from package metadata, so adapters do not hand-copy version constants.
- `dsh-llm-deepseek` sends the shared `User-Agent` on every request and its mock-server suite asserts the exact value.
- `dsh-llm-pi-ai` sends the same `User-Agent` through pi-ai's `StreamOptions.headers` hook and its mock-server suite asserts the exact value.
- No adapter sends OpenRouter-specific attribution headers (`HTTP-Referer`, `X-OpenRouter-Title`, `X-Title`, `X-OpenRouter-Categories`) as part of this RFC.
- No app-attribution field carries secrets, local paths, session ids, prompt text, model output, user email, or per-user stable identifiers.
- The adapter READMEs state the `User-Agent` attribution policy and explicitly avoid documenting OpenRouter app attribution as implemented behavior.
## Alternatives considered
**OpenRouter app attribution now.** Rejected for this RFC. Sending `HTTP-Referer` plus `X-OpenRouter-Title` would satisfy OpenRouter rankings, but those headers are a provider-specific product feature, not the provider-neutral model-request attribution this RFC is trying to standardize. Supporting them should be an explicit OpenRouter adapter/mode decision later, not hidden inside the first shared attribution helper.
**OpenRouter headers everywhere.** Rejected. It would treat a custom OpenRouter contract as a universal standard and send fields with misleading semantics to providers that did not ask for them. It also risks using `HTTP-Referer` as a generic app URL field even though standard HTTP already has `User-Agent` for product identity and `Referer` for a different browsing-context concept.
**Only provider account/project identity.** Rejected. Organization/project headers, API keys, cloud accounts, and billing projects identify who pays or owns the request, not which application is sending traffic. They also expose no public app title/category and do not help gateways like OpenRouter build app rankings.
**End-user `user`/`metadata` fields.** Rejected for this RFC. Those are valuable for abuse monitoring and customer support but describe the human or tenant behind a request. App attribution must be static product identity and safe to send on every request.
**Config-only opt-in attribution.** Rejected. A default-off setting is exactly how adapters keep drifting. The policy is mandatory default attribution with overrideable public values, not optional attribution.
**Product-named token (`deepseek-harness-sdk`).** Considered for the `User-Agent` token, since the product name is DeepSeek Harness SDK. `deepseek-harness` won on continuity: it is the identity providers already see from this codebase, it matches the org/repo identity and package scope, and it keeps wire attribution stable while display copy carries the product name.
## Consequences
**Providers see that traffic comes from the harness.** That is the point, but it means deployments that previously blended into generic SDK traffic become identifiable. Mitigation: send only static public product data and let forks/white-label deployments pass their own `AppIdentity`.
**The app URL points at a repository that does not exist yet.** `deepseek-ai/deepseek-harness-sdk` is the planned public home; until it is created the URL is a dangling promise. The `FIXME` marker on the constant blocks a release from shipping with it unresolved (see `docs/development.md` marker semantics).
**Header support differs by client library.** The hand-rolled adapter sets headers directly; the pi-ai-backed adapter depends on pi-ai continuing to honor `StreamOptions.headers` (merged last over provider defaults). The wire-level mock-server tests are the guard: if a pi-ai upgrade stops delivering the header, the suite goes red. This is useful pressure on the abstraction: a provider adapter that cannot set mandatory headers cannot fully implement the harness LLM contract.
**OpenRouter rankings do not benefit yet.** `User-Agent` is the correct baseline for provider-neutral HTTP identity, but it will not create OpenRouter app pages or rankings because OpenRouter requires `HTTP-Referer` for that product feature. That is deliberate: public app marketplace participation is a separate product decision, not a prerequisite for mandatory request attribution.

View File

@@ -4,17 +4,17 @@ Status: implemented
## Problem
The harness needs model-facing web tools without binding the model contract to one vendor's API shape. Search is the immediate pressure point: the first version should support at least Exa search and Perplexity search — two deliberately different provider shapes (Exa returns a flat `results[]` of `{title, url, highlights, publishedDate}`; Perplexity returns a generated answer plus citations), which is what proves the normalized seam does not just mirror one vendor. Fetch is a separate capability: an anonymous public HTTP(S) fetch backend has transport, security, redirect, decoding, and size-limit concerns that are not the same as provider-backed search.
The harness needs model-facing web tools without binding the model contract to one vendor's API shape. Search is the immediate pressure point: supporting both Exa search and Perplexity search from the start — two deliberately different provider shapes (Exa returns a flat `results[]` of `{title, url, highlights, publishedDate}`; Perplexity returns a generated answer plus citations) — is what proves the normalized seam does not just mirror one vendor. Fetch is a separate capability: an anonymous public HTTP(S) fetch backend has transport, security, redirect, decoding, and size-limit concerns that are not the same as provider-backed search.
The model-facing surface should stay stable while backends change. A search provider swap should not change how the model asks for a query, and a fetch implementation swap should not change how the model asks for a URL. Conversely, a provider package should not expose its own model-facing tool schema just because it has extra provider-specific knobs.
The model-facing surface must stay stable while backends change. A search provider swap should not change how the model asks for a query, and a fetch implementation swap should not change how the model asks for a URL. Conversely, a provider package should not expose its own model-facing tool schema just because it has extra provider-specific knobs.
Putting search and fetch directly in `dsh-tool-web` would make the model-facing tool own provider selection, backend request mapping, transport policy, result normalization, prompt guidance, presentation, and schema registration at once. Letting each provider register its own tool has the opposite problem: tool availability, names, descriptions, and parameters would depend on whichever provider packages happen to load, and provider-specific fields would leak into the model contract.
There is also a provider-selection question. Existing `tool-bash` and `tool-fs` can rely on Cordis `inject` because there is one backend service key. Web has two independent capabilities (`search` and `fetch`) and potentially multiple providers per capability. `inject: ['web']` proves the seam exists; it does not prove a usable search or fetch provider exists, and it does not define which provider should win when several are registered.
## Proposal
## Decision
Introduce web access as a first-class capability seam following [the capability-seam RFC](../../implemented/architecture/2026-06-13-capability-seams.md):
Web access is a first-class capability seam following [the capability-seam RFC](../../implemented/architecture/2026-06-13-capability-seams.md):
1. `@deepseek-ai/dsh-web` (`packages/web/web`) owns `ctx.web`, provider registration, provider selection, shared request/result vocabulary, and web-specific errors.
2. Provider packages implement concrete backends and register capabilities with `ctx.web`, for example `@deepseek-ai/dsh-web-search-exa`, `@deepseek-ai/dsh-web-search-perplexity`, `@deepseek-ai/dsh-web-search-deepseek`, and `@deepseek-ai/dsh-web-fetch-local`.
@@ -22,22 +22,21 @@ Introduce web access as a first-class capability seam following [the capability-
Providers do not register tools. Providers register capabilities. `dsh-tool-web` is the only owner of model-facing names, descriptions, prompt guidance, JSON schemas, and presentation.
Search and fetch are separate capabilities and separate model-facing tools, but they are deliberately one seam. `ctx.web` is a single web-access middle layer between provider packages on one side and the tool consumer on the other: one service to inject, one provider-selection policy owner, one abort/error vocabulary, one place a product configures "how this harness reaches the web." The two halves do not share a request schema and have no shared business logic — search normalizes provider-backed discovery into a portable result with optional answer text and citeable sources, while fetch retrieves a concrete public HTTP(S) URL and returns a status code plus bounded decoded content — but they are parallel registries on one capability surface, not two surfaces. The cost is a `WebService` whose registry/status/exec methods come in `Search`/`Fetch` pairs; that parallelism is intentional, not a missed extraction. Splitting into `dsh-search` and `dsh-fetch` is the rejected alternative below.
Search and fetch are separate capabilities and separate model-facing tools, but they are deliberately one seam. `ctx.web` is a single web-access middle layer between provider packages on one side and the tool consumer on the other: one service to inject, one provider-selection policy owner, one abort/error vocabulary, one place a product configures "how this harness reaches the web." The two halves do not share a request schema and have no shared business logic — search normalizes provider-backed discovery into a portable result with optional answer text and citeable sources, while fetch retrieves a concrete public HTTP(S) URL and returns a status code plus bounded decoded content — but they are parallel registries on one capability surface, not two surfaces. The cost is a `WebService` whose registry/exec methods come in `Search`/`Fetch` pairs; that parallelism is intentional, not a missed extraction. Splitting into `dsh-search` and `dsh-fetch` is the rejected alternative below.
`dsh-tool-web` should register model-facing web tools when the product has enabled those tools and the `ctx.web` seam is present. Backend availability is an execution-time concern, not a schema-registration concern:
`dsh-tool-web` registers model-facing web tools when the product has enabled those tools and the `ctx.web` seam is present. Backend availability is an execution-time concern, not a schema-registration concern:
- Register `web_search` when web search is enabled for the product/app.
- Register `web_fetch` when web fetch is enabled for the product/app.
- Do not unregister a tool merely because its selected provider is missing, misconfigured, missing credentials, ambiguous, or temporarily unavailable.
- Resolve the provider at execution time, and return a structured `WebError` when the selected capability cannot run.
- `web_search` is registered when web search is enabled for the product/app, `web_fetch` when web fetch is.
- A tool is never unregistered merely because its selected provider is missing, misconfigured, missing credentials, ambiguous, or temporarily unavailable.
- The provider is resolved at execution time, and a structured `WebError` is returned when the selected capability cannot run.
This keeps the model schema stable without making plugin load order, credential state, or HMR timing part of the model-facing contract. If web search is enabled but no usable search provider exists, `web_search` remains visible and execution fails with a structured `WebError` such as `WEB_PROVIDER_UNAVAILABLE` or `WEB_PROVIDER_CONFIGURED_UNAVAILABLE`. If a provider appears after `dsh-tool-web`, the next execution can use it without changing the schema. If a provider disappears mid-call, execution fails with a structured `WebError` instead of silently choosing another provider or falling through to `UNKNOWN_TOOL`.
The first version's provider-change signal is intentionally small. `web/providers-change` has no payload, carries no capability graph, and does not expose provider metadata. It means only "the provider registry changed; observers may recompute status from `ctx.web`." `searchStatus()` and `fetchStatus()` remain derived, not stored, and they are diagnostics plus execution-resolution inputs rather than tool-schema visibility switches.
The seam deliberately exposes no observation surface — no registry-change event and no aggregated capability-status query. Unavailability is a fact a caller observes by executing: `search()`/`fetch()` resolve the provider at call time and throw the structured `WebError` that names what failed. [The observation-surface RFC](../simplification/2026-07-04-drop-unconsumed-web-observation-surface.md) records that judgment: derived-on-call selection and enablement-based registration leave no consumer that needs a change signal or an availability probe distinct from executing and routing the error, and a future provider-status panel reintroduces the smallest signal or query it actually consumes.
## Package topology
The three-package interface/implementation/consumer split follows bash and filesystem, but the *interface* package is closer to the LLM seam. `LlmService` (`packages/llm/llm/src/index.ts`) is a name-keyed provider registry: `registerAdapter(models, adapter)` stores adapters in a `Map`, returns a disposer, throws `DUPLICATE_ADAPTER` on duplicate keys, and throws `NO_ADAPTER` at resolution time. `ctx.web` follows that registry shape, but has two capability kinds and one small selection-status layer so diagnostics and execution can explain why a search or fetch capability can or cannot run.
The three-package interface/implementation/consumer split follows bash and filesystem, but the *interface* package is closer to the LLM seam. `LlmService` (`packages/llm/llm/src/index.ts`) is a name-keyed provider registry: `registerAdapter(models, adapter)` stores adapters in a `Map`, returns a disposer, throws `DUPLICATE_ADAPTER` on duplicate keys, and throws `NO_ADAPTER` at resolution time. `ctx.web` follows that registry shape, but has two capability kinds and a richer selection policy (a configured provider id, or auto-select when exactly one usable provider is registered), so the `WebError` an execution throws can explain why a search or fetch capability cannot run.
The dependency direction mirrors bash and filesystem:
@@ -52,7 +51,7 @@ The dependency direction mirrors bash and filesystem:
implementation
```
At runtime, provider packages register capabilities with `ctx.web`; `tool-web` reads capability status and registers stable tools with `ctx.tools`:
At runtime, provider packages register capabilities with `ctx.web`; `tool-web` registers stable tools with `ctx.tools` and executes through the seam:
```mermaid
flowchart LR
@@ -60,20 +59,20 @@ flowchart LR
perplexity["@deepseek-ai/dsh-web-search-perplexity"] -->|registerSearchProvider| web
deepseek["@deepseek-ai/dsh-web-search-deepseek"] -->|registerSearchProvider| web
fetchLocal["@deepseek-ai/dsh-web-fetch-local"] -->|registerFetchProvider| web
toolWeb["@deepseek-ai/dsh-tool-web"] -->|searchStatus/fetchStatus| web
toolWeb["@deepseek-ai/dsh-tool-web"] -->|search/fetch| web
toolWeb -->|ctx.tools.register| webSearch["tool: web_search"]
toolWeb -->|ctx.tools.register| webFetch["tool: web_fetch"]
```
`@deepseek-ai/dsh-web` depends only on Cordis and low-level harness support. It declares `ctx.web`, provider interfaces, request/result types, status types, and error codes. It does not import tool, agent, session, LLM, or provider packages.
`@deepseek-ai/dsh-web` depends only on Cordis and low-level harness support. It declares `ctx.web`, provider interfaces, request/result types, the provider status type, and error codes. It does not import tool, agent, session, LLM, or provider packages.
Provider packages depend on `@deepseek-ai/dsh-web` and Cordis. They own credentials, endpoint config, provider-specific request mapping, provider-specific response parsing, and provider-specific error translation into `WebError`. They issue network requests with the platform-native `fetch` (Node 24), mirroring `@deepseek-ai/dsh-llm-deepseek`'s adapter, NOT a cordis HTTP-client service (`ctx.http`/`@cordisjs/plugin-http`) — even where a Perplexity provider's request is shaped like an OpenAI-compatible chat completion, that wire shape is a provider-private detail and does not make the provider depend on `ctx.llm`. A provider does NOT own the `ctx.web` key (two search providers cannot both own it): like `dsh-llm-deepseek`, each provider package is a function/namespace plugin (`inject: ['web']`) whose `apply` constructs the backend and calls `ctx.web.registerSearchProvider` / `registerFetchProvider`. `@deepseek-ai/dsh-web` is the `export default` service that owns the key.
Provider packages depend on `@deepseek-ai/dsh-web` and Cordis. They own credentials, endpoint config, provider-specific request mapping, provider-specific response parsing, and provider-specific error translation into `WebError`. They issue network requests with platform-native `fetch` at the repo's Node floor, mirroring `@deepseek-ai/dsh-llm-deepseek`'s adapter, NOT a cordis HTTP-client service (`ctx.http`/`@cordisjs/plugin-http`) — even where a Perplexity provider's request is shaped like an OpenAI-compatible chat completion, that wire shape is a provider-private detail and does not make the provider depend on `ctx.llm`. A provider does NOT own the `ctx.web` key (two search providers cannot both own it): like `dsh-llm-deepseek`, each provider package is a function/namespace plugin (`inject: ['web']`) whose `apply` constructs the backend and calls `ctx.web.registerSearchProvider` / `registerFetchProvider`. `@deepseek-ai/dsh-web` is the `export default` service that owns the key.
`@deepseek-ai/dsh-tool-web` depends on `@deepseek-ai/dsh-web`, `@deepseek-ai/dsh-tools`, `@deepseek-ai/dsh-system-prompt`, and Cordis. It never imports concrete provider packages.
## `ctx.web` contract
`ctx.web` is a provider registry plus a provider-selecting execution surface. The registry half should stay close to `LlmService`: a `Map<id, provider>` per capability kind, `registerSearchProvider` / `registerFetchProvider` methods that return disposers, duplicate ids that throw `WebError`, and execution-time resolution that throws when the selected provider is absent or unusable. The exact TypeScript signatures belong to the implementation PR, but the seam should expose this shape:
`ctx.web` is a provider registry plus a provider-selecting execution surface. The registry half stays close to `LlmService`: a `Map<id, provider>` per capability kind, `registerSearchProvider` / `registerFetchProvider` methods that return disposers, duplicate ids that throw `WebError`, and execution-time resolution that throws when the selected provider is absent or unusable. The authoritative signatures live in `packages/web/web/src/types.ts`; the seam's shape:
```ts
interface WebSearchProvider {
@@ -92,9 +91,6 @@ interface WebService {
registerSearchProvider(provider: WebSearchProvider): () => void
registerFetchProvider(provider: WebFetchProvider): () => void
searchStatus(): WebCapabilityStatus
fetchStatus(): WebCapabilityStatus
search(request: WebSearchRequest, exec?: WebExecContext): Promise<WebSearchResult>
fetch(request: WebFetchRequest, exec?: WebExecContext): Promise<WebFetchResult>
}
@@ -104,43 +100,37 @@ interface WebExecContext {
}
```
`WebExecContext` is execution control, not business input. The first version should carry only `signal` so `tool-web` can propagate turn cancellation, tool timeout, and agent disposal into provider network requests, SSE readers, and expensive decoding. It should not pass `ToolExecution` through the seam, because that would make `dsh-web` depend on `dsh-tools`.
`WebExecContext` is execution control, not business input. It carries only `signal`, so `tool-web` propagates turn cancellation, tool timeout, and agent disposal into provider network requests, SSE readers, and expensive decoding. It does not pass `ToolExecution` through the seam — that would make `dsh-web` depend on `dsh-tools`.
`@deepseek-ai/dsh-web` should also declare a Cordis event named `web/providers-change`. Provider ids are stable strings and unique within their capability kind. Registering a duplicate search provider id or duplicate fetch provider id should fail rather than silently replace the old provider. Provider registration returns a disposer, emits `web/providers-change` after successful registration, and emits it again when the provider is disposed. The registry should follow the existing `ctx.tools.register()` / `ctx.systemPrompt.section()` pattern: wrap the mutation in `ctx.effect()`, install the rollback disposer before emitting `web/providers-change`, and let a throwing registration-time change listener roll back the just-added provider instead of leaking it into the registry.
Provider ids are stable strings and unique within their capability kind. Registering a duplicate search provider id or duplicate fetch provider id fails rather than silently replacing the old provider. Provider registration returns a disposer and follows the existing `ctx.tools.register()` / `ctx.systemPrompt.section()` pattern: the mutation is wrapped in `ctx.effect()` so the registration is torn down with the contributing fiber.
## Provider status and selection
Provider status and capability selection are separate concepts, but both stay minimal. A provider reports only whether that concrete implementation is usable by cheap local checks such as credential presence or parseable endpoint config. A provider `status()` must not make network calls. The service reports whether the capability has a selected usable provider, or why execution would fail.
Provider status and capability selection are separate concepts, but both stay minimal. A provider reports only whether that concrete implementation is usable by cheap local checks such as credential presence or parseable endpoint config. A provider `status()` must not make network calls.
`LlmService` has no status type at all: availability is expressed as registry membership plus a resolution-time throw. `ctx.web` needs a small status answer because product apps, diagnostics, tests, and execution can report precise provider-selection failures without probing individual providers from the tool layer. Status must be derived from the configured provider id, registered providers, and each provider's cheap local `status()` on each call; it must not be stored as mutable service state.
`LlmService` has no status type at all: availability is expressed as registry membership plus a resolution-time throw. `ctx.web` follows the same discipline. The seam exposes no aggregated capability-status query — `search()` / `fetch()` derive the selection on each call from the configured provider id, the registered providers, and each provider's cheap local `status()`, and a selection failure is the structured `WebError` thrown at execution time, whose code answers "in which broad category does this capability fail" and whose message answers "exactly which provider/ids/reason." A caller that needs to know whether a capability can run executes and routes that error; nothing is stored as mutable service state.
`WebCapabilityStatus` stays intentionally small: `available` plus a `reason` discriminant, and the selected `providerId` on the available branch so diagnostics can report which provider won. It does NOT carry the per-reason payload (the unavailable provider id, the ambiguous candidate set, the underlying provider-unavailable reason). That branchable detail lives in the structured `WebError` thrown at execution time, which is the surface callers route on; duplicating it into the status union would give the same fact two homes that can disagree. `searchStatus()` / `fetchStatus()` answer "can this capability run, and if not, in which broad category does it fail" — enough for startup diagnostics and the execution-resolution decision — and the thrown error answers "exactly which provider/ids/reason."
`WebProviderStatus` is an input to selection, not a health system. `tool-web` reads only the aggregated `searchStatus()` / `fetchStatus()`, never each provider's `status()` directly, so selection policy has one owner.
`WebProviderStatus` is an input to selection, not a health system. `tool-web` never calls a provider's `status()` directly — its only path into the seam is `search()` / `fetch()` — so selection policy has one owner.
```ts
type WebProviderStatus =
| { readonly available: true }
| { readonly available: false; readonly reason: 'missing-credential' | 'misconfigured' }
type WebCapabilityStatus =
| { readonly available: true; readonly providerId: string }
| { readonly available: false; readonly reason: 'none' | 'configured-missing' | 'configured-unavailable' | 'ambiguous' }
```
Selection must not depend on registration order. Cordis load order, config ordering, and HMR timing are not product semantics.
| Situation | Status / behavior |
| Situation | Execution behavior |
|---|---|
| A configured provider id is registered and `status().available === true` | `available: true` for that provider |
| A configured provider id is not registered | `configured-missing`; execution fails with `WEB_PROVIDER_CONFIGURED_MISSING` |
| A configured provider id is registered but unavailable | `configured-unavailable`; execution fails with `WEB_PROVIDER_CONFIGURED_UNAVAILABLE` |
| No provider id is configured and exactly one provider for that kind is registered and available | `available: true` for that single provider |
| No provider id is configured and no provider for that kind is registered | `none`; execution fails with `WEB_PROVIDER_UNAVAILABLE` |
| No provider id is configured and multiple usable providers for that kind are registered | `ambiguous`; execution fails with `WEB_PROVIDER_AMBIGUOUS` rather than choosing by registration order |
| No provider id is configured and providers exist but none are usable | `none`; execution fails with `WEB_PROVIDER_UNAVAILABLE` |
| A configured provider id is registered and `status().available === true` | runs that provider |
| A configured provider id is not registered | fails with `WEB_PROVIDER_CONFIGURED_MISSING` |
| A configured provider id is registered but unavailable | fails with `WEB_PROVIDER_CONFIGURED_UNAVAILABLE` |
| No provider id is configured and exactly one provider for that kind is registered and available | runs that single provider |
| No provider id is configured and no provider for that kind is registered | fails with `WEB_PROVIDER_UNAVAILABLE` |
| No provider id is configured and multiple usable providers for that kind are registered | fails with `WEB_PROVIDER_AMBIGUOUS` rather than choosing by registration order |
| No provider id is configured and providers exist but none are usable | fails with `WEB_PROVIDER_UNAVAILABLE` |
The "single provider auto-selects" rule is for tests, demos, and simple deployments. Product configs should set explicit provider ids:
The "single provider auto-selects" rule is for tests, demos, and simple deployments. Product configs set explicit provider ids:
```yaml
- id: web
@@ -165,26 +155,26 @@ The "single provider auto-selects" rule is for tests, demos, and simple deployme
name: '@deepseek-ai/dsh-tool-web'
```
Operational overrides such as environment variables may exist, but they must feed the same explicit selection path. For example, `DSH_WEB_SEARCH_PROVIDER=perplexity` is equivalent to config `searchProvider: perplexity`; it is not a hidden priority chain inside `dsh-tool-web`.
Operational overrides feed the same explicit selection path: `DSH_WEB_SEARCH_PROVIDER=perplexity` is equivalent to config `searchProvider: perplexity`, not a hidden priority chain inside `dsh-tool-web`.
`ctx.web.search()` and `ctx.web.fetch()` resolve the provider at execution time using the same rules as the status query. If the selected capability is unavailable, they throw `WebError` with a structured code such as `WEB_PROVIDER_UNAVAILABLE`, `WEB_PROVIDER_CONFIGURED_MISSING`, `WEB_PROVIDER_CONFIGURED_UNAVAILABLE`, or `WEB_PROVIDER_AMBIGUOUS`. If no provider is explicitly configured and no usable provider exists, the status and execution error are both the generic `none` / `WEB_PROVIDER_UNAVAILABLE` case; the first version should not add a diagnostic summary of every unavailable provider.
`ctx.web.search()` and `ctx.web.fetch()` resolve the provider at execution time using the selection rules above. If the selected capability is unavailable, they throw `WebError` with a structured code such as `WEB_PROVIDER_UNAVAILABLE`, `WEB_PROVIDER_CONFIGURED_MISSING`, `WEB_PROVIDER_CONFIGURED_UNAVAILABLE`, or `WEB_PROVIDER_AMBIGUOUS`. If no provider is explicitly configured and no usable provider exists, the execution error is the generic `WEB_PROVIDER_UNAVAILABLE` case; there is deliberately no diagnostic summary of every unavailable provider.
## Search request and result schema
The first `web_search` model-facing tool should be small. The only model-facing argument is:
The `web_search` model-facing tool is small. The only model-facing argument is:
- `query`: required string.
`max_results` is NOT exposed to the model in the first version. It is a `dsh-tool-web`-layer decision: the tool sets the result bound — a default of `8` (aligning with OpenCode's Exa default), as an exported constant mirroring `dsh-tool-fs`'s `READ_LIMIT` / `GREP_LIMIT` — and passes it to the seam as `maxResults` on the `WebSearchRequest`. Keeping it off the model schema means the model just asks a question and the product controls how much context comes back; the field can be promoted to a model-facing argument later without breaking the seam.
`max_results` is NOT exposed to the model. It is a `dsh-tool-web`-layer decision: the tool sets the result bound — the `searchMaxResults` plugin config, default `8` (aligning with OpenCode's Exa default), mirroring `dsh-tool-fs`'s `readLimit` — and passes it to the seam as `maxResults` on the `WebSearchRequest`. Keeping it off the model schema means the model just asks a question and the product controls how much context comes back; the field can be promoted to a model-facing argument later without breaking the seam.
`maxResults` flows tool → seam → provider, and the bound is enforced on the way back:
- `dsh-tool-web` owns the value and puts it on `WebSearchRequest.maxResults`.
- `ctx.web` passes the request through to the selected provider unchanged.
- A provider should apply `maxResults` at the request layer when its API supports it (Exa's `numResults`), as a cost/latency optimization.
- A provider applies `maxResults` at the request layer when its API supports it (Exa's `numResults`), as a cost/latency optimization.
- `ctx.web` enforces the bound on the result: if a provider returns more than `maxResults` sources — because its API has no result-count control (Perplexity) or ignored the hint — the seam truncates `sources[]` to `maxResults` and sets `WebSearchResult.truncated` to `true` before returning. This makes the bound a single cross-provider guarantee the model-facing layer can rely on, rather than something each provider must remember to honor.
The seam request should not include provider-specific controls such as Perplexity model selection, search recency, domain filters, Exa `livecrawl`, Exa `type`, regional hints, generated-answer budgets, or search depth in the first version. Those fields should be added only when they have provider-neutral semantics that both the tool schema and selected providers can honor honestly.
The seam request carries no provider-specific controls — no Perplexity model selection, search recency, domain filters, Exa `livecrawl`, Exa `type`, regional hints, generated-answer budgets, or search depth. Such a field is added only when it has provider-neutral semantics that both the tool schema and selected providers can honor honestly.
```ts
interface WebSearchRequest {
@@ -209,24 +199,24 @@ interface WebSearchSource {
}
```
`content` is optional provider-generated answer text, search context, or summary. `sources[]` is the portable citation surface. A source always has a URL; title, snippet, and `publishedAt` are optional because not every provider returns them. `title` should not be required: Perplexity-style citations may provide only URLs, and forcing adapters to invent titles would make the seam lie. `dsh-tool-web` can render `title ?? hostname(url)` for display. `publishedAt` is an optional publication/crawl timestamp as an ISO-8601 string — Exa returns it as `publishedDate` on each result and Perplexity returns a `date` on search results, so it is real provider data, not derived; the seam carries it as a string and leaves date parsing to the consumer.
`content` is optional provider-generated answer text, search context, or summary. `sources[]` is the portable citation surface. A source always has a URL; title, snippet, and `publishedAt` are optional because not every provider returns them. `title` is not required: Perplexity-style citations may provide only URLs, and forcing adapters to invent titles would make the seam lie. `dsh-tool-web` renders a `title ?? hostname(url)`-style fallback label for display. `publishedAt` is an optional publication/crawl timestamp as an ISO-8601 string — Exa returns it as `publishedDate` on each result and Perplexity returns a `date` on search results, so it is real provider data, not derived; the seam carries it as a string and leaves date parsing to the consumer.
Exa search should map each entry of the provider's flat `results[]` into a `WebSearchSource`: `url` ← `url`, `title` ← `title`, `snippet` ← the first `highlights[]` entry (an entry with no highlight has no portable snippet and is dropped), `publishedAt` ← `publishedDate`. Exa returns no provider-generated answer, so `content` is omitted. Perplexity search should map `choices[0].message.content` to `content` and prefer the structured top-level `search_results[]` for `sources[]` — `url` ← `url`, `title` ← `title`, `snippet` ← `snippet` (often empty), `publishedAt` ← `date` — falling back to the URL-only `citations[]` array only when `search_results` is absent (those sources carry just a `url`). If a provider returns fewer structured fields than the seam supports, the adapter omits those optional fields.
Exa search maps each entry of the provider's flat `results[]` into a `WebSearchSource`: `url` ← `url`, `title` ← `title`, `snippet` ← the first `highlights[]` entry (an entry with no highlight has no portable snippet and is dropped), `publishedAt` ← `publishedDate`. Exa returns no provider-generated answer, so `content` is omitted. Perplexity search maps `choices[0].message.content` to `content` and prefers the structured top-level `search_results[]` for `sources[]` — `url` ← `url`, `title` ← `title`, `snippet` ← `snippet` (often empty), `publishedAt` ← `date` — falling back to the URL-only `citations[]` array only when `search_results` is absent (those sources carry just a `url`). If a provider returns fewer structured fields than the seam supports, the adapter omits those optional fields.
Full page retrieval remains the job of `web_fetch(url)`. Search snippets are discovery context, not fetched page bodies.
## Fetch request and result schema
The first `web_fetch` implementation should be an anonymous public HTTP(S) fetch provider, likely `local-http`. It should fetch bytes from a concrete URL, apply the basic transport hygiene below (http/https-only, credential rejection, byte/time caps, cross-origin redirect blocking), decode textual content, and return only the minimal model-useful result: final URL, status code, body, and truncation. It should not carry browser cookies, editor credentials, git credentials, internal auth tokens, or implicit access to private services. (Full SSRF / private-network blocking is deferred — see [Deferred work](#deferred-work).)
The `web_fetch` implementation is an anonymous public HTTP(S) fetch provider, `local-http`. It fetches bytes from a concrete URL, applies the basic transport hygiene below (http/https-only, credential rejection, byte/time caps, cross-origin redirect blocking), decodes textual content, and returns only the minimal model-useful result: final URL, status code, body, and truncation. It carries no browser cookies, editor credentials, git credentials, internal auth tokens, or implicit access to private services. (Full SSRF / private-network blocking is deferred — see [Deferred work](#deferred-work).)
The first seam request should stay smaller than OpenCode's model-facing tool:
The seam request stays smaller than OpenCode's model-facing tool:
- `url`: required HTTP(S) URL.
- `timeoutMs`: optional positive number capped by the provider.
The seam request deliberately does not include `format`, `prompt`, or provider-specific extraction controls. `format` is a presentation decision over a fetched resource; `prompt` is a higher-level LLM summarization instruction; extraction APIs such as Firecrawl, Exa, Tavily, or Parallel may not expose a concrete HTTP response. If the product later needs provider-backed page extraction, add a separate `web_extract` capability or explicitly widen this RFC before implementation. Do not smuggle extract semantics into `web_fetch` by making every HTTP field optional.
The seam request deliberately does not include `format`, `prompt`, or provider-specific extraction controls. `format` is a presentation decision over a fetched resource; `prompt` is a higher-level LLM summarization instruction; extraction APIs such as Firecrawl, Exa, Tavily, or Parallel may not expose a concrete HTTP response. If the product later needs provider-backed page extraction, that is a separate `web_extract` capability or a deliberate widening of this seam — extract semantics are never smuggled into `web_fetch` by making every HTTP field optional.
HTTP status is part of the fetched resource state, not automatically a tool failure. A successful network fetch of a `404` or `500` response should return `WebFetchResult` with the status code and a bounded decoded body when the content type is supported. `WebError` is for failures to safely retrieve or represent the resource: invalid or blocked URL, redirect policy violation, timeout, abort, response too large, unsupported content type, provider failure, or network failure.
HTTP status is part of the fetched resource state, not automatically a tool failure. A successful network fetch of a `404` or `500` response returns `WebFetchResult` with the status code and a bounded decoded body when the content type is supported. `WebError` is for failures to safely retrieve or represent the resource: invalid or blocked URL, redirect policy violation, timeout, abort, response too large, unsupported content type, provider failure, or network failure.
```ts
interface WebFetchRequest {
@@ -247,21 +237,19 @@ type WebFetchBody =
| { readonly kind: 'text'; readonly content: string }
```
`WebFetchResult.url` is the final URL after allowed redirects. The request URL is already present in `WebFetchRequest`, so the first version should not add separate `requestedUrl` and `finalUrl` fields.
`WebFetchResult.url` is the final URL after allowed redirects. The request URL is already present in `WebFetchRequest`, so there is no separate `requestedUrl`/`finalUrl` pair.
`WebFetchBody` is a CLOSED discriminated union owned by `dsh-web`, not a merge-extensible map. The merge-extensible pattern (`ContentBlockMap`) exists for variants that independent plugins introduce and the seam cannot foresee; body kinds are not that — `dsh-web` declares the kind, the fetch provider decodes it, and `dsh-tool-web` renders it, so a new kind is a coordinated change across three known packages, not a plugin extension. Keeping it closed buys compile-time exhaustiveness: consumers `switch` on `kind` ending in `default: assertNever(body, …)`, so adding a kind breaks compilation at every consumer that must render it (e.g. `tool-web`'s `html`→markdown vs `text` passthrough) until that arm is written. Each arm stays its own object literal even when the fields coincide today, leaving room for arm-specific fields (a future `pdf` body's `pageCount`, a `json` body's parsed value) without reshaping the type. Since the harness is unreleased, extending this closed union later is free (no migration, no compat shim).
The provider owns safe resource retrieval: URL validation, HTTP transport, redirect policy, timeout, abort propagation, byte caps, charset decoding, content-type classification, and binary rejection. `dsh-tool-web` owns presentation: HTML-to-markdown, HTML-to-text, truncation formatting for the model, and future summaries.
The fetch provider must define resource controls before the tool ships:
The fetch provider's resource controls:
- Accept only `http:` and `https:` URLs.
- Reject credentials in URLs.
- Enforce maximum URL length, response byte cap, decoded body character cap, timeout, and redirect hop cap.
- Propagate abort signals through network fetches and expensive decoding.
- Automatically follow only same-origin redirects.
- Fail cross-origin redirects with `WEB_REDIRECT_BLOCKED`, requiring a fresh tool call and therefore a fresh provider/permission decision. (Claude Code's WebFetch uses this same model — it does not auto-follow a cross-host redirect; it returns the redirect target to the model for a fresh call.)
- Use an explicit product user agent rather than silently impersonating a browser by default.
- Only `http:` and `https:` URLs are accepted; credentials in URLs are rejected.
- Maximum URL length, response byte cap, decoded body character cap, timeout, and redirect hop cap are enforced.
- Abort signals propagate through network fetches and expensive decoding.
- Only same-origin redirects are followed automatically; a cross-origin redirect fails with `WEB_REDIRECT_BLOCKED`, requiring a fresh tool call and therefore a fresh provider/permission decision. (Claude Code's WebFetch uses this same model — it does not auto-follow a cross-host redirect; it returns the redirect target to the model for a fresh call.)
- Requests carry an explicit product user agent rather than silently impersonating a browser.
SSRF / private-network protection (blocking private, loopback, link-local, multicast, and otherwise non-public destinations, with DNS-resolve-then-validate to defeat rebinding and per-hop re-validation on redirects) is **deferred** — see [Deferred work](#deferred-work). Until it lands, `web_fetch` is an SSRF primitive and must not be enabled in a deployment that can reach sensitive internal network targets.
@@ -269,25 +257,19 @@ SSRF / private-network protection (blocking private, loopback, link-local, multi
`dsh-tool-web` owns two `ToolDefinition`s: `web_search` and `web_fetch`. It owns model-facing JSON schemas, snake_case argument names, prompt sections, result rendering to `ContentBlock[]`, `presentCall`, and `presentResult`.
`dsh-tool-web` must not enumerate providers or call provider `status()` directly. Its execution path is `ctx.web.search()` / `ctx.web.fetch()`, and any optional startup diagnostics should read only `ctx.web.searchStatus()` / `ctx.web.fetchStatus()`. That keeps provider selection in one layer; otherwise the tool package could decide one provider is usable while execution resolves a different state.
`dsh-tool-web` must not enumerate providers or call provider `status()` directly. Its only path into the seam is `ctx.web.search()` / `ctx.web.fetch()`. That keeps provider selection in one layer; otherwise the tool package could decide one provider is usable while execution resolves a different state.
Tool registration in the first version is a minimal stable sync:
1. On plugin startup, read the `dsh-tool-web` `Config` (`search?: boolean`, `fetch?: boolean`, both default `true`) that enables or disables each web tool.
2. If web search is enabled, register `web_search` (its disposer is fiber-scoped via the effect-based registry).
3. If web fetch is enabled, register `web_fetch` (likewise fiber-scoped).
4. Do not dispose either tool merely because `ctx.web.searchStatus()` or `ctx.web.fetchStatus()` is unavailable.
5. Disposing the `tool-web` fiber tears down its registrations automatically.
Tool registration is a minimal stable sync: on plugin startup the `dsh-tool-web` `Config` (`search?: boolean`, `fetch?: boolean`, both default `true`) enables or disables each web tool; an enabled tool is registered with a fiber-scoped disposer via the effect-based registry; neither tool is disposed merely because its selected provider is missing, unusable, or ambiguous; disposing the `tool-web` fiber tears down its registrations automatically.
Provider status changes affect execution results and diagnostics, not whether the model-facing schema exists. If a product wants no web tools at all, it disables `dsh-tool-web` or the individual web tool in config; if it wants web tools but the backend is misconfigured, the model sees a structured tool error at execution time.
Prompt guidance should explain the semantic split: use `web_search` for discovery and current information, then use `web_fetch` when the model needs the content of a specific URL. The prompt and tool result should tell the model to cite relevant URLs with markdown links.
The prompt guidance explains the semantic split — `web_search` for discovery and current information, `web_fetch` when the model needs the content of a specific URL — and the prompt and tool result tell the model to cite relevant URLs with markdown links.
The model-facing output should be text-first because current tool results are `ContentBlock[]`, but the seam outcome should stay structured so UI presentation and future adapters do not have to scrape rendered text.
The model-facing output is text-first because tool results are `ContentBlock[]`, but the seam outcome stays structured so UI presentation and future adapters do not have to scrape rendered text.
## Errors
`dsh-web` should define `WebError extends HarnessError` with stable codes. Initial codes should include only states that callers may reasonably branch on:
`dsh-web` defines `WebError extends HarnessError` with stable codes, covering only states that callers may reasonably branch on:
- `WEB_PROVIDER_UNAVAILABLE`
- `WEB_PROVIDER_CONFIGURED_MISSING`
@@ -303,40 +285,13 @@ The model-facing output should be text-first because current tool results are `C
- `WEB_UNSUPPORTED_CONTENT_TYPE`
- `WEB_PROVIDER_ERROR`
`WEB_DUPLICATE_PROVIDER` is thrown synchronously from `registerSearchProvider` / `registerFetchProvider` when an id is already registered for that capability kind (the analogue of `LlmService`'s `DUPLICATE_ADAPTER`); it is a registration-time programming error, not an execution outcome, but shares the `WebError` code space so callers see one taxonomy. `WEB_PROVIDER_ERROR` is the catch-all for a provider's own failure surfaced through the seam, including network/transport failure in `web-fetch-local` (DNS, connection refused, TLS); the first version does not split out a separate `WEB_NETWORK` code, but the provider should set a descriptive message so the model and logs can tell a network failure from a provider API failure.
`WEB_DUPLICATE_PROVIDER` is thrown synchronously from `registerSearchProvider` / `registerFetchProvider` when an id is already registered for that capability kind (the analogue of `LlmService`'s `DUPLICATE_ADAPTER`); it is a registration-time programming error, not an execution outcome, but shares the `WebError` code space so callers see one taxonomy. `WEB_PROVIDER_ERROR` is the catch-all for a provider's own failure surfaced through the seam, including network/transport failure in `web-fetch-local` (DNS, connection refused, TLS); there is deliberately no separate `WEB_NETWORK` code — the provider sets a descriptive message so the model and logs can tell a network failure from a provider API failure.
Tool execution should let these errors flow through `ToolRegistry.execute()`, which already converts `HarnessError` into an error tool result with structured metadata. The model gets a readable error message; hooks, tests, and UI code can route on the stable code.
Tool execution lets these errors flow through `ToolRegistry.execute()`, which already converts `HarnessError` into an error tool result with structured metadata. The model gets a readable error message; hooks, tests, and UI code can route on the stable code.
## Tests
## Testing
Tests should prove the seam contract without turning this RFC into an implementation checklist.
`dsh-web` tests cover provider registration and disposal, duplicate provider ids, `web/providers-change` emission, rollback when a registration-time `web/providers-change` listener throws, `searchStatus()` and `fetchStatus()` for the selection table above, execution-time provider resolution, `maxResults` truncation of `sources[]` with `truncated` set when a provider over-returns, abort propagation through `WebExecContext.signal`, and structured `WebError` codes.
Search provider tests cover request mapping, response parsing into `content` plus `sources[]`, missing credentials, provider errors, timeout/abort, truncation, and a self-skipping with-key smoke test for each real provider. Perplexity fixtures must include URL-only citations so the optional source fields stay honest.
`dsh-web-fetch-local` tests cover real HTTP behavior using a local test server: valid text and HTML fetches, non-2xx HTTP responses returned as results, byte/decoded-body caps, timeout, abort, invalid URLs, credential-in-URL rejection, cross-origin redirect blocking, unsupported content types, and product user agent. (Private-destination/SSRF blocking tests come with that deferred work.)
`dsh-tool-web` tests execute through the real tool registry. They verify schema registration follows product/app tool enablement rather than provider availability, unavailable or ambiguous providers produce structured execution errors, argument validation, formatting of successful search/fetch results, structured error propagation, and cleanup on disposal.
Integration tests should load the real seam, provider, and tool packages together and execute through `ctx.tools.execute()` rather than calling providers directly. If wiring the tools into an ACP-facing example changes editor-visible transcripts, add or update the relevant snapshot scenario in the same change.
At least one test must drive these packages through their REAL cordis Loader/export path, not a hand-built `ctx.plugin({...})` mount, so a broken export shape is caught (see [docs/postmortem/0001](../../../postmortem/0001-acp-default-export-drops-inject.md) and `packages/AGENTS.md` § plugin-export-shape). The two shapes need different guards: `dsh-web` is a **service** (`export default` the class) and a stray extra export would surface as a missing service; the provider packages and `dsh-tool-web` are **namespace plugins** (named `name`/`inject`/`apply`, NO default), and because each has `inject`, a stray `export default apply` makes `unwrapExports` drop the `inject` and the plugin throws `cannot get property … without inject` the moment it loads — so a Loader smoke that boots tool-web over `ctx.web` catches it (and each provider's registration test mounts it the real way and asserts no default export). Prove the guard bites: add `export default apply` to `tool-web`, watch the smoke go red, revert.
## Migration plan
This is new capability work, so no compatibility migration is required while the harness is unreleased.
Land the work in seam order:
1. Add `packages/web/web` with `ctx.web`, provider registration, provider status, capability status, selection, request/result/error types, and contract tests.
2. Add `packages/web/web-search-exa` with parser/unit tests and a self-skipping real-provider smoke test.
3. Add `packages/web/web-search-perplexity` with parser/unit tests and a self-skipping real-provider smoke test.
4. Add `packages/web/web-search-deepseek` with parser/unit tests and a self-skipping real-provider smoke test.
5. Add `packages/web/web-fetch-local` with local HTTP behavior tests.
6. Add `packages/web/tool-web` with config-driven tool registration, prompt sections, model formatting, presentation, and tool-registry tests.
7. Wire product app/example configs only after package behavior is stable, because tool schemas and prompt sections affect agent behavior and snapshots.
8. Update `docs/architecture.md`, `packages/README.md`, package READMEs, generated Cordis catalogs if new events/services are added, and maintenance scripts.
Each layer is pinned at its own seam: the registry/selection/truncation/abort contract and the `WebError` codes in `dsh-web`; per-provider request/response mapping over recorded fixtures (Perplexity fixtures include URL-only citations so the optional source fields stay honest) plus a self-skipping with-key smoke per real provider; real local-HTTP behavior in `web-fetch-local`; and enablement-driven registration, structured execution errors, and result formatting through the real tool registry in `dsh-tool-web`. A real-Loader smoke guards the two export shapes ([postmortem 0001](../../../postmortem/0001-acp-default-export-drops-inject.md)): `dsh-web` is a default-exported service, while the providers and `tool-web` are namespace plugins where a stray `export default` would drop `inject`.
## Alternatives considered
@@ -364,19 +319,19 @@ Rejected for the first version. Those providers often return extracted or summar
Rejected for the seam. `prompt` turns fetch into LLM summarization and couples public-web retrieval to a model provider. The harness seam should fetch and decode deterministically; `dsh-tool-web` can later offer summaries as a presentation mode without making `ctx.web` depend on `ctx.llm`.
## Risks
## Consequences
**The search schema may be too thin.** Exa and Perplexity both expose useful provider-specific controls. The first version should resist adding them until they can be defined provider-neutrally and enforced honestly by both tool registration and provider execution.
**The search schema is deliberately thin.** Exa and Perplexity both expose useful provider-specific controls; a control is added only once it can be defined provider-neutrally and enforced honestly by both tool registration and provider execution.
**Perplexity citations may be sparse.** A citation may be only a URL. Making `title` and `snippet` optional keeps the seam truthful but means `tool-web` must render useful fallback labels.
**Perplexity citations can be sparse.** A citation may be only a URL. Making `title` and `snippet` optional keeps the seam truthful but means `tool-web` renders fallback labels.
**Stable tool registration can defer misconfiguration to execution.** Keeping the tool visible is correct when the product enabled web access, but product apps that expect web search should surface `configured-missing`, `configured-unavailable`, and `ambiguous` loudly during startup diagnostics so users do not discover setup problems only after the model calls the tool.
**Stable tool registration defers misconfiguration to execution.** Keeping the tool visible is correct when the product enabled web access, but product apps that expect web search should surface the structured `WEB_PROVIDER_CONFIGURED_MISSING` / `WEB_PROVIDER_CONFIGURED_UNAVAILABLE` / `WEB_PROVIDER_AMBIGUOUS` failures loudly so users do not discover setup problems only after the model calls the tool.
**Provider state can change after startup.** A tool can be visible in the request assembled at step start and lose its provider before execution. The execution path must resolve again and fail with a structured error.
**Provider state can change after startup.** A tool can be visible in the request assembled at step start and lose its provider before execution. The execution path resolves again and fails with a structured error.
**Fetch is a network boundary, not just a read-only tool.** `web_fetch` can still reach sensitive network targets or exfiltrate data through URLs. The first version ships only the basic transport hygiene (http/https-only, credential rejection, byte/time caps, cross-origin redirect blocking); SSRF / private-network blocking is deferred (see [Deferred work](#deferred-work)), so until it lands `web_fetch` must not be enabled where it can reach internal targets.
**Fetch is a network boundary, not just a read-only tool.** `web_fetch` can reach sensitive network targets or exfiltrate data through URLs. Only the basic transport hygiene ships (http/https-only, credential rejection, byte/time caps, cross-origin redirect blocking); SSRF / private-network blocking is deferred (see [Deferred work](#deferred-work)), so until it lands `web_fetch` must not be enabled where it can reach internal targets.
**Large web content can damage context quality.** Providers must enforce byte/character caps and report `truncated`; `tool-web` must format bounded model output with clear continuation or follow-up guidance.
**Large web content can damage context quality.** Providers enforce byte/character caps and report `truncated`; `tool-web` formats bounded model output with clear continuation or follow-up guidance.
## Deferred work
@@ -388,5 +343,5 @@ Rejected for the seam. `prompt` turns fetch into LLM summarization and couples p
## Open questions
- Should product app packages treat `configured-missing`, `configured-unavailable`, and `ambiguous` as fatal startup errors when web is explicitly configured, or should `dsh-web` only report status and let apps decide?
- Should product app packages probe web configuration at startup (treating `WEB_PROVIDER_CONFIGURED_MISSING`, `WEB_PROVIDER_CONFIGURED_UNAVAILABLE`, and `WEB_PROVIDER_AMBIGUOUS` as fatal when web is explicitly configured), or leave misconfiguration to surface at the first execution?
- Where should permission policy for public web access live once the deferred permission system lands: a dedicated web permission plugin on `tools/execute`, provider config, or both?

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@@ -152,21 +152,17 @@ Both mutations are still atomic (the backend's per-target lock is unconditional)
This amends — does not reverse — [the split-fs-seam RFC](../simplification/2026-06-26-fsspec-style-fs-seam.md). The four-layer split, the provider contract, and the freshness *policy* are all kept. What changes is the **coupling between the tool and the policy layer**: a mandatory method service became a plugin-owned event gate, and the fs I/O + read windowing moved from `fileContext` up into `dsh-tool-fs`. The split-fs-seam RFC's description of `dsh-tool-fs` injecting `fileContext` and of `fileContext` owning `read`/`write`/`edit` was updated to match in the same change.
## Acceptance Criteria
## Verification
- The `dsh-tool-fs` root plugin injects `fs` (+ `tools`/`systemPrompt`), not `fileContext`; it calls `ctx.fs` directly and dispatches the `fs/write-intent`/`fs/edit-intent` waterfalls (passing `exec` as the actor) and the `fs/observed` emit. Read rendering lives in `dsh-tool-fs`. (No subpath plugins — see the Tool contract above.)
- `dsh-fs` declares the three events with `@mode` tags and an opaque `object` actor argument (no agent/session structure leaks into the provider vocabulary); the generated cordis catalog is regenerated.
- `dsh-fs-policy` is a plugin, not a service: it does not register `ctx.fileContext`, has no public `read`/`write`/`edit`/`resolve` methods, and does not inject `fs`; it registers the three listeners, keeps observed-state, and has HMR/disposal coverage (dispose the fiber, assert the gate no longer rewrites).
- **Bare-provider test**: a config WITHOUT `dsh-fs-policy` boots the `dsh-tool-fs` root plugin, and `read`/`write`(create AND overwrite)/`edit` work against the real `dsh-fs-local`; an `edit` of an unread existing file and an overwrite of an existing unread file both succeed (unconditional bare-provider behavior), proving the tool carries no `fileContext` dependency. A bare-provider edit of a missing target reports `FS_STALE_VERSION`. With `dsh-fs-policy` present, the same unread `edit` is rejected `FS_NOT_OBSERVED` and the same unread overwrite uses `createIfAbsent` (rejected on an existing file).
- **Single-slot semantics**: a test registers a second `fs/edit-intent` listener AFTER `dsh-fs-policy` and asserts it is NOT reached (first-wins short-circuit), and documents in a comment that a decider registered before/`prepend`ed would instead win — the slot is first-wins by convention, not an enforced invariant.
- **Fire-and-forget recording**: `fs/observed` is emitted via a plain `ctx.emit` after the mutation succeeds; a listener is contractually synchronous and side-effect-only, so the tool does not guard it.
- `dsh-fs` `writeText`/`editText` make `expected` optional (omit ⇒ unconditional); the `FsWriteIntent` union is unchanged, and `dsh-fs-policy`'s guarded paths (`createIfAbsent`/`replaceIfVersion`/`{ version }`) behave exactly as today. A bare-provider test exercises an unconditional overwrite, an unconditional edit, and a missing-target edit reporting `FS_STALE_VERSION`.
- Freshness is enforced by provider CAS when guarded: an edit after a stale read reports `FS_STALE_VERSION` (regression test); `dsh-fs-policy` performs no `stat`.
- `stat` budget: read = 1, write = 0, edit = 0 — in the tool, with or without `dsh-fs-policy` (the bare default returns `undefined`, never stats). A test asserts neither write nor edit stats in the tool on either path.
- Model-facing schemas stay byte-for-byte unchanged; snapshot transcript goldens are unaffected (or the diff is reviewed and re-recorded with justification).
- Docs/artifacts updated in the same change: `docs/architecture.md`, fs package READMEs, `docs/core-data-structures/filesystem.md`, the split-fs-seam RFC's now-amended description, type-equiv blocks + manifest, cordis catalog, module graph. Gates green: `doc-sync`, `knip`, `test:coverage` (100% per-file).
The decoupling and its semantics are pinned by tests: a bare-provider config (no `dsh-fs-policy`) boots the `dsh-tool-fs` root plugin and `read`/`write` (create and overwrite)/`edit` work against the real `dsh-fs-local` — an unread edit and an unread overwrite both succeed, proving the tool carries no `fileContext` dependency, while the same operations with `dsh-fs-policy` present are rejected `FS_NOT_OBSERVED` / gated `createIfAbsent`. A second `fs/edit-intent` listener registered after `dsh-fs-policy` is asserted NOT reached (first-wins short-circuit). A stale-read edit reports `FS_STALE_VERSION` through provider CAS, with `dsh-fs-policy` performing no `stat`; the tool's `stat` budget (read = 1, write = 0, edit = 0, on both paths) is asserted directly. Model-facing schemas stayed byte-for-byte unchanged, so snapshot transcript goldens are unaffected.
## Risks
## Alternatives considered
- **Keep `ctx.fileContext` as an in-path method service** — the shape [the split-fs-seam RFC](../simplification/2026-06-26-fsspec-style-fs-seam.md) first landed; rejected because the tool could not run without the policy layer, making policy load-bearing for basic operation instead of an opt-in tightening.
- **Policy-side version checking** (`dsh-fs-policy` stats and compares in its waterfall handler) — rejected for the TOCTOU gap between that check and the tool's actual write; the provider's mutation critical section is the only race-free place, so the policy only chooses the CAS basis and gates on prior observation.
- **Per-tool `/read`/`/write`/`/edit` subpath plugins** — dropped on implementation: no consumer needed a single-tool deployment, and subpath publishing forced bespoke `tsdown`/`tsconfig`/`files`/workspace-constraint handling no sibling tool package carries; the per-tool registration helpers remain internal modules the root plugin composes.
## Consequences
- **Event indirection over a method call.** A waterfall + emit is less direct than `await ctx.fileContext.edit(...)`. The payoff is removing the tool-to-policy method dependency while keeping the default policy plugin; the cost is one more event vocabulary to learn. Mitigated by keeping the three events narrow and documenting the default-thunk semantics on each.
- **Policy events in the storage seam.** `dsh-fs` gains two version-decision events plus a recording event though it is "just storage". This is the price of decoupling (the emitter cannot depend on the policy plugin). The events carry only `dsh-fs` vocabulary plus an opaque `object` actor and no model-facing concepts, so the seam stays free of line-window/observation policy types and of the agent/session owner structure.

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@@ -1,10 +1,8 @@
# RFC: stdin + extra env on the bash seam
Status: implemented (accepted 2026-06-30)
Status: implemented
<!-- XXX: legacy ADR/RFC body format, not yet normalized to a unified RFC template. -->
## Context
## Problem
The hooks subsystem runs external hook commands the way Claude Code and Codex do: a hook is a shell command that receives its event payload as **JSON on stdin** and reads context from a handful of **environment variables** (`CLAUDE_PROJECT_DIR`, `CLAUDE_PLUGIN_ROOT`, `PLUGIN_ROOT`, …). The harness already has a perfectly good command runner behind the `ctx.bash` capability seam ([dsh-bash](../../../../packages/bash/bash) → [dsh-bash-local](../../../../packages/bash/bash-local)), with process-group kills, output truncation/spill, and a credential scrub. Reusing it for hook execution means a hook bridge does not re-implement subprocess plumbing — but the seam had no way to write stdin or set extra env. This RFC adds those two inputs.
@@ -24,7 +22,7 @@ Three deliberate choices:
`dsh-bash-local` spawns stdin as a `'pipe'` (writing the supplied bytes, then closing) ONLY when a caller set `stdin`; with none supplied it uses `'ignore'` — fd 0 → `/dev/null` — the exact pre-seam default. This distinction is observable and deliberate: a closed empty pipe and `/dev/null` are NOT the same file type (node's spawn pipe is an `AF_UNIX` socket, so `test -c /dev/stdin` holds for `/dev/null` but not for an empty pipe), so the no-stdin path — every model-driven call — must keep `/dev/null` rather than regress to an always-open pipe. Each branch's `stdio` tuple is a literal, which preserves the typed `spawn` overload that guarantees non-null `stdout`/`stderr`. When stdin IS written, a child that exits without reading makes the write fail EPIPE; that error is swallowed (the command's outcome rides on its exit code/output, not the write) so it never crashes the host or rejects `done`.
## Scope: configurable scrub pattern is NOT included
## Alternatives considered
An earlier sketch of this work also proposed making `SENSITIVE_ENV_PATTERN` configurable. Validating against the code, that is **speculative and already subsumed**: `run.ts` documents a configurable whitelist as future work, and the new explicit `env` field — merged after the scrub — already gives a caller full control, including over credential-shaped vars. There is no current caller that needs to *broaden* the ambient scrub (the hazard runs the other way). Adding a config knob now would be a speculative surface with no consumer. If a real workflow ever needs to forward a specific ambient credential, the explicit `env` field is the supported path; a configurable scrub can be reconsidered then.

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@@ -1,8 +1,8 @@
# RFC: Event-domain semantics — session is the fact log, agent is the live surface
Status: implemented (accepted 2026-06-30)
Status: implemented
## Context
## Problem
The harness extends the agent loop through a Cordis event taxonomy (see [the microkernel event-taxonomy RFC](2026-06-11-microkernel-event-taxonomy.md)). As that taxonomy grew, the line between the three event domains blurred:
@@ -19,7 +19,7 @@ This is the foundational change in a stack that adds a Hooks subsystem; it estab
**Three domains, one job each, with a single boundary rule.**
- **`session/*` — the durable, replayable FACT log.** Owns `SessionEventMap`; every entry is JSON-only (no live objects). One `session/event` emit per append, plus the `session/flush` parallel durability checkpoint. It is also the live transcript feed: a consumer that wants to render or react to what happened subscribes here, so live rendering and `session/load` replay share one path.
- **`agent/*` — the LIVE runtime surface.** Always carries the live `Agent`. Two shapes: INTERCEPTION waterfalls (`agent/request`, `agent/step-result`, `agent/turn-continuation`) that mutate or veto, and TRANSIENT emits (`agent/status`, `agent/error`, `agent/created`/`agent/disposed`, `agent/queued`, `agent/steering`) that notify with the `Agent` in hand. Turn and step BOUNDARIES are NOT here — they are durable session events read off `session/event`, and so is the token stream (`assistant/chunk`).
- **`agent/*` — the LIVE runtime surface.** Always carries the live `Agent`. Two shapes: INTERCEPTION waterfalls (`agent/request`, `agent/step-result`, `agent/turn-continuation`) that mutate or veto, and TRANSIENT emits (`agent/status`, `agent/error`, `agent/created`/`agent/disposed`, `agent/queued`) that notify with the `Agent` in hand. Turn and step BOUNDARIES are NOT here — they are durable session events read off `session/event`, and so are the token stream (`assistant/chunk`) and mid-turn steering (`steering/message`).
- **`tools/*` — the tool registry + execution seam.**
**The boundary rule:** a durable, replayable fact is a `SessionEvent`; a live interception or a transient/live-object signal is an `agent`/`tools` Cordis event. A turn or step boundary is a durable fact, so it lives in the session log and is read off the `session/event` feed — it is NOT mirrored as an `agent/*` emit.
@@ -31,5 +31,7 @@ This is the foundational change in a stack that adds a Hooks subsystem; it estab
- The loop no longer emits any boundary mirror; `closeStep` appends `step/end` only and `closeTurn` appends `turn/end` only. A throwing `step/end`/`turn/end` session-event listener is the surviving boundary-listener failure path (contained inside `closeStep`/`closeTurn` — `Session.append` pushes the event before notifying listeners, so the boundary is durable and the turn closes balanced regardless).
- Tests that observed boundaries via the removed emits now observe the durable `turn/start`/`turn/end`/`step/start`/`step/end` session events — the behavior they pin (boundary ordering, step counting) is unchanged; only the feed they read moved to the canonical one. The tests that exercised a *throwing turn-boundary emit listener* were deleted, because that code path no longer exists (there is no emit to throw from). Per [AGENTS.md "tests document behavior, not golden truth"](../../../../AGENTS.md), the behavior and its test moved (or died) together.
- The loop marks the step open (`stepOpen = true`) BEFORE appending `step/start`, because `Session.append` pushes the event to the log before notifying `session/event` listeners (validation throws happen earlier, before the push — see [the session append contract](../../../core-data-structures/session.md)). So a throwing `step/start` session-event listener runs with the step already open and the event already in the log: the loop's outer catch then calls `closeStep()`, which appends the balancing `step/end`, and the turn closes balanced with an error (`turn/start → step/start → step/end → turn/end` — verified by the invariants oracle in the regression test). Closing the open step is owed precisely because the marker is set first.
- The full realization of this is [the simplification RFC "Stop mirroring durable boundaries as agent events"](../simplification/2026-06-20-remove-agent-boundary-mirror-events.md): all four boundary mirrors are removed and every consumer reads boundaries off `session/event`. `agent/steering` (a live control signal, not a boundary mirror) is retained; see that RFC's scope section.
- The cordis catalog (`docs/cordis-catalog/events-and-services.md`) is regenerated to drop the mirror events.
- The full realization of this is [the simplification RFC "Stop mirroring durable boundaries as agent events"](../simplification/2026-06-20-remove-agent-boundary-mirror-events.md): all four boundary mirrors are removed and every consumer reads boundaries off `session/event`. `agent/steering` (not a boundary mirror) stayed outside that RFC's scope and was removed by its own follow-up, [Remove the `agent/steering` mirror emit](../simplification/2026-07-04-remove-agent-steering-mirror.md) — it mirrored the durable `steering/message`.
- The cordis events catalog (`docs/cordis-catalog/events.md`) is regenerated to drop the mirror events.
<!-- rfc-format: alternatives-not-recorded (pre-format RFC) -->

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@@ -16,7 +16,9 @@ Thread the caller's session cwd into path resolution, exactly as `dsh-tool-bash`
- `dsh-fs-local.resolve` uses `resolveLocalTarget(opts?.cwd ?? this.config.cwd, path)`. `config.cwd` stays the default for a caller that supplies none (non-ACP / no-session use, and the single-session stdio demo where `process.cwd()` IS the workspace).
- `dsh-tool-fs`'s `read`/`write`/`edit` derive the session cwd through a shared `sessionCwd(exec)` helper (`exec.agent?.session.header.cwd`, mirroring bash's `resolveWorkdir`) and pass it to `resolve`. A non-agent / headerless caller yields `undefined`, so the backend applies its default.
## Why the caller supplies the cwd (not the provider)
## Alternatives considered
### Why the caller supplies the cwd (not the provider)
The provider seam must not depend on `dsh-agent` / `dsh-session` — it is a text-storage backend that a sandboxed or remote implementation also satisfies, and those have no notion of an "agent session". The tool already receives the `ToolExecution` (`exec`), which carries the agent, so the tool is the right place to project `exec → cwd` and hand the provider a plain string. This is the "explicit > implicit at package seams" convention: the base directory arrives as an explicit argument the provider acts on, not smuggled in by having the provider reach into a session it should not know about. It also matches `dsh-tool-bash` one-to-one, so the two model-facing file surfaces resolve paths identically.

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@@ -37,9 +37,13 @@ Per the [capability-seam split](2026-06-13-capability-seams.md), the storage bac
`ToolResultView` gains a `DiffResultView { card:'diff'; title?; diffs: FileDiff[] }`; the bridge's result-side `switch (view.card)` gets a `diff` arm emitting the `{type:'diff'}` `ToolCallContent` blocks (mirroring the call-side arm). An ACP `tool_call_update.content` REPLACES the call's content in an editor, so the result diff **supersedes** the call-time snippet (and keeps the model-facing result text from clobbering it) — the two-update sequence (call snippet, then result diff) matches `claude-agent-acp` exactly.
### The diff algorithm — a third-party runtime dependency over vendoring
## Alternatives considered
Computing hunks-with-context is a solved problem with sharp edge cases (grouping, context coalescing, the trailing-newline marker). Rather than hand-roll it, `dsh-tool-fs` takes a runtime dependency on the npm [`diff`](https://www.npmjs.com/package/diff) package (a `^9.0.0` range, exact-pinned by the lockfile; it ships its own types) and uses its `structuredPatch`. The repo's default is to vendor Cordis-framework source, but that policy is about the *framework*; a leaf tool package taking a small, well-known, self-typed utility dependency is the same shape as `dsh-acp` depending on `@agentclientprotocol/sdk`. Vendoring a diff algorithm would be re-implementing a battle-tested one for no benefit — the [pre-release "foundation over blast radius"](../../../../AGENTS.md) reasoning does not argue for re-deriving standard algorithms. The dependency's output is normalized in one small module (`packages/fs/tool-fs/src/diff.ts`).
**Hand-rolling or vendoring the diff algorithm.** Computing hunks-with-context is a solved problem with sharp edge cases (grouping, context coalescing, the trailing-newline marker). Rather than hand-roll it, `dsh-tool-fs` takes a runtime dependency on the npm [`diff`](https://www.npmjs.com/package/diff) package (a `^9.0.0` range, exact-pinned by the lockfile; it ships its own types) and uses its `structuredPatch`. The repo's default is to vendor Cordis-framework source, but that policy is about the *framework*; a leaf tool package taking a small, well-known, self-typed utility dependency is the same shape as `dsh-acp` depending on `@agentclientprotocol/sdk`. Vendoring a diff algorithm would be re-implementing a battle-tested one for no benefit — the [pre-release "foundation over blast radius"](../../../../AGENTS.md) reasoning does not argue for re-deriving standard algorithms. The dependency's output is normalized in one small module (`packages/fs/tool-fs/src/diff.ts`).
## Consequences
`tool/result` events may now carry a tool-private `meta` payload — part of the on-disk vocabulary, runtime-gated to JSON by `Session.append` — and any tool can attach durable result presentation without another core change. The diff card reproduces on session reload and snapshot replay for free: it is read back from the log, never recomputed. The costs: an overwrite holds both the prior and new text in memory to compute a UI-only hunk (`TODO(overwrite-diff-bound)`), and `dsh-tool-fs` carries a small, well-known runtime dependency.
## Non-goals

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@@ -58,6 +58,16 @@ interface TerminalResultView { card: 'terminal'; title?: string; output?: string
`claude-agent-acp` relativizes a file card's title path against the session cwd (`toDisplayPath`) — `Read src/foo.ts`, not `/abs/proj/src/foo.ts` — while keeping `locations[]`/`diff.path` **raw** (the editor opens the real path). Our `presentCall` is pure/args-only and cannot see the session cwd, so this relativization happens at the **bridge**, which already threads the session cwd into tool-call rendering (the same cwd it uses to resolve a terminal card's header). The bridge relativizes the title only, by an exact structured replace of the known `locations[0].path`/`diffs[0].path` substring — generic over the file-card kinds, never special-casing tool names.
## Alternatives considered
- **Delete tool-owned presentation entirely** — [the rejected collapse proposal](../../rejected/simplification/2026-06-20-generic-tool-rendering.md); its own verdict deferred to exactly this union once two real tools and two real consumers existed, and that bar is now met.
- **A merge-extensible union** (the `ContentBlockMap` pattern) — rejected: a new render intent needs new bridge code to render it anyway, so a plugin-added variant the bridge silently drops would be worse than the compile error the closed union raises at the bridge's `assertNever` switch.
- **Keeping the optional-field bag** — the status quo the Problem dissects: invalid states representable, undocumented field interactions, and no way to ask for a diff card at all.
## Consequences
A new render intent is a compile-breaking change at the bridge switch — deliberately: rendering code must exist before a card kind does. Invalid card/field combinations are now unrepresentable, and the bash fallback derivation lives in the bridge, so a tool returns one structured shape. The bar for a fourth card (a table, a chart) is writing its bridge arm in the same change.
## Non-goals
- **Live incremental `terminal_output_delta` streaming** and **command classification** — the terminal-rendering RFC's own deferred follow-ups, untouched here.

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@@ -1,10 +1,8 @@
# Add direct directory listing to the filesystem seam
# RFC: Add direct directory listing to the filesystem seam
## Status
Status: implemented
Implemented.
## Context
## Problem
`@deepseek-ai/dsh-fs` is the provider seam for filesystem access, with local and future non-local backends behind the same `ctx.fs` contract. Before this change it could resolve paths, stat targets, read text, stream text, write text, and edit text. That was enough for model-facing file tools, but not for non-model-facing consumers that need to enumerate directories without importing `node:fs`.
@@ -36,7 +34,7 @@ Broken or disappeared children may be represented as `type: 'other'` without `ve
- `FS_IO_ERROR` for other backend I/O failures.
- `FS_ABORTED` for aborted calls.
## Rejected alternatives
## Alternatives considered
**Add a model-facing list tool now.** Rejected for this PR. The immediate request is the provider seam, and the user explicitly asked not to change skill loading or other upper layers in this branch. A model-facing tool needs prompt/schema/rendering decisions that should be reviewed separately.

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@@ -0,0 +1,70 @@
# RFC: Prompt variables and tool-guidance ownership
Status: implemented
## Problem
The assembled system prompt had four defects, all of one family: facts the harness already knows were restated by hand somewhere else, and drifted.
**The model could not know its own name.** `AgentOptions.model` drives every request, but no prompt text carried it — and nothing COULD carry it: sections in `dsh-system-prompt` were context-global while the model name is per-agent, and `assemble()` took no per-agent input at all.
**Tool guidance was hand-written prose in leaf YAML.** The bash/subagent/todo_write usage guidance lived in the `systemPrompt` strings of `examples/coding-agent/cordis.yml` and `examples/acp-agent/cordis.yml` — two drifting copies (the ACP one was already abridged) — while `dsh-tool-fs` and `dsh-tool-web` owned their guidance as `ctx.systemPrompt.section()` contributions. Loading or dropping a tool plugin meant editing every deployment's persona by hand; both YAMLs carried a `FIXME(config-comments)` apologizing for a symptom of the split, and the stdio welcome banner hand-enumerated the tool set too.
**The persona rendered after tool guidance.** The loop string-joined `agent.options.systemPrompt` AFTER the assembled sections, so the model read "Use the read tool…" before "You are coding-agent" — backwards relative to the identity-first convention (Claude Code, Codex) and a second composition path besides the section pipeline.
**The fork tool's description was false.** `dsh-tool-subagent` hardcoded one description written for spawn semantics — "a separate agent that works in its own context … it does not see this conversation" — and the `subagent_fork` instance (whose child inherits the parent's completed turns) got the same words; the YAML prose corrected the lie out-of-band. Minor kin: `PromptSection.name` was documented "(diagnostics / dedup)" but duplicates were silently accepted.
## Decision
**One principle: every fact in the prompt has exactly one owner.** The model name and workspace are config/session facts → the harness exposes them as variables and the persona references them. Per-tool semantics and when-to-use → the tool's `description`. Cross-call habits a description cannot carry → the tool package's prompt section. Identity and behavior → the deployment's persona, and nothing else.
### Assemble context
`SystemPrompt.assemble(context)` takes an `AssembleContext` — declared EMPTY and merge-extensible in `dsh-system-prompt` (the package stays agnostic of who assembles); `dsh-agent` declaration-merges `agent?: Agent` onto it (a new type-level edge `agent → system-prompt`, no cycle — `tools` already depends on both). The loop passes `{ agent }` each step; section text providers become `string | ((context) => string)` (zero-arg providers stay valid), and the `system-prompt/assemble` waterfall gains the context parameter so a listener can filter or extend per agent.
### Prompt variables
Plugins contribute named values via `ctx.systemPrompt.variable(name, provider)`; prompt text references them as `{{name}}`. Providers are functions of the `AssembleContext` and may return `undefined` — "no value for THIS assembly". `assemble()` resolves every registered variable into `PromptAssembly.variables` (waterfall listeners can see, add, or override); `renderPrompt` interpolates. Rendering is STRICT — fail loud beats shipping a malformed prompt: a reference to an unregistered name throws (listing what exists; lookup is `Object.hasOwn`, so a prototype property like `{{constructor}}` is unknown, not a function spliced into the prompt), a registered-but-valueless reference throws, a complete `{{…}}` group that is not a well-formed name (`[a-z][a-z0-9_]*`, e.g. `{{ model }}`) throws, and a `{{` that opens no complete group while a `}}` still follows (`{{{model}}}`, `{{a{b}}`) throws. A lone `{{` with no `}}` anywhere after it is ordinary prose and passes through verbatim; substituted values are never re-scanned. Registration rejects duplicate and unreferenceable names, mirroring the tool registry — and `section()` now rejects duplicate section names, making the documented dedup real.
`dsh-agent-loop` registers the two built-ins, both pure projections of the context agent: `model` (= `options.model`) and `cwd` (= `session.header.cwd`). The example personas write `powered by the {{model}} model` — the model name is stated once, in the `model:` config key. `{{cwd}}` is demonstrated in the ACP example only: every ACP session carries the client's cwd, while config-pre-created stdio agents have none (a persona claiming `{{cwd}}` there fails the turn — by design). The variables stay on the loop plugin (unlike the sections below): they are runtime facts of the agents THIS loop drives, and a replacement loop supplies its own.
### Persona as the order-0 section
`dsh-system-prompt` itself registers the two harness-owned sections (they must survive a swapped loop plugin, so they do NOT live on `dsh-agent-loop`): the static `harness:identity` at order `-100` — every prompt opens by stating the agent is powered by the DeepSeek Harness SDK — and `deployment:persona` at order 0, whose text is the plugin's own `persona` config. The persona is per-DEPLOYMENT, not per-agent: every agent in the context (subagents included) renders the same one, `AgentOptions.systemPrompt` is deleted along with the per-agent forwarding plumbing (the app configs' `systemPrompt` keys become a `persona` key routed to this plugin through `dsh-agent-core`), and the ACP bridge and `dsh-tool-subagent` stop carrying persona configuration entirely. The loop's special-case join is deleted: `fullSystemPrompt ≡ renderPrompt(assembly)`, one ordered pipeline for everything the model sees, and `agent/pre-step` (compaction's token-pressure input) measures exactly the real prompt. Order bands are now convention: harness identity `-100`, persona `0`, tool guidance `100–199`; other negative orders also render before the persona.
### Tool guidance ownership
Per-tool semantics and when-to-use live in tool DESCRIPTIONS, which already ship in every request — the YAML prose was ~fully redundant with them. Sections carry only the cross-call habits a single call's description cannot: `dsh-tool-bash` contributes `tool:bash` (order 105) — check the `[exit code: N]` marker on every result; `dsh-tool-fs`'s read section gains the "not shell commands like cat" contrast. `todo_write` and the subagent tools need NO section — their descriptions already carry the whole contract. The leaf personas shrink to identity + behavior (verify your work; keep answers brief), and the welcome banner stops enumerating tools.
### The subagent context contract
`SubagentProvider` gains `readonly inheritsParentContext: boolean` — a DESCRIPTIVE fact beside `capabilities`, not in it (capabilities are start-time validation; nothing validates against this flag). Spawn and ACP declare `false`, fork declares `true`. `dsh-tool-subagent` derives both the tool description and the `prompt` parameter description from the flag (`providerWording`): the fork instance now tells the model the child inherits the conversation's completed turns (not the in-flight turn) and that its prompt should state only what is new. Deriving the description from a provider that arrives on its own fiber is what forced the provider-lifecycle events and the tool's reactive registration — that mechanism, its Loader-concurrency rationale, and its rejected alternatives are recorded in [the provider-lifecycle-events RFC](2026-07-05-subagent-provider-lifecycle-events.md).
## Alternatives considered
- **The loop composes an identity line itself** — hardcodes model-facing prose in the one package that must stay thin ("plugins, not loop changes"), and outside the section pipeline it would be a second composition path. (The identity DOES ship as a code literal — but as an ordinary section registered by `dsh-system-prompt`, whose `system-prompt/assemble` waterfall remains the escape valve for a deployment that must drop it.)
- **Inject the model name via the `agent/request` waterfall** — prompt text composed in two places, and `agent/pre-step`'s `fullSystemPrompt` would omit it, so compaction would measure a prompt that is not what the model sees.
- **Hand-write the model name in each persona** — duplicates the `model:` key one line above and silently lies after a config edit; the exact disease this RFC cures.
- **Lenient interpolation (leave unknown refs verbatim, or substitute empty)** — a typo ships `{{modle}}` (or a hole) to the model and nobody notices until transcript review.
- **Per-instance subagent wording in config** — returns model-facing prose to every deployment × instance, the P2 disease again. **Keying wording off the provider NAME** — `providerName` is itself config, so a renamed provider silently gets the wrong words.
- **Resolving the provider at `apply` time (a load-order requirement)** and **section-only subagent wording (lazily resolved at assemble)** — the alternatives to the provider-lifecycle events; both rejected in [the provider-lifecycle-events RFC](2026-07-05-subagent-provider-lifecycle-events.md).
## Out of scope
- Further variables (`date`, platform, git state) — the registry makes each a one-line contribution by whichever plugin owns the fact; none is claimed here.
- A config `cwd` for pre-created stdio agents (would let the stdio persona use `{{cwd}}` and partition persistence by real path) — deferred until the session-cwd story is revisited.
## Shipped invariants
- `renderPrompt(assemble({ agent }))` for the coding-agent example renders the persona FIRST (with the agent's model name interpolated), then the fs/bash/web guidance sections; the loop has no other prompt-composition path.
- The `subagent_fork` schema description says the child inherits the conversation; the `subagent` one says it does not. The tool follows its provider: absent before the backend activates, present after, gone when the backend unloads, re-worded from the fresh provider on reload.
- Unknown/valueless/malformed/unbalanced `{{…}}` references throw with the section name in the message; duplicate section, variable, and tool-name registrations all throw.
- Snapshot goldens are prompt-independent by construction: llm-replay keys replay on (turn, step) chunk streams and never re-verifies the outgoing request.
## Consequences
- Every fact in the assembled prompt now has exactly one owner, and the hand-maintained tool prose in leaf YAML is gone: loading or dropping a tool plugin no longer means editing any deployment's persona.
- `{{model}}` reflects `AgentOptions.model` at assembly time. A plugin that switches models in the `agent/request` waterfall makes the prompt's claim stale for that step, and one that SUPPLIES the model there (options.model unset — the loop's documented fallback) leaves the variable valueless at render, failing a `{{model}}` persona before the waterfall runs. Both have the same remedy, and it is the ownership rule itself: the plugin that owns the late-bound model fact states it early on the `system-prompt/assemble` waterfall (`assembly.variables['model'] = …`) — one owner, both statements; a loop test pins the supply path end-to-end. Accepted.
- While a bound provider is absent (not yet activated, unloaded, mid-HMR-reload), the subagent tool does not exist and a model request in that window simply lacks it. That is the honest state — the alternative was a registered tool whose description or execution could not be trusted.
- Strictness means a persona can fail a turn at render (e.g. `{{cwd}}` on a cwd-less session). The failure is contained — the turn ends `error`, the loop survives — and it is an authoring error we WANT loud.
- No escape syntax for a literal `{{name}}` in prompt prose yet; add one if a real prompt ever needs it.

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@@ -0,0 +1,53 @@
# RFC: Every LLM request is reconstructable from the session log
Status: implemented
## Problem
Two gaps shared one root. First, provider KV caching (DeepSeek context caching) is prefix-based — a request pays full price only for the tokens after the longest stored prefix it matches — yet nothing in the request pipeline stated, checked, or measured prefix stability: every registered [`PromptSection`](../../../../packages/core/system-prompt/src/index.ts) happened to be static, the tool set happened not to change mid-session, no listener happened to rewrite requests. A single time-interpolating section would have silently multiplied context cost, and no test or metric would have moved. Second, and deeper: the session log — the system's single source of truth — could not actually answer *what the model saw*. It recorded every message but never the system prompt, the tool schemas, or even which model; the mutable `agent/request` waterfall handed listeners the whole `GenerateOptions` to rewrite per call; replay equivalence was therefore a property of the plugin population, not of the design.
The reference shape for the happy path is MiniCode's `LLMClient`: a stateful conversation client, appended to — never rebuilt — as the conversation advances, resetting only when the system prompt, tool set, or compaction genuinely changes what the model must see. The design question this RFC answers is how to get that discipline without giving up event-sourcing.
## Decision
### The principle
**Model-visible ⟺ logged.** Anything that reaches a model request must be recorded in the session log. The checkable consequence: **every conversation request the loop sends is a pure function of the session log** — anyone holding the log reconstructs it byte-for-byte. Scope, stated precisely: the guarantee covers the loop-built `GenerateOptions`; provider wire bytes follow from it because both adapters' serialization is a pure per-message function at a pinned code version; direct one-shots (compaction's summarize call) log their envelope scalars (`compact/summary.{model, maxTokens}`) and their input is deterministic code over the logged region — reconstructable from log + code, outside the invariant by the unfrozen-request marker.
Prefix-cache stability is corollary #1, not the headline: an append-only log projected by a per-node pure function yields requests that are append-extensions of their predecessors whenever the header is unchanged — stability is emergent, not managed. Byte-exact audit/replay is corollary #2; resume and fork with *attributable* drift is corollary #3.
### The mechanism
**Messages.** `Session.deriveMessages()` is cached: each surface node is projected exactly once, when first seen, through the public per-node function `deriveEventMessage(event)`; a surface rewrite (a compaction `replace` — `SurfaceManager.replaceGeneration`) rebuilds. Callers get a fresh array per call over shared, deep-frozen messages: mutating logged history through a projection is unrepresentable (it throws), replacing the old clone-per-call isolation. External reconstructors fold the same public function over a log prefix, so no two paths can disagree.
**The header.** The request's non-history half — `EpochHeader`: call config (`LlmCallConfig`: model + sampling scalars), rendered system prompt, assembled tool schemas, and the session prefix (`messagePrefix`, below) — is logged session state, in canonical form (empty system/tools/prefix ≡ absent). Two log-only, turn-enclosed events in dsh-session carry it: `request/header`, a full snapshot with reason `'initial' | 'resume' | 'fallback'`, and `request/header-delta`, an amendment (`SystemDelta`: a common-prefix/suffix line trim; `ToolsDelta`: name-keyed added/removed/changed; `config`: replaced whole; `messagePrefix`: replaced whole, an empty array encoding the transition to absence — an arm the loop never exercises in practice, kept for codec totality). The pure trio `foldRequestHeader` / `diffHeader` / `applyHeaderDelta` reconstructs; the live session tracks the fold with the same lazy cursor as the message cache. Snapshots anchor the fold where a fold needs anchors — conversation birth and process boundaries — and each loop instance appends one on its first request (`'initial'` when the log has none, `'resume'` otherwise, even when nothing changed: the boundary itself is a recorded fact, and cross-restart drift becomes attributable while an unchanged header resumes byte-identical). Deltas are an encoding optimization with a safety valve, never a correctness dependency: the writer verifies `applyHeaderDelta(prev, delta)` reproduces the new header exactly and records a `'fallback'` snapshot when the encoding cannot express a change (a pure tool reordering), so a well-formed log always folds.
**The loop, transmission-stateless.** Per step: render assembly (every step — value comparison needs no change-signal discipline, and a section that varies per step surfaces as a *logged* header event per step instead of a silent bust) → on the instance's FIRST step only, the `agent/session-prefix` waterfall — request-ONLY messages fronting the entire derived history (a frozen empty seed, contributions returned as an extension of `next()`; the home for session-stable openers that must NOT become history — a skills catalog, an AGENTS.md digest), deep-frozen and cached on the instance so reuse is structural and the prefix cannot drift mid-session — → `agent/pre-step`, carrying the composed prefix (compaction's surface mutations land before derivation, and its pressure gate counts the prefix this instance will actually send — never a previous instance's logged one, which could under-gate a resumed/forked instance whose contributor grew) → **messages snapshot, then `step/start` appended as the next operation in the same synchronous frame** → seed the call config (first request of the instance: from `AgentOptions`, so explicit options always beat the logged baseline — fork model-overrides and resume reconfiguration stay correct; afterwards: from the folded header) → the `agent/request` waterfall, re-typed `(agent, turn, step, config: LlmCallConfig, next) → LlmCallConfig` — a frozen seed and a returned replacement are ALL a listener shapes; durable content flows through the log channels (`inject()`, steering, prompt-submit `additionalContext`, sections via `system-prompt/assemble`) — → the header event the request owes the log, carrying the prefix as `messagePrefix` (no session event carries it, so the header is its only durable record; resume = a new instance = a recompose, anchored by its `'resume'` snapshot) → build `GenerateOptions` from `messagePrefix + snapshot` + header, deep-freeze (`deepFreeze` exempts the `AbortSignal`, the one live control channel — freezing one breaks `AbortController.abort()`), dispatch. The loop's per-instance bookkeeping is one boolean plus the cached prefix: whether this instance has logged its anchoring snapshot, and what it composed.
**The reconstruction boundary is `step/start`, unconditionally.** A step's messages are the derivation over `events[0..stepStartSeq)`. Because the snapshot precedes the `step/start` append in the same synchronous frame, nothing can enter this request past the boundary: an `agent.inject()` from an `agent/request` listener (or any concurrent task, or a `session/event` listener firing on `step/start` itself) lands in the log after the boundary and joins the NEXT request. For waterfall-window appends this matches the prior loop (it also derived before its waterfall); for a synchronous `step/start` listener it is a deliberate change — such a listener could previously reach the current request — and `agent/pre-step` is the sanctioned seam for content that must affect the CURRENT request. A step's header for reconstruction is the fold after its own `request/header*` event (which sits between its `step/start` and first response event) or the fold carried forward.
**Enforcement.** Dev-mode ([dsh-invariants](../../../../packages/support/invariants/src/index.ts)), on `llm/stream`: a frozen request with a live `sessionId` — the loop-built marker; hand-built one-shots are unfrozen and skipped — must carry messages deep-equal to the folded header's `messagePrefix` followed by the boundary derivation — the derivation rebuilt through a FRESH `Session` over `events[0..stepStartSeq)` so the live cache cannot vouch for itself — and header fields equal to `foldRequestHeader` over the log. There is no divergence allowance and nothing to allow: no seam can put unlogged content into a request — the `agent/session-prefix` seam's product enters only because the header event records it first. `prepend: true` only defends against the replay adapter's short-circuit (an append-registered listener); two prepended listeners have no defined mutual order in cordis, so correctness rests on the seq-bounded fold, never on listener timing. Measurement stays lean: the with-key e2e ([request-cache.e2e.ts](../../../../packages/core/agent-loop/tests/request-cache.e2e.ts)) proves `usage.cacheReadTokens > 0` on every request after the first against the live API, and per-step usage in the log is the production observable — a header event or compaction shows up as a cache-read collapse on the next step.
### The MiniCode shape: adopted, with the provenance arrow inverted
What survives from `LLMClient`: the conversation is maintained, not rebuilt — one projection per message, ever; requests advance append-only; resets happen only for a system-prompt/tool change, a config change, or compaction, each now a *logged* fact. What is deliberately inverted: MiniCode's client is the source of truth and its event stream derives from client appends (`on_event(MessageAdded)`), which suits an advisory event stream. Here the log is contractual — persistence, crash recovery, fork seeding, transcript rendering, and the snapshot harness all replay it — and it carries strictly more than a message list (turn/step boundaries, raw chunk streams, tool-call pairing, provenance, log-only records), so a message-list client cannot generate it. The arrow therefore points log → client: the conversation state IS the log plus two cached folds inside `Session` (messages, header), and the "client" the loop talks to is the session itself. What the inversion buys over the original: the reconstruction is *checkable* against an independent record on every request — MiniCode's client has nothing to check itself against.
## Alternatives considered
- **Client as source of truth** (literal MiniCode): a second operative truth beside the log — the two drift and nothing notices; see the section above.
- **A stateful transmission client mirroring the log** (a `PromptPrefix` class holding committed/open message zones with an append/editTail/reset vocabulary, the log pushed into it per event): behaviorally equivalent on the happy path, but it duplicates conversation state outside the session, needs transactional rollback around listener seams, keeps an unlogged content-shaping surface (`editTail`) whose divergence the invariant must specially allow, and still cannot answer "what header did the model see" from the log. Dissolving it into the session's own caches plus logged header events made every one of those problems unrepresentable instead of guarded. (PR #162 is the archaeology of this alternative, three designs deep.)
- **Per-call request scalars** (a freely mutable config handed to each `agent/request` dispatch): a listener flips the model per call with zero accounting, silently abandoning the provider cache this design exists to protect. Config is per-conversation logged state; the waterfall proposes, the log records.
- **Detect-and-report** (compare consecutive requests, warn on divergence): catches violations after the fact; a violating request is still constructible and ships. Rejected for interface-level unrepresentability.
- **Event-driven assembly** (re-render only on change signals): a missed-signal bug class — a tool registered mid-session emits `tools/change`, not `system-prompt/change`, and a third-party provider may emit nothing. Per-step render + value compare is robust with zero signal discipline.
- **Narrative fields on the header events** (a `reason`/`changed` list on deltas): derivable by diffing consecutive events — one home per fact; snapshots carry a reason because an anchor's cause is NOT derivable from the data.
## Consequences
- A request that is not explained by the log cannot be constructed by accident — not by the loop, not by a listener; mutating a built request throws; every header change is a durable, diffable log event.
- Choosing between the advisory channels is a change-frequency decision, and the design makes the stable one structural: an `agent/session-prefix` contribution is composed once per loop instance and reused verbatim, so it extends the cacheable prefix at zero marginal cost and CANNOT bust the provider cache mid-session; content that changes mid-session flows through the append-only history channels — `agent.inject()`, a `tools/post-execute` decision's `additionalContext`, prompt-submit `additionalContext` — each a durable `context/message` paid once and prefix-cached thereafter, at the price of accumulating in history and the log. Route session-frozen openers to the prefix and change notices to the history channels; a per-step request-only tail slot was deliberately dropped (no consumer, and a durable append covers every current update pattern).
- What still costs full price at the provider is inherent and logged: compaction (its `compact/*` events and replace node), a real prompt/tool change (`request/header-delta`), a config switch (ditto), a process boundary with drift (`'resume'` snapshot differing from its predecessor). The provider's own reasoning-content exclusion is managed server-side.
- The `step/start`-listener behavior change (above) is the one observable semantics change for plugins; `agent/pre-step` is the current-request seam.
- Tool-result trimming (planned) needs no new mechanism: a logged single-node surface replace (`start === end`) carrying a trimmed `tool/result` under the same `callId` — compaction-family, replay-correct, cache-bust batched by the same pressure logic.
- Session logs grow one `request/header` snapshot per conversation (system + tool schemas: the dominant term), plus deltas on real changes — small next to `assistant/chunk` volume; `SESSION_FORMAT_VERSION` stays `0` (pre-release churn is absorbed, backends reject-not-migrate).
- Snapshot goldens changed once (every transcript gains its header events); the fs-writing fixtures are stored in the normalized authored form with cwd-relative tool arguments, because replay only round-trips cwd-independent argument paths.
- FIXME(call-config-shape): revisit `LlmCallConfig`'s exact field set — which fields are genuinely epoch-level for cache purposes (`model` certainly; the sampling scalars sit there out of caution), and where provider-specific extras (reasoning options, extra body params) belong when an adapter needs them.

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# RFC: Subagent provider-lifecycle events — `subagent/provider-added` / `subagent/provider-removed`
Status: implemented
## Problem
[The prompt-variables RFC](2026-07-05-prompt-variables-and-tool-guidance-ownership.md) makes `dsh-tool-subagent` DERIVE its model-facing wording from its provider: `SubagentProvider.inheritsParentContext` (spawn/ACP `false`, fork `true`) drives both the tool description and the `prompt` parameter description (`providerWording`), so the fork tool stops lying about context inheritance. That fix created a cross-fiber data dependency: a tool's description is fixed at TOOL REGISTRATION (deliberately — the description is where tool-choice guidance lives), but the provider arrives on its own plugin fiber, on no particular schedule.
The first implementation resolved the provider at the tool plugin's `apply` time and threw when it was absent — an implicit load-order requirement ("list the backend before the tool in cordis.yml"). Review reproduced the failure that requirement hides: the cordis Loader starts sibling entries CONCURRENTLY (`Promise.all` over the group) and `Entry.init()` does not await activation, so a backend whose activation is delayed leaves the tool's fiber permanently failed even when "listed first". The ordering the requirement leaned on is not a contract the Loader offers — "async state is not synchronous state" ([defensive patterns](../../../defensive-patterns.md)).
## Decision
The registry announces provider membership as typed events, and the consumer mirrors them instead of assuming order:
- **`subagent/provider-added(provider)`** — a provider became resolvable in the `ctx.subagents` registry. Emitted on registration.
- **`subagent/provider-removed(name)`** — a provider left the registry (its plugin's fiber was disposed — an unload or an HMR reload). Emitted from the registration's disposer.
`dsh-tool-subagent` mirrors its named provider's lifecycle: it registers the tool when the provider is (or becomes) available — deriving the wording from that provider at that moment — unregisters the tool when the provider goes away, and re-derives on re-registration (HMR reload). While the provider is absent the tool does not exist, which cannot lie to the model. There is deliberately NO load-order requirement left to document: the events make the ordering question disappear instead of pinning it.
The events also complete the seam's vocabulary: `ctx.subagents` is a named registry on which multiple delegation backends coexist (`spawn`, `fork`, `acp`), and a registry whose contents other plugins derive state from should announce membership changes as typed events rather than requiring polling or load-order faith.
## Alternatives considered
- **Resolving the provider at `apply` time and throwing when absent (a load-order requirement)** — the first implementation, rejected after review reproduced the failure above. Documenting the requirement ("list backends first") would pin a guarantee the Loader does not make.
- **Retrying the lookup (poll until the provider appears)** — converges eventually but invents a private readiness protocol beside the one the framework already has (effect registration + disposal); it also cannot notice a provider LEAVING, so HMR would strand a tool whose wording describes a disposed backend.
- **Section-only subagent wording, lazily resolved at assemble time** — tolerates any load order too, but moves tool-choice guidance out of the DESCRIPTION, contradicting the ownership rule the prompt-variables RFC establishes (per-tool semantics and when-to-use belong in the description). Reactive registration keeps the description authoritative AND order-free.
- **Keying wording off the provider NAME instead of the provider object** — `providerName` is itself config, so a renamed provider silently gets the wrong words; deriving from the resolved provider's own `inheritsParentContext` cannot drift.
## Consequences
- Consumers deriving state from a named provider react to `subagent/provider-added`/`-removed` instead of reading the registry at `apply` time; `dsh-tool-subagent` is the reference implementation.
- **The two emits carry asymmetric failure semantics, deliberately.** `provider-removed` fires inside the registration's disposer and is delivered with PER-LISTENER containment (the service's `emitLifecycle`, not raw `ctx.emit`, which halts dispatch on the first throw): a throwing subscriber is logged, never starves a later mirror into holding a stale tool, and never disrupts the backend fiber's teardown — dispose reaches quiescence. `provider-added` propagates: it fires at registration time, where a throwing listener unwinds the yielded rollback — the same fail-loud register-time semantics as the system-prompt registries. The run-time backstop bounds what a stale mirror could cost anyway: `start()` re-resolves the provider by name per run, so a tool that outlived its provider fails that call cleanly instead of dispatching into a dead backend. The [events catalog](../../../cordis-catalog/events.md) carries the exact signatures, and the [producer/consumer map](../../../event-producer-consumer.md) shows `dsh-subagent` emitting and `dsh-tool-subagent` consuming both events.
- **A window where the tool is absent.** Between backend disposal and re-registration (an HMR reload), the model sees no subagent tool. This is the honest state — the alternative is a tool that dispatches into nothing — and the tool registry's `tools/change` emit keeps prompt assembly current.
- **Two waiting fibers sharing a `toolName` is an invalid config caught late.** If two loads of `dsh-tool-subagent` name different providers but the same `toolName`, both wait, and whichever provider arrives first registers; the second registration throws only when ITS provider arrives. `TODO(subagent-dup-toolname)` in the plugin records this blast radius; the tool registry's duplicate-name rejection remains the backstop.

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# RFC: A shared timeout/deadline primitive, with hard-kill left to each capability
Status: implemented
## Problem
Timeout handling was drifting apart across the tool-bearing capabilities, and the divergence was not superficial — it was the same logic re-implemented three ways, each with its own subtle correctness burden.
- **bash** ([packages/bash/bash-local/src/run.ts](../../../../packages/bash/bash-local/src/run.ts)) had a full, correct timeout inside the process plumbing: a config-clamped `timeoutMs`, two independent triggers — a `killTimer` for the timeout and an `onAbort` listener for upstream cancellation — each calling one `kill()` closure that escalates SIGTERM→grace→SIGKILL on the process group, and two orthogonal outcome booleans (`timedOut`, `aborted`) latched independently.
- **web_fetch** ([packages/web/web-fetch-local/src/provider.ts](../../../../packages/web/web-fetch-local/src/provider.ts)) had a correct but *hand-rolled* timeout: it constructed an `AbortController`, wired `setTimeout(() => controller.abort(new WebError(…, 'WEB_FETCH_TIMEOUT')))`, manually added and removed the upstream-signal listener, cleared the timer in a `finally`, and recovered the timeout reason from `signal.reason` in a `translateAbortOrNetwork` helper because the reader surfaces a bare `AbortError`.
- **web_search** ([packages/web/tool-web/src/search.ts](../../../../packages/web/tool-web/src/search.ts)) had **no timeout at all**: `WebSearchRequest` ([packages/web/web/src/types.ts](../../../../packages/web/web/src/types.ts)) carries no `timeoutMs` field, and each provider's `search()` only forwards `exec.signal`. (web_search stays untimed here — see Consequences.)
Each new external-process or network tool re-derived the same four things — clamp the requested value, start a timer, fuse the timeout with upstream cancellation, and distinguish "timed out" from "cancelled" on the way out — and the fusion and reason-recovery are exactly the parts that are easy to get subtly wrong (web_fetch's `signal.reason` dance is evidence). At the same time, the *termination* each performs is irreducibly different: bash kills an OS process group (work runs in a child process, outside this runtime, reachable only by signal), while web aborts an in-process `fetch` (undici tears down the socket). There is no single mechanism that can stop all of them.
The two reference agents surveyed converged on the same split. Codex models "what will end this exec early" as one value (`ExecExpiration`, an enum fusing timeout and a cancellation token) whose `wait_with_outcome()` returns `TimedOut | Cancelled`, while the actual `kill_process_group` lives outside it — and that abstraction is reused *only* across the exec family, with MCP, model-stream, and guardian each keeping their own bespoke `tokio::time::timeout`. Claude Code shares nothing: bash and ripgrep each own a private SIGTERM→SIGKILL kill and distinguish timeout from cancellation by throwing distinct error types, while file I/O has no timeout. Both confirm the boundary drawn here: the timing-and-classification half is worth sharing within a family of like-terminated operations; the termination half is not shareable and stays in each capability.
## Decision
`@deepseek-ai/dsh-timeout` lives under `packages/util/` (peer to `dsh-brand`) and owns the *timing and classification* half of timeout; the *termination* half — the hard kill — stays in each capability's implementation. It is a library of pure functions, **not** a cordis service or plugin: it takes no `ctx`, registers nothing, holds no cross-call state, and emits no events. There is deliberately no central "timeout service" that would have to know how to stop every capability's work — that knowledge is exactly what a microkernel keeps out of shared layers, and what Codex's exec-only `ExecExpiration` scope demonstrates.
### The library surface
Three functions plus one reason type:
```ts ignore-check
/** The internal reason attached to a timeout abort, so consumers can classify it after the fact. */
export class TimeoutReason extends Error {
override name = 'TimeoutReason'
constructor(readonly code: string, readonly timeoutMs: number) {
super(`${code} after ${timeoutMs}ms`)
}
}
/** Validate/fill a caller's optional positive hint from the backend's default, then cap at its max. */
export function clampTimeout(
requested: number | undefined,
def: number,
max: number,
name = 'timeoutMs',
): number
/**
* Build a deadline signal that aborts on upstream cancellation OR on timeout,
* with the timeout carrying a `TimeoutReason`. `timeoutMs <= 0` means "no
* timeout" (background tasks): forward only the upstream signal, arm no timer.
* The returned object's `[Symbol.dispose]` clears the timer — `using` for a
* scope-lifetime consumer, a manual call for an event-lifetime one.
*/
export function deadline(
upstream: AbortSignal | undefined,
timeoutMs: number,
code: string,
): { signal: AbortSignal; [Symbol.dispose](): void }
/** Recover the TimeoutReason from an aborted signal (or error); `code` scopes the match to this deadline's timer. */
export function timeoutOf(x: AbortSignal | { reason?: unknown }, code?: string): TimeoutReason | undefined
```
`deadline` is `AbortSignal.any([upstream, <timeout controller>])` with three things the standard library does not give: a typed, identifiable `TimeoutReason` on the timeout abort (native `AbortSignal.timeout()` yields a fixed `TimeoutError`, indistinguishable across timeout kinds), an internal `timeoutMs <= 0` "no timeout" sentinel for backend-owned background work, and a `Symbol.dispose` cleanup that works with both `using` and manual disposal. `AbortSignal.any` is a Node ≥ 20 primitive; it is the single mechanism that fuses two abort sources into one, adopting the reason of whichever fires first. External request hints validate as positive finite numbers via `clampTimeout` before they reach `deadline`; `0` is not a model-/plugin-facing "disable timeout" value. When `timeoutMs <= 0` and no upstream signal is present, `deadline()` returns a never-aborting signal plus a no-op disposer so callers keep one call shape. `TimeoutReason` is an internal classification reason: providers translate it into seam-specific public errors or result fields before returning to callers. `timeoutOf`'s optional `code` scopes classification to the caller's own deadline: when the `upstream` is itself a deadline (a future `tools/execute` middleware arming a per-call deadline), `AbortSignal.any` preserves the outer `TimeoutReason` if it fires first, and an unscoped match would misreport the outer timeout as the inner capability's own; scoping to `code` reads a foreign timeout as an ordinary upstream cancel.
### The division of labor
| Concern | Owner |
|---|---|
| Validate request hint and clamp default/max | `dsh-timeout` (`clampTimeout`) — pure arithmetic plus the shared positive-finite request contract |
| Arm timer, abort on deadline, carry reason, fuse with upstream cancel | `dsh-timeout` (`deadline`) |
| Clear the timer | `dsh-timeout` (`[Symbol.dispose]`) |
| Classify the first abort reason after abort | `dsh-timeout` (`timeoutOf`) |
| **Actually terminate the work** | the capability's implementation |
| The default/max *values* | the capability's config |
| The timeout `code` string | the capability (`WEB_FETCH_TIMEOUT` ≠ `BASH_TIMEOUT`) |
The signal only *notifies*; termination is always the listener's job, and the listener differs by capability. bash writes its own `addEventListener('abort', kill)` because the OS process lives outside this runtime and nothing else will kill it; web hands `d.signal` to `fetch` and undici tears down the socket. This is why file read/write/edit take **no** `timeoutMs`: a local syscall is best-effort-abortable at most, a timeout could not force `fsync`/`rename` to stop, and adding one would be an implicit default that violates explicit-over-implicit. Both reference agents leave file I/O untimed for the same reason.
### How each capability consumes it
- **web_fetch** — the tool stays validate-and-forward; the provider's hand-rolled controller + `setTimeout` + manual listener + `finally` + `signal.reason` recovery is replaced by provider-owned `deadline`/`timeoutOf`. A pre-aborted upstream signal still throws `WEB_ABORTED` up front; otherwise `fetch` runs against the fused `d.signal`, and `translateAbortOrNetwork` classifies a thrown error by the signal (`timeoutOf` → `WEB_FETCH_TIMEOUT`, else aborted → `WEB_ABORTED`, else network → `WEB_PROVIDER_ERROR`). The public error-code contract is unchanged, and `TimeoutReason` never crosses the web seam as the public error.
- **bash** — `resolve()` stays a pure request-to-spec step: it clamps with `clampTimeout(request.timeoutMs, config.timeoutMs, config.maxTimeoutMs, 'bash-local: request.timeoutMs')` and carries `request.signal` through unchanged. Foreground `run()` owns the timeout: `using d = deadline(spec.signal, spec.timeoutMs, 'BASH_TIMEOUT')`, then `runBash` receives only `d.signal`. `runBash` no longer owns any timer — it listens for abort and runs its existing SIGTERM→grace→SIGKILL process-group kill, and its `SpawnSpec`/`SpawnOutcome` no longer carry `timeoutMs`/`timedOut`/`aborted` (the executor classifies from the deadline signal instead). `run()` computes `timedOut = timeoutOf(d.signal, 'BASH_TIMEOUT') !== undefined` and `aborted = d.signal.aborted && !timedOut`, so the public seam booleans (`BashRunResult.timedOut`/`aborted`) are mutually exclusive — the shared deadline reports the cause that first cut the command short, and the `code` scope keeps a nested outer deadline from being misread as bash's own timeout. Background `start()` creates no deadline and forwards only the upstream signal, so background tasks stay timeout-free; a task's killed-vs-completed status reads its own `spec.signal.aborted`.
## Consequences
- `runBash`'s outcome no longer independently latches `timedOut` and `aborted`; a timeout and a user abort racing before process close now report a single first-abort cause instead of both being true. The uniform SIGTERM→grace→SIGKILL kill is unchanged, and the seam type `BashRunResult` keeps both booleans (now mutually exclusive), so `dsh-tool-bash`'s result rendering is untouched.
- `SpawnSpec.timeoutMs` and `SpawnOutcome.timedOut`/`aborted` were removed rather than kept as always-zero/always-false vestiges: with `runBash` owning no timer and the executor owning classification, they were read nowhere. This is the one deviation from the literal proposal shape (which passed `timeoutMs: 0` into `runBash`); an always-0 field read by nothing is dead weight under the per-file coverage gate.
- web_fetch shed its bespoke controller/timer/listener/reason-recovery; the classifier now keys off the deadline signal (`timeoutOf` + `aborted`) rather than the thrown error's shape, which is robust across both the request-phase reject-with-reason and the read-phase bare-`AbortError`.
- `AbortSignal.any` and `using`/`Symbol.dispose` enter the repo for the first time here (Node ≥ 24 baseline, already met).
Out of scope, named to mark the boundary: `web_search` can gain an optional model-facing `timeout_ms` once its tool-schema/snapshot coverage is planned; future ripgrep-backed fs discovery tools can consume the same provider-owned deadline shape once they exist; a `tools/execute` waterfall middleware could arm a default deadline for every tool call by driving `exec.signal` — that would be a plugin that *consumes* this library and still only notifies, the hard kill remaining each capability's job.
## Alternatives considered
**A unified timeout *plugin* / `ctx.timeout` service.** Rejected on microkernel grounds. A service that could stop any tool's work would have to understand every capability's termination mechanism (process-group SIGKILL, socket teardown, syscall-boundary checks) — the "kernel knows too much" the architecture forbids. Codex's `ExecExpiration` is scoped to the exec family precisely because the kill it drives (`killpg`) is process-family-specific; MCP and model-stream keep their own. There is no coherent middle layer that owns termination for everything, so the shared piece can only be the pure timing/classification half — a library, not a service.
**Per-tool ad-hoc timeout, no shared code (the prior status quo, and Claude Code's choice).** Rejected because it was already producing divergence and duplicated correctness burden: web_fetch hand-rolled the exact controller/reason logic that future network/process-backed tools would each have to re-derive, and the fusion + `signal.reason` recovery are the error-prone parts. Claude Code tolerates full duplication; this repo has a single shared abort channel (`exec.signal` on every `execute`) that makes a small shared primitive strictly cleaner, so the cost/benefit differs.
**A `withTimeout(promise, ms)` wrapper instead of a signal factory.** Rejected because racing a promise against a timer resolves the *tool-call* promise on deadline without stopping the underlying work — the child process or fetch socket leaks on. Handing out a signal and requiring the capability to listen is what forces a real termination path to exist. This mirrors the "dispose must reach quiescence, not just request it" defensive rule.
**Keep bash's two independent triggers (`killTimer` + `onAbort`) rather than fusing.** Rejected for the convergence goal: fusing into one `deadline` signal removes bash's bespoke timer and gives every capability one shape. The trade-off is that bash's `timedOut`/`aborted` booleans become first-abort classifications rather than independent facts that can both be true when timeout and user abort race before process close. That is acceptable because the result reports the cause that first cut the command short; the termination action stays the same uniform SIGTERM→grace→SIGKILL kill. Note the deliberate non-alignment with Codex: Codex forks its kill by outcome (timeout → immediate SIGKILL; cancel → SIGTERM + 50 ms grace → SIGKILL), whereas the fused signal drives one uniform `kill()` for both, matching Claude Code's unified bash kill. Splitting the kill by `timeoutOf` is possible later if a need appears; there is none now.

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# RFC: Tool-call timeout policy as a plugin
Status: implemented
## Problem
The [timeout/deadline RFC](2026-07-06-timeout-deadline-library.md) extracted the timing-and-classification primitive into `@deepseek-ai/dsh-timeout`, but timeout policy was still attached to individual capabilities and model-facing schemas. `bash` exposed `timeoutMs`; `web_fetch` exposed `timeout_ms`; `web_search` had no model-facing timeout even though providers already honor `exec.signal`; a future grep/glob tool would either import the timeout library directly or invent its own timeout policy. That is the wrong authoring shape for a plugin SDK: a tool author should normally forward `exec.signal` to the implementation it calls, and deployment policy should decide the budget.
At the same time, not every timeout in the repo is a model-facing tool-call budget. Hooks execute command hooks by calling `ctx.bash` directly, not through `ctx.tools.execute()`, and the `bash` model tool multiplexes foreground execution, background start, background polling, and hook reuse through the same backend. Moving every timeout into a tool plugin in one step would conflate those paths and risk breaking hook timeout semantics.
## Decision
Tool-call timeout is a policy that applies only to model-facing tool execution, in three parts:
- `@deepseek-ai/dsh-timeout` remains the shared library that owns `deadline()` and `timeoutOf()`.
- `@deepseek-ai/dsh-tools` has an around-dispatch waterfall, `tools/execute`, between `tools/pre-execute` and `tools/post-execute`.
- `@deepseek-ai/dsh-timeout-policy` reads each tool's declared `timeoutMs` from the registry and wraps a call that has one by deriving a new `exec.signal`.
The execution pipeline is:
```text
ctx.tools.execute(exec)
-> tools/pre-execute
-> tools/execute
-> registry dispatch (the base next())
-> tool.execute(args, exec)
-> thrown tool errors normalize to ToolExecutionResult
-> tools/post-execute
```
The default behavior is conservative: a tool that declares no `timeoutMs` receives no `TOOL_TIMEOUT` deadline from the plugin.
### The `tools/execute` around seam
`@deepseek-ai/dsh-tools` declares a `tools/execute` waterfall whose base `next()` is the dispatch-with-normalization thunk — the same inner `try`/`catch` that turns a thrown tool (or unknown tool) into an `isError` `ToolExecutionResult`. A listener receives `(exec, next)`: it calls `next()` to delegate to dispatch (returning its result, optionally wrapped) or returns a replacement result to short-circuit dispatch. The whole pipeline still sits inside `execute`'s outer try/catch, so a throwing listener becomes an `isError` result, never a turn failure.
That the catch is the base `next` — not something outside the waterfall — is load-bearing: when a provider sees the timeout signal and throws its own upstream-abort error, registry dispatch first converts it to a normal error result, and only then can `timeout-policy` replace the final result with `TOOL_TIMEOUT`.
### The `timeout-policy` plugin
The plugin is `@deepseek-ai/dsh-timeout-policy`, a zero-config function/namespace plugin (`name` / `inject` / `apply`) in the `packages/timeout/` group. The per-tool budget is DECLARED on the tool, not on this plugin: a `ToolDefinition` carries an optional `timeoutMs`, which the owning tool plugin sets from its own config. `dsh-tool-web`, for example, resolves `fetchTimeoutMs` / `searchTimeoutMs` (default 30000) onto the `web_fetch` / `web_search` definitions:
```yaml
- id: timeout-policy
name: '@deepseek-ai/dsh-timeout-policy'
- id: tool-web
name: '@deepseek-ai/dsh-tool-web'
config:
fetchTimeoutMs: 30000
searchTimeoutMs: 30000
```
Keeping the tool name out of this plugin's config is deliberate: a budget keyed by a free-text tool name could be mistyped (`web_fech`) and then silently apply to nothing. Declaring `timeoutMs` on the tool makes that failure class structurally impossible — the enforcer reads `ctx.tools.get(exec.name)?.timeoutMs`, and `exec.name` is the tool being dispatched, so the lookup always resolves and there is no unknown-name path to warn or throw about. `timeoutMs` is validated positive-finite by `defineTool` at definition time. For a tool that declares a budget the listener arms `deadline(exec.signal, timeoutMs, 'TOOL_TIMEOUT')`, swaps the derived signal onto `exec` for the downstream dispatch, restores the caller's own signal afterward, and returns a structured `TOOL_TIMEOUT` result when `timeoutOf(d.signal, 'TOOL_TIMEOUT')` matches. A tool with no declared budget delegates unchanged.
Signal replacement is by **in-place mutation of `exec.signal`**, not by passing a new object to `next()`. Cordis's waterfall `next()` ignores any arguments handed to it and re-invokes downstream listeners with the shared payload array (`vendor/cordis/src/events.ts`), so the documented cordis idiom — mutate the shared object, then delegate — is the only mechanism that reaches dispatch. The plugin restores `exec.signal` to the caller's original in a `finally` so `tools/post-execute` never sees this plugin's (possibly already-aborted) deadline signal.
`timeout-policy` owns both uses of the `TOOL_TIMEOUT` code: the internal deadline code passed to `deadline()`/`timeoutOf()` (scoped so a nested outer deadline reads as an ordinary cancel) and the structured tool-result error code. Its replacement result is:
```ts ignore-check
function toolTimeoutResult(callId: CallId, timeoutMs: number): ToolExecutionResult {
return {
callId,
content: [{ type: 'text', text: `Error: tool call timed out after ${timeoutMs}ms` }],
isError: true,
error: { name: 'ToolTimeoutError', code: 'TOOL_TIMEOUT' },
}
}
```
This is a cooperative deadline. It does not kill arbitrary work by racing the tool promise; the tool or the capability it calls must honor `exec.signal` and reach quiescence. Declaring `timeoutMs` therefore MEANS "this tool is cooperative with `exec.signal`", which the plugin README states as its contract.
No new session event is needed for reconstructability: `TOOL_TIMEOUT` is the final model-facing `tool/result` for that call, so the existing session log already records the content and structured `{ name, code }` error the next model request sees.
### Existing tool adaptation
`web_fetch` and `web_search` are migrated. `dsh-tool-web` keeps ownership of their model-facing schemas, and those schemas expose no timeout knob: `web_fetch` dropped its `timeout_ms` parameter to match the reference-agent shape, and `web_search` stays query-only. The tool bodies do not import `@deepseek-ai/dsh-timeout`; they forward `exec.signal` to `ctx.web`.
`dsh-web-fetch-local` keeps a provider-level timeout (`timeoutMs`/`maxTimeoutMs`) as a large resource backstop for direct `ctx.web.fetch()` callers and misconfigured deployments; it owns no model-facing timeout. When a `TOOL_TIMEOUT` signal reaches the fetch provider first, provider-scoped classification treats it as upstream `WEB_ABORTED`, and the outer `tools/execute` wrapper replaces the final tool result with `TOOL_TIMEOUT`. A shipped web-tool deployment configures the provider backstop above the `timeout-policy` budget so the tool-call policy normally wins for model calls.
`bash` stays on the current backend timeout path. `dsh-tool-bash` continues to expose `timeoutMs` and `run_in_background`; `dsh-bash-local` continues to use `@deepseek-ai/dsh-timeout` for `BASH_TIMEOUT`; hook bridges continue to call `runHook()` and pass `timeoutMs` through `ctx.bash`. This keeps foreground/background/hook behavior stable.
`read`, `write`, `edit`, `todo_write`, `bash_output`, and `bash_kill` do not opt into tool-call timeout: they are local filesystem or short registry/session operations where a deadline would be best-effort only or unnecessary.
A future model-facing grep/glob tool can be implemented on top of `ctx.bash` without importing `@deepseek-ai/dsh-timeout`: it forwards `exec.signal` to `ctx.bash`, and declares its own `timeoutMs` (from its plugin's config) for the enforcer to apply. If bash-local's backend timeout becomes a problem for such a tool, the bash seam can later add a caller-owned-deadline mode; that is outside this cut.
## Alternatives considered
**Name the plugin `tool-timeout`.** The literal RFC name matched the `gen-tool-catalog` completeness guard's `packages/*/tool-*` glob, which requires every match to register a model-facing tool. This plugin registers none — it is a `tools/execute` wrapper — so a `tool-*` name would either fail `verify-tool-catalog` or force a misleading boot entry. The package is `@deepseek-ai/dsh-timeout-policy` in a new `packages/timeout/` group; the cordis.yml `id` can still be `timeout-policy`.
**Keep per-tool timeout handling only.** This was the shape for `bash` and `web_fetch`, and it matches Claude Code and Codex for shell commands. It loses for web-style tools because every new timeout-capable tool must choose validation, cap semantics, docs, snapshots, and classification. The plugin centralizes policy and classification while leaving each tool's schema focused on business input.
**Move all timeout policy out of bash-local immediately.** Cleaner long-term — bash-local would become a pure subprocess executor and all callers would own their deadlines. It loses as the first step because hooks call `ctx.bash` directly and the bash model tool has foreground/background semantics that are not the same tool-call lifetime. Keeping `BASH_TIMEOUT` preserves those paths while tool-call timeout proves itself on simpler tools.
**Use a global default budget for every tool.** Convenient, but it surprises tool authors: any tool that accidentally runs longer than the global budget would start failing once the plugin loads. A per-tool declared budget makes adoption deliberate.
**Expose a model-facing `timeout_ms` override.** Claude Code's `WebFetch`/`WebSearch` and Codex's web tools keep timeout out of the model-call shape. A model override would make timeout part of prompt semantics and force schema/argument-stripping rules into `timeout-policy`. Web timeout stays deployment policy only.
**Let `timeout-policy` match tool arguments itself.** A rule engine such as "disable timeout when `bash.run_in_background` is true" would make the policy plugin know tool-specific argument semantics. Avoided by not migrating bash to tool-call timeout.
**Use `tools/pre-execute` plus `tools/post-execute` instead of a new around seam.** A pre listener could arm a deadline and mutate `exec.signal`; a post listener could classify and replace. That loses because the deadline lifetime would cross two independent waterfalls: a call-id map, cleanup on every pre-deny/tool-throw/post-throw/dispose path, and ordering rules with every other listener. `tools/pre-execute` is also the allow/deny gate, not an execution wrapper. `tools/execute` gives the timeout one lexical scope: arm, delegate, classify, dispose.
**Use `Promise.race` to enforce timeouts for non-cooperative tools.** Rejected for the same reason as the timeout-library RFC: it returns control to the caller while the underlying process, fetch, or provider operation may still be running. The plugin only sends a signal; termination remains the implementation's responsibility.
## Consequences
- `@deepseek-ai/dsh-tools` gains an around-dispatch surface after the interception seams deliberately split pre/post tool hooks. Its contract is narrow — wrap registry dispatch, not replace the pre-gate or post-result policy — and the base `next()` is dispatch-with-normalization so a wrapper never sees a raw tool throw.
- Multiple `tools/execute` listeners compose by ordinary Cordis waterfall order: a listener that calls `next()` wraps downstream listeners plus dispatch; one that returns without `next()` short-circuits them. A deployment combining timeout with a future retry/sandbox/metrics wrapper chooses semantics by registration order ("timeout covers the whole retry" vs "timeout covers each attempt").
- Opt-in by declaration is a deliberate misconfiguration risk: a tool can declare a `timeoutMs` without honoring `exec.signal`, and that tool will not stop on timeout. The plugin contract states that declaring a budget means cooperative; the web tools prove the pattern on tools that already forward the signal.
- During the transition `bash` and the migrated web tools use different timeout paths on purpose: `TOOL_TIMEOUT` is the model-facing tool-call budget, while `BASH_TIMEOUT` remains the bash backend timeout used by bash and hooks.
- Deviation from the literal proposal, recorded per the implemented-RFC rule: the plugin package is `@deepseek-ai/dsh-timeout-policy` (not `tool-timeout`), signal replacement is in-place `exec.signal` mutation before `next()` (not `next({ ...exec, signal })`, which cordis ignores), and the per-tool budget is declared on the `ToolDefinition` (`timeoutMs`, set by the owning tool plugin from its config) rather than mapped by tool name in this plugin's config — so the enforcer is zero-config and a mistyped tool name is impossible. All three are described in `## Decision` above.

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# RFC: Agent Client Protocol (ACP) support — drive the coding agent from external editors
Status: implemented
## Problem
The harness originally exposed agents only through a readline loop. That surface could carry text, but it gave an editor no structured way to create or resume sessions, correlate prompt completion, stream reasoning and tool activity, render tool-specific UI, ask for permission, or cancel one conversation without disturbing another. ACP defines those interactions as JSON-RPC over stdio, and Zed is the target client used to make concrete compatibility decisions.
The bridge must preserve the harness's existing ownership boundaries. It cannot depend on the concrete agent loop, bypass the tool registry, execute shell commands in the editor, or invent a second source of session truth. stdout is also the protocol transport, so any accidental log output corrupts the connection.
## Decision
`@deepseek-ai/dsh-acp` is a UI/client-driver plugin under `packages/ui/acp`. It uses `@agentclientprotocol/sdk`'s `AgentSideConnection` over stdin/stdout and programs only interface services: the agent create/resume factory, session persistence, tool registry, user interaction, and optional approval/bash capabilities. It does not change the agent loop and is not a capability-seam implementation.
The bridge implements the following stable session path:
- `initialize` negotiates the protocol version, advertises text plus `resource_link` prompts, and advertises `loadSession`.
- `session/new` validates an absolute `cwd`, stores it in `SessionHeader`, creates an agent through `ctx.agents`, and returns any composition-backed config options.
- `session/load` validates the requested cwd against persisted metadata before constructing an agent, reserves the id across the asynchronous resume, replays user/assistant/tool events as ACP updates, and reports the resumed config-option fold.
- `session/prompt` accepts text and resource links, rejects unsupported or empty content, allows one in-flight prompt per session, and settles against that prompt's owning `turn/end`. An error turn rejects the RPC; other closed turn reasons map through a total ACP stop-reason codec.
- `session/cancel` calls the queue-aware agent cancel path and settles only the addressed session's prompt.
Tool-call presentation remains tool-owned. A tool's `presentCall` and `presentResult` return the `generic`, `terminal`, or `diff` render-intent variants; the bridge switches on that union and maps it to ACP. Presenter-less tools receive a generic fallback. Bash terminal cards use Zed's capability-gated `_meta.terminal_info`, `_meta.terminal_output`, and `_meta.terminal_exit` convention; the harness still executes the command through `ctx.bash`, preserving sandbox, environment scrub, ownership, and cwd. Clients without that extension receive ordinary text content. Filesystem tools provide diff cards and file locations without hard-coded tool-name branches in the bridge.
Permission handling is an answerer on the [user-approval seam](2026-07-06-approval-seam.md), not an ask-every-tool policy in ACP. An `approval/request` for a bridge-owned agent with a call id becomes `session/request_permission` on that agent's editor session, with one-shot allow/reject choices. Foreign or call-less requests delegate; a missing or failed answerer remains fail-closed. The plugin that asks—such as a pre-execute policy or bash escalation—owns the decision to ask.
The bridge advertises ACP config options instead of session modes. `sandbox-mode` exists only when the mounted bash executor reports sandbox capability, and `approval-policy` exists only when `ctx.approval` is composed. Each option is an independent select whose current value is the session event fold over the composition default. `session/set_config_option` validates against the owning domain vocabulary and writes through `setSandboxMode` or `setApprovalPolicy`. An open-turn switch appends immediately; an idle switch is overlaid in the response and anchored at the next turn start. Until that anchor it is memory-only and a crash reverts to the durable fold. ACP session modes are deliberately not modeled because one mode list cannot represent these orthogonal knobs and config options are the forward protocol surface. Runtime model selection remains outside this decision; `AcpConfig.model` is connection-wide.
The bridge also provides the ACP-backed `UserInteractionProvider`: `ask_user_question` requests become form elicitations on the owning session. Select, multi-select, option descriptions, and custom-answer override semantics are preserved.
Lifecycle ownership is explicit. The bridge holds an `AgentHandle` per live session. Disconnect and Cordis disposal cancel pending prompts, dispose every handle in parallel, await loop quiescence and persistence flush, and then remove the records. Stream notification failures are contained so a vanished client cannot corrupt an agent turn. The ACP app composition loads no stdout logger; a test guards stdout as framed JSON-RPC only.
The precise supported and deferred protocol rows live in [`packages/ui/acp/acp-feature-support.md`](../../../../packages/ui/acp/acp-feature-support.md); the package README is the operational contract.
## Alternatives considered
**A prepended `tools/execute` listener that asks on every ACP-owned call** — rejected. It would hard-code permission policy into the UI bridge, ask even when no policy requires it, and could not serve approval requests that arise after execution begins. The shared user-approval seam keeps mechanism, asking policy, and UI answerer separate.
**Inject the concrete `agentLoop`** — rejected. Agent creation, resume, idle observation, and disposal are interface-level ownership operations on `dsh-agent`; a UI plugin does not need a dependency-rule exception.
**Execute bash through ACP `terminal/*`** — rejected. That would move execution outside the harness and bypass its sandbox, credential scrub, task ownership, cwd resolution, and session log. Terminal metadata is presentation only.
**Represent sandbox and approval as ACP session modes** — rejected. They are independent composable settings, while a single current mode is mutually exclusive. ACP config options represent both without a cross-product and match the protocol's forward direction.
**Hijack stdout defensively** — rejected. Process-wide monkey-patching is outside Cordis effect ownership and races the protocol transport. The app composition owns stdout purity.
## Consequences
Editors can create, load, prompt, cancel, render, ask, and reconfigure multiple harness sessions over one ACP connection without a loop-specific dependency. The session event log remains the durable source for replay, prompt settlement, cwd, and per-session configuration. Tool presentation and human-answer channels remain extensible plugin contracts instead of ACP-specific behavior.
The bridge deliberately does not implement session list/delete/resume/close capabilities, MCP passthrough, additional directories, image/audio/embedded-resource prompts, runtime model selection, plans, slash commands, usage updates, editor filesystem delegation, or the ACP terminal execution sub-protocol. The feature checklist records these as unsupported rather than silently accepting them.
An idle config selection is truthful in the live response but not durable until the next turn anchors it. Crashing before that boundary loses the pending selection; this is the cost of keeping session events turn-enclosed and replay-safe.
## Verification
The ACP suites cover the in-memory protocol codec, create/load replay, exact prompt settlement, cancellation races, unsupported content, tool presentation, terminal capability fallback, permission outcome mapping, config-option validation and persistence, multi-session isolation, disconnect/disposal quiescence, and HMR cleanup. Snapshot and built-bin tests exercise the app composition, while the real-API e2e self-skips without a key.

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# RFC: Multiplex concurrent ACP sessions over one connection
Status: implemented
## Problem
An ACP editor can keep several conversations alive over one agent subprocess. A single-active-session bridge would force extra processes and would not match Zed's client model, which tracks multiple session ids and concurrent loads. Multiplexing introduces isolation risks: events, prompt completion, cancellation, permission prompts, config selections, and predictable background-task ids must never cross session boundaries.
## Decision
The ACP bridge stores live sessions in `Map<SessionId, SessionRecord>` and keeps a `WeakMap<Agent, SessionId>` reverse index for agent-scoped callbacks. A record owns its agent handle, in-flight prompt, live tool-call presentation state, pending idle config switches, session cwd, and client capability snapshot. A separate loading-id set reserves each id before asynchronous resume so two pipelined loads cannot construct duplicate agents; distinct ids may load concurrently.
Every `session/event` and `agent/status` callback resolves the owning record before sending or settling anything. Each session permits one in-flight prompt independently. The prompt records a log watermark, captures its own `turn/start`, and settles only on the matching `turn/end`; a late end from a cancelled prior turn cannot resolve a newer prompt. `session/cancel` addresses one record and calls only that agent's queue-aware cancel path.
Permission ownership uses the same reverse index. The ACP `approval/request` answerer prompts only the editor session that owns the requesting agent and delegates foreign requests. User-interaction elicitations likewise route by agent ownership. Per-session sandbox and approval config values fold only that session's events, with pending idle switches stored on that record until the next turn anchors them.
Background bash tasks carry an opaque owner token equal to the owning session id. `bash_output` and `bash_kill` compare the caller's token with the executor's task ownership before reading or killing; a predictable task id alone grants no access. Ownership is stored with the executor task, so a tool plugin reload does not erase it.
Connection teardown clears the live map, settles each pending prompt as cancelled, and disposes all `AgentHandle`s in parallel. Each handle stops and awaits its loop, flushes the session while attached, unregisters the agent, and removes the session. Teardown is memoized and shared by client disconnect and plugin disposal.
## Alternatives considered
**One live session per connection** — rejected. It adds process overhead and contradicts the target client's multi-session shape without removing multiplexing needs from the editor.
**A per-session `ctx.extend()`** — rejected. A child context does not by itself create a child plugin fiber, so listeners would still belong to the bridge fiber. The implemented bridge instead uses global listeners with explicit O(1) demultiplexing and per-session owned records; agent lifecycle is owned by `AgentHandle`.
**Agent object identity as bash-task ownership** — rejected. A resumed or replaced agent object may legitimately represent the same durable session. The opaque session token is the cross-boundary identity that should survive plugin reloads.
## Consequences
N sessions can stream, prompt, request permission, switch config, and run background tasks concurrently without interleaving or cross-settling. A cancel or dispose in one session does not affect its neighbors. The bridge pays for explicit maps and isolation tests, but it does not add one listener set per session and therefore avoids listener fan-out during long-lived connections.
The bridge still exposes no protocol method to close one live session independently. Today records leave together on connection teardown; session close/resume lifecycle capabilities remain deferred in the ACP feature checklist.
## Verification
The multi-session suite drives concurrent sessions through interleaved updates, independent in-flight prompts, targeted cancellation, same-id and distinct-id load races, permission routing, config isolation, and teardown. Tool-bash tests prove one session cannot read or kill another session's background task.

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# RFC: Code Mode — the model writes TypeScript against the tool registry
Status: implemented
## Problem
Today the agent loop advertises every registered tool to the model as a native JSON-schema function definition. `ToolRegistry` contributes its schemas to the system-prompt assembly, the assembly's `tools` land on the wire (and in the logged request header), the model invokes one `tool-call` block per step, and the loop dispatches each call through `ctx.tools.execute()` **sequentially** (parallel tool execution is an explicit open TODO in `dsh-tools` and [docs/architecture.md](../../../architecture.md)), with **every** intermediate `tool-result` re-entering the model's context on the next request.
For multi-step tool work this is token-heavy and serial. The model cannot compose tools — loop over a result set, branch on an intermediate value, fan out, post-process — without a full model round-trip per call, and each round-trip drags the entire intermediate result back into context whether the model needs it or not.
Cloudflare's [Code Mode](https://blog.cloudflare.com/code-mode/) proposes an alternative grounded in a simple observation: LLMs are better at writing code than at emitting tool calls, because they have seen millions of lines of real code and comparatively few contrived tool-calling traces. Instead of one tool call per step, the model writes a TypeScript program against a generated API over the tools, the program executes in a sandboxed runtime, and the model curates what comes back — only what it prints or returns — instead of every intermediate result.
An earlier draft of this RFC designed Code Mode as an add-on consumer plugin with zero core changes, deferring the execution substrate to a follow-up. Both constraints are dropped here, deliberately. First, the harness is pre-release and optimizes for the correct foundation over blast radius: tool presentation is the registry's own concern, and bolting a second presentation onto it from outside means transforming the registry's contribution after the fact — a waterfall listener whose correctness depends on listener ordering, which fights the [reconstructable-requests](../../implemented/architecture/2026-07-05-reconstructable-requests.md) design instead of riding it (that refactor removed request mutation from `agent/request`, the seam the old draft relied on). Second, the substrate question is answerable now: a Node `worker_threads` runtime gives real containment — separate isolate, empty environment, heap caps, and a `terminate()` that reliably stops a hot synchronous loop — where the old draft's `node:vm` stub had none of those, and it fits the harness's existing trust model (§Trust posture) without a hardening follow-up.
## Decision
Three decisions, each elaborated in its own section below:
1. **Code Mode is a first-class presentation mode of `ToolRegistry`** (`dsh-tools`), selected by a validated `mode` config: `'native'` (today's behavior, the default), `'code'` (the wire carries exactly one tool, `run_code`, plus a generated SDK `.d.ts` in the system prompt), or `'both'` (native schemas *and* `run_code` + SDK). The registry's existing tool-schema provider contributes whatever the mode dictates, so the wire tool list is shaped at its source — no interception, no listener-ordering caveats — and the logged request header records it for free.
2. **Code execution is a capability seam** — a new group `packages/code-runtime/` with the interface package `@deepseek-ai/dsh-code-runtime` owning `ctx.codeRuntime` ([capability seams](../../implemented/architecture/2026-06-13-capability-seams.md); consumer = `dsh-tools`, with core-consumes-a-seam precedent in `agent-loop` → `dsh-llm`). The runtime knows nothing about tools: it is handed a program and named async bindings, runs the program, and reports `{ value, logs, error? }`. Language and substrate are backend properties, so a future Python or container backend is a new implementation package, not a redesign.
3. **The shipped implementation is `@deepseek-ai/dsh-code-runtime-worker`**: one fresh Node worker thread per run, executing the model's TypeScript after type-strip, with bindings bridged over the message port, an empty environment, configurable heap/output/time caps, and hard termination. Its trust posture is bash-equivalent by design — no unsafe-acknowledgement flags — because the harness already ships `dsh-bash-local`, which executes arbitrary model-written shell commands with strictly *more* ambient authority.
### The registry owns the mode
`ToolRegistry` gains a schemastery-validated config (`static Config`), its first: `mode: 'native' | 'code' | 'both'`, default `'native'`. A deployment flips it from `cordis.yml` (`tools: { mode: code }`) — no code edit, per the no-hardcoded-tunables convention.
**Wire tool list = the registry's contribution.** The registry already feeds the assembly through `ctx.systemPrompt.tools(() => this.schemas())`; the provider becomes mode-aware: `'native'` contributes all schemas (unchanged), `'code'` contributes only `run_code`'s schema, `'both'` contributes all schemas plus `run_code`. Because [`PromptAssembly.tools` is the single source the loop's request header snapshots](../../../../packages/core/system-prompt/src/index.ts), the collapse is automatically logged and reconstructable — model-visible ⟺ logged holds with zero new mechanism. Scope of the guarantee, stated honestly: the mode governs the **registry's** contribution, and the registry is the only shipped schema source — but `systemPrompt.tools()` is a public multi-provider API and the `system-prompt/assemble` waterfall may transform the assembly, so a deployment that wires a second direct provider (or a mutating listener) owns what it adds, exactly as in native mode. Those are deliberate acts; what the design eliminates is the *accidental* leak the old draft worried about — a listener-ordering race around an after-the-fact collapse — and the shipped-configuration invariant (`'code'` ⇒ assembled tools exactly `[run_code]`) is pinned by tests and, like every request, by the logged header.
**Interaction with `toolOrder`, stated up front:** a configured `systemPrompt.toolOrder` naming native tools rejects every assembly under `mode: 'code'` (those names are no longer contributed), by the existing fail-loud rule for unlisted names. This is correct behavior, not a bug: a deployment switching modes updates its order config or drops it.
**The SDK prompt section.** Under `'code'` and `'both'` the registry registers one lazy prompt section (`tools:sdk`, in the 100–199 tool-guidance order band) whose thunk regenerates, at each assembly, a TypeScript declaration of every registered tool except `run_code` itself, plus fixed usage instructions. The thunk reads the live store and emits tools in lexicographic name order, so its output is deterministic and stable across steps — an unchanged tool set produces byte-identical text (prefix-cache-friendly; a mid-session registration surfaces as one logged header delta, exactly like a native-mode tool change).
**Codegen.** A pure `jsonSchemaToTs(schema)` module inside `dsh-tools` (sibling of `json-schema.ts` — `schemas()` and the SDK are two projections of the same store) maps the JSON-Schema subset the `defineTool` DSL emits (object/string/number/boolean/array, `properties`, `required`, string `enum` → literal union, nested objects, array `items`, `description` → JSDoc) to a TS type literal. It is **total**: any construct outside that subset (`$ref`, `oneOf`/`anyOf`, `integer`, future MCP shapes, …) degrades to `unknown` without throwing. Because `ToolSchema.name` is an arbitrary string, the SDK is declared as one object constant — `declare const tools: { "some-mcp-tool"(args: …): Promise<string>; bash(args: …): Promise<string>; … }` — quoted keys make every name reachable with no sanitization or alias-collision logic. Typing is advisory (the runtime executes type-stripped JS); the instructions say so.
### The run_code tool and the dispatch bridge
Under `'code'` and `'both'` the registry registers `run_code` in itself as an ordinary tool — one required parameter `{ code: string }` — so the unchanged loop dispatches it through the normal pipeline and `tools/pre-execute` / `tools/post-execute` gate it like any other call (a permission plugin can inspect the program text before it runs). Its `execute(args, exec)`:
1. **Builds the bindings**: the bridge owns a **run-scoped `AbortController`** whose signal follows `exec.signal` (an outer cancel propagates in) and which the bridge itself fires the moment the run settles for any reason — completion, program exception, `computeMs`/`maxWallMs` expiry, worker exit. For every registered tool except `run_code`, the binding is an async function that (a) checks the run signal before and after (throwing stops the program — necessary because `ctx.tools.execute()` converts errors to `isError` data), (b) **JSON-normalizes the argument** — a `JSON.parse(JSON.stringify(args))` round-trip, rejecting that one call with a descriptive `Error` when the value does not survive (`BigInt`, circular structures) — because the seam's structured-clone boundary is wider than JSON while the session log accepts only JSON: normalizing BEFORE dispatch makes the dispatched form and the logged form the same JSON value by construction, so an executed sub-call can never fail at logging time, (c) awaits its turn on the **per-run serialization queue** (below), (d) calls `this.execute({ callId, name, arguments, agent: exec.agent, signal: runSignal })` with a deterministic sub-id `` CallId(`${exec.callId}:code:${n}`) `` — the run signal, not the bare outer one, so a budget expiry aborts an in-flight sub-tool (`bash-local` kills on its spec signal) instead of orphaning it, (e) appends a `tool/code-dispatch` session event, and (f) maps the result: success → the text-block contents joined as a `string` (non-text blocks become placeholders, an MVP limitation), `isError` → **the binding rejects** with an `Error` carrying the result text. Rejection is the deliberate model-facing contract — real code signals failure by throwing, `try/catch` and `Promise.all` short-circuiting behave as every model has seen them behave — where the old draft's `{ output, isError }` envelope made error handling a bespoke convention.
2. **Runs the program**: `ctx.codeRuntime.run({ program: args.code, bindings: [{ global: 'tools', functions }], signal: exec.signal })`.
3. **Surfaces the outcome — after reaching quiescence.** When `ctx.codeRuntime.run()` resolves, the bridge fires the run-scoped abort (cancelling any in-flight sub-dispatch and abandoning queued-unstarted ones), then **awaits the dispatch queue's drain before returning**, per the dispose-to-quiescence rule in [defensive patterns](../../../defensive-patterns.md): an aborted in-flight sub-call still settles and logs its `isError` `tool/code-dispatch` event *inside* the open turn, and nothing can append after `run_code` returns. A successful run then returns one text block — the captured console/stdout output followed by the rendered return value (if any) — plus a `meta` payload (capped logs, dispatch count) for presentation. A run with `result.error` throws a `CodeRunFailedError extends HarnessError` (`code: 'CODE_RUN_FAILED'`, message = the error kind and text plus captured logs so the model can self-correct); the registry's existing catch turns it into a structured `isError` result.
**Sub-call `additionalContext` is suppressed, deliberately.** A `tools/post-execute` hook may attach `additionalContext` to a call; for loop-dispatched calls the loop buffers those and appends each as a `context/message` only after the step's `tool/result`s, preserving call/result adjacency. A sub-dispatch result's `additionalContext` has no such safe outlet from inside a running `run_code`: injecting immediately would land a `context/message` between the parent's `tool/call` and its `tool/result` (breaking the adjacency the buffering exists to protect), and `PostToolDecision.additionalContext` is singular where a program may produce many. The MVP therefore drops sub-call `additionalContext`, pinned by a test and stated in the hooks bridge's docs; the follow-up (a plural context channel or loop-level sub-dispatch buffering) is deferred until a real hook needs it through Code Mode.
**Concurrency: serialized, enforced by the binding.** The bindings are async, so a model writing `Promise.all([tools.a(…), tools.b(…)])` starts both immediately — concurrent dispatch would be the *default*, while the tool contract still carries no concurrency-safety metadata (the open parallel-execution TODO). Each `run_code` invocation therefore owns a dispatch queue and every binding call chains onto it, so even `Promise.all` executes the underlying `ctx.tools.execute()` calls one at a time in submission order; when the run settles, queued-but-unstarted dispatches are abandoned. Lifting this per-tool once tools can declare themselves concurrency-safe is deferred work, same as before.
**Presentation.** `run_code`'s render intent is decided here per the [render-intent RFC](../../implemented/architecture/2026-07-02-tool-render-intent-union.md): `presentCall` → a `generic` card, `kind: 'execute'`, title `Run code`, `rawInput` = the program text; `presentResult` → a `generic` card whose content is the captured output (from `meta`). Not a `terminal` card: that card's semantics are "a shell command in a working directory", which a program is not.
### Observability: `tool/code-dispatch`
Each sub-dispatch appends one session event, declared by `dsh-tools` via `SessionEventMap` declaration merging (the map is merge-extensible for exactly this; `todo/write` is the log-only precedent): `tool/code-dispatch` with `{ parentCallId, subCallId, name, arguments, isError, resultSummary }` — `arguments` being the bridge's JSON-normalized value, the very one dispatched, so the append cannot fail on payload shape. It is log-only — `deriveEventMessage()` ignores unknown event types by design, so sub-calls never re-enter model context — but persistence and UIs get every call. As a log event it carries JSDoc prose but **no `@mode` tag** (that vocabulary belongs to cordis bus events; the persistence-catalog generator hard-errors on one) and lands in the regenerated `docs/persistence-catalog.md`; appends happen inside `run_code`'s execution, so the turn-enclosure invariant is satisfied by construction. A `run_code` execution arriving without `exec.agent` (the loop always supplies it; direct programmatic calls may not) still runs and simply skips event logging, exactly as the `ToolExecution` contract allows.
### The code-runtime seam
`packages/code-runtime/code-runtime/` — `@deepseek-ai/dsh-code-runtime`, depending only on `cordis`. An abstract `CodeRuntime extends Service` (`super(ctx, 'codeRuntime')`) plus the vocabulary:
- `CodeRunRequest = { program: string; bindings: CodeBindingNamespace[]; signal?: AbortSignal }`
- `CodeBindingNamespace = { global: string; functions: Record<string, (args: unknown) => Promise<unknown>> }` — the runtime exposes each namespace as a global object of async functions inside the program; binding arguments and resolutions must be structured-cloneable (a runtime may cross a serialization boundary; ours does).
- `CodeRunResult = { value?: unknown; logs: CodeLogEntry[]; error?: CodeRunFailure }` — an error is a field on a resolved result, never a rejection of `run()`.
- `CodeLogEntry = { source: 'console' | 'stdout' | 'stderr'; level?: 'log' | 'info' | 'warn' | 'error' | 'debug'; text: string }`
- `CodeRunFailure = { kind: 'exception' | 'timeout' | 'abort' | 'worker-exit'; message: string }` — orthogonal outcomes reported independently per [defensive patterns](../../../defensive-patterns.md); a timed-out run is not an exception, an abort is not a timeout.
- Two readonly backend descriptors, informational not gating: `language` (what the program must be written in — `'typescript'` for the shipped backend; a Python backend would say so, and pair with its own SDK generator on the presentation side) and `isolation` (`'worker-thread'` for the shipped backend; `'process'`, `'container'`, … for future ones). `dsh-tools` requires `language === 'typescript'` in the MVP — its codegen emits TS — and fails the assembly loudly otherwise, the same misconfiguration idiom as `toolOrder` violations (as when `mode` is non-native with no `ctx.codeRuntime` loaded at all).
Per explicit-over-implicit at seams, the request spells out everything the runtime acts on; defaulting (timeouts, caps) is the implementation's validated config, never a hidden `??` inside `run()`. Consumption uses the loop's established optional-backend idiom: cordis has no optional injection — every `inject` entry gates activation — so a static `inject` on the registry would hold `ctx.tools` (and every tool plugin behind it) hostage to a code runtime existing even under `mode: 'native'`; instead the registry reads `ctx.get('codeRuntime')` at use time, exactly as `agent-loop` consumes `sessionPersistence`, with absence failing loud in the provider thunk as above. The seam split is justified by real planned divergence on both axes — substrate (worker now; container/microVM later) and language (the Python/AssemblyScript direction sketched in the earlier draft survives as future work) — not by speculation: `dsh-tools` consumes the interface today and tests against a trivial in-repo fake, exactly the interface/implementation/consumer shape of the bash template.
### The worker-thread runtime
`@deepseek-ai/dsh-code-runtime-worker`, the second package of the `packages/code-runtime/` group. Per `run()`:
1. **Type-strip host-side** with Node's built-in `stripTypeScriptTypes` (`node:module`; present across the repo's whole engines range, `^22.19.0 || >=24.0.0`, and position-preserving, so runtime error line numbers match the model's source). Strip-only mode rejects non-erasable syntax (`enum`, namespaces) — that rejection returns as `error.kind: 'exception'` with Node's message, the SDK instructions say "erasable TypeScript only", and the model self-corrects like any other program error. A syntax-level failure never spawns a worker.
2. **Spawn one fresh `Worker` per run** from the package's own bootstrap module: `env: {}` (truly empty — stronger than the scrubbed-env rule for spawned commands), `resourceLimits` from config, `stdout`/`stderr` captured into `logs` rather than inherited. No pooling and no cross-run state: a program's world dies with its worker, which keeps runs reconstructable from the log alone and makes state bleed unrepresentable.
3. **Execute** in the bootstrap: the stripped program becomes the body of an `AsyncFunction` whose parameters are the binding globals and a capturing `console` shim, so top-level `await` and `return` work and the program's completion value is the run's `value` (structured-cloneable values cross as-is; anything else is replaced by its `util.inspect` rendering, documented).
4. **Bridge bindings over the message port**: each binding function in the worker posts `{ id, global, name, args }` and awaits the reply; the host validates the name against the request's bindings, invokes, and replies `{ id, ok, value }` or `{ id, ok: false, message }` (a host-side binding rejection becomes a program-side rejection). The worker-side namespace objects are built null-prototype via `defineProperty`, so a binding named `__proto__`, `constructor`, or `toString` is an ordinary own property, not a prototype collision. Unknown names, duplicate ids, and post-settlement messages are rejected or ignored — the port protocol assumes a hostile peer, because the peer runs model code.
5. **Enforce caps — two independent budgets, because the peer is hostile.** The compute budget (`computeMs`) meters the worker's *measured busy time* via `worker.performance.eventLoopUtilization()` polling — not host-side "is an RPC pending" bookkeeping, which a program defeats by firing an un-awaited call at a slow tool and then spinning hot while the host thinks it is waiting. Measured busy time cannot be gamed: a hot loop accrues it whether or not a dispatch is in flight, and a program genuinely awaiting a slow tool accrues none, so a long-running `bash` sub-call still does not kill an innocent run. The wall ceiling (`maxWallMs`) never pauses for anything and backstops what busy-time cannot see (a program awaiting a promise nobody will resolve). Budget expiry, `signal` abort, and run completion all funnel into `worker.terminate()`, which ends hot synchronous loops too (measured; this was `node:vm`'s unfixable gap); the failure reports which budget fired. Heap overflow surfaces as the worker's OOM exit → `error.kind: 'worker-exit'`. Log and value sizes are capped by config, truncation marked in-band. All caps are validated config fields with defaults (`computeMs: 60_000`, `maxWallMs: 600_000`, `maxLogBytes: 65_536`, `maxValueBytes: 32_768`, `maxOldGenerationSizeMb: 512`), changeable from `cordis.yml`.
6. **Dispose to quiescence**: the service's own disposal terminates in-flight workers and *awaits* their exits before resolving, per [defensive patterns](../../../defensive-patterns.md).
### Trust posture
The worker runtime is **containment, not a security boundary**, and the RFC says so without ceremony. Model code in the worker can reach Node globals — `fetch`, `process` (with an empty env), dynamic `import()` of built-ins — so a deliberately adversarial program has ambient authority comparable to what the harness's own `bash` tool already grants every model turn: `dsh-bash-local` runs arbitrary model-written commands with the host filesystem, network, and a scrubbed-but-populated environment. One asymmetry runs the other way and is stated plainly: `worker.terminate()` ends the thread, not OS processes a program may have spawned via `node:child_process` — weaker than `bash-local`'s process-group kill for direct children (equivalent for double-forked daemons, which survive both); the wall-clock ceiling bounds the worker itself, and orphan cleanup is the same deployment-level concern it already is for bash. Code Mode is gated where bash is gated — `tools/pre-execute`, where permission/sandbox plugins veto or approve the program before it runs — and adds containment bash does not have: empty env, heap caps, hard termination of the program itself, a separate isolate. The earlier draft's two-flag unsafe ceremony (`{ unsafe: true }` constructor + `allowUnsafeRuntime`) existed for a `node:vm` stub with *no* containment and is dropped with it; demanding scarier flags for the better-contained executor than for bash would be posture theater. A deployment that needs a hard boundary (untrusted multi-tenant input) needs it for bash too; that is a future `isolation: 'container'` backend, and the `isolation` descriptor exists so such a deployment can tell backends apart.
### What the model sees
The `tools:sdk` section carries the `.d.ts` plus fixed instructions: the program is the body of an async TypeScript function (erasable syntax only — no `enum`/namespaces; type annotations are advisory); call tools as `await tools.name(args)` (quoted access for exotic names); a failed tool call **rejects** with an `Error` carrying the tool's error text — catch it to handle and continue; calls run **sequentially** even under `Promise.all`; emit results via `return` and/or `console.log`, and only that curated output returns to the context — intermediate tool results never do. That last line is the payoff the whole design serves: output-side context cost becomes the model's own editorial decision. On the input side the `.d.ts` is not free — for a large tool surface it can rival the native JSON schemas it replaces (and `'both'` pays for the two side by side) — but it is prefix-stable, so provider prefix caching amortizes it; the win is workload-dependent and the RFC claims no more.
## Consequences
The design shipped as four stacked changes — this RFC, the `dsh-code-runtime` interface package, the `dsh-code-runtime-worker` backend, and the `dsh-tools` integration — each gates-green with docs in the same change; review fixes landed on the change that introduced them and merged down.
What exists now:
- **The seam**: `packages/code-runtime/` — `@deepseek-ai/dsh-code-runtime` (abstract `CodeRuntime`, the vocabulary above, `ctx.codeRuntime`) and `@deepseek-ai/dsh-code-runtime-worker` (the worker-thread backend, every cap a validated config field). Rows in the service map, capability-seams graph, config catalog, and cordis catalog.
- **The registry surface**: `ToolRegistry`'s first config (`mode`), the mode-aware wire contribution, the `tools:sdk` section, `jsonSchemaToTs`/`renderToolsSdk` (exported), `run_code` + the dispatch bridge + `CodeRunFailedError`, and the `tool/code-dispatch` log event (declaration-merged into `SessionEventMap`, regenerated into the persistence catalog; `run_code` in the tool catalog).
- **The composed surface**: the `tools` config forwards through `agent-core` and both app packages (`stdio-agent`, `acp-agent`); `demo:code-mode` boots each UI example's `code-mode.cordis.yml` overlay (the worker runtime + `mode: 'code'` over the base tree); the adding-a-tool cookbook states that a registered tool is reachable from programs for free, and the tool-pipeline doc shows sub-dispatches re-entering both waterfalls.
- **Interactions inherited by deployments**: a `toolOrder` naming native tools rejects every assembly under `'code'` (update or drop the order config when switching modes); sub-call `additionalContext` is dropped by the bridge (a plural context channel is deferred until a real hook needs it through Code Mode); sub-dispatch stays serialized until tools can declare concurrency safety — the same metadata the native parallel-dispatch TODO waits on.
## Testing
What the suites pin, per tier:
- **Unit — worker runtime** (real workers, no mocks): output/value capture and log-source attribution; error kinds (exception incl. non-erasable syntax, abort, worker-exit under OOM); the two budgets from both sides (a hot loop behind an un-awaited pending dispatch dies at `computeMs` busy time; a program idling on a slow binding outlives `computeMs` and dies only at `maxWallMs`); binding-bridge hostility (junk/forged port traffic incl. non-object messages and forged `log`/`done` cap bypass attempts, unknown names, duplicate ids, post-settlement replies, `__proto__`/`constructor`/`toString` binding names); structured-clone fallback and cap truncation; `env` emptiness verified from inside a program; dispose-awaits-exit. A real-load-path e2e runs the BUILT package under plain `node` so the worker entry resolves both unbuilt (tsx) and built — the published-artifact guard from [docs/testing.md](../../../testing.md).
- **Unit — registry integration**: the codegen table (DSL subset, quoted names, `unknown` degradation, byte-identical determinism); provider contribution per mode (`'native'` unchanged, `'code'` exactly `[run_code]`, `'both'` all + `run_code`); `toolOrder × mode` rejection; missing-runtime / wrong-language loud failures; serialization non-overlap (a probe tool records enter/exit under `Promise.all`); abort aborting the in-flight sub-dispatch and abandoning queued ones; binding rejection on `isError` and on JSON-unrepresentable arguments; `CodeRunFailedError` → structured `isError` carrying kind + logs; `tool/code-dispatch` payloads (JSON-normalized arguments identical to what dispatched); `deriveMessages()` ignoring the event; sub-call `additionalContext` suppression; HMR safety (disposing the registry removes the tool and the section).
- **e2e (with-key, self-skips)**: a real model under `mode: 'code'` composes two bash calls in one program (`examples/coding-agent/tests/code-mode.e2e.ts`) — every logged `request/header` carries exactly `[run_code]`, the dispatch events land under the parent call, the file the program wrote exists, and the final answer is the curated output.
- **Snapshot (keyless replay)**: goldens for a `run_code` turn under `'code'` and `'both'` (`code-mode-turn`, `both-mode-turn`), each its own header-pinning class — the SDK section text, the collapsed header tool list, the dispatch events, and the result card are committed and replayed.
## Alternatives considered
**An add-on consumer plugin, zero core changes (the previous draft of this RFC).** Rejected on both halves. The wire-collapse half aged out from under it: it targeted the `agent/request` waterfall, which [reconstructable requests](../../implemented/architecture/2026-07-05-reconstructable-requests.md) has since re-typed to call-config-only, and the surviving alternative — transforming the assembly a waterfall listener receives — is strictly worse than contributing the right list in the first place (transformation must undo `toolOrder` canonicalization it cannot see the config for, and its correctness depends on where it sits in a listener chain). The deeper reason is ownership: which tools the model is offered, in which representation, is the registry's single concern — `schemas()` for function calling and the SDK for Code Mode are two projections of one store, and splitting the second projection into a satellite package would preserve a boundary the domain does not have.
**`node:vm` as the reference runtime, hardening deferred (also the previous draft).** Rejected: `node:vm` is not isolation (prototype-chain escapes reach the host realm), cannot interrupt a hot loop, and forced the draft into a two-flag unsafe ceremony plus a mandatory follow-up RFC. The worker thread delivers the missing properties now — separate isolate, empty env, `resourceLimits`, reliable `terminate()` (all verified by probe before this revision) — at bash-equivalent trust, so the reference implementation and the production one are the same package and the ceremony dissolves.
**Result elision / summarization over native tool-calling.** Addresses only the context-bloat half of the problem: trimming old `tool-result`s (now cheap to add as a logged surface replace, per the reconstructable-requests consequences) still pays one model round-trip per call and cannot express loops, branches, or joins. Complementary, not competing; it can layer under Code Mode for residual native calls.
**Parallel native dispatch in the loop.** The other answer to round-trip cost; still valid future work (the open TODO), still blocked on concurrency-safety metadata, and still no composition — it parallelizes calls the model already decided on in one step. Code Mode's serialized-queue decision keeps the two compatible: when the metadata lands, both native parallel dispatch and per-tool binding parallelism unlock together.
**Always-exclusive (Cloudflare-faithful, no mode).** Rejected for this SDK's primary consumer: a coding agent's bread-and-butter single calls (`bash`, `read`, `edit`) are already ideal as native calls, and forcing every edit through a program taxes the common case. The mode config keeps the faithful form (`'code'`) one line away without imposing it.
**Per-tool visibility tiers (this tool native, that tool code-only).** Deferred again, knowingly: it needs per-tool metadata and a presentation split that `'native' | 'code' | 'both'` does not, and every learning it depends on (how models actually split usage under `'both'`) arrives only after this ships.
**Sanitized identifier aliases in the SDK** (`my-tool` → `my_tool`, Cloudflare's approach). Rejected: quoted keys on a `declare const` make every name reachable with zero alias-collision logic; models handle `tools["my-tool"](…)` fine.
**A REPL-style persistent kernel** (state survives across `run_code` calls). Rejected for the MVP: cross-call state would be invisible to the session log, breaking the reconstructability guarantee that every request is a pure function of the log; fresh-per-run keeps it. A kernel-style backend remains expressible behind the seam later, with its own logging story.
## Risks
**The worker is not a hard security boundary.** Deliberate and documented (§Trust posture): posture equals the existing bash tool, containment exceeds it, gating uses the same seams. Deployments needing more need a future `isolation: 'container'` backend — tracked as the seam's designed extension, not a TODO on this design.
**`stripTypeScriptTypes` is marked experimental.** It is the same engine (amaro/swc) behind Node's own native `.ts` execution, exposed as an API across this repo's whole engines range. Mitigations: the runtime's unit suite pins the behaviors relied on (position preservation, erasable-only rejection message shape loosely), the call sits behind one private function, and `amaro`/`sucrase` are drop-in replacements if the API shifts. The erasable-only subset is a model-facing contract line, and the error path is a working feedback loop, not a dead end.
**Prompt cost of the SDK, especially under `'both'`.** The `.d.ts` can rival the native schemas it complements; `'both'` carries two representations. Prefix stability + provider caching amortize per-session cost; the mode is per-deployment; the RFC makes no unconditional-savings claim. Measured guidance (when to prefer which mode) is explicitly post-ship learning.
**Registry scope growth.** `dsh-tools` absorbs codegen, a tool, a bridge, and an event. Contained by module boundaries inside the package (`ts-types.ts`, `code-mode.ts` beside `schema.ts`/`json-schema.ts`/`presentation.ts`) and by the seam: everything substrate-shaped lives behind `ctx.codeRuntime`.
**Structured-clone limits at the binding boundary.** The seam's clone boundary admits values JSON does not (`Date`, `Map`, `BigInt`), and the session log accepts only JSON — left unhandled, a sub-call could execute and then fail at `tool/code-dispatch` append time. Closed by the bridge's JSON-normalization step (§ the dispatch bridge): what does not survive the round-trip rejects that binding call before dispatch, so every executed sub-call is loggable by construction. The seam itself keeps the wider structured-clone contract (it is about the port, and stated so a future binding producer cannot discover it in production); consumers with stricter payload needs enforce them at their own boundary, as the bridge does. Non-text sub-result content is reduced to placeholders — a known MVP limitation, recorded in the SDK instructions.
**Serialized-only sub-dispatch.** `Promise.all` gains no wall-clock parallelism yet, only fewer round-trips; models may over-expect. The instructions state it; lifting it is tied to the same concurrency-safety metadata the native parallel-dispatch TODO needs.
**Budget metering reads the event loop, not a flag.** Busy-time polling (`eventLoopUtilization()`) is coarser than an exact CPU meter — a budget expires up to one poll interval late — and its correctness claim ("a pending dispatch cannot pause it") is load-bearing against a hostile program. Both sides are unit-tested (hot loop with a pending decoy dispatch dies at `computeMs`; idle-on-slow-binding survives to `maxWallMs`), and the poll interval is an internal constant, not config — nothing a deployment could mis-tune into a bypass.

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@@ -8,7 +8,7 @@ Status: implemented
The schema should be small enough to implement in the first `dsh-tool-fs` pass, but stable enough that future local/remote/sandboxed filesystem backends do not require model-facing churn. It should also avoid importing every option from reference systems. Claude Code and OpenCode expose similar core file tools but differ in naming style and extra flags; this RFC chooses the minimal shared surface for the prototype.
## Proposal
## Decision
`@deepseek-ai/dsh-tool-fs` exposes these three model-facing tools in the first filesystem suite:
@@ -78,7 +78,7 @@ Default native projections:
| `write` | create/update operation, target display path, new file version | concise create/update success text |
| `edit` | replacement count, replace-all flag, target display path, new file version | concise edit success text |
The structured outcome should not restate model arguments such as `file_path`, `old_string`, or `content` unless the backend has resolved them into new information such as `displayPath`, `targetKey`, or a new version. Token-conscious truncation is part of the model projection, not the backend's canonical result.
The structured outcome does not restate model arguments such as `file_path`, `old_string`, or `content` unless the backend has resolved them into new information such as `displayPath`, `targetKey`, or a new version. Token-conscious truncation is part of the model projection, not the backend's canonical result.
## Deferred
@@ -91,22 +91,19 @@ The following are deliberately out of scope for the first filesystem schema pass
- Code Mode projection values for filesystem tools.
- A canonical edit diff format.
## Tests
## Testing
`dsh-tool-fs` schema tests should assert:
Schema tests pin the required/optional argument set per tool, empty-`old_string` rejection, the `replace_all` default, the snake_case field names, description prose that states the observation policy, and root-plugin suite registration; integration tests execute all three tools through `ctx.tools.execute()` against the real `dsh-fs-local` provider and verify the model arguments translate into the expected `ctx.fs` calls and `fs/*` dispatches.
- `read` requires `file_path` and accepts optional positive integer `offset` / `limit`.
- `write` requires `file_path` and `content`.
- `edit` requires `file_path`, `old_string`, and `new_string`, accepts optional boolean `replace_all`, rejects empty `old_string`, and defaults `replace_all` to false.
- The registered JSON schemas use the snake_case field names in this RFC.
- The tool descriptions accurately describe that, under the default fs-policy, existing-file `write` and `edit` require a prior observation (any windowed read counts) in the same execution context, while new-file `write` does not.
- The `tool-fs` root plugin registers all three schemas.
## Alternatives considered
Integration tests should execute `read`, `write`, and `edit` through `ctx.tools.execute()` against the real `dsh-fs-local` provider and verify that model arguments are translated into the expected `ctx.fs` calls and `fs/*` dispatches.
- **A Codex-style patch grammar or multi-mode edit API** — rejected: one strict literal replacement mode keeps the model-facing contract simple and lets the backend own exact-match, duplicate-match, line-ending, and stale-version semantics.
- **camelCase argument names (OpenCode's style)** — snake_case aligns with Claude Code and the existing harness tool-schema examples, and naming is public surface once shipped.
- **Model-facing `expected_hash` / `expected_version` / `create_only` parameters** — rejected: stale checks are driven by backend-minted versions and the policy plugin's observed state, never by fragile model-copied tokens.
## Risks
## Consequences
**The first schema is intentionally smaller than Claude Code's.** Dropping PDF pages, multimodal read, rich grep/list flags, and expected hash fields keeps the first implementation focused, but users may ask for those quickly. They should be added as separate RFCs or focused follow-ups rather than overloaded into the initial schema.
**The first schema is intentionally smaller than Claude Code's.** Dropping PDF pages, multimodal read, rich grep/list flags, and expected hash fields keeps the implementation focused, but users may ask for those quickly. They arrive as separate RFCs or focused follow-ups rather than overloads of the initial schema.
**No explicit model-facing stale guard in v1.** The schema does not ask the model to provide an expected hash/version. That is intentional: stale checks come from backend-produced versions and the `dsh-fs-policy` plugin's observed state, not from fragile model-copied tokens. Filesystem safety failures surface through structured `FsError` codes owned by `dsh-fs`, not through model-supplied version fields.

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@@ -4,7 +4,7 @@ Status: implemented
## Problem
The ACP bridge lets each tool own its call rendering via `presentCall`/`presentResult` (see [tool-call UI presentation](../../proposed/feature/2026-06-14-acp-agent-client-protocol.md) and `packages/core/tools`). For `bash` we surface the exact command as the `tool_call` title, the model's `description` as a content text block, `kind: 'execute'`, and the completed output wrapped in a fenced ` ```console ` text block.
The ACP bridge lets each tool own its call rendering via `presentCall`/`presentResult` (see [tool-call UI presentation](../../implemented/feature/2026-06-14-acp-agent-client-protocol.md) and `packages/core/tools`). For `bash` we surface the exact command as the `tool_call` title, the model's `description` as a content text block, `kind: 'execute'`, and the completed output wrapped in a fenced ` ```console ` text block.
That is a correct, capability-free baseline, but not how the reference editors render a *terminal* tool at its best. An editor like Zed has a dedicated terminal tool-call card — a header showing the working directory, the command as the label, the command output rendered as a terminal, and an exit-status pill — but it only builds that card when the `tool_call` carries terminal metadata (below). With a plain text block the output appears as static markdown and there is no cwd header. (Zed also HIDES `rawInput` for `kind: 'execute'`, which is why the command IS the title — both reference adapters do the same. The human-readable description rides as a separate content block above the card; note this is a DELIBERATE divergence — claude-agent-acp DROPS the description in terminal mode and renders only the card — we keep the summary visible alongside.)
@@ -28,7 +28,12 @@ Keep `dsh-bash` agent-side execution; render the terminal card via the `_meta` c
3. **Bridge mapping.** When the client advertised the capability, the bridge maps that presentation to: on `tool_call`, `content:[…, {type:'terminal', terminalId}]` (any tool `content`, e.g. the description, rendered BEFORE the terminal block) + `_meta.terminal_info.{terminal_id,cwd}`; on `tool_call_update`, `_meta.terminal_output.{terminal_id,data}` (the captured output) + `_meta.terminal_exit.{terminal_id, exit_code|signal}` (the parsed exit), with the update's text `content` OMITTED (an ACP `tool_call_update.content` REPLACES the call's content collection, so re-sending the fenced block would clobber the terminal content block). `terminalId` is derived from the harness `callId` (stable, unique per call). When the capability is absent, the bridge sends the description content block on the call and the existing ` ```console ` text content on the update — unchanged.
4. **The exit pill is parsed from the rendered output; no new execution path, no live streaming.** Output is attached at completion (from the agent's own `tool/result`), not streamed token-by-token. The exit-status pill (`_meta.terminal_exit.{exit_code,signal}`) IS emitted: the pure `presentResult(args, result)` seam sees only content blocks, so `dsh-tool-bash` recovers the structured exit by parsing the status markers (`[exit code: N]` / `[killed by signal: …]`) that `renderResult` appended — the parse is the exact inverse of the marker emission, the two co-evolve in one file, and a round-trip test guards the pair. Disposal is unaffected: nothing new to tear down, since the bridge never creates a client-side terminal.
## Risks / trade-offs
## Alternatives considered
- **The ACP client-side terminal sub-protocol (`terminal/create`)** — explicitly rejected: the editor would execute the process, bypassing `dsh-bash`'s env scrub, background-task ownership, and per-session cwd, and forking execution into two backends. Both reference agents reject it the same way (the key finding above); agent-side execution plus the `_meta` convention is the only shape that yields the terminal card while keeping the harness's execution policy.
- **Threading a structured exit through the event schema** — rejected in favor of the marker round-trip: the pure `presentResult(args, result)` seam sees only content blocks, and the parse is the exact inverse of the marker emission, co-evolving in one file under a round-trip test.
## Consequences
- **Zed-convention `_meta` keys.** The terminal card rides on Zed-specific keys (`terminal_info`/`terminal_output`/`terminal_exit`) inside ACP's spec-blessed `_meta` extensibility point, NOT on the ACP terminal sub-protocol. A client that doesn't recognize the keys still gets the text fallback (the capability gate ensures we only emit them when the client opted in via `_meta.terminal_output`), so a non-Zed client is never worse off. If ACP later standardizes agent-executed terminals, migrate to that and drop the convention keys.
- **Capability honesty.** Emit terminal metadata ONLY when the client advertised `_meta.terminal_output`; the text fallback is the contract for everyone else and must never regress. Covered by a no-capability test asserting the ` ```console ` path.
@@ -38,4 +43,4 @@ Keep `dsh-bash` agent-side execution; render the terminal card via the `_meta` c
## Out of scope / non-goals
The text-block baseline stays the no-capability default. Client-side `terminal/create` execution is explicitly rejected (it bypasses `dsh-bash`). Two follow-ups are deliberately NOT built here and would each warrant their own RFC when someone takes them on: **live incremental streaming** (`_meta.terminal_output_delta` as chunks arrive, which needs an incremental-output seam on `dsh-bash`), and **command classification** (parsing a `cat`/`sed` as a `read` card with a file location, a `grep` as a `search`, etc., falling back to the terminal card — display-only, must never change what executes).
The text-block baseline stays the no-capability default. Two follow-ups are deliberately NOT built here and would each warrant their own RFC when someone takes them on: **live incremental streaming** (`_meta.terminal_output_delta` as chunks arrive, which needs an incremental-output seam on `dsh-bash`), and **command classification** (parsing a `cat`/`sed` as a `read` card with a file location, a `grep` as a `search`, etc., falling back to the terminal card — display-only, must never change what executes).

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@@ -1,14 +1,14 @@
# RFC: Compaction as a capability seam (abstract contract + basic backend)
Status: implemented (2026-06-18; retention/seam reform 2026-06-26)
Status: implemented
## Context
## Problem
A long-running agent conversation grows without bound. As the event log accumulates turns, the derived message history eventually approaches the model's context window — the model then truncates mid-response (`max-tokens`) or degrades. **Compaction** is the mitigation: replace a run of older history with a concise summary, keeping recent context intact.
The [session surface](../../implemented/architecture/2026-06-18-session-surface.md) was built as the foundation for exactly this — a linked list over the event log with a `surfaceOp: { op: 'replace', start, end }` operation purpose-built to shadow a range of nodes and insert a replacement, with `sourceEventSeqs` recording provenance so the decision replays deterministically. What remained was the plugin that *decides what to compact and produces the summary*.
Two forces shape the design. First, compaction is **swappable**: token counting can be a char/4 heuristic or a real tokenizer, and summarization can be a model call, a template, or a remote service — these vary independently of *when* and *which range* to compact. Second, a later commit (`ce43c25`) closed `SurfaceEventType` to five event types (`user/message`, `assistant/message`, `tool/result`, `context/message`, `steering/message`); only those may carry `surfaceOp`. A bespoke `compaction/*` event therefore **cannot** itself appear on the surface — the compiler rejects `surfaceOp` on it and the invariants plugin rejects it at runtime.
Two forces shape the design. First, compaction is **swappable**: token counting can be a char/4 heuristic or a real tokenizer, and summarization can be a model call, a template, or a remote service — these vary independently of *when* and *which range* to compact. Second, `SurfaceEventType` is closed to five event types (`user/message`, `assistant/message`, `tool/result`, `context/message`, `steering/message`); only those may carry `surfaceOp`. A bespoke `compaction/*` event therefore **cannot** itself appear on the surface — the compiler rejects `surfaceOp` on it and the invariants plugin rejects it at runtime.
## Decision
@@ -17,7 +17,7 @@ Two forces shape the design. First, compaction is **swappable**: token counting
Per the [capability-seams RFC](../../implemented/architecture/2026-06-13-capability-seams.md), compaction ships as separate packages so the contract, the algorithm, and (later) the consumer surface evolve independently:
1. **Interface** — `@deepseek-ai/dsh-compact`: an abstract `CompactService` owning the `ctx.compact` key, the `CompactionResult` vocabulary, and the `compact/*` session events. It declares `compactIfNeeded()` and `compactRegion()` as **abstract** — the contract states *what* compaction does, not *how*.
2. **Implementation** — `@deepseek-ai/dsh-compact-basic`: a concrete `BasicCompactService` that owns the entire algorithm — token estimation (char/4 + per-block overhead), the tail→head retention walk, summarization via `ctx.llm.stream()`, the surface replacement, the lock, and the `agent/pre-step` auto-compaction listener. A tokenizer-based or template-based backend is a sibling package (or a subclass overriding the two protected estimation/summarization hooks).
2. **Implementation** — `@deepseek-ai/dsh-compact-basic`: a concrete `BasicCompactService` that owns the entire algorithm — token estimation (chars per token — the `charsPerToken` config, default 4 — + per-block overhead), the tail→head retention walk, summarization via `ctx.llm.stream()`, the surface replacement, the lock, and the `agent/pre-step` auto-compaction listener. A tokenizer-based or template-based backend is a sibling package (or a subclass overriding the two protected estimation/summarization hooks).
3. **Consumer** — deferred. A `/compact` tool and slash command will `inject: ['compact']` and call the contract; they are intentionally out of scope here so the seam settles first.
### The contract depends on `dsh-session` and `dsh-llm` — a deliberate deviation
@@ -103,6 +103,13 @@ Two failure paths, both documented:
**Core session repair stays compaction-agnostic — deliberately.** `interruptedTurnClosers` is never taught about `compact/*`. Teaching it would force every future `xxx/start … xxx/end` plugin pair to patch a core module — exactly the coupling the capability-seam architecture exists to avoid. Because the log-only orphan is inert, no special repair is needed: generic turn-repair plus the inertness of an un-landed surface mutation is sufficient.
## Alternatives considered
- **The full algorithm as concrete interface methods** (only estimation/summarization abstract) — the earlier draft; rejected because it recouples the contract to one retention strategy. Both core methods are abstract; the `protected` estimation/summarization hooks are the backend's private factoring, not the contract's.
- **Compaction on the `agent/request` waterfall** — the earlier cut; rejected for the double-derive it forced and for handing the listener context it structurally cannot compact. The dedicated `agent/pre-step` seam makes the layering correct by construction.
- **A separate `compact/error` event** — rejected: `compact/end` keeps an `error?` field, mirroring `tool/result`'s self-contained error — one event tells success from failure without correlating a sibling.
- **Teaching core turn-repair about `compact/*`** — rejected: the log-only orphan is inert, and a core module patched for every future `xxx/start … xxx/end` plugin pair is exactly the coupling the capability-seam architecture exists to avoid.
## Consequences
- **New packages**: `packages/compact/compact` (interface) and a sibling `compact-basic` (backend) under `packages/compact/`, wired into the root tsconfigs. The consumer tier is deferred.

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@@ -2,11 +2,11 @@
Status: implemented
> **Implementation status:** shipped across four PRs. PR1 landed this proposal + the `dsh-subagent` interface, the `dsh-subagent-mock` test backend, and the `dsh-tool-subagent` consumer; PR2 the two in-process backends (`dsh-subagent-spawn`, `dsh-subagent-fork`); PR2.5 the nested-agent snapshot infrastructure (see [Per-session snapshot replay for nested agents](../testing/2026-06-22-subagent-snapshot-replay.md)); PR3 the out-of-process `dsh-subagent-acp` backend (see [ACP subagent backend](2026-06-22-acp-subagent-backend.md)). The design below is amended to describe what actually landed.
> The full seam is shipped: the `dsh-subagent` interface, the `dsh-subagent-mock` test backend, and the `dsh-tool-subagent` consumer; the two in-process backends (`dsh-subagent-spawn`, `dsh-subagent-fork`); the nested-agent snapshot infrastructure ([per-session snapshot replay](../testing/2026-06-22-subagent-snapshot-replay.md)); and the out-of-process `dsh-subagent-acp` backend ([its RFC](2026-06-22-acp-subagent-backend.md)).
## Problem
The harness has a long-deferred seam for **subagents** — an agent delegating work to another agent. The intent was sketched in the `Agent`/`AgentLoop` interfaces ([packages/core/agent/src/types.ts](../../../../packages/core/agent/src/types.ts), [packages/core/agent-loop/src/index.ts](../../../../packages/core/agent-loop/src/index.ts)): a creation option referencing a parent agent (fork = seed the child session with the parent's event log; spawn = fresh session), with the child returned as an `Agent` handle so steering and event subscription work uniformly. This RFC realizes that seam (see the implementation-status banner above for what has landed); the design below is the proposal it was argued from, when no service, vocabulary, or implementation yet existed.
The harness has a long-deferred seam for **subagents** — an agent delegating work to another agent. The intent was sketched in the `Agent`/`AgentLoop` interfaces ([packages/core/agent/src/types.ts](../../../../packages/core/agent/src/types.ts), [packages/core/agent-loop/src/index.ts](../../../../packages/core/agent-loop/src/index.ts)): a creation option referencing a parent agent (fork = seed the child session with the parent's event log; spawn = fresh session), with the child returned as an `Agent` handle so steering and event subscription work uniformly. This RFC realizes that seam; the banner above lists what shipped.
The distinctive requirement — the one that shapes the whole design — is that **multiple subagent implementations must coexist at runtime**. A parent may want a cheap in-process child for a scoped subtask AND an isolated out-of-process child (over ACP) in the same session. The transports we foresee:
@@ -14,11 +14,13 @@ The distinctive requirement — the one that shapes the whole design — is that
- **ACP** — act as an ACP *client* driving another agent process (which can be another instance of ourselves);
- later: **A2A**, the **Codex app-server**, and the **Claude Code Agent SDK** — each the same out-of-process "start a child, prompt it, stream updates, cancel" shape as the ACP backend.
## Why not the bash seam shape
## Alternatives considered
### Why not the bash seam shape
The bash seam ([capability seams](../../implemented/architecture/2026-06-13-capability-seams.md)) registers exactly one `BashExecutor` per context; loading a second throws. That is correct for bash (one machine, one way to run a command) but wrong here: coexistence is the requirement. So the subagent service is a **named-provider registry** — each implementation registers under a unique name and a caller picks one by name — mirroring the **LLM adapter registry** (`LlmService.registerAdapter`), not the single-service bash executor. The seam is still three-package (interface / implementation / consumer); only the "one vs. many implementations" axis differs.
## Proposal
## Decision
### The three-package seam
@@ -27,11 +29,11 @@ A new package group `packages/subagent/`:
| Package | Role |
|---|---|
| `@deepseek-ai/dsh-subagent` | interface: `SubagentService` (`ctx.subagents`), `SubagentProvider`, `SubagentRun`, the request/result/capability vocabulary, the `subagent/*` events |
| `@deepseek-ai/dsh-subagent-spawn` | implementation: a fresh in-process child via `ctx.agents.create` (PR2) |
| `@deepseek-ai/dsh-subagent-fork` | implementation: an in-process child seeded with a snapshot of the parent's log (PR2) |
| `@deepseek-ai/dsh-subagent-acp` | implementation: an ACP client driving a configured child process (PR3) |
| `@deepseek-ai/dsh-subagent-mock` | support: a scripted provider for testing the seam through the real load path (PR1) |
| `@deepseek-ai/dsh-tool-subagent` | consumer: the model-facing `subagent` tool over `ctx.subagents` (PR1) |
| `@deepseek-ai/dsh-subagent-spawn` | implementation: a fresh in-process child via `ctx.agents.create` |
| `@deepseek-ai/dsh-subagent-fork` | implementation: an in-process child seeded with a snapshot of the parent's log |
| `@deepseek-ai/dsh-subagent-acp` | implementation: an ACP client driving a configured child process |
| `@deepseek-ai/dsh-subagent-mock` | support: a scripted provider for testing the seam through the real load path |
| `@deepseek-ai/dsh-tool-subagent` | consumer: the model-facing `subagent` tool over `ctx.subagents` |
### The primitive: `start → SubagentRun`
@@ -44,7 +46,7 @@ A provider exposes `start(request) → SubagentRun`. The run carries a `result`
### Fork vs. fresh are separate backends, not a flag
Rather than a `context: 'fresh' | 'fork'` request field, the distinction is the provider's identity: `dsh-subagent-spawn` (fresh, isolated, own system prompt) and `dsh-subagent-fork` (seeded from the parent's log) are two registered providers. You pick behavior by picking a provider — consistent with the registry being the selection mechanism.
Rather than a `context: 'fresh' | 'fork'` request field, the distinction is the provider's identity: `dsh-subagent-spawn` (fresh, isolated, own system prompt) and `dsh-subagent-fork` (seeded from the parent's log) are two registered providers. You pick behavior by picking a provider — consistent with the registry being the selection mechanism. The fork backend seeds only a **balanced, completed-turn prefix** of the parent log: at tool-execute time the parent's turn is open (it holds the `assistant/message` and the dangling spawn `tool/call` with no `tool/result`), and seeding that raw prefix would give the child an unbalanced turn the [invariants](../../../../packages/support/invariants/src/index.ts) freeze-check rejects.
### Child isolation and the parent log
@@ -58,13 +60,11 @@ The `dsh-tool-subagent` consumer awaits `run.result` and returns the child's fin
`dsh-tool-subagent` binds to exactly one provider name (`Config.provider`); the model sees only `{ description, prompt }`. To expose more than one transport, load the tool plugin more than once, each bound to a different provider and a distinct `toolName` (the tool registry rejects a duplicate name). The *service* holds the multi-provider registry; the *tool* picks one — no provider/type parameter in the schema this cut.
## Plan (three PRs, each converged with Codex separately)
## Testing
1. **PR1 — interface + tool + mock.** This RFC, `dsh-subagent` (service, registry, vocabulary, `subagent/*` events), `dsh-subagent-mock` (scripted provider), `dsh-tool-subagent`. Wire the new `packages/subagent/` group into the tsconfigs, the build references, the package hierarchy docs, and the module graph. Tests: registry HMR-safety, duplicate-name rejection, start-time capability rejection, and at least one test driving the tool through the **real cordis Loader / export path** (a hand-built `ctx.plugin` mount bypasses `unwrapExports` and cannot catch a broken export shape — see [postmortem 0001](../../../postmortem/0001-acp-default-export-drops-inject.md)).
2. **PR2 — in-process backends.** `dsh-subagent-spawn` and `dsh-subagent-fork` over `ctx.agents.create` + `AgentHandle.dispose`. The fork backend must seed only a **balanced, completed-turn prefix** of the parent log: at tool-execute time the parent's turn is open (it holds the `assistant/message` and the dangling spawn `tool/call` with no `tool/result`), and seeding that raw prefix gives the child an unbalanced turn the [invariants](../../../../packages/support/invariants/src/index.ts) freeze-check rejects. Depth tracking (parent depth + 1, refused past `maxDepth`) and its exact storage are settled in PR2.
3. **PR3 — ACP backend.** `dsh-subagent-acp` as an ACP client over a configured spawn command (stdio); point it at our own `acp-agent` example to "talk to our own process". Minimal client stub: advertise no optional client capabilities, auto-resolve `session/request_permission` via a configured default, consume `session/update` without surfacing it this cut. Decide the `@agentclientprotocol/sdk` version (recommended: bump to 0.28.x for the fluent client API; the bump is shared with the existing `dsh-acp` bridge, so re-run its snapshot + e2e).
The seam is tested through the real cordis Loader / export path, not a hand-built `ctx.plugin` mount (which bypasses `unwrapExports` and cannot catch a broken export shape — [postmortem 0001](../../../postmortem/0001-acp-default-export-drops-inject.md)); the registry pins HMR-safety, duplicate-name rejection, and start-time capability rejection; the nested-agent snapshot scenarios replay keyless in the default gate ([per-session snapshot replay](../testing/2026-06-22-subagent-snapshot-replay.md)); in-process backends carry real-loop unit tests plus a with-key e2e.
## Risks and deferrals
## Consequences
- **Recursion.** Without a guard, an in-process child inherits the spawn tool and can spawn unboundedly. Depth-limit is an optional capability (the in-process backends enforce it; ACP advertises it off and rejects a `maxDepth` request); tool-filtering is likewise optional. Tool-filtering, when implemented, needs a `tools/pre-execute` deny in the child context — schema filtering alone is insufficient because a model can hallucinate a denied tool name.
- **Blocking the parent turn.** Synchronous collect holds the parent's `runStep` open for the child's full duration. This is acceptable for the first cut; **background / poll / spill semantics are deferred to a future redesign that unifies long-running-tool handling across subagents AND bash** (a sub-agent and a long `bash` background task pose the same "the model started something slow, how does it collect later" problem, and should share one mechanism rather than each inventing its own).

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@@ -12,7 +12,7 @@ The subagent seam ([the seam RFC](2026-06-21-subagent-capability-seam.md)) was b
### Fresh process per run
Each `start` spawns a new child, runs exactly one ACP session (`initialize` → `newSession` → `prompt`), and `dispose` kills the subprocess and awaits its exit. This is the simplest lifecycle and mirrors the in-process one-child-per-run shape. Persistent-process pooling (reuse a warm child across runs) is a performance optimization deferred to future work — it adds session-lifecycle and crash-recovery complexity the first cut does not need.
Each `start` spawns a new child, runs exactly one ACP session (`initialize` → `newSession` → `prompt`), and `dispose` kills the subprocess and awaits its exit. This is the simplest lifecycle and mirrors the in-process one-child-per-run shape.
### Minimal client stub
@@ -26,10 +26,6 @@ The provider's `capabilities` are all `false`. An out-of-process child cannot ho
ACP `StopReason` → harness `SubagentStopReason`: `end_turn`→`completed`, `max_tokens`→`max-tokens`, `refusal`→`refusal`, `cancelled`→`aborted`, `max_turn_requests`→`error` (no clean equivalent — the task did not finish), unknown→`error`. A spawn/transport/RPC failure resolves `error` (or `aborted` if a cancel was requested); `result` never rejects on a child-level failure, per the seam contract.
### SDK version: stayed on 0.25.1
The plan proposed bumping `@agentclientprotocol/sdk` 0.25.1 → 0.28.x for the new fluent `acp.client()` / `ActiveSession.nextUpdate()` API. Validating that against the code (the AGENTS.md "RFC is a proposal, not golden truth" discipline) reversed the decision: the backend only needs `ClientSideConnection` + `ndJsonStream` + `PROTOCOL_VERSION` + the `Client`/`Agent`/`StopReason` types, **all present and non-deprecated in 0.25.1**. The fluent API and `unstable_forkSession` that motivated the bump are never used here, so the "cleaner client code" benefit did not materialize. Worse, 0.28.x **deprecates both** `ClientSideConnection` AND `AgentSideConnection` (it wants all callers on the fluent builders), which turns the `no-deprecated` lint red across the entire existing ACP layer — 33 usages including the server bridge this PR has no business rewriting. That cross-cutting connection-API migration is its own PR, not baggage for "add an ACP subagent backend". So the bump was reverted and the backend is written against 0.25.1 (the plan's own fallback clause: "if the bump proves disruptive, fall back to `ClientSideConnection` (0.25.1), which is sufficient"). Migrating the whole ACP layer to the fluent API on a later 0.28.x bump is a worthwhile standalone follow-up.
### Security: scrubbed child environment
The child is a separate process, so it inherits an environment. Credential-shaped ambient vars (`/KEY|SECRET|TOKEN/i`) are NOT forwarded by default — the parent harness's own secrets must not leak into a spawned process implicitly (the same policy the bash executor applies). The child's OWN credentials (it needs a model key) are supplied EXPLICITLY via `config.env`, layered AFTER the scrub, so an intended `DEEPSEEK_API_KEY` survives while an incidental `AWS_SECRET_ACCESS_KEY` does not. Child stderr is inherited to the parent's stderr (diagnostics surface naturally); a spawn-level `error` event (e.g. ENOENT for a bad command) is captured and raced against the ACP drive, so a bad command settles `error` instead of crashing the parent with an unhandled error.
@@ -40,7 +36,21 @@ Designed at every tier the backend touches, per the root AGENTS.md rule that a n
- **Keyless unit/integration** (`subagent-acp.spec.ts`): spawns a scripted mock ACP server subprocess (`tests/mock-acp-server.ts`) and drives it through the real backend over real ACP stdio. Covers: the prompt round-trip + output accumulation; every StopReason mapping; cancellation via `run.cancel()` and via the request signal; the already-aborted-before-start case; the cancel-races-ahead-of-newSession case; a torn-pipe-after-cancel (child crashes on cancel) settling `aborted`; permission auto-answer under both policies (including the allow-policy-no-allow-option fallback); a non-message update consumed but not accumulated; a nonexistent-command spawn failure settling `error`; HMR provider cleanup; and the namespace export shape. 100% per-file coverage.
- **With-key e2e** (`subagent-acp.e2e.ts`): the harness drives ITSELF — the backend spawns the real `acp-agent` example process and a real model in that child answers a prompt (PONG) and does real file work (writes `proof.txt`, verified on disk). Self-skips without `DEEPSEEK_API_KEY`. This is the "talk to our own process" smoke and the out-of-process analogue of the in-process spawn e2e.
- **Snapshot**: deferred as `TODO(acp-subagent-replay)`. An ACP child is a distinct replay shape — each child is its own PROCESS with its own single-agent replay (booted under `DSH_SNAPSHOT=replay` with its own sessions-root + fixture), unlike the in-process per-session keying that [PR2.5](../testing/2026-06-22-subagent-snapshot-replay.md) added. The keyless mock-server tests give deterministic coverage of the backend in the meantime; the snapshot follow-up would record the parent driving a real-but-replayed ACP child.
- **Snapshot**: deferred as `TODO(acp-subagent-replay)`. An ACP child is a distinct replay shape — each child is its own PROCESS with its own single-agent replay (booted under `DSH_SNAPSHOT=replay` with its own sessions-root + fixture), unlike the in-process per-session keying that [the per-session replay RFC](../testing/2026-06-22-subagent-snapshot-replay.md) added. The keyless mock-server tests give deterministic coverage of the backend in the meantime; the snapshot follow-up would record the parent driving a real-but-replayed ACP child.
## Alternatives considered
### Why not the 0.28.x SDK bump?
The plan proposed bumping `@agentclientprotocol/sdk` 0.25.1 → 0.28.x for the new fluent `acp.client()` / `ActiveSession.nextUpdate()` API. Validating that against the code (the AGENTS.md "RFC is a proposal, not golden truth" discipline) reversed the decision: the backend only needs `ClientSideConnection` + `ndJsonStream` + `PROTOCOL_VERSION` + the `Client`/`Agent`/`StopReason` types, **all present and non-deprecated in 0.25.1**. The fluent API and `unstable_forkSession` that motivated the bump are never used here, so the "cleaner client code" benefit did not materialize. Worse, 0.28.x **deprecates both** `ClientSideConnection` AND `AgentSideConnection` (it wants all callers on the fluent builders), which turns the `no-deprecated` lint red across the entire existing ACP layer — 33 usages including the server bridge this backend has no business rewriting. That cross-cutting connection-API migration is its own change, not baggage for "add an ACP subagent backend". So the bump was reverted and the backend is written against 0.25.1 (the plan's own fallback clause: "if the bump proves disruptive, fall back to `ClientSideConnection` (0.25.1), which is sufficient"). Migrating the whole ACP layer to the fluent API on a later 0.28.x bump is a worthwhile standalone follow-up.
### Why not a persistent child process?
Persistent-process pooling (reuse a warm child across runs) is a performance optimization deferred to future work — it adds session-lifecycle and crash-recovery complexity the first cut does not need; each `start` spawning a fresh child mirrors the in-process one-child-per-run shape.
## Consequences
Every run pays a fresh subprocess (spawn + `initialize` + `newSession`). The parent surfaces only the child's final answer: `session/update` thoughts and tool-call cards are consumed and dropped, and permission prompts never reach a human — the configured policy answers them. The child's environment is credential-scrubbed by default, so its own model key is supplied explicitly via `config.env`.
## Future providers

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@@ -0,0 +1,49 @@
# RFC: Ask-user question capability
Status: implemented
## Problem
The agent sometimes cannot proceed safely from model inference alone: it needs the human to choose a path, confirm a risky/default action, or provide missing information. Before this change, the only way to get that answer was for the model to ask in assistant text and then stop, which broke the normal tool-call loop: the agent had no structured way to pause, no option metadata for UIs, no abort/error taxonomy, and no way for non-stdio front doors to present the question consistently.
This is a user-facing capability, but it also crosses package boundaries. A model-facing tool needs a provider-neutral request vocabulary; each UI surface needs to decide how to show and collect the answer; the agent loop should remain unchanged because a tool call already has the right async shape.
## Decision
Introduce `dsh-user-interaction` as the provider-neutral interface package for `ctx.userInteraction`, colocated with the model-facing consumer `dsh-tool-ask-user` under `packages/ui`. The grouping is intentional: asking a human is a UI-backed product affordance, not part of the providerless core spine. The seam still owns the stable request/answer/error vocabulary, while UI product surfaces provide the concrete provider that collects the answer. The tool registers `ask_user_question`, forwards `{ questions, agent, signal }`, and returns the provider-computed structured answers as the tool result.
The model-facing request vocabulary is deliberately aligned with the product-research schema: `ask_user_question({ questions: [{ id, question, header?, options?: [{ label, description? }], multi_select? }] })`. `id` is supplied per question and echoed in the result so a batch can be routed without relying on question text. `label` is both user-facing display text and the selected value returned to the model; there is no separate `value`, no `recommended`, no `allow_custom`, and no `desc` alias.
Providers return `{ answers: [{ id, selected, custom? }] }`. `selected` is always an array of selected option labels, so single-select and `multi_select` answers share one result shape. `custom` carries a free-text "Other" answer; optionless questions collect `custom` directly. When `custom` is present, it overrides any selected choices and `selected` is empty.
`UserInteractionError` extends `HarnessError`, so failures such as `NO_PROVIDER`, `ASK_ABORTED`, ACP cancellation, or missing session routing survive `ctx.tools.execute()` as machine-routable `{ name, code }` tool errors. This matches the structured-error taxonomy and lets the model or a wrapping plugin distinguish "user cancelled" from a generic thrown exception.
## UI mappings
`dsh-stdio-agent`'s in-package readline module renders each question, shows each option's `description` on the next line, supports comma/space-separated numeric choices for `multi_select`, accepts free-form custom answers, and rejects pending questions on abort, provider disposal, or stdin EOF. A batched request is asked in order and resolved as one answer object. The stdio provider serializes simultaneous requests with an internal queue so only one prompt owns stdin at a time.
`dsh-acp` provides the same seam for ACP sessions. It routes an ask request from the calling `Agent` through the bridge's `agent→sessionId` reverse map and calls ACP `unstable_createElicitation` with a session-scoped form for each question. Single-select options become a `choice` string enum; `multi_select` options become a `choice` array enum; optionless questions use a required `custom` text field. If the client returns both `choice` and non-empty `custom`, the custom answer wins. ACP `decline`/`cancel`, a missing answer, a missing session, and a client without elicitation support all become structured `UserInteractionError`s.
The ACP mapping deliberately uses elicitation, not `session/request_permission`. `request_permission` is still reserved for the separate permission gate: it is a yes/no-or-policy authorization protocol around tool execution. `ask_user_question` is a general information-gathering tool with optional free-form answers, so ACP form elicitation is the closer protocol fit. The bridge's session routing is shared with the future permission gate, but the user intent is different.
## Alternatives considered
**Assistant text followed by a stopped turn.** The model could ask the user in plain assistant text and then stop. That loses the structured option metadata, gives UIs no provider-neutral way to render a choice, and forces the next human answer to arrive as a new user prompt rather than as the result of the operation that needed the answer.
**Core-owned ask-user packages.** The first implementation split the seam and the model-facing tool across `packages/core` and `packages/ui`, but both names describe one UI-backed human-interaction affordance. The seam remains provider-neutral, but it is not providerless core infrastructure like sessions, tools, or the agent registry. Keeping `dsh-user-interaction` and `dsh-tool-ask-user` together under `packages/ui` makes the package map match the product boundary: apps and bridges provide the human-answer provider, and the stdio app opts into the model-facing tool.
**ACP `session/request_permission`.** Permission requests are authorization around tool execution; `ask_user_question` is information gathering with optional free-form answers. Using permission for general questions would collapse two different product concepts and make the future permission gate harder to reason about.
**A loop-level pause primitive.** The agent loop already knows how to await a tool call and resume from a tool result. Adding a new loop special case would duplicate that async shape and make every loop implementation learn about a UI concern.
## Consequences
ACP elicitation is currently marked unstable in the SDK. The fallback is still structured: if a client does not implement it, the tool returns `ASK_FAILED` rather than hanging. A later ACP stabilization may rename or reshape the method; that migration should stay inside `dsh-acp` because the core `ctx.userInteraction` vocabulary is provider-neutral.
The feature gives the model a powerful pause primitive, so prompt guidance matters. The tool description tells the model to ask concise questions and use options when possible. Product policy can later wrap `tools/execute` to restrict when the tool is allowed, but the loop should not special-case it.
`dsh-user-interaction` and `dsh-tool-ask-user` both live in `packages/ui` because they form one product-facing human-interaction capability. `agent-core` does not load either the tool or a provider. `stdio-agent` opts into the seam, its readline provider, and the model-facing tool. `acp-agent` keeps only the `userInteraction` seam/provider by default: ACP elicitation support is still client-dependent, so an ACP leaf must opt into the model-facing tool deliberately once its client can complete elicitation requests.
## Testing
Unit coverage pins provider registration/disposal, duplicate-provider rejection, abort-before-provider, empty-question rejection, structured tool errors through `ctx.tools.execute()`, batched answers, multi-select answers, custom answers, and the model schema including the removal of `value`, `recommended`, `allow_custom`, and `desc`. `dsh-stdio-agent` tests cover option descriptions, queued requests, EOF/abort cleanup, optionless free-form input, invalid option reprompts, duplicate multi-select numbers, and batched question flows. ACP bridge tests drive a real in-memory ACP connection with the real `ask_user_question` tool and verify selected-option, custom-overrides-choice, multi-select, and optionless free-form elicitation paths continue the agent loop.

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@@ -51,8 +51,12 @@ Four tiers, designed up front:
- **`session/load` replay** — a persisted `todo/write` re-emits the `plan` update when a fresh ACP bridge loads the session.
- **With-key e2e + snapshot** — a real prompt induces a `todo_write`; the snapshot golden gains the `plan` notification and the log event.
## Alternatives rejected
## Alternatives considered
- **In-memory `ctx.todos` service** — would reinvent durability, replay, and `session/load` reconstruction the log gives for free.
- **Per-item delta protocol** — only needed for a shared multi-owner list, which is out of scope; whole-list replace is simpler and matches the references.
- **Tool in `core/`** — `todo_write` is an extension tool registering on `ctx.tools`, not part of the spine; it lives in its own `packages/todo/` group like other tool families.
## Consequences
The todo list is durable, replayable session state: a persisted `todo/write` re-emits the editor's `plan` update on `session/load`, and the log — not plugin memory — is the single source of truth. Whole-list replace means one tool call per update with last-write-wins; there is no delta protocol to reconcile. The event stays off the surface, so a todo update never perturbs the derived model history — the model sees only its own tool call and result.

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@@ -1,10 +1,8 @@
# RFC: dsh-hooks-claude + dsh-hooks-codex — the Claude Code / Codex hook bridges
Status: implemented (accepted 2026-06-30)
Status: implemented
<!-- XXX: legacy ADR/RFC body format, not yet normalized to a unified RFC template. -->
## Context
## Problem
The harness's extension surface is its typed interception seams ([the interception-seams RFC](2026-06-30-interception-seams.md)): a "native hook" is just an ordinary cordis plugin subscribing to `agent/session-start`, `agent/prompt-submit`, `tools/pre-execute`, `tools/post-execute`, `agent/turn-continuation`, `subagent/start`, `subagent/end`. But users arrive with **existing** Claude Code (CC) and Codex hook configs — a `hooks.json` (or a settings file's `hooks` key) full of shell-command hooks — and want those to run unmodified. This RFC introduces the two **bridge plugins** that translate that external shell-hook protocol onto the typed seams, built on the shared wire-protocol library ([the hook-protocol-lib RFC](2026-06-30-hook-protocol-lib.md)).
@@ -55,14 +53,14 @@ Two different cwds, kept distinct on purpose. The hooks **themselves** run in th
- **Tool-input rewrite.** A CC/Codex `updatedInput` is logged + warned, not honored — input rewrite is a deferred consistency-design problem ([the pre-tool-input-rewrite RFC](../../proposed/feature/2026-06-30-pre-tool-input-rewrite.md)), because the pre-execution args are read by `tool/call` audit + `assistant/message` history + ACP/tool-bash presentation, so an honest rewrite is a design unit, not a field.
- **Stop loop-guard** (`TODO(stop-loop-guard)`). CC/Codex break an infinite force-continue with `stop_hook_active` (true once a Stop hook fired this run) plus a max-consecutive cap; both are deferred. Today `stop_hook_active` is always `false`, so a Stop hook that unconditionally blocks would force-continue every step — a hook author must self-limit until the guard lands.
- **Permission `ask`** degrades to `deny` at the `tools/pre-execute` seam (`FIXME(permissions)` in the interception-seams RFC) — there is no interactive permission prompt yet.
- **Permission `ask`** — deferred at landing, since serviced: the [approval seam](2026-07-06-approval-seam.md) resolves `ask` through `ctx.approval` (ACP prompts over `session/request_permission`), degrading to `deny` only where no approval service is composed.
- **Hook `continue:false` (hard halt).** A hook can ask to halt the whole run (CC/Codex `continue:false`); the shared merge folds it into `MergedHookOutcome.stop`/`stopReason`, but no bridge acts on it (`TODO(hook-continue-false)`) — the interception seams have no "hard-halt the agent" primitive yet (a Decision blocks/steers a single point, not the run). Deferred with the loop-guard work; the halt request is recorded in the `hook/result` log, and the hook keeps its per-point effect (decision/context) meanwhile.
- **Config discovery.** The path is explicit in `cordis.yml` and process-level (see above); the full multi-layer CC/Codex precedence walk, per-session project-local discovery, and the trust/hash model are not reimplemented (`TODO(per-session-hook-config)`).
- **Session-start / subagent-start context is best-effort, not gated (`TODO(session-start-gating)`).** `agent/session-start` is a synchronous emit and the bridge runs its hook on a detached `.then`, so the injected `additionalContext` is not guaranteed to land before the first turn reaches the model — a slow hook can miss the first request (the context then arrives as a later injection). `subagent/start` is sharper: an in-process provider may have already queued the child's prompt before the listener runs, and a short-lived child can finish before the detached inject fires. Making startup context a gated/awaited primitive is a loop-level change deferred to the interception seams; today the contract is "injected as soon as the hook resolves", not "before the first request". The bridge tests do NOT wait on the injection where they assert the guaranteed-timing behavior, so they document the real (best-effort) timing rather than masking it.
### Multiple hooks on one point run serially, not concurrently
## Alternatives considered
The reference engines run a point's matched hooks concurrently and fold the results. These bridges run them **serially** (`await` per hook inside the match loop) and fold with the same most-restrictive merge. Serial is deliberate: it keeps each hook's `hook/invoked`/`hook/result` pair adjacent and in a deterministic order in the session log, and the fold is order-independent for the decision (`deny > ask > allow`) so the outcome matches. The cost is latency (hook *N* waits for hook *N−1*) and that per-hook timeouts are not overlapped — acceptable for the hook counts real configs use; revisit if a config ever fans out enough for the wall-clock to matter.
**Concurrent per-point hook execution.** The reference engines run a point's matched hooks concurrently and fold the results. These bridges run them **serially** (`await` per hook inside the match loop) and fold with the same most-restrictive merge. Serial is deliberate: it keeps each hook's `hook/invoked`/`hook/result` pair adjacent and in a deterministic order in the session log, and the fold is order-independent for the decision (`deny > ask > allow`) so the outcome matches. The cost is latency (hook *N* waits for hook *N−1*) and that per-hook timeouts are not overlapped — acceptable for the hook counts real configs use; revisit if a config ever fans out enough for the wall-clock to matter.
## Consequences

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@@ -1,10 +1,8 @@
# RFC: dsh-hook-protocol — the shared Claude Code / Codex hook wire-protocol core
Status: implemented (accepted 2026-06-30)
Status: implemented
<!-- XXX: legacy ADR/RFC body format, not yet normalized to a unified RFC template. -->
## Context
## Problem
The hooks subsystem ships two bridge plugins: one that runs a user's existing Claude Code (CC) hooks, one for Codex hooks. Studying the reference implementations (`~/repos/refs/claude-code`, `~/repos/refs/codex`) surfaced a decisive fact: **Codex deliberately reimplements a SUBSET of the CC hook protocol.** Its engine reads the same `hooks.json`, uses the same matcher-group shape, the same exit-code/structured-stdout output contract, and the same command-hook execution model — Codex's source even names the engine after Claude's and comments where it "intentionally diverges." So the two bridges would otherwise duplicate the bulk of the protocol.
@@ -16,16 +14,16 @@ A new `packages/hooks/` group with `hook-protocol` as a pure library. It owns fo
**Shared (here):**
- **Matcher** — `matchesMatcher(pattern, query, mode)`. The ONE axis the dialects differ on is collapsed to the `mode` parameter: `claude` treats a pure `[A-Za-z0-9_|]+` pattern as a literal (pipe = exact-match alternation) and anything else as a regex; `codex` is always an unanchored regex. Match-all on absent/`''`/`'*'`; an invalid regex matches nothing (never throws into the loop).
- **Execution** — `runHook(bash, hook, options, now)`. Runs a command hook through the `ctx.bash` seam rather than a bespoke `spawn`: the executor already provides the scrubbed-but-overridable env, process-group kills, and timeout the protocol needs, and `dsh-bash`'s `stdin`/`env` fields (added in the bash-seam PR for exactly this) are the trusted-plugin surface an in-process bridge is allowed to use. It serializes the bridge-built payload to stdin (trailing newline iff CC), honors the hook's `timeoutSec`, and never throws (an executor rejection becomes a non-blocking-error `HookOutput`).
- **Decode** — `parseHookOutput(exit, stdout, stderr)`, the exit-code + structured-stdout codec, producing a dialect-neutral `HookOutput`. Exit `0` → lenient JSON parse of stdout; exit `2` → blocking error with `stderr` as the reason (surfaced as `decision: 'block'` so no caller needs a separate exit-code branch); other → non-blocking error. Parses the full CC superset (`continue`/`stopReason`/`suppressOutput`/`decision`/`hookSpecificOutput.{permissionDecision,additionalContext,updatedInput}`/`systemMessage`); the bridge honors only the subset meaningful for its dialect.
- **Execution** — `runHook(bash, hook, options)`. Runs a command hook through the `ctx.bash` seam rather than a bespoke `spawn`: the executor already provides the scrubbed-but-overridable env, process-group kills, and timeout the protocol needs, and `dsh-bash`'s `stdin`/`env` fields (added for exactly this) are the trusted-plugin surface an in-process bridge is allowed to use. It serializes the bridge-built payload to stdin (trailing newline iff CC), honors the hook's `timeoutSec` (else `DEFAULT_HOOK_TIMEOUT_MS`, the 10-minute reference default both dialects share), and never throws (an executor rejection becomes a non-blocking-error `HookOutput`).
- **Decode** — `parseHookOutput(exit, stdout, stderr)`, the exit-code + structured-stdout codec, producing a dialect-neutral `HookOutput`. Exit `0` → lenient JSON parse of stdout; exit `2` → blocking error with `stderr` as the reason (surfaced as `decision: 'block'` so no caller needs a separate exit-code branch); other → non-blocking error. Parses the CC structured-stdout fields that have a consumer on some path (`continue`/`stopReason`/`decision`/`hookSpecificOutput.{permissionDecision,additionalContext,updatedInput}`/`systemMessage`); the bridge honors only the subset meaningful for its dialect. Fields with no consumer on any path are not parsed at all (CC's `suppressOutput` — hook stdout never enters a transcript here, so there is nothing to suppress; see [the tighten-hook-protocol-contract RFC](../simplification/2026-07-04-tighten-hook-protocol-contract.md)).
- **Merge** — `mergeHookOutputs(outputs)`, folding multiple matched hooks into one most-restrictive `MergedHookOutcome`: permission precedence **deny > ask > allow**, halt sticky on the first `continue:false`, block reasons joined `\n\n`, context/system-messages accumulated in order.
- **`hook/*` session events** — `hook/invoked` / `hook/result`, declaration-merged into `SessionEventMap` (log-only, like `compact/*` — NOT `SurfaceEventType`s), with `appendHookInvoked`/`appendHookResult` helpers so the invoked/result pairing and turn-enclosure stay consistent across bridges.
- **`hook/*` session events** — `hook/invoked` / `hook/result`, declaration-merged into `SessionEventMap` (log-only, like `compact/*` — NOT `SurfaceEventType`s), with `appendHookInvoked`/`appendHookResult` helpers so the invoked/result pairing and turn-enclosure stay consistent across bridges. `appendHookResult` also owns the durable record's semantics — the decision string (the hook's parsed decision, else `'stop'` on `continue:false`, else `'pass'`) and the 500-character `stderrSummary` truncation derive from the `HookOutput` here, not per-bridge.
**Per-dialect (the bridge plugins):** building each event's stdin payload (CC's base+per-event field sets vs Codex's snake_case with `turn_id`/`model` extras), the dialect's env + `${CLAUDE_PLUGIN_ROOT}` substitution (CC) vs none (Codex), and mapping the neutral `HookOutput`/`MergedHookOutcome` onto the harness's seam-specific typed Decisions (`PreToolDecision`, `PromptDecision`, `ContinuationDecision`, `PostToolDecision`).
### Why "shared core + per-dialect adapters", not "one parameterized engine"
## Alternatives considered
A single engine parameterized by a full `dialect` descriptor was considered and rejected. The payload construction and decision mapping are where the dialects genuinely diverge (different field names, different supported outputs, CC's env/substitution); folding those into a data-driven descriptor would make the *bridge* logic indirect — a reader of `dsh-hooks-claude` would have to chase a descriptor to see what payload it sends. Keeping the truly-identical primitives shared (matcher, codec, runner, merge, events) and letting each bridge write its own straightforward payload+mapping keeps each bridge readable standalone, at the cost of a little duplication in the payload shape. The primitives are the part where duplication would actually be dangerous (a divergent matcher or exit-code rule is a correctness bug); the payload is the part where explicitness beats sharing.
**One parameterized engine.** A single engine parameterized by a full `dialect` descriptor was considered and rejected. The payload construction and decision mapping are where the dialects genuinely diverge (different field names, different supported outputs, CC's env/substitution); folding those into a data-driven descriptor would make the *bridge* logic indirect — a reader of `dsh-hooks-claude` would have to chase a descriptor to see what payload it sends. Keeping the truly-identical primitives shared (matcher, codec, runner, merge, events) and letting each bridge write its own straightforward payload+mapping keeps each bridge readable standalone, at the cost of a little duplication in the payload shape. The primitives are the part where duplication would actually be dangerous (a divergent matcher or exit-code rule is a correctness bug); the payload is the part where explicitness beats sharing.
## Consequences

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@@ -1,10 +1,8 @@
# RFC: Interception seams — the typed-Decision surface a hook programs against
Status: implemented (accepted 2026-06-30)
Status: implemented
<!-- XXX: legacy ADR/RFC body format, not yet normalized to a unified RFC template. -->
## Context
## Problem
The harness needs a hooks subsystem: users extend or gate the agent at lifecycle points the way Claude Code (CC) and Codex do. The key reframe driving this design is that **"native hooks" are not a package** — a native hook is just an ordinary Cordis plugin subscribing to the canonical lifecycle events. So the real product is a *powerful, well-typed canonical event surface*; the CC/Codex bridges (the `dsh-hooks-claude` / `dsh-hooks-codex` packages) are merely translators that map an external shell-hook protocol onto that same surface. Anything a bridge can do, a plain plugin can do directly — more powerfully (no serialization boundary, full `ctx`, typed returns).
@@ -38,7 +36,12 @@ Add/​reshape the interception seams so every one returns a small, seam-specifi
### What this PR does NOT do
It does **not** declare `hook/*` SessionEvents (the durable hook-invocation log) — those belong to the `dsh-hook-protocol` library, because a native plugin can already use the typed Decisions without a durable hook log. A worked native-plugin example/test in this PR (`packages/core/agent-loop/tests/interception.spec.ts`) proves all the seams compose end-to-end through the REAL loop with NO `hook/*` involved — the concrete proof that "native hooks are just a plugin". Compaction (`PreCompact`/`PostCompact`), the Notification hook, Codex `PermissionRequest`, the permission/`ask` system, and the Stop loop-guard remain deferred (`FIXME(permissions)` marks the `ask`→deny degrade).
It does **not** declare `hook/*` SessionEvents (the durable hook-invocation log) — those belong to the `dsh-hook-protocol` library, because a native plugin can already use the typed Decisions without a durable hook log. A worked native-plugin example/test in this PR (`packages/core/agent-loop/tests/interception.spec.ts`) proves all the seams compose end-to-end through the REAL loop with NO `hook/*` involved — the concrete proof that "native hooks are just a plugin". Compaction (`PreCompact`/`PostCompact`), the Notification hook, Codex `PermissionRequest`, and the Stop loop-guard remain deferred; the permission/`ask` system has since landed as the [approval seam](2026-07-06-approval-seam.md), whose `ctx.approval` services the `ask` this PR shipped degraded to deny.
## Alternatives considered
- **Shipping pre-tool INPUT rewrite as part of this seam set** — deferred as the over-reach signal; the section above carries the consistency problem (audit, history, and presentation all read `tool/call.arguments` logged before execution), and [the pre-tool input-rewrite proposal](../../proposed/feature/2026-06-30-pre-tool-input-rewrite.md) owns the design.
- **Declaring the durable `hook/*` SessionEvents alongside the seams** — rejected: a native plugin uses the typed Decisions with no hook log at all (the worked example proves it), so the durable log belongs to [the hook-protocol library](2026-06-30-hook-protocol-lib.md), not the seam surface.
## Consequences

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@@ -0,0 +1,41 @@
# RFC: SessionStore fork API
Status: implemented
## Problem
The event-sourced session log already has the primitive a fork needs: create a new session with a seed event prefix, then derive model history from that seeded log exactly as replay does. That primitive is intentionally low-level: `ctx.sessions.create(id, { seed, meta })` accepts any valid seed, but ordinary live-session branching needs policy around which prefix can be copied, which metadata is stamped on the child, and how errors are classified.
The semantic hazard is the fork boundary. A valid user-visible fork seed must be contiguous and turn-enclosed. Forking inside an active turn would copy an open `turn/start`, possibly an open `step/start`, and possibly dangling tool calls. That violates turn-enclosure and provider-transcript invariants, and it creates a misleading child history that appears to have participated in an unfinished parent turn. The existing [subagent seam](../../implemented/feature/2026-06-21-subagent-capability-seam.md) deliberately solves a different problem: tool-triggered subagent forks usually happen while the parent turn is open, so `dsh-subagent-fork` clips the seed to the parent's last completed-turn prefix. A general session fork should not silently clip; it should either fork the requested boundary or reject it.
## Decision
`dsh-session` owns ordinary live-session forking directly on `ctx.sessions`. There is no separate `dsh-session-fork` package or `ctx.sessionFork` service: the API has no independent backend, event vocabulary, lifecycle, or persistence behavior, and all durable work delegates to the existing session store and persistence backends.
The store exposes one operation:
```ts ignore-check
type SessionForkSource = Session | SessionId
class SessionStore extends Service {
fork(source: SessionForkSource, boundary?: number, childSessionId?: SessionId): Session
}
```
`boundary` is the inclusive source event `seq` to copy through. When omitted, it defaults to the source session's current last event; on an empty source, omitted `boundary` creates an empty child. Fork-specific validation only checks that the requested boundary exists and is a `turn/end`. The selected prefix is then deep-cloned into the child seed. The child inherits the source session's `cwd`, stamps `parentSession` to the source id, and sets `seedLength` to the copied prefix length. When `childSessionId` is omitted, `SessionStore` generates one using its existing id policy.
The boundary rule is structural: an empty selected prefix is forkable, and any non-empty selected prefix must end at `turn/end`, regardless of the turn-end reason (`completed`, `aborted`, `error`, `disposed`, `max-tokens`, `interrupted`, or a future merge-extensible reason). A boundary that is not an existing event seq, is not a safe integer, or does not point at `turn/end` is rejected with a typed `SessionForkError` code. Broader session-log sanity remains in the existing invariant/repair layers: `dsh-invariants` checks turn enclosure and richer event ordering in dev, while persistence repair handles the valid crash-tail case of a final interrupted turn. The API also classifies non-live source ids (`SESSION_NOT_FOUND`), stale `Session` object references whose id is live on a different instance (`SESSION_NOT_LIVE`), duplicate requested child ids (`SESSION_ALREADY_EXISTS`), and invalid boundary values (`INVALID_BOUNDARY`).
## Alternatives considered
**Separate `ctx.sessionFork` service.** This was the first implementation, but review showed it overfit the capability-seam pattern. The code had no swappable backend, no extra event surface, no independent ownership lifecycle, and no durable behavior beyond `ctx.sessions.create({ seed, meta })`. Keeping a separate package would make callers discover and install a second service just to perform policy around a session-store primitive.
**Two functions: `snapshot()` plus `fork()`.** This preserved a reusable seed/metadata computation, but the only supported consumer created a session immediately. It also made the surface feel more abstract than the concrete operation users need. A single `fork()` with an explicit `boundary` keeps the API direct while still supporting previous-point forks.
**Silently clip open turns to the last completed boundary.** That is correct for `dsh-subagent-fork`, where delegation often starts while the parent turn is open and the child should inherit only the completed prefix. It is wrong for ordinary user/session branching because it hides that the requested fork point was not actually a valid boundary and silently drops the parent turn tail.
## Consequences
The public surface stays small and discoverable: live session branching is part of `ctx.sessions`, next to `create({ seed })`, rather than a standalone service or a two-step helper pair. Persistence continues to work through existing `session/created` and `session/flush` behavior: a forked child starts life with seeded events, so existing backends persist that seed once and preserve `parentSession` / `seedLength` in the header.
The v1 scope still excludes ACP `session/fork`, unloaded persisted-session forking, model-facing tools, and subagent refactors. If a future ACP method is added, it should advertise the capability only after it has transcript/snapshot coverage; this RFC adds no editor-facing updates, so no ACP snapshot is required now. Fork-child replay remains covered by the existing [seed-boundary testing RFC](../../implemented/testing/2026-06-22-fork-child-replay-seed-boundary.md), while this API gets focused `dsh-session` unit tests plus JSONL persistence coverage.

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@@ -1,17 +1,8 @@
# RFC: Subagent lifecycle enrichment — lastAssistantMessage (observe-only)
Status: implemented (accepted 2026-06-30)
Status: implemented
<!-- XXX: legacy ADR/RFC body format, not yet normalized to a unified RFC template. -->
<!-- An earlier draft also added an `agentType` subagent-kind label (the harness
analogue of CC's `subagent_type`) to the request + both lifecycle payloads.
It was dropped in review: it is a Claude-Code concept that does not fit our
own seam (nothing here interprets it, and the only consumer was a CC-dialect
bridge). The CC bridge instead feeds Claude Code's own default matcher value
`"general-purpose"` for its SubagentStart/Stop `agent_type` matcher. So this
RFC ships ONE enrichment: `lastAssistantMessage`. -->
## Context
## Problem
The hooks subsystem ([interception seams RFC](2026-06-30-interception-seams.md)) lets a plugin observe and gate the agent at lifecycle points. Claude Code and Codex both expose **SubagentStart / SubagentStop** hooks, and CC's carry the subagent's final message. The harness already emits `subagent/start` and `subagent/end` lifecycle events ([the subagent capability-seam](2026-06-21-subagent-capability-seam.md)), but their payloads were minimal (`provider`, `id`, and on end `stopReason`) — not enough for a hooks bridge to report WHAT a subagent produced without separately reaching for the live run.
@@ -23,6 +14,12 @@ This RFC enriches the end payload. It is deliberately **observe-only**: no contr
Both events stay plain **`emit`s**. `subagent/end` fires from a detached `.then` on `run.result` and awaits no listener, so it is genuinely observe-only by construction — a `subagent/start` listener can still reach the live child via `ctx.agents.get(info.id)` and `inject()` into it; a `subagent/end` listener can only observe (the run has settled). Per-listener containment (already in place) keeps one bad subscriber from stranding a live run or surfacing as an unhandled rejection on the detached settle hook.
## Alternatives considered
**An `agentType` subagent-kind label** (the harness analogue of CC's `subagent_type`) on the request + both lifecycle payloads — an earlier draft shipped it; dropped in review because it is a Claude-Code concept that does not fit our own seam (nothing here interprets it, and the only consumer was a CC-dialect bridge). The CC bridge instead feeds Claude Code's own default matcher value `"general-purpose"` for its SubagentStart/Stop `agent_type` matcher, so this RFC ships ONE enrichment: `lastAssistantMessage`.
**A control-flow `subagent/end`** — deferred; see below.
## Why observe-only, and what is deferred
A control-flow `subagent/end` (an awaited waterfall returning a stop/continue decision, like the other interception seams) would require: reshaping `subagent/end` from emit to waterfall, restructuring `SubagentService.start` to await listeners before settling, and implementing the `resume` capability in the in-process provider so a "continue" can actually re-run the child. That belongs to the background/steering subagent redesign the [capability-seam RFC](2026-06-21-subagent-capability-seam.md) already defers (the same redesign that unifies long-running-tool handling across subagents and bash). This RFC ships the observe-only enrichment a hooks bridge needs today; `FIXME(subagent-continuation)` / `TODO` anchors mark where the control-flow version would land if and when that redesign happens.

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# RFC: Dynamic workflows — a script-driven multi-agent orchestration seam
Status: implemented
## Problem
The harness can delegate ONE task to ONE child (`dsh-tool-subagent`), but work that fans out across many independent pieces — an audit over many files, a migration, multi-angle research, adversarial verification of findings — forces the model to orchestrate turn by turn: every intermediate result lands in the parent context, the plan lives nowhere durable, and coordination costs a model round-trip per step. Claude Code ships this capability as [dynamic workflows](https://code.claude.com/docs/en/workflows): the model writes a JavaScript orchestration script, a runtime executes it, and the script — not the conversation — holds the loop, the branching, and the intermediate results.
## Decision
A workflow capability family at `packages/workflow/` in the bash seam shape (interface / implementation / consumer), plus the structured-output foundation it needs on the subagent seam.
### The script contract (Claude Code-compatible)
A workflow call is two parts: a `meta` JSON parameter (the identity block — `name`, `description`, optional `whenToUse`/`phases`; the field vocabulary matches Claude Code's meta block) and a `script` — a plain-JS body with top-level `await`, ending in `return <json-value>`. Meta is DATA, never code: the engine shape-validates it and evaluates no script text to obtain it (a body still opening with a CC-style `export const meta` statement is rejected with a pointed message). The body sees exactly: `agent(prompt, {label, phase, schema, model})`, `parallel(thunks)`, `pipeline(items, ...stages)` (NO cross-stage barrier; `(prev, item, index)` callbacks), `phase(title)`, `log(message)`, and `args`. CC semantics are preserved where they matter to script authors: a failed child resolves `null` (scripts `.filter(Boolean)`); an ordinary stage throw nulls the ITEM and skips its remaining stages. CC's determinism bans (`Date.now()`/`Math.random()`/argless `new Date()` throwing) are NOT enforced — they exist for CC's journaling/resume, which this cut defers — so a CC-authored BODY runs unchanged (its meta header moves into the parameter) while scripts written here may freely read the clock.
One deliberate strictness DIVERGENCE from CC: hook misuse — unknown or deferred options (`effort`/`isolation`/`agentType`), malformed arguments, schemas outside the supported subset, tripped caps, seam start failures — throws a `WorkflowError` with `fatal: true`, and the combinators RE-THROW fatal errors instead of nulling the item. Without this, a typo'd option dissolves into a `null` indistinguishable from a child failure — the accepted-then-ignored failure mode this repo bans. One addition: the tool's `args` parameter is a JSON OBJECT (a bare list is wrapped as a field) so the wire schema stays honest.
### The seam (dsh-workflow)
`ctx.workflows` is an abstract `WorkflowService` in the bash shape — one engine per context, no named-provider registry (engines are deployment swaps, not co-residents). `start(request)` throws synchronously for a script that cannot begin; a returned `WorkflowRun`'s `result` NEVER rejects (failures resolve as `stopReason: 'error' | 'cancelled'`). The `workflow/*` events are observe-only emits carrying DATA SNAPSHOTS (id + meta; `workflow/end` omits the result value), per-listener contained, mirroring `subagent/start`/`subagent/end` — control stays with the run's holder. Vocabulary details: [core-data-structures/workflow.md](../../../core-data-structures/workflow.md).
### The engine (dsh-workflow-workerthread): one worker thread per run
**Trust premise (governs every engine decision below)**: workflow scripts are MODEL-WRITTEN — the same trust level as the model's existing bash access — so the engine defends against BUGGY scripts, never hostile ones. In scope: `result` never rejects, no unhandled rejections from dropped hook promises, loud rejection of values JSON cannot carry, fatal-vs-null hook discipline, cancellation that always frees the caller. Out of scope, deliberately: adversarial values (throwing/spinning accessors, proxies with hostile traps, prototype forgery, `prepareStackTrace` hijack) AND Node-API escape from the script's context — the vm context shares object machinery with its surrounding realm, so a script can reach the `Function` constructor (`globalThis.constructor.constructor`) and from it `process` and every Node builtin; the absent globals are API surface, not containment, and a worker thread is NOT a security boundary (an escapee holds process-wide privileges — Node's permission model is per-process). Worker-side code MAY run script code while reading script values, and that is accepted: a synchronous spin costs the script its OWN thread (terminated at the post-cancel grace), never the host loop, so containing error VALUES would be cost without a threat model. Genuine sandboxing (isolated-vm, a separate process) remains an engine swap behind the seam, not incremental defenses here.
**Why node:worker_threads**: one run = one worker thread, no pooling — a run is heavyweight (many children), so thread spin-up (~tens of ms) is noise. The script runs in a vm context INSIDE the worker, keeping the script-visible surface exactly the hook contract above (a bare worker realm would leak `setTimeout`/`fetch`/`process` as accidental API), and every `agent()` bridges to `ctx.subagents` by message-port RPC — children are I/O-bound LLM loops and stay on the host loop; the thread isolates the SCRIPT, the only part that can spin. What the thread buys: `start()` never blocks the host (an in-process engine runs the initial synchronous slice inline and cannot kill a spin past the first await — it could only ABANDON such a script, leaving the spin on the host loop), the post-cancel grace ends in a REAL `worker.terminate()`, and the value boundary is serialization by construction. isolated-vm was rejected for actual sandboxing: maintenance mode, `--no-node-snapshot` on EVERY consumer process (including published bins) on Node ≥ 20, node-gyp source-build fallback. Key mechanics (details in the package README): meta shape-validation and a body pre-parse stay HOST-side (preserving the seam's synchronous throws), a ready→go handshake keeps a run cancelled before start from ever executing the body, `cancel()` drives both child-cancel channels host-side (the shared request signal AND each child's explicit `cancel()` — a wedged worker cannot relay its own cancel RPCs), a host-side child registry backs worker-death reaping and `dispose()` quiescence, the wire protocol is enum-keyed payload maps private to the package, and on a termination path `agentsStarted` degrades to the host-observed count. Coverage puts the worker-side session on an in-process `MessageChannel` (real-Worker code is invisible to main-process v8) and proves the built `lib/worker.js` — a second tsdown entry, sanctioned in the workspace-constraints gate by the `"./worker"` subpath export — under plain node in the built-bin smoke gate.
**Meta as data, never evaluated**: the meta block reaches the seam as a plain JSON request field (the tool's schema-validated `meta` parameter) and the engine only shape-validates it, every violation named. This is a host-isolation invariant, not a convenience: evaluating a meta literal host-side — even one contractually "pure", in an empty timed vm context — hands script-controlled getters a host stack with no timeout the moment the result is READ, defeating the exact spin isolation the worker thread buys.
**Value boundary**: values leaving the script (meta, hook options, schemas, the return value) go through `materializeFromRealm` — a plain recursive walk that rejects loud everything JSON cannot carry (exotic prototypes, functions, symbols, cycles, sparse arrays, non-finite numbers, nested `undefined`), copying via `Object.defineProperty` so a `"__proto__"` key becomes a data property, never a prototype mutation; getters are read ordinarily and their RESULT crosses (a throwing read fails loud) — which is also what makes every later postMessage hop total. Values entering the realm (`args`, `agent()` results, hook promises and failures, combinator arrays) are handed over directly as worker-realm values — the script is trusted, so outer prototypes are not a leak; `args` rides the `workerData` structured clone (the caller-isolation copy) and is cloned once more so a script scribbling on it cannot mutate the session's init object. Hook failures are `WorkflowError`s built OUTSIDE the script's context: the combinators recognize fatality by `instanceof` against the engine's own class (unforgeable from the script), and the script-visible consequence — in-script `instanceof Error` is `false` for hook errors; branch on `e.name`/`e.code` — is documented in the engine README. Realm functions (stages, thunks) are called, never materialized. Thrown script values are rendered by a total renderer (stack → message → `String()`, fixed label if rendering throws), so `result` cannot reject. Caps (`maxConcurrentAgents` auto = `min(16, max(1, availableParallelism() - 2))`, `maxTotalAgents` 1000, `maxItemsPerCall` 4096) and timeouts are validated Config, not literals.
### The consumer (dsh-tool-workflow)
A `workflow` tool mirroring `dsh-tool-subagent`'s synchronous shape: start, await, `try/finally` dispose, abort-bridge `exec.signal`, non-`completed` → `isError`. Render intent: a `generic` card titled by the call's `meta.name` parameter (presentation is a pure function of args). The tool description IS the model-facing authoring spec. The usage policy ships with the tool as its own `tool:<toolName>` prompt section (explicit-ask-only guidance — tool guidance lives in tool plugins, never in the deployment persona); the harness has no ultracode-style effort gate.
### The foundation: structured output on the subagent seam
`agent({schema})` needs `SubagentStartRequest.outputSchema` to actually work; it was vocabulary without an implementation (`outputSchema: false` everywhere). Implemented in `dsh-subagent-inprocess` for both in-process backends: a globally registered `structured_output` capture tool whose per-child schema is enforced by a `prepend: true` `system-prompt/assemble` listener doing FINAL-ASSEMBLY enforcement (post-processing `await next()` — cooperative mutation would not survive a downstream listener returning a replacement assembly; the calling instruction rides as a trailing prompt section, since `AgentOptions` carries no per-agent prompt field, and the loop logs the result as the step's `request/header`, keeping the injection reconstructable), a `prepend: true` `agent/turn-continuation` veto after capture (no wasted extra model step) plus a `tools/pre-execute` deny for calls arriving after the capture (terminal within the step, not only at its end), and validation-retry in-turn via `ToolArgsError`. The schema is `structuredClone`d at `start()` (caller mutation cannot drift enforcement). Deliberately NO re-prompt: a child that finishes cleanly without calling the tool settles `error` to the parent. Lifetime is refcounted by backends (plugin lifetime) AND live runs (start → settle). The seam's `outputSchema` type became the raw JSON-Schema SUBSET (`StructuredOutputSchema` in dsh-tools: single-string `type`, `properties`/`required`/`additionalProperties`, `items`, scalar `enum`/`const`; anything unenforced is rejected loud) — the schema travels verbatim to the model as the forced tool's parameters, so the wire format, not the author DSL, is the right vocabulary.
## Deferred (documented non-goals of this cut)
- **Background collection** (start tool → run id → completion notice → collect), designed alongside bash/subagent background unification.
- **Journaling + resume** (`resumeFromRunId`, cached agent() prefixes) — implementing it reintroduces CC's determinism bans as a script-contract tightening (scripts may read the clock today).
- **Saved/bundled workflows** (a `.deepseek/workflows/` registry, slash-command surface) and **script persistence to a run directory** (the tool-call event already records the script durably).
- **Nested `workflow()`**, **token `budget`**, and the `effort`/`isolation`/`agentType` agent options (each rejects loud with a message naming it deferred).
- **An overall run wall-clock timeout** — cancellation always frees the caller (result settles within the grace), so a cap on total run time is a policy knob for the background redesign, not a correctness need here.
- **Engine hardening beyond worker threads**: an isolated-vm or separate-process engine behind the same seam (actual sandboxing; memory limits).
- **ACP progress UI** over the `workflow/*` events (a `/workflows`-style view); the events exist for it.
- **ACP-backend structured output** and **`toolFilter`** (both still capability-gated `false`).
## Alternatives considered
- **Hostile-value containment in the host** (trap-free proxy rejection, accessor-never-invoked descriptor walks, realm-side pre-rendering of thrown values, realm-built promises/arrays/error clones with structural fatal recognition): an earlier revision built all of it, and review showed the cost was real while the threat model was not — every one of those defenses guards against an author the premise already trusts. Removed in favor of the plain boundary above; the thread boundary makes such machinery redundant anyway (serialization by construction).
- **In-process `node:vm` execution** (the first cut of this RFC shipped it): mechanically simplest — no RPC, no thread — but `start()` blocks the caller for the script's initial synchronous slice, a synchronous spin past the first await cannot be killed in-process (the vm `timeout` covers only that first slice), and `dispose()` could only ABANDON an unsettling script, leaving the spin on the host loop. Superseded by the worker-thread engine, which keeps the same vm-context script surface while unblocking the host and making termination real.
- **Background execution as the default** (CC's shape): deferred; foreground-synchronous matches `dsh-tool-subagent`'s cut, and background semantics should be designed ONCE across bash/subagent/workflow rather than per-tool.
- **Workflow-layer JSON parsing for `agent({schema})`**: duplicating a seam concern at one consumer while the seam's capability flag stayed dishonestly `false`.
- **Meta embedded in the script as `export const meta = {...}`** (CC's exact format; the first cut shipped it): keeps scripts self-contained and CC scripts drop-in, but obtaining meta means evaluating model-written text on the HOST — the shipped extractor ran the literal in an empty timed vm context, yet reading the RESULT still executed script-controlled getters on the host stack outside any timeout, re-opening the host-spin hole the worker thread exists to close. A JSON parameter deletes the scanner, the evaluation, and the hole outright; the cost is that a CC script's meta header must move into the parameter (the body stays drop-in).
- **`SchemaSpec` as the outputSchema type**: the author-facing DSL cannot express what arrives as data and cannot be validated against without conversion loss.
- **A schema-object library (zod, or the repo's schemastery) for the structured-output subset**: the schema is wire data — plain JSON that crosses the vm realm boundary in `agent({schema})` and lands verbatim in the forced tool's parameters — exactly where live schema objects cannot sit; consuming raw JSON Schema at runtime would need a third-party converter on top (zod core only emits JSON Schema, not the reverse), and it would put a second schema language beside schemastery's config role.
- **ajv for value validation**: it validates FULL JSON Schema, so the subset gate — the module's actual point, since every accepted keyword must be one the harness enforces — would remain hand-written regardless; it compiles validators through `new Function`; and it would be dsh-tools' first runtime dependency, all to replace the ~70-line value walker while the path-qualified, every-violation error reporting stays custom either way.
- **Provider JSON mode (`response_format: {type: json_object}`) instead of the forced capture tool**: the official API guarantees valid JSON, not schema-conforming JSON (no `json_schema` type; the docs' own guidance is to validate client-side, with the schema riding in the prompt), so both walkers survive untouched and only the capture-tool mechanics could go — at the cost of tools during a structured child's run (whether `response_format` composes with tool calling is undocumented), the in-turn validation retry (`ToolArgsError` keeps recovery inside the turn; a JSON-mode empty body — a documented failure mode — ends the turn, and the only recovery is the re-prompt loop this design rejects), and a new per-adapter `LlmCallConfig` surface. The accepted upgrade path is strict TOOL schemas (provider-side constrained decoding on tool parameters) when available: the same forced tool and subset gate, with the gate narrowed to the provider's strict subset.
## Consequences
The harness gains CC-compatible script orchestration: fan-out plans live in a rerunnable artifact instead of the parent context, and the structured-output half of the subagent seam is now real (the vocabulary stopped lying about `outputSchema`). What it cost, all bounded by the trust premise: a worker thread per run (~tens-of-ms spin-up), every hook crossing a message port as RPC, and a termination-path `agentsStarted` that degrades to the host-observed count; in exchange `start()` never blocks the host, a post-cancel grace ends in a real `worker.terminate()`, and the value boundary is serialization by construction. A worker thread is still NOT a security boundary — scripts share the model's trust level, and actual sandboxing names its exit (the isolated-vm/separate-process engine swap behind the seam). The fatal-vs-null strictness divergence from CC means a CC-authored script that RELIES on option typos dissolving to `null` behaves differently here — judged worth it to keep the repo's no-accepted-then-ignored rule. Consumers must hold the run handle for control (`cancel`/`dispose`); observers get data snapshots only, so no listener can extend a run's lifetime or corrupt another's view.

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# RFC: Skill system — progressive disclosure instructions for agents
Status: implemented
## Problem
Agent products have converged on a skill pattern: keep the request prompt small by listing only available instruction bundles, then load the full body when the model decides a task matches. Codex, Claude Code, OpenCode, and Kimi Code differ in details, but all separate discovery metadata from complete instructions so a workspace can carry reusable behavior without paying the full prompt cost on every turn.
DeepSeek Harness uses the same primitive so project-specific review, plugin-authoring, and tool-usage guidance lives next to the workspace or the user's agent configuration instead of being hard-coded into the loop.
## Decision
`@deepseek-ai/dsh-skill` is the pure provider registry (`ctx.skills`), `@deepseek-ai/dsh-skill-local` is the shipped local filesystem provider, and `@deepseek-ai/dsh-tool-skill` owns the session-prefix catalog and model-facing loader tool. `dsh-agent-core` loads the registry, local provider, and consumer by default so stdio and ACP apps get the same behavior while embedded or remote providers contribute skills without changing the registry or consumer. Its `skills` config forwards `registry`, `local`, and `tool` branches to those owners.
Provider plugins register synchronously during `apply()`. Provider catalogs return ranked candidates from awaited `list()` calls, where remote providers perform initialization, authentication, and discovery while honoring the lookup abort signal. The registry validates each candidate, resolves same-name skills first-wins by rank, provider registration order, and provider-local order, then sorts summaries by skill name for deterministic consumers. It caches only completed catalog snapshots and retries when a provider/runtime revision changes during discovery, so an unload cannot freeze a stale, unresolvable skill into a session prefix. Runtime `ctx.skills.register(...)` remains a convenience for embedded in-process skills and uses project-over-user priority; `runtime` is reserved as the registry-owned provider name.
The local provider scans cwd-sensitive project roots, custom roots, and user roots in first-wins rank order: project `.dsh`, project `.agents`, `customSkillDirs`, user `.dsh`, then user `.agents`. The user `.dsh/skills` scan skips `.system` so a system-owned directory is not treated as normal user content. DeepSeek Harness does not ship built-in system skills; embedded or remote providers supply additional skills when configured.
Each skill is either `<name>/SKILL.md` or `<name>.md` with YAML frontmatter. `name` and `description` are required; `whenToUse`, `disableModelInvocation`, and `metadata` are optional. Names are kebab-case. YAML frontmatter is parsed with the `yaml` package instead of `js-yaml` or a hand-written parser: `yaml` is the already-declared modern parser for this package's limited frontmatter needs, and a narrow parser would either reject valid YAML users expect to work or grow into an unreviewed YAML subset.
Local skill filesystem I/O goes through `ctx.fs` when a filesystem service is loaded: project-root lookup probes `.git` with `resolve` and `stat`, root discovery uses `listDir`, and skill reads use `readText`. The Node filesystem remains a fallback for minimal contexts that mount `dsh-skill-local` without the fs seam. Missing roots, unreadable or malformed skill files, and transient provider `list()` failures degrade to warn-and-skip so one bad source does not make every agent request fail; malformed candidates still fail fast because they are provider contract violations.
`dsh-tool-skill` contributes one user-role `<system-reminder>` catalog through [`agent/session-prefix`](2026-07-07-session-prefix.md). The catalog contains sorted skill name and description only; it excludes bodies, paths, sources, providers, and routing hints. Descriptions are whitespace-normalized, XML-escaped, and capped by `catalogDescriptionMaxLength`, whose default is `500` and minimum is `3`. The session-prefix seam freezes the request-only catalog per loop instance and records it in the request header, preserving reconstructability without adding it to durable history. Full skill bodies are never included in the catalog.
The `skill({ name })` tool loads one full skill for the current agent cwd and returns a tool result containing `<skill_content name="...">`, `<skill_resources>`, and `<skill_instructions>`. `resourceBase` supplies a directory, URL, or opaque provider-managed base for explicitly referenced scripts, references, and assets; resources load only as needed, without directory enumeration. An unresolved name reports that the skill is unknown or no longer available; invalid names and skills marked `disableModelInvocation` retain distinct tool errors. The tool result is the model-visible disclosure path.
The data structures and catalog/tool contract are documented in [skills.md](../../../core-data-structures/skills.md), with service signatures in the generated [services catalog](../../../cordis-catalog/services.md).
## Alternatives considered
**Inject full skill bodies into every system prompt.** Rejected because it destroys progressive disclosure and makes every request pay for instructions that may not apply.
**Expose skills only as slash commands.** Rejected because model-initiated loading is the core capability; slash/ACP command advertisement does not change discovery.
**Put local filesystem scanning directly inside `ctx.skills`.** Rejected because coding agents, web agents, and future plugin ecosystems need different skill sources. A provider registry mirrors the subagent seam: the registry owns conflict resolution and consumers, while implementations own loading.
**Use a system-prompt section.** Rejected because the rendered system prompt is a single string, while the catalog is a user-role `<system-reminder>` message with request-only lifecycle requirements. [`agent/session-prefix`](2026-07-07-session-prefix.md) is the selected mechanism: it places the catalog ahead of derived history and records the composed message in the request header.
**Materialize built-in DSH authoring skills under `~/.dsh/skills/.system`.** Rejected because bundled skills do not write user home on startup, and embedded or remote providers supply configured skills.
**Recursively discover nested `**/SKILL.md`.** Rejected. Flat files and one-level directory bundles cover the configured roots while keeping duplicate handling and catalog order easy to reason about.
**Hand-parse frontmatter.** Rejected because the accepted schema includes an open `metadata` object. A narrow parser would either reject valid YAML users expect to work or grow into an unreviewed YAML subset.
## Consequences
The agent-core spine includes one session-prefix contributor, one local provider, and one model-facing tool. Skill discovery is cwd-sensitive, so callers that create agents with different session cwd values can observe different project skill overrides by design.
The catalog is deterministic for a fixed root set and runtime registration revision, but disk changes are not watched; discovery is memoized until runtime registration invalidates the cache or the process restarts.
## Deferred
Forked skill contexts (`context: fork`), direct user/slash invocation (`user-invocable`), parameter declarations and hints (`arguments` and `argument-hint`), and per-skill tool constraints (`allowed-tools` and `disallowed-tools`) are outside the shipped contract. The registry, local provider, and model-facing tool do not parse, advertise, or enforce these fields.

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# RFC: The approval seam — one-shot permission decisions over a waterfall of answerers
Status: implemented
## Problem
Two callers need to put one question — "may this specific action proceed?" — to a human, and neither has a channel. `tools/pre-execute`'s `ask` decision (produced today by the Claude-Code hook bridge's `permissionDecision: ask`) degrades to deny because nothing services it. The [sandbox RFC](2026-07-06-sandbox.md)'s escalation phase needs the same channel for its post-denial one-shot retry. Without a shared seam, each would invent its own outcome vocabulary, UI routing, cancellation, and audit trail — and a deployment with no UI at all needs a guarantee that an unanswerable question can never grant anything.
The routing problem is ownership: an approval prompt must reach the editor session that owns the asking agent (the ACP bridge multiplexes N sessions over one connection), fail closed for agents nobody owns (in-process subagents, tests), and stay out of deployments that compose no UI (headless, CI).
## Decision
One package, `dsh-user-approval` (`packages/ui/user-approval`), owning the vocabulary and the `ctx.approval` service — the MECHANISM. The POLICY — who answers, and whether a session is asked at all — lives outside it: answerers are `approval/request` waterfall listeners registered by the plugins that own the channel (the ACP bridge; future terminal UIs; test scripts), and a per-session policy tier can decide before any human is involved. Consumers (`dsh-tools`' ask routing, the sandbox escalation gate) resolve a question to a closed outcome and derive their own tool results from it. Deliberately ONE package, not the capability-seam three (see Alternatives).
### How a deployment uses it
One `cordis.yml` entry mounts the seam; not loading it is the opt-out — consumers degrade to their historical fail-closed behavior with zero approval code registered:
```yaml
- id: approval
name: '@deepseek-ai/dsh-user-approval'
# config:
# policy: never # deployment default for sessions without an override; 'ask' when omitted
```
The entry alone provides mechanism, not a channel: with no answerer composed, every ask resolves `unavailable` and the asking tool call denies — fail-closed needs no configuration. Composing the ACP app (`@deepseek-ai/dsh-acp-agent`, as in [the sandbox example](../../../../examples/sandbox-acp-agent/README.md)) completes the loop: its bridge registers an answerer that prompts the owning editor session via `session/request_permission`, so a hook's `ask` or an escalation request surfaces as a one-shot Allow/Reject prompt attached to the already-streamed tool call. `policy: never` is the unattended stance — every ask auto-rejects deterministically, stated in the system prompt, no human in the loop. `policy` is validated against the closed list at plugin load; anything else throws.
What a composed deployment observes: `allowed-once` lets exactly that call proceed; rejection, dismissal, and channel absence deny with three distinct reasons the model can tell apart; every ask lands a durable `approval/asked`/`approval/decided` pair on the asking agent's session log; nothing about a grant persists past the call that asked.
One ask under this composition, verbatim from the sandbox example's recorded `escalation-approved` scenario — the model requests a sandbox escalation, the gate asks, the bridge prompts the owning editor, the user clicks Allow once:
```
tool/call bash {"command": "printf 'escalated\n' > escalated.txt && cat escalated.txt",
"sandbox_permissions": "workspace-write",
"justification": "the user asked to write escalated.txt in the workspace"}
approval/asked {"toolName": "bash", "callId": "call_00_…",
"reason": "escalate sandbox to workspace-write: the user asked to write escalated.txt in the workspace"}
→ session/request_permission {"toolCall": {"toolCallId": "call_00_…"},
"options": [{"optionId": "allow-once", "name": "Allow once", "kind": "allow_once"},
{"optionId": "reject-once", "name": "Reject", "kind": "reject_once"}]}
← the user picks "Allow once" on the prompt the editor attaches to the streamed bash call
approval/decided {"outcome": "allowed-once"}
tool/result "escalated" — this one call ran under the wider mode; the grant died with it
```
The `escalation-rejected` twin ends in `{"outcome": "rejected"}` instead: nothing executes, and the model's result carries the asker's verbatim fail-closed text (`the user rejected escalating this command to "workspace-write"`). A hook's `permissionDecision: ask` rides the identical wire; only the asker and its deny texts differ (§ Ask routing in dsh-tools). Headless, the same request skips the prompt entirely and settles `unavailable`.
### Design detail
#### The seam: mechanism and policy split
`ApprovalService.request(req)` always resolves to a closed `ApprovalOutcome` — `allowed-once` / `rejected` / `cancelled` / `unavailable` — and never rejects. The service is the mechanism: it dispatches the `approval/request` waterfall, races the request's `AbortSignal` (abort settles `cancelled`; a late answer is discarded, never double-audited), contains a throwing answerer as `unavailable`, normalizes a rogue non-vocabulary return to `unavailable`, and lands the log-only audit pair `approval/asked`/`approval/decided` (paired by the branded `ApprovalRequestId`) on the requesting agent's session log. Grants are one-shot by definition: `allowed-once` authorizes the single asked-about action, never a class of future ones, and the service stores nothing between requests. The one precondition: `request()` throws (before appending anything) when the agent's session has no open turn — the audit pair must be turn-enclosed, the turn being the durable log's commit/replay boundary (a bare event between turns is dropped as crash tail on reload); every shipped ask path runs mid-turn already, and idle asks are a deferred design.
Answerers are the policy, and they are `approval/request` waterfall listeners. The waterfall buys exactly what the seam needs: with zero listeners the dispatch falls through to the caller-supplied default — `unavailable`, so fail-closed needs no configuration and no code in any deployment; a listener that recognizes the request's agent answers by returning an outcome without calling `next()` (the decision slot is single-occupancy, first answer wins — the same documented semantics as the `fs/write-intent` gate); a listener that does not recognize the agent MUST delegate via `next()` so another answerer or the default gets the question; and listeners dispose with their owning fiber, so an unloaded UI plugin degrades the next ask to `unavailable` instead of leaving a dangling channel. Registration order across sibling plugins is not load-order deterministic (the loader starts siblings concurrently), so a deployment composes ONE terminal answerer and reserves `prepend` listeners for decide-or-delegate gates.
`ApprovalRequest` carries the asking `agent` (routes the question; receives the audit events), the `toolName`, the optional exact `callId`, the asker's human-readable `reason`, and the optional `signal`. The vocabulary is deliberately self-contained — it names the tool-call by the `CallId` brand from `dsh-llm` and never imports `dsh-tools` — because `dsh-tools` depends on `dsh-user-approval` (the ask routing) and a `ToolCallView` import would close a package cycle. It deliberately does NOT carry tool arguments: a UI answerer attaches the prompt to the already-streamed tool call via `callId` instead of re-rendering the call.
#### Ask routing in dsh-tools
`ToolRegistry.execute()` resolves an `ask` decision through the seam before the shared deny path: `allowed-once` proceeds to dispatch, and the three non-grants deny with distinct reasons — "the user rejected…", "…was cancelled", "…no approval channel is available" — so the model can tell a human "no" from an absent channel. The seam is consumed opportunistically (`ctx.get('approval')`, the `tool-bash`/`agent-loop` pattern), not statically injected: a deployment that composes no ApprovalService keeps the historical ask→deny degrade verbatim, an unmount mid-session degrades the same way on the next ask, and the registry's fiber never gates on the seam's presence. An agent-less execution also degrades — without an agent there is no session to audit to and no UI to route to.
#### The per-session policy tier
The seam also owns the session-scoped approval policy — the approval knob of the two-knob per-session switching design ([the sandbox RFC](2026-07-06-sandbox.md) § Per-session modes is the pattern's home: one log-only event per knob, a pure fold, THE write path, ACP config-option advertisement, and turn-anchoring). `ApprovalPolicy` is `'ask' | 'never'`, and `effectiveApprovalPolicy(events) ?? Config.policy` (default `'ask'`) decides every request BEFORE any interactive answerer: the service resolves a `'never'` session to `'rejected'` INSIDE `request()`, before dispatching the waterfall at all — no listener registration, including a later `prepend`, can sit ahead of it — while `'ask'` dispatches unchanged (fail-closed `'unavailable'` with nobody composed, exactly the prior behavior). Visibility follows the switching design's two layers with one asymmetry: the prompt section states ONLY `'never'` (deterministic, availability-independent — "you will be prompted" would overclaim in a composition with no answerer, and absence under a logged header is exactly how the narrator reads `'ask'` back), the narrator injects at most one coalesced notice per switch, and the audit pair still lands on every ask, including the policy's auto-rejections.
#### The ACP answerer
The bridge registers the first real answerer: it resolves the owning session through its existing `WeakMap<Agent, sessionId>` reverse map, issues `session/request_permission` with the request's `callId` as the `toolCall` reference and the one-shot options `allow_once`/`reject_once`, and maps the response — selected `allow-once` → `allowed-once`, any other selection → `rejected` (an unknown optionId from a non-conforming client never grants), client `cancelled` → `cancelled`. A request for a foreign agent — or one without a `callId`, since the protocol prompt must attach to a tool call — delegates via `next()`. A rejected RPC (client gone mid-prompt) propagates to the service, which contains it as `unavailable`. Whether a call ASKS at all is policy — a hook or `tools/pre-execute` plugin returning `ask` — never the bridge's own judgment.
The reverse-map ownership seam [the ACP support RFC](../../implemented/feature/2026-06-14-acp-agent-client-protocol.md) laid down is exactly what the answerer routes through, and per-session permission ownership (the blocker recorded in [the multi-session RFC](../../implemented/feature/2026-06-14-acp-multi-session.md)) is what it implements.
#### Audit, and what the model sees
`approval/asked` / `approval/decided` are log-only session events (the `hook/invoked`/`hook/result` precedent): durable, replayable, never in the model transcript. The model's entire view of an approval is the tool result the asker derives from the outcome — reconstructability holds because that result is an ordinary logged `tool/result`. One `decided` per `asked`, whatever the outcome, including an already-aborted signal (settled `cancelled` without dispatching) and a contained answerer failure.
#### Entities and dependencies
One package, no cycles: `dsh-user-approval` peers on `cordis`, `dsh-session` (event-map merge + append), `dsh-agent` (the `Agent` type), `dsh-llm` (`CallId`, via `dsh-brand`). `dsh-tools` and `dsh-acp` each peer on it; the escalation phase's asker lives in `dsh-tool-bash` (see [the sandbox RFC](2026-07-06-sandbox.md) § Escalation), so the sandbox family keeps its ZERO-edge relation (the executor contributes the per-call override mechanism, and transport seams never ask humans questions). The seam is one package, not the capability-seam three: the service body (dispatch + audit) has no replaceable implementation — the replaceable part is the answerer listeners, and those live with their owners (the bridge; future terminal UIs; test scripts). `@cordisjs/plugin-capability` stays orthogonal (a static grant registry answers "is this already authorized", not "ask the user now"), and `subagent-acp`'s child-side `permission` auto-answer is untouched — routing a child's approvals to the parent session is deferred (§ Deferred).
### Testing
Unit tier: the service's outcome branches (fail-closed default, first-wins slot, delegation, containment, rogue-value normalization, abort-before and abort-during with late-answer discard, fresh ids, fiber-disposal degradation) and the policy tier (both values × dispatch/decide, a `'never'` decision unbypassable even by an answerer prepended AFTER the service, audit pair intact) in `dsh-user-approval`; the ask routing matrix (grant dispatches; three non-grant reasons pinned verbatim; unmounted and agent-less degrades; the registry's own exhaustiveness backstop against a non-conforming stand-in) in `dsh-tools`; the answerer (wire shape of the prompt, outcome mapping, unknown-option conservatism, foreign-agent and call-less delegation) driven through a real bridge + scripted client in `dsh-acp`.
Snapshot tier: the harness accepts scripted permission answers (`permissionAnswers` in a scenario's `input.json`, consumed FIFO; an unscripted prompt answers `cancelled`, fail closed). The seam's wire is recorded end to end in the sandbox example's suite: both escalation branches drive `session/request_permission` through this seam over scripted answers (grant and rejection), and the recorded `mode-switching` scenario pins the `'never'` prompt sentence and the policy-switch notice ([the sandbox RFC](2026-07-06-sandbox.md) § Testing).
## Deferred
- **`allow_always` grant storage** — honoring a persistent grant means designing storage, scope identity (call? path? prefix? session? time window?), and revocation; until designed, only the one-shot options are advertised ([the sandbox RFC](2026-07-06-sandbox.md) § Escalation records the open scope question).
- **A recorded hook-driven `ask` scenario** — the wire is recorded via the sandbox example's escalation branches; the hook-producer variant stays on the unit tier and the hook matrix's `hook-cc-pretool-ask`, with its deny texts pinned verbatim there.
- **Routing a child agent's approvals to the parent session** — `subagent-acp`'s child today auto-answers its own `permission` requests; surfacing them to the parent's editor is its own design.
## Alternatives considered
- **A single registered provider instead of waterfall listeners** — rejected: a `registerProvider()` surface forces every composition question — allowlist pre-filters, external hook deciders, scripted test answers, a policy gate in front of a human — inside one provider implementation. The waterfall gets composition, fail-closed absence, and HMR disposal from machinery the runtime already has; the seam's JSDoc pins the single-decision-slot convention instead of inventing a provider registry.
- **[The ACP support RFC](../../implemented/feature/2026-06-14-acp-agent-client-protocol.md)'s inline `tools/pre-execute` permission gate** — rejected, and superseded by this seam: prompting for every bridge-owned call hardwires the asking POLICY into the UI plugin, cannot serve a second asker (sandbox escalation happens after execution starts, with no pre-execute moment), and leaves hooks' `ask` — the vocabulary the interception seams already ship — unserviced.
- **A generic user-interaction seam (`ctx.userInteraction`) instead** — rejected: the two share a skeleton (route by agent, block for a human, handle absence), but approval's contract is narrower in every dimension that matters: a closed outcome vocabulary instead of free text, a protocol-native prompt attached to a tool call instead of a generic form, mandatory fail-closed absence, and audit events. The generic seam has since shipped (`packages/ui/user-interaction`, the `ask_user_question` tool over ACP elicitation) and approval deliberately still does not ride it — an elicitation form is not a permission prompt, and a free-text answer is not a closed outcome; sharing provider plumbing stays open if the two ever converge.
- **Static optional injection in `dsh-tools`** — rejected: the vendored cordis `Inject` type has no optional flag — the object form maps service names to intercept config, and a declared inject gates the fiber. `ctx.get('approval')` is the documented opportunistic-consumption pattern (the `tool-bash` owner-token lookup, the loop's persistence probe), reads presence per call, and degrades correctly across HMR without extra machinery.
- **The capability-seam three-package split** — rejected: interface/implementation/consumer fits a seam whose implementation is swappable (bash-local vs bash-sandbox). Here the service body is fixed mechanism and the variable part is listeners that live with their owners — splitting would manufacture an implementation package with nothing in it ("don't split preemptively").
- **Offering `allow_always` now** — rejected: the protocol can express it, but honoring it means designing grant storage, scope identity, and revocation (§ Deferred). Advertising an option the harness cannot honor manufactures doomed grants.
## Consequences
What shipped pins — the suites in Testing hold each:
- With an ApprovalService and an answerer composed, a hook's `ask` reaches a human and `allowed-once` dispatches the tool; every other outcome denies with its distinct reason.
- A `'never'` session auto-rejects every ask without prompting anyone, states the policy in its prompt, and narrates switches (the shared switching mechanics are pinned in [the sandbox RFC](2026-07-06-sandbox.md)).
- Every unanswerable path fails closed to `unavailable`: no service (degrade, verbatim historical text), no listener, a foreign or agent-less request, a throwing answerer, a rogue return value, a dead client connection.
- Every `request()` lands exactly one `approval/asked`/`approval/decided` pair on the asking agent's log, replayable, invisible to the model transcript.
- Prompts route per-session through the bridge's ownership map; one session's prompt can never reach another session's editor.
- A deployment that composes nothing new behaves byte-identically (the snapshot suite's goldens are unchanged).
Costs and accepted limits:
- **Two decide-eager answerers race for the slot.** Sibling-plugin listener order is not deterministic, so the seam cannot referee competing terminal answerers — mitigated by convention (one terminal answerer per deployment; `prepend` only for decide-or-delegate gates) rather than a priority mechanism the event bus does not have.
- **Production exercise rests on one composition.** `ask` has two producer families — the hook bridges through `tools/pre-execute`, and sandbox escalation through its own gate — with the wire recorded in the sandbox example's snapshot suite, so the seam's real-world coverage is that one composition until more deployments compose it.
- **Ownership keys on `Agent` object identity.** The answerer resolves sessions through the bridge's existing WeakMap; every current path hands the same object through the loop and the seams, but a future boundary that clones or proxies agents would make the bridge delegate and fail closed — safe, but silently UI-less — and would need session-id matching instead.
## FAQ
Behavioral and usage questions only — every "why not X?" design question lives in [Alternatives considered](#alternatives-considered), whose job is exactly that.
- **What happens in a deployment with no answerer at all (headless, CI)?** Every ask falls through the empty waterfall to `unavailable` and the tool call denies with the "no approval channel is available" reason. Fail-closed is the zero-listener default, not a configuration.
- **Can a grant persist — "always allow this"?** No. `allowed-once` authorizes the single asked-about action and the service stores nothing between requests; `allow_always` is deliberately not advertised until grant storage is designed (§ Deferred).
- **What does the model see of an approval?** Only the tool result the asker derives from the outcome — the audit pair never enters the transcript. The three non-grant reasons are distinct, so the model can tell a human "no" from a dismissed prompt from a missing channel.
- **Who decides whether a call asks in the first place?** Policy producers: a hook returning `permissionDecision: ask`, any `tools/pre-execute` listener, or the sandbox escalation gate. The seam and the bridge only route and answer; neither injects its own judgment about what deserves a prompt.
- **What happens when the user dismisses the prompt, or the turn aborts mid-ask?** Dismissal maps to `cancelled` with its own deny text. An already-aborted signal settles `cancelled` without dispatching; an abort during the ask discards the late answer — one audit pair either way, never two.
- **What if the client answers with an option the harness never offered?** Any selection other than the offered `allow_once` maps to `rejected` — an unknown optionId from a non-conforming client can never grant.
- **How do subagents' approvals route?** An agent no answerer owns delegates through the whole waterfall and fails closed — in-process subagents are unanswerable today by design. `subagent-acp`'s child-side auto-answer is untouched; routing a child's asks to the parent's editor is deferred (§ Deferred).
- **What does `policy: 'never'` actually change at runtime?** The service resolves every ask for that session to `rejected` before dispatching any answerer (in-service, so no registration order can bypass it); the system prompt states the policy; switches are narrated at boundaries; the audit pair still lands for every auto-rejection.
- **What happens across a hot reload, or when the UI plugin unloads mid-session?** Answerers dispose with their owning fiber, so the next ask degrades to `unavailable` instead of hanging on a dead channel; remounting re-registers the answerer with no catch-up state.
- **Where does the user see what they are approving?** On the tool call itself: the prompt attaches to the already-streamed call via `callId` — arguments included — and adds the asker's human-readable `reason`; the request carries no argument copy of its own.
## Prior art
In-repo precedents this design copies or contrasts with:
- The `fs/write-intent` gate (`packages/fs/fs/`) — the documented single-occupancy decision-slot waterfall semantics (first answer wins, delegate via `next()`) the answerer contract reuses.
- `hook/invoked`/`hook/result` — the log-only audit-pair precedent `approval/asked`/`approval/decided` follows; [the hook-bridges RFC](2026-06-30-hook-bridges.md) ships `permissionDecision: ask`, the first producer.
- [The interception-seams RFC](2026-06-30-interception-seams.md) — the `tools/pre-execute` `allow`/`deny`/`ask` vocabulary whose `ask` this seam services.
- [The ACP support RFC](../../implemented/feature/2026-06-14-acp-agent-client-protocol.md) — the `WeakMap<Agent, sessionId>` ownership seam the answerer routes through; [the multi-session RFC](../../implemented/feature/2026-06-14-acp-multi-session.md) — the per-session permission-ownership blocker this implements.
- The opportunistic `ctx.get()` consumption pattern (`tool-bash`'s owner-token lookup, the loop's persistence probe) — how `dsh-tools` consumes the seam without gating its fiber on it.

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# RFC: Explicit model-facing tool order
Status: implemented
## Problem
The order of the tool list a model call carries — `request/header.tools` on the session log and `GenerateOptions.tools` on the wire — was an emergent artifact: the tool registry returns schemas in registration order, the system-prompt assembly concatenates providers in registration order, and the loop logged and dispatched the result verbatim. Registration order is plugin load order, and plugin load order is a race: the cordis loader imports every `cordis.yml` entry concurrently, so which tool plugin registers first depends on module-import completion timing. The plugin dependency relation cannot rescue this — it is a partial order under which independent tool plugins (e.g. `tool-subagent` vs `tool-todo`) are incomparable, so both interleavings are legal linearizations. This stopped being theoretical when a CI runner resolved the race differently from every recording machine: snapshot goldens pinned one permutation of `request/header.tools`, the `node 22.18` CI leg produced the other, and 5/5 snapshot tests failed on a diff that was pure array reordering. Tool order is part of the request bytes (prompt-cache stability, potentially model behavior) and, since the reconstructability contract, part of the durable session log — it must be a decision, not a residue.
## Decision
The system-prompt assembly owns the canonical model-facing tool order, exactly where it already owns section order. `toolOrder?: string[]` on `dsh-system-prompt` is the optional explicit policy:
- A listed tool that is registered takes its listed position.
- A listed name with no registered tool is a configuration error. Shape errors (rest entry missing or duplicate names) fail from the service constructor; an unregistered name rejects every `assemble()` — the earliest moment the registered tool set exists to check against (tool plugins register after the service constructs), and the only universal one (registrations can change at any time; cordis has no "all plugins loaded" event). Under the shipped loop the first turn fails before any model request — see the consequences below for the exact blast radius.
- A registered tool absent from the list is inserted at the `'<unlisted-tools>'` rest entry (`TOOL_ORDER_REST`), in lexicographic name order among the other unlisted tools.
- No collected tool may use `TOOL_ORDER_REST` as its `ToolSchema.name`; the assembly rejects that reserved name before ordering.
- The list must contain the rest entry exactly once and no duplicate names.
- When `toolOrder` is unset, the canonical order is plain lexicographic name order (code-unit comparison, locale-independent), so determinism requires no configuration.
The policy is applied where the list is born: `assemble()`, before the `system-prompt/assemble` waterfall. The assembly canonicalizes the tools it collects from providers the same way it sorts sections by their `order` field — on the initial assembly, killing the registration-order entropy at its source. Everything downstream inherits the order untouched: the waterfall, the loop's `EpochHeader`, the `request/header` event, the deep-frozen request, and the dev invariant's cross-check all see one deterministic list, with no new loop change.
Scope is deliberately narrow: this fixes the REGISTRATION-ORDER race, not plugin behavior. A `system-prompt/assemble` listener may still add, remove, or rearrange tools — same as it may edit sections after their sort — and owns the determinism of what it emits; the waterfall contract already demands deterministic listeners (the reconstructability invariant would catch a listener that diverges between build and replay).
Config plumbing follows the `persona` precedent, and `toolOrder` sits beside it: the app configs (`dsh-stdio-agent`, `dsh-acp-agent`) accept the key and forward it through `dsh-agent-core` (whose schema is the intersection of the owners' schemas) to the `SystemPrompt` child. One schemastery footnote is load-bearing: a schemastery array defaults to `[]`, but an omitted `toolOrder` must stay ABSENT (= lexicographic) rather than become an explicitly-configured empty list (invalid — it lacks the rest entry), so every schema on the chain forces the default to `undefined`.
## Alternatives considered
- **Registration order (the status quo)** — a concurrent-import race, host-dependent (the CI flake above), invisible in review.
- **A linearization of the plugin dependency graph** — the relation is partial and independent tool plugins are incomparable; the flake happened with the partial order fully satisfied.
- **Per-plugin `weight` on each tool contribution** — scatters the order across plugins yet still needs a global numbering convention nobody owns (the section `order` bands show that coordination cost being paid by hand).
- **Sorting in `ToolRegistry.schemas()` (the registry layer)** — equally deterministic, but the registry is a membership store consumed by more than the assembly; ordering is a prompt-composition concern, and the assembly already owns the composition policy for sections.
- **A `LlmService` config + `orderTools()` method the loop calls before logging the header** — works, but adds a public service method and a loop edit solely to apply a policy at a distance; every future request composer must remember the call. Canonicalizing where the list is born makes an unordered list unrepresentable, with zero new surface.
- **Normalizing inside `llm.stream()`** — runs after the header event is logged (the flake survives) and rebuilds the deep-frozen envelope, silently disarming the reconstruction invariant.
- **An exhaustive list (no rest entry)** — every newly loaded tool plugin would break boot; the mandatory rest entry keeps unlisted tools deterministic and their position explicit.
- **A boot-time validation pass (a `SystemPrompt.assertToolOrderSatisfied()` called by `dsh-app-boot` after `loader.await()`)** — would turn the misconfiguration into a startup death instead of a first-turn failure, but costs a public service method plus a structural coupling from the generic boot glue to one service, and cannot replace the assembly-time check anyway (embedded callers never run app boot; registrations change after boot). No existing event can host the check either: cordis v4 has no ready-like event, `loader/entry-init`/`internal/status` fire mid-load (racy against tool registration, the very entropy this RFC kills), and the agent lifecycle events are no earlier than the assembly. One enforcement point at `assemble()` was judged worth the later failure moment.
## Consequences
- Every assembly — and therefore every `request/header` event and model request — has a deterministic tool order on every host; the CI-vs-local golden flip is structurally gone. The default order is lexicographic, no longer registration order.
- `PromptAssembly.tools` itself is canonical, so every assembly consumer (the loop, waterfall listeners, any future prompt inspector) sees the model-facing order; provider registration order is observable nowhere downstream of the registry.
- The snapshot suite's single pinned request-header fixture (`text-turn`) carries the new canonical tool order; every other ACP snapshot keeps the header bulk scrubbed as `{{system}}`/`{{tools}}`, per the pinned-header design.
- A pure tool reordering between steps is representable only as a `request/header` `'fallback'` snapshot (the name-keyed `ToolsDelta` cannot express it); with a stable canonical order such reorders no longer occur in practice, so the fallback path stays a safety valve.
- The `toolOrder` key rides the app → `agent-core` → `SystemPrompt` forwarding chain, so deployments set it next to `persona` in the app config; `dsh-llm` and the agent loop are untouched.
- A misspelled or unloaded tool name in `toolOrder` fails the turn at prompt assembly, not the boot: the loop assembles inside the turn (after `turn/start`, before `step/start`), so the rejection reaches the turn's outer catch — the turn closes balanced with an `error` reason carrying the message, `agent/error` mirrors it, no step opens, no `request/header` is logged, no request reaches the adapter, and the agent returns to idle. Every turn fails identically until the config is fixed; the process itself stays up (matching the repo rule that explicit config references must not be silently ignored — the enforcement point is the assembly because no earlier universal moment exists).
- A tool provider that returns the reserved rest-entry name has the same prompt-assembly failure shape as an unknown listed name. This keeps the sentinel from becoming an ambiguous real tool and preserves the "never drops a tool" ordering contract.
## Testing
Unit tests on `dsh-system-prompt` pin the ordering semantics (lexicographic default, listed/rest placement, unknown-name rejection at assembly, reserved tool-name rejection, stable handling of shared names, provider-order independence), the pre-waterfall contract (listeners observe the canonical list; a listener-appended tool is not re-sorted), and each invalid-list rejection at load. Loop-level tests assert the `request/header` fold carries the canonical order for scrambled registration orders (identical across permutations), that a configured `toolOrder` reaches both the logged header and the dispatched deep-frozen request, that the frozen loop-built envelope survives to the adapter, and that an unregistered `toolOrder` name fails the turn with a balanced `error` `turn/end`, an `agent/error`, no step, no logged header, and no dispatched request. Forwarding is asserted at every level that exposes the key (`dsh-agent-core`, `dsh-stdio-agent`, `dsh-acp-agent`). The snapshot tier replays all scenarios while only the pinned `text-turn` header carries the full canonical tool list; non-pinning fixtures continue to compare through `{{tools}}`.

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# RFC: The subprocess sandbox — confinement seam, native runners, escalation, and per-session modes
Status: implemented
## Problem
A coding agent needs this product path: bash subprocesses — and the hook commands that ride them — execute under a restricted file sandbox by default; if and only if the sandbox actually denies an operation, the model may request one user approval for that same operation and, once granted, retry it once with wider permissions. An every-tool boundary is deliberately NOT the claim: fs/web/todo execute in-process where an `execve` wrapper is meaningless (§ In-process tools), and the cross-family boundary is staged follow-up work (§ Deferred phases). Without a shared vocabulary, every tool reinvents approval fields, denial parsing, retry matching, and permission-state hints.
The harness is an SDK, so confinement must be a capability developers COMPOSE: whether to sandbox, and which backend per platform, belongs in the leaf `cordis.yml` as a first-class entry — not inside one executor's private machinery. And the first-choice runner, `bwrap`, is unusable on exactly the hosts a sandbox matters most (minimal containers, disabled unprivileged userns, LSMs that deny `mount`), so a fallback runner has to ship with the SDK rather than be assumed on the host.
Confinement alone leaves two gaps. A denial with no escalation path is terminal — the model can only give up, which pressure-cooks operators into configuring `workspace-write` or `danger-full-access` globally and defeats the sandbox. And the model-visible knobs (the sandbox mode, the approval policy) change over an agent's lifetime — an ACP user flips a per-session setting, an operator edits `cordis.yml` while the process is down — while the model must never act on a stale belief about them: what IS the state on every request, what changed while the agent lives, and what changed while nobody was watching all need answers.
## Decision
One seam, one per-platform chain of local backends, one consumer, and two levers on top: a per-call escalation path and per-session runtime modes. Everything below composes from the leaf `cordis.yml`; nothing touches `agent-loop`. The scope is deliberately bounded: the phases this RFC names but does not design — per-session workspace root, cross-family fs enforcement, the `subagent-acp` consumer, more environments, a Windows chain — are listed under § Deferred phases, each a follow-up design, not a config knob.
### How a deployment uses it
Three `cordis.yml` entries turn an unconfined coding agent into the sandboxed product path; [`examples/sandbox-acp-agent`](../../../../examples/sandbox-acp-agent/README.md) is this composition, live:
```yaml
- id: sandbox
name: '@deepseek-ai/dsh-sandbox-local' # the per-platform runner provider (ctx.sandbox)
- id: bash
name: '@deepseek-ai/dsh-bash-sandbox' # the confined executor, replacing dsh-bash-local behind ctx.bash
config:
mode: read-only # the deployment default every session starts from
workspaceRoot: !!js process.cwd() # the boundary workspace-write may write under
- id: approval
name: '@deepseek-ai/dsh-user-approval' # the escalation gate's channel (the approval RFC)
```
The swap is invisible to every consumer of `ctx.bash`: the bash tools, hook commands, and background tasks run exactly as before, spawned through the wrapped argv the provider returns. Deleting the `sandbox` and `bash` entries and loading `@deepseek-ai/dsh-bash-local` instead is the opt-out — execution is unconfined again and the escalation fields vanish from the tool schema, because they are capability-gated on the mounted executor, not on configuration. Omitting only `approval` keeps confinement but fails every escalation closed with its own error text.
Misconfiguration fails loud: `mode` outside the closed vocabulary is rejected at plugin load, and a host with no usable backend throws the structured `SANDBOX_UNAVAILABLE` — at `confine()` before the command ever spawns — rather than degrading to unconfined execution. `runnerCommand` on `dsh-sandbox-local` is the operator's explicit assertion of a bwrap-compatible runner (chain and probes skipped); it doubles as the deterministic fake-runner seam for keyless tests.
What the model then experiences: denied file effects come back as result facts with a `[sandbox: file access denied under <mode> mode]` marker plus standing instructions not to retry around them; under a confining executor the schema offers `sandbox_permissions` + `justification` for the one-approval escalated retry (validated strictly wider than the session's effective mode at execution); the system prompt deliberately does NOT state the sandbox mode — the model learns the boundary from the marker (which names the mode) when it hits it, instead of preemptively refusing work a standing declaration discourages. What an ACP editor experiences: a `sandbox-mode` and an `approval-policy` config-option select per session (each advertised only when its knob is composable), switchable at runtime; a sandbox switch simply changes what subsequent commands may do, while an approval-policy switch to `'never'` is stated in the prompt and narrated.
The product path, concretely (the escalation arc is verbatim from the recorded `escalation-approved` scenario; the denial leg is pinned on the real-kernel e2e tier):
```
tool/result … [sandbox: file access denied under read-only mode] ← the write RAN; the kernel refused it
tool/call bash {"command": "printf 'escalated\n' > escalated.txt && cat escalated.txt",
"sandbox_permissions": "workspace-write",
"justification": "the user asked to write escalated.txt in the workspace"}
→ the editor is prompted on this very call (session/request_permission through the approval seam); Allow once
tool/result "escalated" — THIS call ran under workspace-write and its result facts say so; the session stays read-only
```
Reject instead and nothing executes: the result is the verbatim `the user rejected escalating this command to "workspace-write"`, and the teaching makes that final — no re-ask.
### Design detail
#### Grounding — verified against the code
- Runtime OS subprocesses exist at exactly two sites: the `ctx.bash` seam's single spawn (`packages/bash/bash-local/src/run.ts`; hook commands flow through `ctx.bash`, so bash confinement covers them transitively) and `subagent-acp`'s child agents (`packages/subagent/subagent-acp/src/run.ts`) — the second consumer that makes a shared seam due rather than preemptive under the [capability seams RFC](../architecture/2026-06-13-capability-seams.md)'s "don't split preemptively" rule.
- Everything else executes inside the harness process (fs is in-process `node:fs`, web is in-process `fetch`, every `ToolDefinition.execute()` closes over `ctx`): an OS sandbox wraps `execve` and cannot wrap an in-process function call, so "sandbox any tool" is policy at each tool's seam, never a mechanical transport change.
- `tools/pre-execute` (`allow`/`deny`/`ask`) exists, with `ask` serviced by [the approval seam](2026-07-06-approval-seam.md); the fs intent gates are version guards with no mode input yet.
- `dsh-bash`'s request/spec split (`BashExecRequest` → `resolve()` → `BashExecSpec`) carries per-call fields the way escalation needs — `owner` is the template: request-optional, spec required-but-nullable, carried verbatim — and the result types already speak `SandboxMode`, so a per-call policy field adds no dependency edge.
- The pinned-header snapshot design means a schema/description change churns at most one pinning fixture per suite, and the escalation fields are advertised only under a sandboxing executor — so they live in exactly one pinned header, the sandbox example suite's `mode-switching` fixture.
#### The seam: `ctx.sandbox`
`dsh-sandbox` owns the vocabulary and the `SandboxProvider` contract: `confine(argv, policy)` returns the argv to spawn INSTEAD of the caller's own — wrapped so the process and everything it spawns run confined — plus the `enforcement` completeness the selected backend achieves, its denial dialect (`denialSignatures`, the stderr substrings that backend's kernel prints on a denied file effect), and its runner-failure dialect (`runnerFailureSignatures`, how the runner ITSELF failing — and therefore the command never running — identifies itself); with no usable backend it throws the fail-closed `SANDBOX_UNAVAILABLE` error, never a silent unconfined passthrough. The vocabulary: `SandboxMode` (`read-only` / `workspace-write` / `danger-full-access`, FILE effects only — network and process visibility are not claimed), `SandboxEnforcement` (`full` / `partial`), `SandboxPolicy` (mode + workspace root).
Policy rides each CALL, not the provider: two consumers may confine under different policies at the same instant (bash under `read-only` while a confined child agent keeps its state directory writable), and an approved escalated retry is a new call with a wider policy — inexpressible under a config-fixed provider mode.
The seam confines SAME-WORLD subprocesses only: a backend shares the host's filesystem and kernel. Containers, microVMs, and remote executors are NOT backends of this seam — they replace whole capability implementations (`ctx.bash`, `ctx.fs`) as environment-coherent groups, because an agent whose bash runs in a container while its fs tools write the host lives in two split worlds.
Left open, for the phase that needs them: whether network restriction arrives as a separate `network_mode` or merges into `sandbox_mode` once a runner enforces both, and whether `SandboxPolicy` grows extra writable-root grants now (the launcher already speaks `--rw <path>`) or only when escalation needs them.
#### Local backends and the shipped launcher
`dsh-sandbox-local` selects BY PLATFORM, once per lifetime, and caches the verdict: each platform names its runner chain, a chain of one is selected directly — probing arbitrates between candidates, and a sole candidate leaves nothing to arbitrate — and a chain of several is probed FUNCTIONALLY in preference order (build and enforce a real profile, never `--version` — a present-but-unusable `bwrap` must fail its probe). Linux: `bwrap` first (its mount profile is closest to the mode vocabulary: whole tree read-only, fresh `/dev`+`/proc`, `workspace-write` adds an ephemeral `/tmp` and rebinds the workspace root; deliberately no `--unshare-pid` and no network claim), else the npm-distributed `landlock-run` Landlock launcher. darwin: `sandbox-exec` speaking a Seatbelt (SBPL) profile — allow-default with `(deny file-write*)` plus write allow-lists, every granted root canonicalized because Seatbelt matches resolved paths (`/tmp` IS `/private/tmp`) — unprobed, the sole candidate. A platform with no chain fails closed at `confine()`; an unprobed runner that turns out unusable fails closed at EXECUTION instead — it refuses to run the command, and every wrap carries `runnerFailureSignatures` (the runner's own error prefix, which also matches the shell's runner-not-found message) so the consumer classifies that as a SANDBOX failure, never a task failure: on either path the command neither runs unconfined nor slips through as a plain failure. A non-empty `runnerCommand` config is the operator's assertion of a runner that fully enforces the bwrap-shaped profile — chain and probes skipped; it doubles as the deterministic fake-runner seam for keyless tests. It is not exempt from fail-closed execution: its wrap carries argv0-scoped outer-shell failure shapes (`exec: <argv0>: not found`, `<argv0>: No such file or directory`, `<argv0>: Permission denied`) as its runner-failure dialect, so a missing or unexecutable configured runner classifies as a sandbox failure like every other rung — never as a failing command, and never as a denial.
The launcher is a ~300-line C program (plain C11 over the raw Landlock UAPI — no libraries beyond a statically linked musl, so the audit surface is that one file plus the kernel's stable syscall contract): `--ro <path>` / `--rw <path>` grants, `--`, the wrapped argv; it installs the ruleset on itself and `exec`s (rulesets are inherited across `execve`, and it sets `no_new_privs` before restricting); `--probe` enforces a maximal ruleset in a short-lived child and exits 0 only when the kernel actually enforces; launcher failures exit 125 without exec'ing.
The launcher lives in its own repository and reaches the harness as the npm package family [`node-addon-landlock-run`](https://www.npmjs.com/package/node-addon-landlock-run) (the per-platform-package pattern of `node-addon-require-builtin` and esbuild): an entry package — `dsh-sandbox-local`'s one runtime dependency — plus per-platform binary packages selected at install time by npm's `os`/`cpu` fields. The entry package owns the launcher's CLI contract end to end (`launcherPath()` resolution with a never-existing fallback, the functional `probe()`, `grantArgs()` flag spelling), versioned together with the binary so probe-report parsing can never drift against it; the harness keeps only the policy side, `landlockProfileArgs()` mapping the mode vocabulary to grants. Native-only per-architecture builds, pack gates (binary presence, executability, ELF architecture), and the byte-pinned publish rehearsal are that repository's release pipeline; this repo's Landlock CI legs install the published family from the registry — the true consumer path — and prove real-kernel confinement through it.
FIXME: Revisit the separate-repository boundary and try to maintain the launcher source and its platform package family inside this monorepo, so the native release surface and harness contract evolve together.
Profile parity is honest rather than identical: under Landlock, `read-only` grants `--ro /` plus `--rw /dev/null` (the node, not `/dev` — the host's `/dev/shm` is a persistent shared tmpfs), and `workspace-write` grants the HOST `/tmp` where bwrap's is ephemeral; under Seatbelt, `read-only` likewise grants only the `/dev/null` literal, and `workspace-write` grants the host `/tmp` plus the per-user darwin temp dir (`os.tmpdir()` — the platform's real temp area for mkstemp-family tools; omitting it would deny what the mode promises). Every wrap carries the rung's denial dialect (`denialSignatures`: EROFS text under bwrap, EACCES under Landlock, EPERM under Seatbelt) so consumers match the active backend rather than a cross-runner union. Enforcement is honest per ABI level: an older kernel enforces the subset its ABI governs (path truncate is ungoverned before ABI v3), the probe's report line distinguishes the cases, and every confined result carries the structured `enforcement: 'full' | 'partial'` fact — refusing partial enforcement would deny the fallback to precisely the older-kernel hosts that need it. The bwrap and Seatbelt profiles govern every promised file effect by construction, so their passing probes always report `full`.
#### The bash consumer
`dsh-bash-sandbox` extends `LocalBashExecutor` (spawn mechanics, process-group kills, spill files, background tasks, credential scrub inherited verbatim) and hands `ctx.sandbox` the exact `['bash', '-c', command]` argv it is about to spawn. A sandbox denial is a RESULT FACT, not an error: the command RAN and the kernel refused a file operation, so `result.sandbox.denied` is orthogonal to `exitCode`/`signal`. Classification is conservative text inference over the collected stderr tail against the WRAP's own dialect, so a backend is never credited with a denial text its kernel does not speak (bare EPERM under a Linux runner names non-file boundaries the mode vocabulary does not govern); the known residual false positive is non-sandbox text in the active dialect (an ssh auth failure under Landlock, a refused `kill` under Seatbelt), and a structured runner signal wins once one exists. A RUNNER failure is the opposite of a denial and outranks it in classification (a runner's error text can itself contain denial words): the wrap's `runnerFailureSignatures` matching a failed run means the sandbox broke and the command NEVER RAN — the foreground path re-throws it as the structured `SANDBOX_UNAVAILABLE` error (the late twin of the confine-time throw, carrying the runner's first stderr line), a settled background task stamps `sandbox.runnerFailed` and `bash_output` renders its own marker — so a broken sandbox can never read as a failing command.
The model's view is result facts only: the static tool description explains the denial marker (`[sandbox: file access denied under <mode> mode]`), encourages attempting commands that may be denied, and forbids retrying around a denial; when the escalation fields are advertised, a denied result additionally carries the escalation hint itself, so the sanctioned same-turn retry is prompted at the decision point rather than depending on the model recalling the description (§ Escalation). No prompt section states the sandbox mode (§ Per-session modes).
#### Escalation: one approved wider retry after a denial
The seam level is mechanism only. `BashExecRequest` carries `sandboxMode?: SandboxMode`, an explicit per-call policy input; `BashExecSpec` carries it required-but-nullable (the `owner` pattern: a forgotten field is a visible `undefined`, and `resolve()` is the one explicit defaulting step); `BashExecutor` exposes the capability fact `get sandboxMode(): SandboxMode | undefined` — `undefined` in the base class, the configured mode in `SandboxBashExecutor` — so the tool layer can advertise only what the mounted executor honors: composition truth, not configuration. The seam honors ANY explicit mode, including a narrower one; the wider-only ladder is escalation policy and lives in the tool. A non-sandboxing executor (`dsh-bash-local`) carries the field verbatim and confines nothing — the field reaching it means the caller bypassed the tool's gate, and its honest behavior stays unconfined execution, not a guess at enforcement it does not have.
`SandboxBashExecutor.resolve()` stamps the effective mode — escalation grant > session override > configured default — so `run()`/`start()` read the spec, never the config. The `danger-full-access` branch, the confine call, and the result facts all key off the spec's mode, and the per-task facts map carries each task's mode alongside its wrap facts (`notifyTaskDone()` stamps from the map entry): one escalated call — foreground or background — reports the mode it ACTUALLY ran under while every neighbor keeps its own.
The tool gate advertises two extra parameters exactly when `ctx.bash.sandboxMode` reports a confining mode at registration: `sandbox_permissions`, an enum of the closed escalation-target vocabulary — `workspace-write`/`danger-full-access`, every mode a session could ever escalate TO — and `justification`, required together with it. The enum is deliberately NOT cut down to the modes wider than the executor's DEFAULT: schemas are registry-global while the effective mode is per-session and switchable, so a default-relative ladder strands a session overridden NARROWER than the default (with a `danger-full-access` default and a `read-only` override it would advertise nothing at all — confined, but with no lever). Strict widening is instead enforced at EXECUTION against the call's effective mode (session override ?? executor default): a request that is not strictly wider fails closed with its own text and prompts no one. An escalating call resolves approval BEFORE anything executes — no `ctx.approval` composed, or no agent on the execution, fails closed with its own text; otherwise `ctx.approval.request({ agent, toolName: 'bash', callId, reason, signal })` with the audit-self-contained reason `escalate sandbox to ${mode}: ${justification}`, while the UI attaches the prompt to the already-streamed call (the command is visible there; the approval RFC's no-arguments rule holds). The four outcomes map to distinct results: `allowed-once` stamps `sandboxMode` onto the bash request and proceeds; `rejected`, `cancelled`, and `unavailable` each produce their own error text, so the model can tell a human "no" from a dismissed prompt from a missing channel. The grant is consumed by the very call that asked; nothing is stored.
The tool description teaches — and a denied result itself prompts — the SAME-TURN flow when the fields exist: on a denial a wider mode would cure, escalate immediately in that turn by retrying the exact command once with `sandbox_permissions` (the narrowest mode that suffices) + `justification`, without detouring through chat to ask first — the approval prompt raised by the retry IS how the user consents. Never speculatively: an escalation is grounded in a real denial — normally the one the command just hit, up front only when the session already denied the same access — and a prompt stating approvals are disabled turns the exception off entirely; a rejected escalation is final for that command. Denial-grounding is deliberately model discipline plus human judgment, not harness bookkeeping — the human sees the exact command and justification on the prompt (see Alternatives for why hard-matching is rejected). No new session events anywhere: the attempt is an ordinary `tool/call` whose logged arguments carry the two fields, the decision is the approval seam's `approval/asked`/`approval/decided` pair, the outcome is an ordinary `tool/result` whose sandbox facts name the mode it ran under. The asker lives in `dsh-tool-bash`, NOT the executor: a transport seam has no `agent`, no `callId`, and no business asking humans questions.
Left open, recorded for the phase that picks them up: what a grant's scope identity is beyond the sandbox mode — the exact call, a path, a command prefix, the session, a time window — the question `allow_always` grant storage must answer before that option can be advertised; how cancellation behaves while an approval prompt is pending; and how escalation is defined for `run_in_background` denials that arrive via `bash_output`.
#### Per-session modes: the session log as the store
```
effective(session) = findLast(the session's own knob events)?.value ?? the composition-config default
```
The default is composition config (`cordis.yml`) — operator-owned, process-wide. A runtime switch is a SESSION-SCOPED override recorded as one log-only event in that session's own log. Restart immunity (resuming a session replays its log, so overrides come back with zero catch-up machinery) and multi-session isolation (one editor tab's `workspace-write` cannot disturb another's `read-only`) both fall out by construction, and no external config store exists anywhere.
**One event per knob, owned by its domain** — the merge-extensible `SessionEventMap` idiom every existing event family already follows (`approval/*` in `dsh-user-approval`, `hook/*` in the hooks packages):
```ts
interface SessionEventMap {
'bash/sandbox-mode': { mode: 'read-only' | 'workspace-write' | 'danger-full-access' }
'approval/policy': { policy: 'ask' | 'never' }
}
```
Each owner exports the same three-piece kit: the event declaration, a pure fold (`effectiveSandboxMode(events)` / `effectiveApprovalPolicy(events)` — a `findLast`, typed to the domain's closed union), and THE write path (`setSandboxMode(session, mode)` / `setApprovalPolicy(session, policy)` — a switch IS its event; nothing mutates state out of band). No shared owner service, no generic facts map, no registry: a third knob copies the ~40-line pattern into its own package. Execution follows the fold on both sides — the bash tool's per-call stamp reads it as the middle rung of the § Escalation precedence chain, and the approval seam's `'never'` gate is [the approval RFC](2026-07-06-approval-seam.md)'s side of the same pattern.
**Visibility is deliberately asymmetric between the knobs.** The SANDBOX mode is stated nowhere and its switches are not narrated: a standing "you are read-only" declaration teaches the model to refuse preemptively (observed live: sessions where the model would not even attempt a write it could have escalated), while the denial marker already names the mode the command ran under at exactly the moment the boundary matters — behavior, not belief, carries the state, and a switch simply changes what the next command does. The APPROVAL policy keeps both layers, because its failure mode is the opposite: an auto-rejected ask under `'never'` returns "the user rejected …" wording no behavior can disambiguate, so the prompt states `'never'` (and ONLY `'never'` — an `'ask'` promise is unknowable without asking, and absence under a logged header is how the narrator reads `'ask'` back), and an `agent/pre-step` narrator injects at most one coalesced notice per policy switch: idle flip-flops collapse to one notice at the next turn's first step, a net-zero round trip to none, and a mid-turn change is narrated no later than the next step. Its "last told" is in-memory with a log-derived fallback (the folded header's system text parsed against the closed candidate sentence; LAST occurrence wins, so a persona quoting it cannot shadow the real section), so restarts lose nothing; attribution is positional (a knob event after the log's last `request/header*` reads `changed by the user`, a drift with no such event reads `changed by the operator/config`).
**The editor surface** is protocol-native [Session Config Options](https://agentclientprotocol.com/protocol/session-config-options) — the spec's replacement for session modes (slated for removal in ACP v2), already SDK-typed. The bridge advertises one independent `select` per composable knob — `sandbox-mode` (category `mode`) iff the mounted executor confines, `approval-policy` iff the approval seam is composed — with `currentValue` folded from each session's own log, in `session/new` and `session/load` responses. `session/set_config_option` validates against the same closed lists, routes to the domain setter, and returns the complete refreshed state (the spec contract).
**Anchoring: turn-enclosure is the commit boundary.** The turn-enclosure contract makes a bare between-turns append invalid (the JSONL backend treats a post-`turn/end` tail as crash garbage; dev invariants throw). A switch while a turn is open appends immediately — openness read from the LOG (last boundary event is `turn/start`), not `agent.status`, which stays `running` between queued turns. An idle switch is held on the bridge's session record and anchored at the next turn's `agent/prompt-submit` — inside the turn, before anything in it assembles or executes, last write per knob, and OUTSIDE any `session/event` emit (appending from inside that feed reorders events for later-registered listeners — a bug the dev invariants caught live). Until anchored, the switch exists only in bridge memory: responses overlay it truthfully, and a crash before the next turn reverts it — `session/load` then reports the fold's truth, so the editor UI self-corrects rather than lies.
#### In-process tools
fs/web/todo execute in-process, so their sandbox semantics are policy at their seams: the fs intent gates deciding by the shared mode vocabulary (§ Deferred phases, cross-family) make `read-only` a real boundary instead of a bash-only approximation — until then the contract says so honestly. No generic per-tool sandbox runtime: a host-mediated tool leaves the process only by returning declarative effects the host validates, which is a rewrite, not a wrapper.
FIXME: Revisit this tool-local boundary. The follow-up design needs to determine whether sandboxing becomes a global harness capability that applies uniformly to every tool, instead of expressing in-process enforcement independently at each tool seam.
### Testing
- Unit tier (no real runner anywhere): profile dialects, per-platform chain selection (sole candidate unprobed, no chain fails closed, multi-candidate probe order), verdict caching, the fail-closed end, probe-report parsing, and the launcher/`sandbox-exec` CLI contracts via fake runner scripts in `dsh-sandbox-local`; wrapping, policy hand-off, fact stamping, and runner-failure-outranks-denial classification (foreground throw, background `runnerFailed` fact) against a fake provider in `dsh-bash-sandbox`; the error's structured identity in `dsh-sandbox`. The escalation matrix spans the three bash packages: verbatim carry-through in `dsh-bash-local`, stamp/branch/per-task-facts in `dsh-bash-sandbox`, and the capability gate, `justification` pairing, fail-closed texts (pinned verbatim), and grant stamping in `dsh-tool-bash`. The switching surface pins the folds, the stamping precedence, the `'never'` gate, per-session section rendering, the full narrator matrix (cold start, coalescing, net-zero, resume drift with operator wording, positional attribution, persona-shadow hardening), and the bridge's advertisement gating, validation rejections, idle-vs-mid-turn anchoring (dev invariants mounted), and `session/load` reporting over a real two-process JSONL round trip.
- Keyless real-runner e2e, split along the seam and per rung: CI's `sandbox-e2e` matrix runs bwrap and Landlock on Linux (the Landlock leg once per architecture, each confining through the registry-installed launcher) and Seatbelt on macOS against real kernels, failing on a silent all-skip. World-proofs live in `dsh-sandbox-local` (denied writes absent on disk, workspace writes landing, temp-area grants pinned, kernel denial text matching the advertised dialect) and `dsh-bash-sandbox` (the through-`ctx.bash` consumer proofs, including denied-then-overridden-write-lands). This package's own publish path is rehearsed without publishing (`packed-install.e2e.ts`): `pnpm pack`, tarballs installed into a throwaway consumer with the launcher family resolving from the registry, plain `node` confining through the INSTALLED launcher — asserted executable apart, so a mode-stripped binary can never masquerade as a non-enforcing kernel. The switching surface has its own keyless e2e (`examples/sandbox-acp-agent`): the real `cordis.yml` tree advertises both options, honors switches end to end, and rejects out-of-vocabulary values.
- With-key e2e (`examples/sandbox-acp-agent/tests/escalation.e2e.ts`): real model + real runner + the REAL bridge answerer, world-verified — denied under `read-only`, escalates with justification, the scripted editor grants and the retried write lands on disk, while a rejected escalation leaves no write. Self-skips without `DEEPSEEK_API_KEY` or a usable runner (e2e.yml installs bubblewrap so it actually executes in CI).
- Snapshot tier (`examples/sandbox-acp-agent/tests/acp.snapshot.ts`): the keyless config-option wire; the recorded mode-switching arc as the suite's pinned header — necessarily, since mid-session switches emit the `request/header-delta`s the uniformity guard licenses only in the pin — committing both switches, the prompt-section delta and one "changed by the user" notice per knob, and a confined write landing under the switched mode; and both recorded escalation branches over scripted `permissionAnswers` (grant runs confined under `workspace-write`; rejection executes nothing and pins the fail-closed text). Replay re-executes every fixture's bash calls under the host's real runner (ci.yml's snapshot lane installs bubblewrap). Deliberately absent: a fixture carrying a real DENIAL — denial stderr is the backend's dialect and would pin a fixture to its recording platform; the escalation prompts assert the prior denial instead, and the denial→marker path stays on the tiers above.
## Deferred phases
Each phase gets its full design when picked up, validated against the code at that time, and lands with unit, real-API e2e, and snapshot coverage at the tiers it touches.
- **Per-session workspace root** — the executor's write boundary stays config-fixed for its lifetime while each ACP session has its own cwd; a per-session root rides the same per-call policy carrier once designed.
- **Cross-family boundary** — the fs intent gates decide by the shared mode, making `read-only`/`workspace-write` real boundaries beyond bash.
- **Second consumer** — `subagent-acp` optionally confines child agents (per-call policy; unconfined default — a child agent must write its own persistence).
- **More environments** — an environment-coherent capability group example (e.g. bash+fs against one container).
- **Windows chain** — `PLATFORM_CHAINS.win32` is reserved and empty (fail-closed); filling it means a confinement runner from the AppContainer/restricted-token family, shipped from its own repository on the `node-addon-landlock-run` template, plus its profile dialect and denial/runner-failure signatures.
## Alternatives considered
- **Command-string heuristic preflight** — rejected: cannot understand expansion/subprocesses/symlinks; the strict attempt (run it, let the kernel decide) is the only trustworthy denial signal.
- **Functionally probe even a platform's sole backend** — rejected: probing arbitrates between candidates; with one there is nothing to decide, and probe cost taxes the first confined command of every session (prohibitive for heavy future backends). The runner's own exec-time fail-closed refusal plus `runnerFailureSignatures` classification carries the safety property instead.
- **Commit the built launcher binaries** — rejected: a binary in a diff is unreviewable and churns history; reviewed source + native CI builds + the launcher repo's byte-pinned publish rehearsal keep bytes out of every tree.
- **Compile the launcher on install** — rejected: pushes a C toolchain onto every consumer; a fallback that exists only where a compiler happens to be is not a fallback.
- **Cross-compile both architectures from one builder** — rejected: requires carrying a pinned cross toolchain (rustup targets, zig, or a container image) solely to rebuild two ~70 KB binaries; per-architecture native runners already exist and each builds its own platform package (the `node-addon-require-builtin` model, the launcher repo's own pipeline).
- **No fallback (bwrap or fail closed)** — rejected: concentrates failure on the hosts a sandbox matters most, degrading to `danger-full-access` by resignation.
- **Keep the mechanism inside `dsh-bash-sandbox`** — rejected: blocks the existing second consumer, makes future phases read mode out of a bash plugin's config, and cannot express escalation.
- **Config-fixed mode on the provider** — rejected: one mode per process; cannot serve concurrent consumers with different policies nor the one-shot widened retry.
- **One interface spanning containers/VMs too** — rejected: `confine(argv)` presupposes a shared filesystem; environment isolation is capability-sibling backends deployed as coherent groups.
- **Generic ToolRuntime wrapping any tool** — rejected: mechanically false for in-process tools (closures over `ctx`); the declarative-effects rewrite is unjustified for fs/web/todo.
- **Ask inside the executor (`dsh-bash-sandbox`)** — rejected: no `agent` to route through, no `callId` to attach the prompt to; adding them teaches a transport seam about sessions and UIs — the tool layer holds both and owns the model-facing vocabulary.
- **Auto-retry inside the same tool call** — rejected: a hidden re-entry the log cannot reconstruct: one `tool/call` would have produced two executions with different policies — the retry is a NEW logged call with its own arguments and result facts.
- **Advertise the escalation fields unconditionally** — rejected: under `dsh-bash-local` they are a dead lever — advertising an option the harness cannot honor manufactures doomed grants; capability-gating costs one registration-time read.
- **A default-relative escalation ladder (advertise only the modes wider than the executor's registration-time default)** — rejected: per-session overrides make the default the wrong baseline — a session switched narrower than the default loses exactly the lever it needs, and under a `danger-full-access` default the fields vanish entirely while a `read-only`-overridden session stays confined with no escalation path. The enum pins the closed target vocabulary; strict widening is a per-call execution check against the session's effective mode.
- **Per-session dynamic tool schemas** — rejected: schemas are registry-global by design (one assembly vocabulary, the pinned-header snapshot contract), and re-registering per session would buy only what the execution-time strict-wider check already guarantees, at the cost of a per-session schema surface and header churn on every switch.
- **Hard-match the retry to a prior denial** — rejected: command-string identity is fragile (quoting, `workdir`, env prefixes, a pipeline retried as its failing stage) — false-rejects honest retries or is trivially satisfied; the real boundary is the human seeing command + justification. Revisit only if `allow_always` grant storage ever needs machine-checkable scopes.
- **A generic `env/state` facts map with an owner service** — rejected: approval and sandbox compose independently, so neither's state may drag in a third package; single-key folds are one `findLast` each, dissolving the owner service; no invariant spans the knobs, so atomic multi-key patches bought nothing.
- **Narrate via `agent/user-message` + a bus event** — rejected: it presupposes a turn-entry seam that does not exist (the real seam is `agent/prompt-submit`), and pre-step's position serves both the coalesced turn-entry notice and the mid-turn immediacy bound with one listener.
- **A standing prompt statement of the sandbox mode (+ a switch narrator)** — shipped first, then removed on live evidence: with `Bash commands run under the "read-only" file sandbox.` in every request, the model refused to ATTEMPT denied-then-escalatable work (five of twelve turns in the first manual session ended with zero tool calls), turning the sandbox into a soft lockout. The denial marker names the mode at the moment it matters and the escalation fields carry the recovery; the approval knob keeps its statement because an auto-rejection is behaviorally indistinguishable from a human "no".
- **Track "last told" with its own bookkeeping events** — rejected: the `request/header*` fold already records the exact prompt the model saw; parsing the closed candidate sentences back replaces a second bookkeeping stream — events are needed only where they ARE the store.
- **ACP session modes instead of config options** — rejected: one mode list cannot carry two orthogonal knobs; config options are the spec's designed surface and modes are slated for removal in ACP v2.
## Consequences
What shipped pins — the tiers in Testing hold each:
- A denied command retried with `sandbox_permissions` + `justification` prompts the user through the composed answerer chain; a grant runs THAT call under the wider mode (result facts say so) while every other call keeps its own effective mode; every non-grant outcome produces its distinct error text and executes nothing.
- The escalation fields exist exactly when the mounted executor confines; a request that is not strictly wider than the call's effective mode fails closed with its own text and prompts no one; a deployment with no ApprovalService fails escalating calls closed and leaves plain calls untouched.
- The system prompt never states the sandbox mode (an approval `'never'` policy is the one stated knob), and the whole exchange — headers, knob events, notices, approvals, results — reconstructs from the session log alone, with no event types beyond the two knob events.
- N idle-time flips produce at most one anchored event per knob (a net-zero sequence anchors none — a no-op push from a client echoing current selections records nothing); an approval-policy switch is narrated in at most one coalesced notice; a mid-turn sandbox switch is honored by the next call's stamp.
- A resumed session's overrides apply and are reported to the editor with no special-casing; a default changed while the process was down is narrated before the session's first new request, attributed to the operator.
- Two concurrent sessions never see each other's state, notices, or config options.
- `agent-loop` is untouched — everything rides `systemPrompt.section`, `SessionEventMap` merging, `agent.inject()`, `agent/pre-step`, `agent/prompt-submit`, and the ACP handler surface.
Costs and accepted limits:
- **The one-wrapper illusion is given up knowingly.** A `tools/pre-execute` wrapper plus prompt conventions does not solve sandbox approval — the correct design costs structured denials, native runner probes, per-call policy carriage, and consistent cross-family enforcement, and this design pays it.
- **`read-only` is not yet a cross-family boundary.** Until the fs intent gates decide by the shared mode, the claim holds for bash only; the contract says so honestly (§ In-process tools).
- **Windows has no backend.** Its chain slot is reserved empty — fail-closed, never a fallthrough; filling it is a deferred phase.
- **The Seatbelt rung leans on Apple's deprecated-but-shipped `sandbox-exec` CLI.** As darwin's sole candidate it is selected without probing, so a future removal surfaces at execution as the runner-failure classification — re-thrown `SANDBOX_UNAVAILABLE`, the command never runs; fail closed, never open.
- **Landlock confinement is only as complete as the running kernel's ABI.** Reported as `enforcement: 'partial'` rather than refused — the deliberate trade that keeps the fallback available on older-kernel hosts.
- **The launcher arrives as a registry dependency.** Trusted through its own repository's release pipeline (reviewed C source, native CI builders, byte-pinned publish rehearsal) plus this repo's version pin — the real-kernel e2e legs are what vouch for behavior through the installed bytes.
- **The model may over-ask.** Escalating without denial grounding, or picking `danger-full-access` where `workspace-write` suffices: the description steers and the enum forces the ladder, but the human prompt is the actual gate; the `approval/asked` reasons make over-asking auditable, and a `prepend` policy answerer can auto-reject patterns a deployment never wants.
- **The advertised target set is static while the effective mode is per-session** (schemas are registry-global) — a session already at the widest mode is still offered the fields. Harmless by construction: the strict-wider check at execution, not the enum, is the safety boundary — a non-widening request fails with its own text and never prompts anyone.
- **A granted escalation is not a working sandbox.** An unavailable backend still fails closed even for a granted escalation to a confining mode — at `confine()` when the platform has no chain or every probe fails, at execution when an unprobed sole runner refuses (classified as a sandbox failure, not a command failure) — while a granted `danger-full-access` run never touches the provider at all: there the grant, not the probe, is the authority.
- **An idle switch lives in bridge memory until the next turn anchors it.** A crash in that window reverts it (reported honestly on `session/load`), and a session that never runs another turn never persists it — accepted, with the loop-owned idle commit turn named as future work if durability becomes a requirement.
- **The approval narrator's restart baseline parses prompt prose.** The closed candidate sentence is owned by the writing module itself, so a wording change is a coordinated writer+parser edit in one file; a session whose headers predate the section silently adopts the current policy without a notice.
- **The approval section is still a dynamic prompt surface** (a `'never'` switch breaks provider prompt-prefix caching for that session). Accepted: policy switches are rare, and a model acting on a stale `'never'` is worse. The sandbox knob no longer touches the prompt at all.
- **The model may hold a stale belief about the sandbox mode** (nothing announces a switch). Accepted deliberately: the next attempt's marker or success corrects it, and the observed failure mode of announcing — preemptive refusal — is worse than one wasted retry.
## FAQ
Behavioral and usage questions only — every "why not X?" design question lives in [Alternatives considered](#alternatives-considered), whose job is exactly that.
- **A command came back with `[sandbox: file access denied under read-only mode]` — did it fail?** It RAN, and the kernel refused a file effect: the denial is a result fact orthogonal to exit code. The teaching forbids retrying around it; the one sanctioned move is the same command retried once with an escalation request.
- **How is a BROKEN sandbox told apart from a failing command?** Runner failure outranks denial in classification: a failed run matching the wrap's `runnerFailureSignatures` means the command NEVER ran — foreground re-throws the structured `SANDBOX_UNAVAILABLE` with the runner's stderr line, a background task stamps `sandbox.runnerFailed` and renders its own marker. A broken sandbox can never read as a failing command, and the command never runs unconfined.
- **What happens on a platform with no backend — Windows today?** `confine()` throws the fail-closed `SANDBOX_UNAVAILABLE` and the command never spawns; `win32` is a reserved EMPTY chain, pinned by test to fail closed identically until a Windows runner fills it (§ Deferred phases).
- **`bwrap` is installed on my host but unusable (disabled unprivileged userns, an LSM denying `mount`) — what happens?** The chain probe is functional — it builds and enforces a real profile rather than checking `--version` — so a present-but-unusable `bwrap` fails its probe, selection falls to the registry-installed Landlock launcher, and the verdict is cached for the provider's lifetime.
- **Does the sandbox restrict network or process visibility?** No — `SandboxMode` claims FILE effects only; the bwrap profile deliberately does not unshare pid, and no backend claims network. Whether network restriction becomes its own knob is left open in § The seam.
- **Which tools actually run confined?** OS subprocesses through `ctx.bash` — the bash tools, and hook commands transitively. fs/web/todo execute in-process, where an `execve` wrapper is mechanically meaningless; their `read-only` semantics arrive with the cross-family deferred phase, and until then the contract says bash-only honestly.
- **Does a granted escalation persist, or cover background tasks?** Neither: the grant is consumed by the very call that asked (foreground or background), that one call reports the mode it actually ran under, and every neighbor keeps its own. How escalation should be DEFINED for a background denial that only surfaces later via `bash_output` is left open in § Escalation.
- **When does an editor's mode switch take effect?** Mid-turn: appended immediately, honored by the very next call's stamp. Idle: held on the bridge's session record, anchored at the next turn's `agent/prompt-submit`, with N flips coalescing to at most one event (none if net-zero); a crash before anchoring reverts it and `session/load` reports the truth. The model is not told — its next command simply behaves under the new mode.
- **What survives a restart — and what if the operator changed the config default while the process was down?** Overrides replay from the session log (`effective = fold ?? config`), so a resumed session keeps its modes with zero catch-up machinery; a default that drifted offline changes behavior the same way a switch does (the approval policy, being stated, is additionally narrated with operator/config attribution).
- **What does `enforcement: 'partial'` on a result mean?** The selected backend enforces the subset its kernel ABI governs — e.g. Landlock before ABI v3 does not govern path truncate — and says so structurally instead of refusing the host; the probe's report line distinguishes the cases. The bwrap and Seatbelt profiles govern every promised file effect by construction, so they always report `full`.
## Prior art
In-repo precedents this design copies or contrasts with:
- [The capability-seams RFC](../architecture/2026-06-13-capability-seams.md) — the interface/implementation/consumer split and the "don't split preemptively" timing rule the second consumer satisfied.
- The `dsh-bash` request/spec split and its `owner` field ([the bash vocabulary catalog](../../../core-data-structures/bash.md)) — the per-call carrier template `sandboxMode` rides, and the explicit-`resolve()` defaulting convention.
- [The approval seam RFC](2026-07-06-approval-seam.md) — the channel escalation asks through; its answerer waterfall, audit pair, and one-package rationale are recorded there.
- [Event-sourced sessions](../architecture/2026-06-11-event-sourced-sessions.md) and [the turn-enclosure invariant](../architecture/2026-06-15-turn-enclosure-invariant.md) — the log-as-store foundation the per-session modes fold over, and the commit boundary the anchoring design obeys.
- [The interception-seams RFC](2026-06-30-interception-seams.md) — the `tools/pre-execute` vocabulary the escalation gate deliberately does not reuse (an escalating call has no pre-execute moment of its own).

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# RFC: The session prefix — request-only messages in front of the derived history
Status: implemented
## Problem
A plugin often owns a session-stable opener the model must always see — a skills catalog, an AGENTS.md digest, a workspace baseline. Before this seam the harness offered two homes, and both are wrong for that content. The system prompt is one rendered string: message-shaped content (a user-role `<system-reminder>` envelope, a multi-message primer) does not fit it, and providers weight conversation messages differently from system text. Durable history (`agent.inject()`, a `context/message` at session start) makes the opener permanent: every `deriveMessages()` consumer replays it, the compaction retention walk owns it, forks bake it in stale, and a resume cannot refresh it — a catalog captured at session birth outlives the world it described.
The obvious third option — let a plugin edit the request's `messages` on the way out — is banned by [the reconstructable-requests RFC](../architecture/2026-07-05-reconstructable-requests.md): every loop-built request is a pure function of the session log, so whatever channel carries the opener must log exactly what it sends. What was missing was a request-only message channel with a durable record.
## Decision
`agent/session-prefix` is a waterfall on the agent event map ([`packages/core/agent/src/types.ts`](../../../../packages/core/agent/src/types.ts)): listeners receive a frozen empty seed and return an extension (the canonical contribution is a prepend, `[mine, ...await next()]`, which yields registration order on the wire). The loop ([`packages/core/agent-loop/src/loop.ts`](../../../../packages/core/agent-loop/src/loop.ts)) fires it once per loop instance, lazily before the instance's first `agent/pre-step`; the composed list is deep-cloned, deep-frozen, cached on the instance, and placed in front of the ENTIRE derived history — directly after the provider's system slot — on every request the instance sends ([wire order](../../../core-data-structures/core.md#the-request-envelope-llmcallconfig-and-the-logged-header)).
Three properties carry the design:
- **Request-only, header-logged.** `deriveMessages()` never returns the prefix; its one durable record is `EpochHeader.messagePrefix` on the instance's anchoring `request/header` snapshot — the channel the reconstructable-requests RFC already owns for the request's non-history half, so no new session event exists. The dev invariant ([dsh-invariants](../../../../packages/support/invariants/src/index.ts)) recomputes `messagePrefix + boundary derivation` against every loop-built request; an unlogged prefix cannot reach the wire.
- **Frozen per instance.** Reuse is structural, not disciplined: the cached product cannot change mid-session, so the provider's prompt cache holds by construction and the prefix extends the cacheable region at zero marginal cost per step. A process restart or `ctx.agents.resume()` is a new instance: it recomposes, and any drift lands attributably on the `'resume'` header snapshot. This is the routing rule the seam creates: session-frozen openers ride the prefix; content that changes mid-session rides the append-only history channels (`agent.inject()`, a `tools/post-execute` decision's `additionalContext`, prompt-submit `additionalContext` — [the interception-seams RFC](2026-06-30-interception-seams.md)), each a durable `context/message` paid once and prefix-cached thereafter.
- **Composed before the pressure gate.** Composition precedes the instance's first `agent/pre-step`, and the seam hands the composed value through: `agent/pre-step` carries a `sessionPrefix` parameter and `CompactService.compactIfNeeded(agent, fullSystemPrompt, sessionPrefix, signal)` counts it in its token-pressure estimate — a gate reading the previous instance's folded prefix instead would under-gate a resumed or forked instance whose contributor grew, skipping compaction and shipping an over-window first request. A composition interrupted by a cancel/dispose landing inside the waterfall is discarded, never cached: an abort-aware listener's degraded fallback cannot leak into later requests, and the next turn recomposes under a live signal.
Because composition runs before the boundary snapshot, a composing listener's session append joins the CURRENT request's derived history. Compaction structurally cannot touch the prefix (or the system prompt): it rewrites surface nodes, and header state never enters the surface.
## Testing
**Unit** — [interception.spec.ts](../../../../packages/core/agent-loop/tests/interception.spec.ts) pins compose-once across turns and steps (one composition, zero `request/header-delta`s), canonical prepend ordering, empty-prefix omission from the header, the frozen seed (in-place push throws), held-reference mutation immunity, and composition-precedes-pre-step with the seam receiving the composed value; [cancel.spec.ts](../../../../packages/core/agent-loop/tests/cancel.spec.ts) pins cancel/dispose landing inside the composition window and the discard-and-recompose stale-cache guard; dsh-session codec tests cover the `messagePrefix` fold/diff/apply arms (empty ≡ absent); dsh-invariants tests pin the `messagePrefix + derivation` equation; dsh-compact-basic tests pin that the pressure estimate counts the handed prefix. **Snapshot** — the acp-snapshot normalizer scrubs header prefixes to count-preserving `{{messagePrefix}}` tokens (unit-covered in dsh-acp-snapshot); header content itself is pinned per [the pinned-header scenario RFC](../testing/2026-07-06-pin-request-header-content-in-one-scenario.md), and the example tree loads no prefix contributor, so live goldens stay prefix-free. **e2e** — none prefix-specific: the seam is provider-independent and deterministic; the with-key cache measurement in [request-cache.e2e.ts](../../../../packages/core/agent-loop/tests/request-cache.e2e.ts) already proves the cacheable-prefix economics the design rests on.
## Alternatives considered
- **Per-request `before`/`after` slots recomputed every step** (the shape first proposed: a waterfall firing on every request, contributing frozen `before` messages ahead of the history and fresh `after` messages behind it) — rejected. A per-step `before` recompose invites silent drift — nothing anchors it to the log short of logging a header delta per step — and an `after` slot sits behind the growing history, so its tokens re-pay on every request and everything after it is uncacheable. Measured against the alternatives, every current update pattern is served cheaper by a durable append (paid once, cache-read thereafter), and the only content with no home was the session-stable opener — which wants freezing, not recomputation.
- **A system-prompt section** (`system-prompt/assemble`) — rejected for this content: the assembly renders to the single `system` string, so message-shaped openers do not fit, and the system prompt is deliberately re-assembled per step (with header deltas when it changes) while the opener wants instance-frozen semantics.
- **A durable history opener** (`inject()` at session start) — rejected: permanent history is the failure mode in the problem statement — replayed everywhere, compactable, stale across resumes.
- **Compose per turn instead of per instance** — rejected: a turn-boundary recompose either desyncs silently from the log or forces a header delta per change, and it busts the provider cache exactly as often as it fires; the legitimate refresh point is the instance boundary, where the `'resume'` snapshot already records drift attributably.
- **Compose lazily at the first request and let compaction read the folded header** (the shape as first merged) — superseded in review: the fold matches the live prefix only from the instance's second request on, so on a resumed/forked instance's first step the pressure gate read the PREVIOUS instance's prefix and could under-gate. Composing before the first pre-step and handing the live value through the seam makes the estimate exact at every step.
- **A dedicated session event carrying the prefix** — rejected: the header events are the request's non-history record by design; a second event would be a second home for the same fact and another codec to keep total.
## Consequences
- `agent/pre-step` and `CompactService.compactIfNeeded` carry a `sessionPrefix` parameter: every pre-step listener and compaction backend sees the real per-instance value (all in-repo implementations updated in the same change, per the pre-release stance).
- A contributor whose content changes mid-session is not re-read until the next instance — by design. A deployment needing mid-session catalog updates routes the change notice through the append-only history channels and pays one durable `context/message`.
- The dropped `after` slot leaves no request-only channel near the request tail; nothing in the repo needs one, and adding it back would re-open the every-step re-pay cost the design exists to avoid.
- The `request/header-delta` `messagePrefix` arm (whole-array replacement, empty array encoding transition to absence) exists for codec totality; the loop never exercises it, because the cached prefix cannot change within an instance.
- An empty composition is canonical absence: no-contributor deployments log no extra header bytes and their requests are the bare derivation.

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# RFC: Repeat-tool-call guard plugin
Status: implemented
## Problem
A model stuck in a loop re-issues the same tool call with byte-identical arguments — re-running a failing grep, re-reading an unchanged file, polling a command that already gave its answer — and each round trip burns tokens, wall-clock, and (for paid APIs) money without adding information. The harness has nothing that notices: the loop has no step budget, no plugin tracks call repetition, and the model only escapes when it happens to vary its own behavior. The failure mode is real and cheap to detect — [pi-repeat-tool-guard](https://github.com/Kingwl/pi-repeat-tool-guard) ships exactly this as a pi coding-agent extension: count consecutive identical calls and, past a threshold, append a `<system-reminder>` telling the model to stop repeating itself and change course.
The harness already has every seam the pi extension uses, and better ones: [the interception-seams RFC](2026-06-30-interception-seams.md) gives `tools/post-execute` a sanctioned way to attach model-facing context to a finished call, the loop buffers and injects that context with call/result adjacency preserved, and injected context is a logged `context/message` — so a native guard satisfies the model-visible ⟺ logged rule with no new session event. What was missing was only the plugin itself.
## Decision
The guard is a loop-hygiene plugin, not a model-facing tool: it never appears in the tool list, never vetoes or rewrites a call, and adds exactly one behavior — it watches each agent's stream of tool calls, counts runs of consecutive calls to the same tool with identical canonicalized arguments, and at configured run lengths injects an escalating advisory reminder telling the model to stop repeating itself, re-read the last result, and either change approach or conclude. The purpose is to break unproductive loops within a few wasted steps instead of letting them run to the turn's natural end — while leaving the decision (retry differently, gather more evidence, or finish) entirely with the model, so a legitimately repeated call is delayed by nothing and blocked by nothing.
The plugin is `@deepseek-ai/dsh-repeat-tool-guard` at `packages/guard/repeat-tool-guard/`, opening the `guard/` group for loop-hygiene plugins (single-package groups have precedent: [the todo-write RFC](2026-06-29-todo-write-tool.md) shipped `todo/tool-todo`). It registers three listeners and holds all state in plugin-local maps keyed by `AgentId` — the tool registry is a context-level singleton whose waterfalls interleave every agent's calls (subagents run on the same context), so per-agent keying is correctness, not polish.
- **`tools/post-execute` (waterfall)** — the one detection point. The listener receives `(exec, result)` together, so counting and reminder delivery need no cross-event pending map (the pi extension needs one only because its `tool_call`/`tool_result` hooks are separate events). It always delegates via `next()` and, when a threshold is hit, folds a reminder onto the downstream decision's `additionalContext` — the observe-and-enrich posture [the hooks bridges](2026-06-30-hook-bridges.md) already use, honoring the waterfall contract. Counting happens here rather than in `tools/pre-execute` because post-execute also runs for denied calls (`ToolRegistry.execute` routes a deny through the same pipeline), and a model hammering a denied call is exactly the loop worth breaking.
- **`agent/prompt-submit` (waterfall)** — pure reset hook: delegate via `next()`, clear the submitting agent's chain. A user interjection changes the context; repetition across it is not a loop.
- **`agent/status` (emit)** — on `disposed`, drop the agent's state, bounding the maps over harness lifetime.
### Detection semantics
The chain key is `(tool name, canonical arguments)`; a call identical to the previous tracked call increments the agent's consecutive counter, a different tracked call resets it to 1. Canonicalization is a deep key-sort plus `JSON.stringify`: `ToolExecution.arguments` is by construction the loop's `JSON.parse` output (or the raw string fallback for malformed argument JSON, which is itself a comparable value), so the pi original's bigint/circular/`undefined` handling has no inputs here and is deliberately dropped.
Two deliberate rules, both documented in [the package README](../../../../packages/guard/repeat-tool-guard/README.md) because they are behavior a reader would otherwise guess at:
- **Untracked calls are transparent to the chain.** A call excluded by `include`/`exclude` neither increments nor resets the counter, so `grep X → todo_write → grep X` still counts as two consecutive `grep X` when `todo_write` is excluded. This is what makes exclusion useful — bookkeeping tools interleaved into a loop must not launder it — and it is the pi extension's (undocumented) semantics, kept on purpose and written down.
- **Calls without an agent are ignored.** A direct `ctx.tools.execute()` caller (tests, non-loop consumers) has no model to remind and no `AgentId` to key on.
### Reminder delivery
Reminders ride `additionalContext` (source `{kind: 'plugin', plugin: 'repeat-tool-guard'}` — the label is load-bearing per `HookContext`), never a `content` replacement: the `tool/result` event stays the tool's own output for audit, and the loop appends buffered context as `context/message`(s) after the step's results, which the session renders as the tagged synthetic-user envelope and derived history replays. Thresholds escalate: the first configured threshold gets a short "you are repeating yourself, analyze the previous result" nudge; each later threshold gets the detailed form naming the tool, the repeat count, and the canonical arguments (head-truncated at `argumentsPreviewChars`, default 500 — a looping `write`-sized payload must not ride into the next request unbounded; the chain key always compares the full canonical string), and stating that the calls made no progress. The pi original hardcodes the gentle text to the literal count 3; the guard keys it to `thresholds[0]`, fixing that bug in the port. When the downstream decision already carries `additionalContext` (a hook bridge on the same call), the guard concatenates content under its own `source` — a `HookContext` holds one `MessageSource`, and `source.kind` is what framing depends on.
### Config
```yaml
- id: repeat-tool-guard
name: '@deepseek-ai/dsh-repeat-tool-guard'
config:
thresholds: [3, 5, 8] # default; consecutive counts that trigger a reminder
include: [] # tool-name patterns to track; empty ⇒ all tools
exclude: [todo_write] # tool-name patterns transparent to the chain
argumentsPreviewChars: 500 # default; cap on arguments quoted in the detailed reminder
```
`thresholds` is validated at load and throws on an empty list, a non-integer, a value below 2, or a duplicate — misconfiguration fails loud, replacing the pi original's silent fall-back to defaults. `include`/`exclude` entries support `*` wildcards. Patterns are predicates over whatever tools exist at call time, not references to a registry entry, so an entry matching no currently registered tool is NOT an error — unlike `toolOrder`'s referent check, `exclude: [mcp_*]` must stay valid in a deployment that loads no MCP tools.
## Testing
**Unit** — the suite drives a real agent loop against a scripted mock adapter (no network) and covers, at per-file 100%: counting/reset semantics (identical, different-tracked, untracked-transparent, prompt-submit reset, disposal cleanup, per-agent isolation), canonicalization (deep key-order insensitivity), threshold escalation including the `thresholds[0]` gentle-text rule, denied-call counting, no-agent transparency, wildcard escaping, config fail-loud cases, and both fold-onto-downstream paths (block and accept-with-replacement). **Snapshot** — the `repeat-tool-guard` scenario in the acp-agent example suite scripts five identical `todo_write` calls and pins both reminder tiers (gentle at the third, detailed at the fifth) as `context/message`s in the ACP transcript and the session log; the guard is loaded in the example's live tree (`cordis.yml`), inert for every other scenario (none repeats a call three times). The scenario is authored keyless (like `error-finish`/`cancel`): deterministically forcing a live model to repeat one call three times is not a stable recording. **e2e** — none: the plugin is provider-independent and deterministic, and the seam contracts it relies on are e2e-covered by their owners.
## Alternatives considered
- **Append the reminder into the tool result** (`accept` with replaced `content` — the pi extension's mechanism, which patches result content because that is the only channel its API offers) — rejected: it makes the logged `tool/result` lie about what the tool returned, and `additionalContext` exists precisely as the separate sanctioned channel for post-execute commentary, with loop-level buffering that preserves call/result adjacency.
- **Count in `tools/pre-execute` with a pending-reminder map** (the pi two-phase shape) — rejected: post-execute alone sees `(exec, result)` together and also fires for denied calls, so one listener with no cross-event state covers strictly more attempts with less machinery.
- **Escalate to `block` at the highest threshold** — rejected for the initial scope: a blocked call punishes legitimate identical repeats (polling a long-running terminal, re-checking a file the agent expects to change), and an advisory reminder keeps the model in control. Revisit with evidence; the decision shape (`PostToolDecision`) already supports it.
- **A per-deployment external hook via the CC/Codex bridges** (a `PostToolUse` script) — rejected as the answer: it works for one deployment, but a shipped, unit-tested, `cordis.yml`-configurable plugin is the harness-native form, without per-call subprocess cost.
- **A loop-level step or repetition budget in `agent-loop`** — rejected: "plugins, not loop changes"; a hard step budget is a blunter, orthogonal control that would need its own proposal.
- **Fuzzy/near-identical detection** (normalized paths, similar-but-not-equal arguments) — rejected: exact match after canonicalization is cheap, deterministic, and explainable to the model; similarity thresholds invite false positives and need evidence before they earn complexity.
- **Placing the package in `core/`** — rejected: core is the product spine; a behavioral guard is an optional leaf plugin, and the `todo/` precedent is a small dedicated group per plugin family.
## Consequences
- The reminder is advisory by design: idempotent polling patterns that repeat identical calls on purpose still receive nudges past the thresholds, and the pressure valves are config (`thresholds`, `exclude`) plus reminder text that explicitly allows finishing when enough evidence has been gathered. Each trigger costs reminder tokens on the next request; thresholds bound the frequency.
- Chain state is in-memory only: a session resumed from persistence starts with a fresh chain, so a loop spanning a resume draws its reminders later than a live one — accepted, the guard is a heuristic nudge, not a logged invariant, and persisting counter state would buy little for real complexity.
- When multiple post-execute producers attach context on one call, the fold concatenates under the guard's `source`; ordering between plugins follows listener registration order. The seam cannot represent mixed provenance — a limit inherited from `HookContext`, not owned by this plugin.
- Implementing the snapshot tier surfaced a hidden assumption in the suite kit: the fixture guard equated "authored model scenario" with "override-driven". The `Scenario` table now carries an explicit `overridden` flag, and the sidecar's presence is checked BOTH ways against it (an unregistered stray sidecar would silently replace the derived script) — the suite kit is stricter than it was before this plugin existed.
## Deferred
- Compaction does not reset chains: a compacted history changes what the model sees, but the repetition risk usually survives compaction.
- Escalating to `block` at a high threshold is not implemented; `PostToolDecision` already supports it if evidence arrives.
- Subagent chains stay isolated per agent; no sharing mechanism exists until a concrete case appears.

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# RFC: The self-referential cordis toolset
Status: implemented
## Problem
Everything in this harness is a cordis plugin, but the agent running inside that plugin runtime cannot see or touch it: it cannot enumerate the services and events around it, cannot extend itself with a new tool mid-session, and cannot compose capabilities it invents. Handing the model that power is worth exploring — a self-referential agent that inspects and modifies its own runtime — but it raises three correctness problems at once, and the design is about answering them rather than the raw "let the model run code" mechanic.
First, model-written registration must be validated where it happens: a malformed tool schema has to fail at registration, not when a later request tries to assemble it into a prompt. Second, model-written code has to call service APIs whose source it has never seen — guessed method signatures and, worse, guessed return-value shapes cost many steps of blind probing. Third, everything the model mounts must be fully disposable, by the model on demand and by the ordinary plugin lifecycle when the host plugin reloads, or a long session accretes orphaned listeners and tools.
## Decision
The toolset ships as [`@deepseek-ai/dsh-tool-cordis`](../../../../packages/cordis/tool-cordis/README.md) — a new top-level `packages/cordis/` group — and is demoed by [`examples/cordis-agent`](../../../../examples/cordis-agent/README.md). It gives the model three tools over the live cordis runtime it is running inside: inspect it, mount model-written plugins into it, dispose them again.
The trust stance, stated once and threaded through the rest: the `node:vm` sandbox isolates the global context only — it prevents accidental global pollution, not malice — and the `ctx` a mounted plugin's `apply` receives is a whitelist façade that narrows the *surface* (framework internals withheld) but not the *privilege* of what it exposes. The verbs the façade does expose reach the real runtime: a mounted tool can shell out through `ctx.bash`, read the filesystem through `ctx.fs`, reach the network through `ctx.web`. Neither the sandbox nor the façade is a security boundary; handing the model this power is the point of the toolset. A deployment loads this plugin exactly as deliberately as it grants a bash tool — an opt-in capability in the app's `cordis.yml`, never a product default.
### The three tools
| Tool | Contract |
|---|---|
| `cordis_inspect` | Read-only report over the live runtime, one Markdown section per `what` value (omit `what` for all sections). Never mutates. |
| `cordis_mount` | Evaluates `code` (the body of an async JavaScript function) in a `node:vm` sandbox; the code must `return` a cordis plugin, which is mounted as a child of the `cordis-dynamic` group fiber and tracked under a fresh id (`dyn-1`, `dyn-2`, …). |
| `cordis_unmount` | Disposes one dynamic mount by id and returns only after disposal reaches quiescence — every registration the plugin made is unwound, not merely requested to stop. |
`cordis_inspect` sections: `services` (every provided ctx service and the owning fiber, non-active owners flagged), `plugins` (a flat list of every loaded plugin with its lifecycle state, from `ctx.registry` — what capabilities are loaded, deliberately not the tree shape), `tools` (what the model can call), `dynamic` (the mount table: id, name, state, provided services, awaited services), `api` (live service signatures + the type shapes they reference, from the generated catalog), and `events` (harness events with dispatch mode and signature). The model-facing tool descriptions carry the operational rules the model needs at call time; [the generated tool catalog](../../../tool-catalog.md) is their exhaustive rendering.
### Sandbox semantics
Mount code runs via `vm.createContext` + `runInContext`, wrapped as the body of an async function under a per-mount filename (`cordis-mount-<id>.js`). The vm gives the code a fresh realm: writes to `globalThis` stay inside the sandbox, and no Node API is handed in — capability access is *steered* toward the cordis services (`ctx.fs` for files, `ctx.web` for HTTP, `ctx.bash` for processes, the `ctx.timer` helpers for timing) rather than Node built-ins, so a well-behaved mount stays inspectable through `cordis_inspect` and disposable with its fiber. This is steering, not containment: consistent with the trust stance above, the small global surface keeps *honest* code on the cordis services but is not a security boundary — the host-realm helpers it exposes (`harness`, `console`, `btoa`) are reachable functions, so mount code that goes looking (through such a helper's `.constructor`, say) can still reach the host realm and Node itself, which is accepted because the `ctx` a mount ultimately receives is fully privileged anyway. The `vmTimeoutMs` config bounds only the synchronous portion of evaluation; an async body escapes the bound (also acceptable under the trust stance).
Sandbox globals are deliberately small: a tagged write-through `console` (`[cordis:<id>] …` on the host stdout/stderr, so a listener that fires long after the mount call still lands somewhere the user sees), the `harness.defineTool` / `harness.registerTool` registration pair, the encoding primitives fresh vm contexts lack (`btoa`/`atob` as host closures over `Buffer` — a sanctioned exception, `Buffer` itself is never exposed — plus `TextEncoder`/`TextDecoder`), and callable traps over the withheld Node APIs (`require`, `setTimeout`/`setInterval`/`setImmediate`/`clearTimeout`/`clearInterval`, `fetch`) that throw a redirect naming the cordis alternative. Only function-shaped globals are trapped; `process` and `Buffer` stay `undefined` so a `typeof` feature probe stays inert rather than detonating a throwing accessor.
Three boundary mechanisms make model-written code behave correctly across the realm seam. **Dual-realm `instanceof`**: most objects sandbox code touches are host-realm (tool `args`, event payloads, service returns), so a plain `x instanceof Array` in the vm would silently be false — a per-sandbox prelude gives the vm realm's own constructors a `Symbol.hasInstance` that checks both the vm constructor and its host counterpart, patching only vm-realm globals. **Realm normalization of tool results**: objects built inside the vm carry the vm realm's `Object.prototype`, which the session log's append-time plainness check (`isJsonValue` in `dsh-session`, a prototype-identity comparison) rejects, so the sandbox's `harness.defineTool` JSON round-trips every `execute` return into the host realm — which also projects it onto exactly what the log durably stores — and then shape-checks it against the two `ToolExecuteReturn` forms, so a JSON-valid but wrong-shape return (a bare string, `{ content: 'ok' }`) fails that one call with a teaching error instead of entering the log as corrupt tool-result content. **A whitelist context façade**: the `ctx` a mounted plugin's `apply` receives is NOT the real context nor a pass-through proxy over it — it is a façade exposing only what a mount legitimately needs (`tools.register` marker-guarded, a read-only `tools.get`/`schemas`, `on`/`once`, `provide`, the timer helpers, and the services the plugin DECLARED in `inject`), with every framework-plumbing member (`root`, `parent`, `fiber`, `reflect`, `registry`, `extend`, `isolate`, `intercept`, `plugin`, `set`, `mixin`, …) denied with a teaching error. This closes an escape *class* rather than a single hole: a proxy that merely special-cased `ctx.tools` still handed back the raw context through `ctx.root`, `ctx.extend()`, or a service instance's `.ctx`, and mount code could then `ctx.root.tools.register({…})` to bypass the marker check and realm normalization — a raw vm-realm result then errors a real agent turn at the plainness check. The façade has no context-valued member to reach, and the one indirect leak (an injected-service method returning a `Context`) is rejected on the way back to sandbox code. Two narrower rules complete the surface. First, **service access requires an `inject` declaration**: reaching a service the mount did not declare is refused even when a global provider is live — otherwise a mount could depend on a provider cordis never sees, and unmounting that provider would neither park the consumer nor unwind the tools it registered, leaving a model-visible tool that fails only at execution time. Because the read is gated on the declaration, cross-mount `provide`/`inject` keeps its lifecycle guarantees (the plugin's own `inject` and the fiber's pending/active gating drive activation and unload); only the `apply`-time `ctx` surface is narrowed. Second, **`ctx.tools.get` returns a read-only schema view** (name/description/parameters), never the live `ToolDefinition` — handing back the definition would expose its `execute`, letting mount code call another tool directly and bypass `ToolRegistry.execute` and its pre/post-execute hooks and accounting; a mount that wants to invoke a tool must go through the registry, and one that wants to introspect gets the same view `schemas()` returns.
Boundary errors are written around the mistakes models actually make (see [Consequences](#consequences) for how each was found), and the boundary normalizes rather than lectures wherever the input has exactly one meaning: schema `parameters` accept the JSON-Schema dialect models write by strong prior — the `{ type: 'object', properties, required: […] }` wrapper unwraps to the SchemaSpec DSL (the `required` array becoming per-property flags, at any nesting level), `type: 'integer'` maps to `number`, and `required: false` reads as optional — while genuinely meaningless input is rejected with the vocabulary enumerated (an unknown type lists the five valid ones; a non-boolean `required` names the rule). The remaining teaching errors: an unbalanced `});` closing gets the vm's offending source line plus a "code is a function body" reminder; TypeScript syntax gets the remove-annotations fix (detected on the failing line only, so an ` as ` inside a description string does not misfire); a forgotten `return` gets the two valid plugin forms; a Node built-in call gets the redirect to its cordis service; a tool-name collision on re-mount gets the unmount-first-then-remount recipe.
### The dynamic group and mount lifecycle
Every dynamic mount is a child of a single `cordis-dynamic` group fiber, itself a child of the `tool-cordis` plugin's fiber. The group exists so the mounts form one subtree: they are disposed as a unit, and disposing `tool-cordis` (HMR reload, config unload) cascades over every mount through the ordinary parent→child fiber lifecycle — no bespoke cleanup. Mounting settles before it reports: the returned fiber is `await()`ed, and a startup error (a throwing `apply`, a duplicate tool name, a duplicate service) disposes the fiber and surfaces as the tool error, so a failed mount never lingers. A settled fiber that is not active is a legal pending mount — cordis semantics for unsatisfied `inject` — kept mounted and reported with what it waits for. Everything the plugin registers is an effect on its fiber, so `cordis_unmount` is nothing but an awaited `fiber.dispose()`.
### Cross-mount composition via provide/inject
Mounts relate to each other through ordinary cordis service semantics, with their ids as the lifecycle handles: mount A calls `ctx.provide('foo', value)`, mount B declares `inject: ['foo']` and activates the moment `foo` exists; mounted first, B stays pending and names the missing service; unmounting A sends B back to pending (its registrations unwound) and a later re-provide re-runs B's `apply` through a fresh sandbox façade; a duplicate provide fails loud with the owning fiber named. One realm caveat: a service value provided by a mount is a vm-realm object — method calls on it work from anywhere, but consumers must not assume host prototypes on it.
### The generated API catalog
`cordis_inspect what:"api"` and `what:"events"` answer from a machine-readable catalog generated at build time, never a hand-maintained table that would drift from the JSDoc it paraphrases. [`scripts/gen-cordis-api.ts`](../../../../scripts/gen-cordis-api.ts) reuses `collectServices` / `collectEvents` from [`scripts/gen-cordis-catalog.ts`](../../../../scripts/gen-cordis-catalog.ts) — the same AST walk that generates [the cordis service catalog](../../../cordis-catalog/services.md) and [events catalog](../../../cordis-catalog/events.md) — and emits `packages/cordis/tool-cordis/src/api-catalog.ts`, a committed, banner-commented data module. The artifact carries, per service, its key + one-line summary + raw method signatures; per event, name + `@mode` + signature + summary; the comment-stripped declarations of every exported type the service signatures reference (transitive closure — so a consumer sees that a bash run's `stdout` is `{ text, truncated }`, not a string); plus the curated inherited `ctx` surface shared with the cordis catalog generator. A type name declared in more than one package (each plugin's `Config`) is dropped as ambiguous, and an oversized declaration is truncated with a marker.
Freshness is gated like every generated artifact: `pnpm run verify-cordis-api` (in `doc-sync`) regenerates in memory and fails on any diff, so a JSDoc edit that changes a public signature cannot ship without regenerating the catalog the model reads. At runtime the inspect tool intersects the catalog with the live runtime rather than dumping it: live catalogued services render summary + signatures, live services without a catalog entry (mount-provided ones) render name + owning fiber, catalogued services with no live provider are listed tersely, and the referenced type shapes follow.
### Configuration, rendering, and observability
The plugin exposes one config field, validated by schemastery and documented in [the config catalog](../../../config-catalog.md): `vmTimeoutMs` (default 5000), the millisecond bound on the synchronous portion of mount-code evaluation. Tool names, the `cordis-dynamic` group name, and the `dyn-` id prefix are structural vocabulary and stay fixed. All three tools render as `generic` cards per [the tool cookbook](../../../cookbook/adding-a-tool.md) (`cordis_inspect` a `read`, `cordis_mount` an `execute` carrying the code as `rawInput`, `cordis_unmount` a `delete`), with no `presentResult` overrides.
Model-visible ⟺ logged holds with no new session event type: a mount or unmount is visible only through its own `tool/call` / `tool/result` pair, which the loop logs, and the changed tool set a mount induces is logged by the request-header delta the loop already emits when schemas change between steps. There is deliberately no `cordis/mount` provenance event — it would duplicate what the tool-call pair records. Dynamic mounts are process-lifetime, not session state: resuming a persisted session rehydrates the conversation but does not re-mount plugins.
## Alternatives considered
**A structured per-capability registration tool instead of `cordis_mount`.** The most tempting alternative is a `cordis_register_tool` with explicit `name` / `description` / `parameters` / `code` fields (and siblings `cordis_register_listener`, `cordis_register_service`, …) rather than a single "mount a plugin" primitive. It was rejected because its one real win — no plugin boilerplate for the single commonest case — does not pay for its costs, while a single mount primitive answers every capability at once.
| Dimension | Structured per-capability tools | Single `cordis_mount` |
|---|---|---|
| Schema correctness | `parameters` is still a model-written JSON object needing SchemaSpec validation, merely one step earlier | The same validation runs at the sandbox boundary, with the same instructive errors |
| The code field | An `execute` body is still model-written JS in a vm; the realm and service-call correctness problems are unchanged | One sandbox, one normalization path, one guarded registration |
| Capability coverage | Tools only; listeners, services, `inject` relations each need another structured tool — a surface that grows without bound | One vocabulary (a cordis plugin) covers every effect, present and future |
| Cross-mount composition | Not expressible in a tool-registration payload | Native `provide`/`inject`, ordinary cordis semantics |
| Inspectability | Registers something the plugin list cannot show as a plugin | What the model mounts is exactly what `cordis_inspect` renders |
| Model ergonomics | Wins for the single most common case (no plugin boilerplate) | Mitigated by the canonical recipe in the mount description plus boundary errors that teach the fix |
The correctness investment therefore goes where it pays for every capability at once: the generated API catalog surfaced through `cordis_inspect`, and sandbox-boundary validation whose error messages teach the correct call. A structured registration tool remains addable later as sugar that synthesizes mount code; nothing here forecloses it.
**A hand-maintained service/event reference in the tool.** The first cut of the inspect tool carried a hand-written table of service method signatures. It was replaced by the generated `api-catalog.ts` because a hand table drifts from the JSDoc the moment a signature changes and nothing gates the drift, whereas the generated artifact is freshness-checked against the same AST the docs use.
**A new `cordis/mount` session event.** A durable provenance event recording each mount (source, name) has clear precedent (`hook/invoked`, `compact/start`). It was declined for v1: mount and unmount are already visible as `tool/call` / `tool/result` pairs and the tool-set change is already logged as a request-header delta, so a dedicated event would only duplicate the record. It remains addable if an audit use case needs mount provenance separable from the tool call.
**A hardened / capability-restricted sandbox.** Trapping Node built-ins and handing mount code a whitelist façade rather than the raw context might suggest an intent to sandbox for safety. It is explicitly not that: the traps and the façade narrow the *surface* mount code sees — steering it onto cordis services and away from leak-prone Node built-ins and framework internals — for correctness and to close the unguarded-context escape, but the capabilities the façade exposes (`ctx.bash`, `ctx.fs`, `ctx.web`) reach the real runtime, so it is not a security boundary. A real one (separate process, permission prompts) was out of scope for a dev/opt-in toolset and would fight the entire point — handing the model the live runtime.
## Consequences
The toolset is a deliberate opt-in with a fully-privileged `ctx`, so a deployment adopts it as consciously as a bash tool. Several facts follow that the tool descriptions warn the model about directly: a waterfall listener (e.g. `tools/pre-execute`) that returns without calling `next()` vetoes the chain, so a mounted listener can lobotomize the agent's own tool dispatch ([waterfall semantics](../../../cordis-primer.md#cordis-waterfall-semantics)); mount code runs inside a tool call of the current turn, so awaiting anything that resolves only after the turn deadlocks; `vmTimeoutMs` bounds synchronous evaluation only; and mounts do not survive session resume.
The instructive boundary errors were not guessed — they were written against live self-design sessions in which a real model was asked to build itself coding tools. Those sessions surfaced the failure modes now mitigated: the model closed a returned plugin object with `});` and got only a bare `Unexpected token ')'` it retried blind; it hit a false-positive "this is TypeScript" hint because a description string contained the word "as"; it guessed a bash run's `stdout` was a string and burned six steps building throwaway debug tools to discover it is `{ text, truncated }`; and it wrote tool schemas in the JSON-Schema dialect (`type: 'integer'`, `required: false`, then the full wrapper) three rejections in a row — the rejection text itself pushing it from a nearly-correct DSL attempt back to raw JSON Schema. The fixes — source-line-plus-caret parse errors, line-scoped TypeScript detection, the type-shape closure in the API catalog, the redirect traps, and schema-dialect normalization in place of rejection — cut later sessions from dozens of tool calls with repeated errors to a first-try success on every capability, including a model that hit a Node-`setTimeout` trap and self-corrected to `inject: ['timer']` in one step.
Coverage is named per tier: package unit specs drive the three tools through a real `ToolRegistry` on a real fiber tree (the mount success/failure family, vm isolation, dual-realm `instanceof`, realm normalization against the real `isJsonValue`, the SchemaSpec and raw-registration rejections, the Node-API traps, the cross-mount provide/inject matrix, catalog-backed `api`/`events` rendering, config validation, presenters, quiescent unmount, and the HMR cascade), a `MockAdapter` loop test proves a tool mounted in one step is dispatchable in the next, and the example carries a keyless Loader smoke plus a with-key smoke that world-verifies a live model mounting a listener, building its own tool, and composing two mounts. No snapshot scenario is added: the toolset ships in no ACP-served app, so it changes no editor-facing transcript, and its presenters are unit-tested pure functions — adding it to the ACP example solely for a golden would rewrite the pinned request-header tool set of every recorded scenario.

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# RFC: Doc-sync enforcement
Status: implemented (accepted 2026-06-14)
Status: implemented
<!-- XXX: legacy ADR/RFC body format, not yet normalized to a unified RFC template. -->
## Context
## Problem
AGENTS.md promises that docs and code stay strictly in sync, but the promise was verified by eyeball. Review caught drift twice — a cookbook example contradicting the type policy, and a README citing the wrong `registerAdapter` call. Out-of-sync docs are worse than no docs, and this codebase is built primarily by agents that follow gates far more reliably than prose (mechanical quality gates). Two classes of doc drift are mechanically checkable: code blocks that no longer compile, and the event-taxonomy table that duplicates the `interface Events` declarations.
@@ -13,15 +11,20 @@ AGENTS.md promises that docs and code stay strictly in sync, but the promise was
Two gates, mirroring the existing `scripts/` style (tsx ESM, one job each):
1. **`doc-typecheck`** extracts every fenced ` ```ts ` block from `README.md`, `docs/**`, and `packages/*/README.md`, writes them to a temp project extending the root `tsconfig.json`, and compiles it with `tsc -b`. The temp project reuses the source `paths` map and the root project references, so documentation examples see source while vendored code remains checked under its own tsconfig settings. A block that is a deliberate sketch opts out with an explicit ` ```ts ignore-check ` info string; the script reports the opt-out ratio and fails if it exceeds half, so the escape hatch can't quietly become the norm.
2. **`verify-event-taxonomy`** extracts the event names from the `interface Events` blocks across `packages/*/src` and from the taxonomy table in `docs/architecture.md`, and asserts the two sets match exactly. Verify, don't generate: the table keeps its hand-written Mode/Purpose columns; only the set of names is checked. (Landing this surfaced three events the table had been missing — `tools/change`, `llm/adapter-change`, `system-prompt/change`.) **Superseded** by [the generated cordis catalog](2026-06-20-generated-cordis-catalog.md): this gate and its `architecture.md` table are retired in favor of a fully-generated `docs/cordis-catalog/events-and-services.md` and its `verify-cordis-catalog` freshness gate. The other gates here (`doc-typecheck`, and the `verify-md-wrap` amendment below) are unaffected.
2. **`verify-event-taxonomy`** extracts the event names from the `interface Events` blocks across `packages/*/src` and from the taxonomy table in `docs/architecture.md`, and asserts the two sets match exactly. Verify, don't generate: the table keeps its hand-written Mode/Purpose columns; only the set of names is checked. (Landing this surfaced three events the table had been missing — `tools/change`, `llm/adapter-change`, `system-prompt/change`.) **Superseded** by [the generated cordis catalog](2026-06-20-generated-cordis-catalog.md): this gate and its `architecture.md` table are retired in favor of the fully-generated `docs/cordis-catalog/events.md` + `docs/cordis-catalog/services.md` and their `verify-cordis-catalog` freshness gate. The other gates here (`doc-typecheck`, and the `verify-md-wrap` amendment below) are unaffected.
Both run via a shared `doc-sync` package.json script that the lefthook pre-push hook and CI both invoke ([mechanical quality gates](2026-06-11-quality-gates.md): hooks and CI call the same scripts, so the gate fires locally before a push — not only after it). They run after `pnpm run typecheck`, which validates the package/vendor build graph that doc-typecheck references. API-extractor golden reports ([the deferred API-extractor-reports proposal](../../proposed/process/2026-06-11-api-extractor-reports.md)) were deliberately **deferred** — low value for an internal monorepo where reviewers already see the source diff, and a heavy, finicky dependency.
Both run via a shared `doc-sync` package.json script that the lefthook pre-push hook and CI both invoke ([mechanical quality gates](2026-06-11-quality-gates.md): hooks and CI call the same scripts, so the gate fires locally before a push — not only after it). They run after `pnpm run typecheck`, which validates the package/vendor build graph that doc-typecheck references.
**Amendment (2026-06-17):** a third gate, **`verify-md-wrap`**, was later folded into `doc-sync`. It parses each in-scope Markdown file (`README.md`, `docs/**`, `packages/*/README.md`, plus `AGENTS.md` / `packages/AGENTS.md`) with `mdast-util-from-markdown` + GFM and fails on any `paragraph` node spanning more than one source line, enforcing the docs/AGENTS.md "one physical line per paragraph" writing rule. Same verify-don't-generate principle: it reports hard-wraps and never rewrites, so it adds no formatting churn. `doc-sync` is now three gates.
## Alternatives considered
- **API-extractor golden reports** ([the deferred proposal](../../proposed/process/2026-06-11-api-extractor-reports.md)) — deliberately deferred: low value for an internal monorepo where reviewers already see the source diff, and a heavy, finicky dependency.
- **Generating the taxonomy table from source** instead of verifying names — rejected as more machinery than the problem warranted; the table kept its hand-written Mode/Purpose columns until [the generated cordis catalog](2026-06-20-generated-cordis-catalog.md) superseded the check entirely.
## Consequences
- Doc drift in the checkable classes now fails the pre-push hook and CI instead of waiting for a reviewer to notice. This is an instance of the "mechanical gates over prose" principle.
- Making doc snippets compile costs a few stub imports/`declare`s; the `ignore-check` ratio must stay low or the gate is theater (the ratio guard enforces this).
- The taxonomy check is name-only — a wrong Mode or Purpose column still needs human review. Generating the table from source was considered and rejected as more machinery than the problem warrants.
- The taxonomy check is name-only — a wrong Mode or Purpose column still needs human review.
- API reports remain available to revisit if the packages are ever published externally.

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# RFC: Mechanical quality gates over prose guidelines
Status: implemented (accepted 2026-06-11)
Status: implemented
<!-- XXX: legacy ADR/RFC body format, not yet normalized to a unified RFC template. -->
## Context
## Problem
This codebase is developed primarily by coding agents. Agents follow enforced gates far more reliably than prose conventions, and "a lot of work" is not a cost argument when agents do the labor. Early evidence: tests that didn't typecheck shipped (vitest doesn't typecheck) and were only caught by a review.
@@ -16,10 +14,12 @@ Every AGENTS.md promise gets a command that exits non-zero, wired into git hooks
- ESLint strict-type-checked + @stylistic (the house style, enforced); vendored code excluded.
- Per-file 100% coverage on `packages/*/src` (v8); unreachable defensive guards carry `/* v8 ignore */ ` with stated reasons instead of deletion.
- knip (dead code/deps), publint (package correctness), workspace constraints (workspace rules: private, cordis peer+dev, uniform version, ESM), and a NodeNext consumer typecheck for built package declarations.
- lefthook pre-commit (lint staged, typecheck, vendor-manifest guard) and pre-push (tests, hygiene); CI runs the full matrix on node 24/26 plus a demo smoke test driving the echo-agent end to end.
- lefthook pre-commit (lint staged, typecheck, vendor-manifest guard) and pre-push (tests, hygiene); CI runs the full matrix on node 22.19/24/26 plus a demo smoke test driving the echo-agent end to end.
## Consequences
- Conventions survive agent turnover; violations fail fast and locally.
- The gates themselves are code to maintain; config changes are reviewed like any change.
- 100%-coverage pressure can produce assertion-free tests — mutation testing is the planned counterweight (see [the mutation-testing proposal](../../proposed/testing/2026-06-11-mutation-testing.md)).
<!-- rfc-format: alternatives-not-recorded (pre-format RFC) -->

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# RFC: tsdown for JS bundling instead of dumble
Status: implemented (accepted 2026-06-11)
Status: implemented
<!-- XXX: legacy ADR/RFC body format, not yet normalized to a unified RFC template. -->
## Context
## Problem
The initial build used **dumble**, the cordiverse zero-config esbuild wrapper that upstream Cordis itself builds with — maximum alignment with the vendored packages' conventions (it reads each package.json and infers entries/formats from the `exports` field). But dumble is a liability as a load-bearing tool in this repo: v0.2.x, ~530 npm downloads/week, effectively one maintainer, and we were invoking it through a custom orchestration script (`scripts/build.ts`) because it has no workspace mode.
@@ -19,7 +17,11 @@ Replace dumble with **tsdown** (rolldown-based, ~2.5M downloads/week, VoidZero-b
- Two per-package overrides in vendor/ (ours, like the regenerated tsconfigs; logged in vendor/README.md): schemastery (dual `.mjs`/`.cjs` via `outExtensions`), logger-console (two single-entry passes so the shared base class is inlined into each entry instead of a hash-named chunk, matching upstream's published shape).
- `scripts/build.ts` deleted; `pnpm run build` = `tsc -b tsconfig.build.json && tsdown`.
Alternatives considered: **direct esbuild script** (most established engine, zero wrapper risk, but hand-maintains the per-package spec table tsdown's workspace mode gives us); **pkgroll** (closest drop-in philosophically, but 78k dl/wk and Rollup-based — strictly weaker maintenance story than tsdown); **keep dumble** (perfect upstream alignment, unacceptable bus factor).
## Alternatives considered
- **A direct esbuild script** — the most established engine and zero wrapper risk, but hand-maintains the per-package spec table tsdown's workspace mode gives us.
- **pkgroll** — the closest drop-in philosophically, but 78k downloads/week and Rollup-based: strictly weaker maintenance story than tsdown.
- **Keep dumble** — perfect upstream alignment, unacceptable bus factor.
## Consequences

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# RFC: Vendor Cordis as source, not npm dependencies
Status: implemented (accepted 2026-06-11)
Status: implemented
<!-- XXX: legacy ADR/RFC body format, not yet normalized to a unified RFC template. -->
## Problem
## Context
DeepSeek Code is built on the Cordis framework. Cordis core was at 4.0.0-rc.6 (a release candidate) when this repo started; the harness depends on framework internals (fiber lifecycle, effect disposal, waterfall dispatch) whose exact behavior matters to the agent loop's correctness guarantees.
DeepSeek Harness SDK is built on the Cordis framework. Cordis core was at 4.0.0-rc.6 (a release candidate) when this repo started; the harness depends on framework internals (fiber lifecycle, effect disposal, waterfall dispatch) whose exact behavior matters to the agent loop's correctness guarantees.
## Decision
@@ -14,6 +12,11 @@ Copy the needed Cordis packages (core, loader, include, group, timer, hmr, logge
`vendor/README.md` is the manifest: upstream repo + commit SHA per package and an exhaustive local-modification log. A pre-commit guard (`scripts/check-vendor-manifest.sh`) rejects vendored-source changes that don't update the manifest in the same commit.
## Alternatives considered
- **Depend on the npm packages** — rejected: core was at a release candidate, and the harness leans on framework internals (fiber lifecycle, effect disposal, waterfall dispatch) whose exact behavior the agent loop's correctness guarantees depend on; an upstream RC bump could break them without a local fix path.
- **Vendor everything transitively** — rejected: truly third-party dependencies (js-yaml, chokidar, @standard-schema/spec, …) stay on npm; only the framework layer whose internals matter is owned.
## Consequences
- The harness fully owns its framework layer: auditable, patchable, pinned — an RC upstream can't break us, and we can fix framework bugs in-tree.

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@@ -1,10 +1,8 @@
# RFC: pnpm as the package manager instead of Yarn 4
Status: implemented (accepted 2026-06-16)
Status: implemented
<!-- XXX: legacy ADR/RFC body format, not yet normalized to a unified RFC template. -->
## Context
## Problem
The repo shipped on **Yarn 4** with the `node-modules` linker — a deliberately conservative choice that behaves like npm's flat layout while giving us Yarn's workspaces and `yarn constraints`. It worked. But Yarn 4's Plug'n'Play heritage makes the `node-modules` linker the off-the-beaten-path mode, and the broader JS ecosystem — tooling defaults, CI actions, Corepack examples, contributor familiarity — increasingly centers on pnpm. For a repo that is built primarily by agents and read by occasional human contributors, "the package manager most tools and people expect" has real value: fewer surprises, better-trodden failure paths, more copy-pasteable answers.
@@ -20,7 +18,11 @@ Adopt **pnpm 11.7.0**, pinned via the `packageManager` field and installed throu
- **Constraints become package-manager-independent.** `yarn.config.cjs` (which imported `@yarnpkg/types` and used `Yarn.workspaces()` / `workspace.set()`) is replaced by `scripts/check-workspace-constraints.ts`, a plain tsx script run as `pnpm run constraints`. It enforces the identical invariants — every package `private: true`; `@deepseek-ai/dsh-*` packages declare `cordis` as both a peer- and dev-dependency with matching ranges, `version: 0.0.1`, `type: module`; vendored packages checked for privacy only — over the same `vendor` + `packages` scope.
- All `yarn …` verbs across CI, lefthook hooks, `package.json` scripts, and docs become `pnpm …` / `pnpm run …`. `yarn.lock` → `pnpm-lock.yaml` (lockfile v9). `.gitignore` swaps `.yarn/` for `.pnpm-store/`. Vendored READMEs (e.g. `vendor/cordis/README.md`) keep their upstream `yarn` examples untouched per the Vendoring Policy.
Alternatives considered: **keep Yarn 4** (zero churn, but bets on the less-traveled linker mode and a constraints engine tied to one package manager); **npm workspaces** (ubiquitous, but no constraints story and weaker monorepo ergonomics); **pnpm with hoisted linker** (smoother migration, but throws away the phantom-dependency safety that is the main correctness reason to move).
## Alternatives considered
- **Keep Yarn 4** — zero churn, but bets on the less-traveled linker mode and a constraints engine tied to one package manager.
- **npm workspaces** — ubiquitous, but no constraints story and weaker monorepo ergonomics.
- **pnpm with the hoisted linker** — smoother migration, but throws away the phantom-dependency safety that is the main correctness reason to move.
## Consequences

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@@ -1,10 +1,8 @@
# RFC: TSC-first build and one tsconfig
Status: implemented (accepted 2026-06-20)
Status: implemented
<!-- XXX: legacy ADR/RFC body format, not yet normalized to a unified RFC template. -->
## Context
## Problem
The current TypeScript build and typecheck setup had these issues:
@@ -57,6 +55,11 @@ tsc -b tsconfig.json
`pnpm run demo:*` still runs `src` directly through tsx and root paths, without a compile step.
## Alternatives considered
- **Keep `tsdown`/oxc as the TypeScript transformer** — oxc's transform is not `tsc` behavior (decorator transform differs, bundled JS differs from per-file emit), and its bundled `.d.ts` conflicts with Cordis' internal relative module augmentation shape.
- **One root strict program over packages, vendor, examples, tests, and scripts** — vendor source triggers type errors outside this project's ownership under the root strict flags; project references with per-project strictness are the boundary that works.
## Consequences
Build responsibilities are clearer:

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@@ -1,8 +1,8 @@
# RFC: Markdown cross-link validity linting
Status: implemented (proposed 2026-06-18, accepted 2026-06-18)
Status: implemented
## Context
## Problem
Docs in this repo link to each other by relative path — `[topic](../implemented/2026-…-….md)`, `[the cookbook](adding-a-tool.md)`, `[architecture.md](../../architecture.md)`. Nothing verified those targets exist. A rename or a move silently breaks every inbound link, and the break is invisible until a reader clicks it. [Doc-sync enforcement](2026-06-11-doc-sync-enforcement.md) already mechanized two classes of doc drift (uncompilable code blocks, a stale event-taxonomy table) and [verify-md-wrap](2026-06-11-doc-sync-enforcement.md) a third (hard-wrapped prose) — but a dead cross-link is a fourth, equally mechanical class that was still verified by eyeball.
@@ -18,11 +18,14 @@ A fourth `doc-sync` gate, `verify-md-links` (`scripts/verify-md-links.ts`), mirr
Scope matches the other gates plus the AGENTS.md pair and the repo-authored agent-skill Markdown under `.agents/skills/` (those skill files cross-link into the docs tree, so this reorg rewrote links in them too): `README.md`, `docs/**/*.md`, `packages/*/README.md`, `AGENTS.md`, `packages/AGENTS.md`, `.agents/skills/**/*.md`, deduped by real path (the `CLAUDE.md` symlinks resolve onto the AGENTS.md files). It is wired into the `doc-sync` script that the lefthook pre-push hook and CI both run, so a broken link fails locally before a push — consistent with [mechanical quality gates](2026-06-11-quality-gates.md).
This gate checks *existence*, not anchor validity: a link to a real file with a `#wrong-heading` fragment still passes (the file resolves; the fragment is stripped). Anchor-level checking is a heavier, lower-value follow-up — file-level dead links are the failure that actually bit us.
This gate checks *existence*, not anchor validity: a link to a real file with a `#wrong-heading` fragment still passes (the file resolves; the fragment is stripped).
## Alternatives considered
**Anchor-level validity checking** — heavier and lower-value; file-level dead links are the failure that actually bit. The scope cut is deliberate: authors verify `#fragment` anchors themselves when linking to one.
## Consequences
- Renames and moves that orphan a cross-link now fail the pre-push hook and CI instead of waiting for a reader to click a dead link. This made the RFC reorganization that introduced the gate self-verifying: the same PR that rewrote forty links also added the check that proves none dangle.
- One more fast tsx script in the `doc-sync` chain; no new dependency (the mdast/GFM stack is already in devDependencies for `verify-md-wrap`).
- Fragment/anchor validity remains unchecked — a known, deliberate scope cut.
- The convention this enforces — cross-reference docs by machine-checkable relative link, never by bare prose or a number — is documented in [docs/AGENTS.md](../../../AGENTS.md) so authors know the gate exists and why.

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@@ -1,10 +1,8 @@
# RFC: Core-data-structures catalog and the `ts type-equiv` drift gate
Status: implemented (accepted 2026-06-20)
Status: implemented
<!-- XXX: legacy ADR/RFC body format, not yet normalized to a unified RFC template. -->
## Context
## Problem
A reader trying to understand the harness could find its *behavior* in [architecture.md](../../../architecture.md) (the service map, the session/turn/step lifecycle, the event taxonomy) but had no single place describing its *vocabulary* — the data structures that behavior moves around. The type shapes lived only in source, scattered across `packages/*/src/types.ts`, so understanding "what is a `Message`, a `SessionEvent`, a `StreamChunk`" meant reading the declarations directly. A prose catalog would help, but a catalog that paraphrases or paste-copies type definitions rots the instant a field changes — and an out-of-sync type doc is worse than none, because a reader trusts it.
@@ -40,6 +38,12 @@ The durability requirement was specific: the doc should show the **literal** cur
`verify-type-equiv` catches a *drifted paste* of an already-documented type, but it cannot tell you a brand-new core type went undocumented. So AGENTS.md and the `dsh-code-review` skill were updated to require keeping the catalog in sync when a change adds or reshapes a documented type — the gate handles drift, the human handles new surface.
## Alternatives considered
- **A flat dump of all cross-package vocabulary** — the `BashExecRequest` test case killed it: if seam vocabulary is "core", the catalog helps no one; the tiered spine-vs-seam structure won.
- **A compiled `_Check` assignability assertion** instead of the verbatim source match — rejected because byte-equality, not assignability, is the property we want: a renamed field with the same type would pass assignability.
- **Provenance as directive comments in the prose** — rejected for the central manifest, whose enforced 1:1 correspondence means a block can never be silently unchecked and an entry can never rot.
## Process
The design was driven entirely by a one-question-at-a-time grilling that walked the scoping decision tree through concrete examples (`BashExecRequest`, `ToolSchema`, `ToolDefinition`, the schema DSL, the presentation types, the session/persistence split) before committing to the spine-vs-seam rule — the rule was the *output* of the examples, not an a-priori axiom. The implementation landed as four commits mirroring the structure of the work: the gate (`e97f94b`), the catalog (`7e33c7b`), the maintenance-guard updates (`53e01a0`), and a review-fix commit (`6da7a0f`).

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@@ -1,10 +1,8 @@
# RFC: Generated cordis events + services catalog
Status: implemented (accepted 2026-06-20)
Status: implemented
<!-- XXX: legacy ADR/RFC body format, not yet normalized to a unified RFC template. -->
## Context
## Problem
A plugin author needs two reference surfaces that no single document gave them: every cordis **event** they can listen to (with its exact signature and dispatch mode) and every `ctx.<key>` **service** they can call (with its exact interface). The pieces existed but were scattered — a hand-maintained event-taxonomy *table* in `docs/architecture.md` (names + prose Mode/Purpose, name-set-checked by `verify-event-taxonomy`), a Service-map table (8 rows of role prose), and the `interface Events` / `interface Context` declarations themselves. The taxonomy table also could not catch a brand-new *undocumented* event: a name-set verifier only checks the names that are already in the table on both sides.
@@ -14,7 +12,7 @@ This is the wiring-axis complement to the [core-data-structures catalog](../../.
Generate the catalog from source instead of hand-maintaining a table and verifying a subset.
`scripts/gen-cordis-catalog.ts` walks the `interface Events` and `interface Context` declarations (plus the service classes) with the TypeScript compiler API and emits `docs/cordis-catalog/events-and-services.md` — one `## Events` section (grouped by scope, each event rendered as signature + mode badge + its source JSDoc) and one `## Services` section (each `ctx.<key>` with its public method signatures + class JSDoc). It mirrors the `gen-module-graph` pattern exactly: `--write` regenerates, `--check` fails if the committed file is stale, output is deterministic (sorted), and the file is a build artifact that is never hand-edited. `verify-cordis-catalog` (the `--check`) runs inside `doc-sync`, so the freshness gate fires in the same lefthook pre-push and CI paths as every other doc gate.
`scripts/gen-cordis-catalog.ts` walks the `interface Events` and `interface Context` declarations (plus the service classes) with the TypeScript compiler API and emits two sibling pages: `docs/cordis-catalog/events.md` (events grouped by scope, each rendered as signature + mode badge + its source JSDoc, plus the dispatch-mode legend) and `docs/cordis-catalog/services.md` (each `ctx.<key>` with its public method signatures + class JSDoc). The two axes are separate documents — a reader is either finding what to listen to or what to call, and each page scans and deep-links as its own reference instead of one long combined scroll. It mirrors the `gen-module-graph` pattern exactly: `--write` regenerates both, `--check` fails if either committed file is stale, output is deterministic (sorted), and the files are build artifacts that are never hand-edited. `verify-cordis-catalog` (the `--check`) runs inside `doc-sync`, so the freshness gate fires in the same lefthook pre-push and CI paths as every other doc gate.
Pure generation is correct here because the codebase is disciplined enough that the AST is the whole truth: every event/service name is a string literal that round-trips to a static declaration — there are no dynamically-named events and no runtime-only services. So a generated doc cannot be wrong, and it closes the undocumented-event gap structurally (generation enumerates source rather than checking a hand-written subset).
@@ -25,7 +23,13 @@ Specific choices:
- **Cross-links to the data-structure catalog.** A type name in a signature (`GenerateOptions`, `StreamChunk`, `ToolDefinition`, …) links to the core-data-structures page that documents it. The map is a small hand-curated const in the generator — NOT `type-equiv.manifest.json`, which documents the `…Map` symbols while signatures reference the derived union names, and lists a few symbols on two pages.
- **A dedicated fence.** Signature blocks use a ` ```ts cordis-catalog ` info string that `doc-typecheck` recognizes and skips (a bare signature fragment is not standalone-compilable), excluded from the opt-out ratio — the same treatment `type-equiv` blocks get.
This **supersedes the event-taxonomy half** of [doc-sync enforcement](2026-06-11-doc-sync-enforcement.md): `verify-event-taxonomy` and its `docs/architecture.md` table are retired (the architecture.md heading stays, its body now points at the catalog; the Service-map role table stays as curated prose). The verify-don't-generate principle that RFC chose for the taxonomy is reversed *for this surface only* — the data here is mechanically complete, so generation is strictly stronger (full signatures, cannot drift, catches undocumented events) than a name-set check of a hand-table. doc-typecheck, verify-md-wrap, verify-md-links, and verify-type-equiv are unchanged.
This **supersedes the event-taxonomy half** of [doc-sync enforcement](2026-06-11-doc-sync-enforcement.md): `verify-event-taxonomy` and its `docs/architecture.md` table are retired (the architecture.md heading stays, its body now points at the catalog; the Service-map role table stays as curated prose). doc-typecheck, verify-md-wrap, verify-md-links, and verify-type-equiv are unchanged.
## Alternatives considered
- **Verify-don't-generate, as the retired taxonomy check did** — reversed *for this surface only*: the data here is mechanically complete, so generation is strictly stronger (full signatures, cannot drift, catches undocumented events) than a name-set check of a hand-maintained table.
- **Walking the vendor AST for the inherited tier** — rejected for the curated table: the cordis-core `Context` mixes true ctx members with non-service fields, and the pinned vendor surface changes only on a deliberate sync.
- **Reusing `type-equiv.manifest.json` as the signature cross-link map** — rejected for a small hand-curated const: the manifest documents the `…Map` symbols while signatures reference the derived union names, and it lists a few symbols on two pages.
## Consequences

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@@ -1,8 +1,8 @@
# RFC: Classify RFCs by kind via path-encoded subdirectories
Status: implemented (proposed 2026-06-20, accepted 2026-06-20)
Status: implemented
## Context
## Problem
`docs/rfc/` grouped RFCs by **lifecycle** only — `proposed/` / `implemented/` / `rejected/`. Nothing recorded what *kind* of decision each RFC was. The index was one flat list per lifecycle, with no way to scan "show me every simplification" or "every testing-strategy decision." A wave of simplification RFCs landing on the same day made the gap concrete: a reader skimming `proposed/` could not tell a new capability from a removal from a tooling-policy change without opening each file.
@@ -29,18 +29,18 @@ The `architecture` / `process` line: **architecture** is about the source we shi
Both are `doc-sync` members, in the `verify-md-wrap` style (tsx ESM, verify-don't-generate, exit non-zero on the first violation):
- **`scripts/verify-rfc-classification.ts`** — the closed set and index completeness. It asserts every file under a lifecycle folder lives in a class folder from the canonical set (a loose `.md` at a lifecycle root, or an unknown class folder, fails), and that `README.md` lists every RFC exactly once under the `###` heading matching its `{lifecycle}/{class}` path. The canonical class set lives as a `const` in this script — the machine source of truth — and [the index](../../README.md) documents it in prose; the two are kept in sync by hand (the README's completeness is gated, its class *descriptions* are not). This mirrors `verify-event-taxonomy`, which checks a doc table against source.
- **`scripts/verify-doc-refs.ts`** — source comments that cite docs. RFC paths are referenced not only from Markdown but from TypeScript doc comments (root-relative prose like `docs/rfc/implemented/testing/2026-06-19-acp-snapshot-tests.md`). `verify-md-links` never saw those, so the reorg could have silently orphaned them. This gate scans repo-authored `.ts` under `packages/**` and `examples/**` (excluding built `lib/` and `vendor/`) for `docs/….md` tokens, resolves each root-relative, and asserts it exists. It requires the `.md` extension so extensionless prose (`docs/postmortem/0001`, `docs/architecture.md § plugin checklist`) is left alone.
- **`scripts/verify-rfc-classification.ts`** — the closed set and index freshness. It asserts every file under a lifecycle folder lives in a class folder from the canonical set (a loose `.md` at a lifecycle root, or an unknown class folder, fails), and that the generated [INDEX.md](../../INDEX.md) byte-matches a fresh render from the tree (see [generate the RFC index tables](2026-07-04-generate-rfc-index-tables.md)). The canonical class set lives as a `const` in `scripts/rfc-index.ts` — the machine source of truth shared with the generator — and [the README](../../README.md) documents it in prose; the class *descriptions* stay hand-written, the index is generated.
- **`scripts/verify-doc-refs.ts`** — source comments that cite docs. RFC paths are referenced not only from Markdown but from TypeScript doc comments (root-relative prose like `docs/rfc/implemented/testing/2026-06-19-acp-snapshot-tests.md`). `verify-md-links` never saw those, so the reorg could have silently orphaned them. This gate scans repo-authored `.ts` under `packages/**` and `examples/**` (excluding built `lib/` and `vendor/`) for `docs/….md` tokens, resolves each root-relative, and asserts it exists. It requires the `.md` extension so extensionless prose (`docs/postmortem/0001`, `docs/architecture.md § Extending The Harness`) is left alone.
### Rejected alternatives
## Alternatives considered
- **A `Classification:` prose line** in each file (next to `Status:`), parsed by the gate. Workable, but it duplicates into the file a fact the path can already carry, and a line can disagree with its folder. Path-encoding makes the label and its storage the same thing — there is nothing to keep in sync.
- **A `refactor` class.** It overlaps `simplification` almost entirely; the only discriminator anyone reached for was "does observable behavior change?", which `simplification` already encodes (it does not). One class, not two.
- **Auto-generating the README index** from the filesystem. Rejected to keep the index hand-written like every other doc here; the completeness gate gives the same drift-protection without generated Markdown in a curated file.
- **Auto-generating the index** from the filesystem. Rejected here to keep the index hand-written; superseded by [generate the RFC index tables](2026-07-04-generate-rfc-index-tables.md) once stacked proposal waves made the hand-written tables the repo's most conflict-prone docs region — the list is now the fully generated [INDEX.md](../../INDEX.md) while the README prose stays curated.
## Consequences
- Every RFC now sits under a class folder, and the index groups by class within each lifecycle. A reader scans one heading to see all simplifications, or all testing decisions.
- Two more fast tsx scripts in the `doc-sync` chain; no new dependency (the mdast/GFM stack was already present for `verify-md-wrap`/`verify-md-links`).
- Adding a class is a deliberate act: amend the `const` in `verify-rfc-classification.ts` and the [Classification section](../../README.md#classification), not just `mkdir` a folder. The gate rejects an unknown folder, so an ad-hoc class can't slip in.
- Adding a class is a deliberate act: amend the `const` in `scripts/rfc-index.ts` and the [Classification section](../../README.md#classification), not just `mkdir` a folder. The gate rejects an unknown folder, so an ad-hoc class can't slip in.
- Source-comment doc references are now gated too — a moved or renamed doc that a `.ts` comment cites fails the pre-push hook, closing a drift class `verify-md-links` structurally could not see.

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@@ -2,5 +2,5 @@
# side as of the last confirmed-consistent state. Both languages carry equal authority;
# after editing either side, bring the other along and re-record with:
# pnpm run verify-translation-pairing --write
2026-07-02-bilingual-docs-and-pairing-gate.md: 764ad5a9345c2a138b56e9cedb54848a5f7d6054
2026-07-02-bilingual-docs-and-pairing-gate.zh.md: c752d76f12f556ce190bf80c4f3a531c0821be8e
2026-07-02-bilingual-docs-and-pairing-gate.md: 8731fef46b16cfa20d223575c70774cff780a6aa
2026-07-02-bilingual-docs-and-pairing-gate.zh.md: ce2589498ab16cf5ca2f5cdb3f58d031aeb8298f

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@@ -1,8 +1,10 @@
# Bilingual documentation via paired sibling files and a pairing gate
# RFC: Bilingual documentation via paired sibling files and a pairing gate
Status: implemented
English | [中文](2026-07-02-bilingual-docs-and-pairing-gate.zh.md)
## Context
## Problem
This repo's README and docs tree are read by people and agents inside and outside the company, in both English and Chinese. Maintaining a second language by hand, with no mechanism, is how translations rot: one side moves on, the other silently lies, and no gate notices. The repo's standing answer to invariants of this kind is to encode them as a mechanical check (see [quality gates](2026-06-11-quality-gates.md) and [doc-sync enforcement](2026-06-11-doc-sync-enforcement.md)), so the bilingual policy ships with one.

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@@ -1,10 +1,10 @@
# RFC: Generated tool-schema catalog (boot-and-harvest)
Status: implemented (accepted 2026-07-02)
Status: implemented
## Context
## Problem
A reader — a plugin author, a prompt engineer, someone auditing what the agent can do — has no single place that lists the model-facing tools the harness ships. The `name` / `description` / JSON-Schema `parameters` a tool contributes are what the model actually receives (via `ctx.systemPrompt.tools()` off `ctx.tools.schemas()`), but they are scattered across each `defineTool` call in each `packages/*/tool-*` package, buried in string concatenation and runtime spreads. The [cordis events & services catalog](../../../cordis-catalog/events-and-services.md) ([its RFC](2026-06-20-generated-cordis-catalog.md)) documents the *wiring* a plugin works against and the [core-data-structures catalog](../../../core-data-structures/core.md) documents the *vocabulary* those signatures move — but neither documents the *tools* the agent is offered. This RFC adds that third reference surface, `docs/tool-catalog/tools.md`, and a freshness gate so it cannot drift.
A reader — a plugin author, a prompt engineer, someone auditing what the agent can do — has no single place that lists the model-facing tools the harness ships. The `name` / `description` / JSON-Schema `parameters` a tool contributes are what the model actually receives (via `ctx.systemPrompt.tools()` off `ctx.tools.schemas()`), but they are scattered across each `defineTool` call in each `packages/*/tool-*` package, buried in string concatenation and runtime spreads. The cordis [events](../../../cordis-catalog/events.md) & [services](../../../cordis-catalog/services.md) catalogs ([their RFC](2026-06-20-generated-cordis-catalog.md)) document the *wiring* a plugin works against and the [core-data-structures catalog](../../../core-data-structures/core.md) documents the *vocabulary* those signatures move — but neither documents the *tools* the agent is offered. This RFC adds that third reference surface, `docs/tool-catalog.md`, and a freshness gate so it cannot drift.
## Decision
@@ -39,6 +39,12 @@ The unit is the PACKAGE, not the deployed tool instance. A package's registered
Schema blocks use ` ```json `, not a bespoke `ts`-family fence. `doc-typecheck` only extracts `ts*` fences, so a JSON block is invisible to it — no `BlockKind` wiring is needed (unlike the cordis catalog's `ts cordis-catalog` fence, which had to be allowlisted so a bare signature fragment isn't compiled).
## Alternatives considered
- **A pure TypeScript-AST pass, like the cordis catalog** — tool schemas are not statically knowable (the crux above): runtime spreads, string concatenation, config-chosen names, and raw `ctx.tools.register()` registrations all make an AST-derived doc lie.
- **Inferring each package's boot recipe from its injects** — the "too clever" path [the discover-package-inventory proposal](../../proposed/process/2026-06-20-discover-package-inventory.md) warns against; the recipe stays hand-written policy while the inventory is discovered and completeness-guarded.
- **A bespoke `ts`-family fence for schema blocks** — unnecessary: a plain ` ```json ` fence is invisible to `doc-typecheck`, so no `BlockKind` allowlisting is needed.
## Consequences
- The catalog cannot drift: a tool schema change the committed file doesn't reflect fails `verify-tool-catalog` in the pre-push hook and CI. A new `tool-*` package not added to the manifest fails the completeness guard outright.

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@@ -0,0 +1,67 @@
# RFC: Documentation graph index for maintainers and SDK users
Status: implemented
## Problem
The repo already had several high-trust documentation surfaces, each on a different axis: [module-graph.md](../../../module-graph.md) is generated from package `peerDependencies`, the generated [Cordis events](../../../cordis-catalog/events.md) and [services](../../../cordis-catalog/services.md) catalogs are generated from Cordis `Events` and `Context` declarations, [tool-catalog.md](../../../tool-catalog.md) is generated by booting shipped tool plugins, and [core-data-structures/](../../../core-data-structures/core.md) uses `ts type-equiv` blocks to keep pasted type definitions synchronized with source.
Those references are accurate, but they are mostly catalogs. A maintainer still has to synthesize the relationships: which packages form a capability seam, which app bundles a concrete spine, which event is durable vs live, where a hook or policy plugin can intercept work, and which model-facing tool depends on which service. An SDK user has the same problem from another angle: "Which package do I install or load for the behavior I want, and which event/service/tool do I extend?"
The hooks subsystem makes event producer/consumer topology and interception points much more important, and the filesystem seam makes capability seams, policy vetoes, tool presentation, and SDK assembly paths much more important — relationship graphs scoped to a small bash/todo/subagent surface would have gone stale immediately.
## Decision
Add generated relationship graph docs, indexed at [docs/graph-atlas.md](../../../graph-atlas.md), produced by focused generators and verified by `pnpm run verify-doc-graphs` / existing catalog freshness checks as part of `doc-sync`.
The index is a relationship layer above the existing catalogs. It does not replace exact references; instead, it links to them and explains how their pieces fit together.
### Maintenance modes
Every graph page declares one maintenance mode:
- **Generated**: all nodes and edges are discovered from source; `--check` fails if the committed artifact is stale.
- **Hybrid generated**: source discovers the inventory, a small manifest classifies irreducible policy, and a completeness guard fails if discovered items are unclassified.
- **Curated**: the diagram explains design intent, temporal order, or ownership; it is emitted by the generator so the graph docs remain a regenerated unit, but the content is deliberately authored.
### First shipped index
The first index links ten relationship surfaces. Package topology and tool-package affordances live in the existing generated catalogs that already own those facts; the remaining focused diagrams are generated by `scripts/gen-doc-graphs.ts`.
| Graph | Maintenance mode | Source of truth |
|---|---|---|
| [module dependency graph](../../../module-graph.md) | generated | `packages/*/*/package.json` peer dependencies plus package group paths |
| [tool schema catalog and package map](../../../tool-catalog.md) | generated | boot-harvested tool schemas plus tool-package service/effect metadata |
| [capability seams and core services](../../../capability-seams.md) | hybrid generated | Cordis service declarations plus a role manifest in `gen-doc-graphs.ts` |
| [echo-agent app composition](../../../../examples/echo-agent/composition.md) | hybrid generated | `examples/echo-agent/cordis.yml` plugin list plus curated app/bundle expansion |
| [coding-agent app composition](../../../../examples/coding-agent/composition.md) | hybrid generated | `examples/coding-agent/cordis.yml` plugin list plus curated app/bundle expansion |
| [acp-agent app composition](../../../../examples/acp-agent/composition.md) | hybrid generated | `examples/acp-agent/cordis.yml` plugin list plus curated app/bundle expansion |
| [event producer/consumer matrix](../../../event-producer-consumer.md) | hybrid generated | Cordis event declarations, AST-scanned `ctx.on/emit/parallel/serial/waterfall` sites, and explicit dynamic dispatch overrides |
| [agent turn and step lifecycle](../../../agent-lifecycle.md) | curated | architecture.md loop lifecycle, Cordis catalog links, and session event semantics |
| [tool execution pipeline](../../../tool-execution-pipeline.md) | curated | tool pipeline semantics and the `tools/execute` waterfall |
| [ACP snapshot replay](../../../../packages/ui/acp/snapshot-replay.md) | curated | snapshot harness behavior |
### Why generators own the docs
Package topology stays in `gen-module-graph.ts`, and tool-package affordances stay in `gen-tool-catalog.ts`, because those generators already own the canonical facts and freshness gates. `gen-doc-graphs.ts` owns the remaining relationship pages and the index. The tradeoff is that curated diagrams are edited in TypeScript string blocks rather than directly in Markdown. That is acceptable for this first cut because the user-facing artifact is still plain Markdown/Mermaid, and a future change can split the curated pages out if authorship ergonomics matter more than regeneration.
### Completeness guards
The hybrid pages must fail loud when their manifests are stale:
- The module graph reads every package's `peerDependencies` and groups each package by its `packages/<group>/<pkg>` path.
- The tool catalog boot-harvests shipped tools and renders the package/service/effect map from the same manifest that its completeness guard already checks.
- The capability seam graph imports the Cordis service collector and asserts every discovered harness `ctx.<key>` is classified in `SERVICE_ROLES`, and every classified key still exists.
- The event producer/consumer matrix labels itself hybrid because subagent lifecycle events deliberately use `ctx.events.dispatch` for per-listener containment; those dynamic edges are explicit overrides rather than invisible omissions.
- `verify-mermaid` parses every repo-authored ` ```mermaid ` fence with Mermaid's own parser, so syntax errors fail `doc-sync` locally and in CI instead of showing up as broken GitHub-rendered diagrams.
## Alternatives considered
Committed diagrams use Mermaid because GitHub renders it in Markdown and it adds no new docs build dependency; dense many-to-many data such as event producer/consumer relationships uses Markdown tables instead. **PlantUML, hosted diagram services, and generated SVGs** were considered and deliberately not adopted until Mermaid becomes the limiting factor.
## Consequences
- Maintainers get visual entry points for topology, seams, event flow, lifecycle, app composition, and snapshot behavior.
- SDK users get a path from use case to package composition instead of only bottom-up package references.
- `doc-sync` now includes `verify-doc-graphs` and `verify-mermaid`, so graph drift and Mermaid syntax errors are caught with the other doc freshness gates.
- Future fs and hooks work has a concrete place to land new complexity: fs should expand the capability docs and tool catalog, while hooks should expand the event matrix and tool execution pipeline.

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# RFC: JSDoc completeness gate for the cordis surface
Status: implemented (accepted 2026-07-04)
Status: implemented
## Context
## Problem
The [generated cordis catalog](2026-06-20-generated-cordis-catalog.md) already walks every harness `interface Events` member and every `ctx.<key>` service class with the TypeScript compiler API, and already hard-errors on a missing `@mode` tag — a forcing function that made dispatch modes impossible to leave undocumented. Nothing equivalent guarded the rest of the JSDoc: a service method could ship with no doc at all, and no event or method documented its parameters or return value individually. A survey at adoption found 5 public service methods with no JSDoc and roughly 139 missing `@param`/`@returns` entries across 15 files — on the product API spine (`ctx.bash`, `ctx.fs`, `ctx.sessions`, …) and the cross-plugin event payload contracts, exactly the surface where "what does this argument mean" is the question a plugin author asks the IDE.
@@ -20,10 +20,16 @@ The contract:
- **Explicitness the walk can check**: the gate is a pure-AST pass (no type checker), so a service method must annotate its return type (an inferred return cannot be classified) and surface parameters must be simple identifiers (a binding pattern has no name for `@param` to match).
- **Violations aggregate** into one error listing every offender — a remediation pass sees the whole list at once. The previously fail-fast `@mode` checks moved into the same aggregated report, with their message texts unchanged.
The tags are **enforcement-only**: `parseJsDoc` now ends description prose at the first block tag (standard JSDoc semantics, which also stops multi-line tag descriptions from leaking into the catalog as prose), so `@param`/`@returns` never change the rendered catalog. Rendering them — restructuring the services section into per-method entries — was considered and deliberately deferred: source JSDoc plus IDE hover is where method docs are consumed, and the catalog stays an index. No escape-hatch tag exists; the surface is small and curated (12 services, 57 methods, 27 events at adoption), and the point is that the check cannot be waved off.
The tags are **enforcement-only**: `parseJsDoc` now ends description prose at the first block tag (standard JSDoc semantics, which also stops multi-line tag descriptions from leaking into the catalog as prose), so `@param`/`@returns` never change the rendered catalog.
Negative-path tests in `packages/core/agent/tests/gen-cordis-catalog.spec.ts` drive `collectEvents`/`collectServices` against synthetic fixtures to prove each guard fires and that the exemptions hold. The authoring rule lives in the root [AGENTS.md](../../../../AGENTS.md) conventions bullet alongside the `@mode` rule.
## Alternatives considered
- **An ESLint rule** — cannot see the scope's machine definition (which `interface Events` members and which `ctx.<key>` classes are the cordis surface); the catalog generator computes exactly that mapping on every run, so the gate lives there.
- **Rendering the tags into the catalog** — restructuring the services section into per-method entries was considered and deliberately deferred: source JSDoc plus IDE hover is where method docs are consumed, and the catalog stays an index.
- **An escape-hatch tag** — none exists; the surface is small and curated (12 services, 57 methods, 27 events at adoption), and the point is that the check cannot be waved off.
## Consequences
- A new event or service method cannot land with an undocumented parameter or result: the generator refuses to regenerate and `verify-cordis-catalog` fails pre-push and in CI. The ~139 gaps found at adoption were filled in the same change, so the gate landed green.

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# Documentation tiers, budgets, and the ceiling gate
# RFC: Documentation tiers, budgets, and the ceiling gate
## Context
Status: implemented
## Problem
The repo's standing docs accrete. Root `AGENTS.md` reached 8,130 words through 50 commits in two and a half weeks — each PR appending its own lesson, none displacing anything — until the same rule was stated two or three times inside one file (the pushed-branch rewrite ban ~600 words across two sections; the with-key e2e policy ~400 words across two), an incident already recorded in [postmortem 0001](../../../postmortem/0001-acp-default-export-drops-inject.md) was retold inline at ~750 words, and the per-package one-liner map existed in five places. [architecture.md](../../../architecture.md) grew the same way: paragraph walls re-narrating RFCs it already links, plus implementation-status annotations that were stale the week after they were written. The writing rules that forbid this (document current state, never history) predate the drift and sat in the very file violating them — prose rules alone do not hold against accretion pressure. The repo's standing answer to an invariant of this kind is a mechanical check ([quality gates](2026-06-11-quality-gates.md), [doc-sync enforcement](2026-06-11-doc-sync-enforcement.md)).
@@ -28,6 +30,5 @@ The repo's standing docs accrete. Root `AGENTS.md` reached 8,130 words through 5
The first audit cycle under the standard, in rough priority order (evidence gathered in the survey that motivated this RFC):
- Package README trims where generated catalogs or JSDoc are restated or history is narrated: `packages/ui/acp`, `packages/core/tools`, `packages/bash/tool-bash`, `packages/core/session`, `packages/compact/compact-basic`, `packages/session-persistence/session-persistence`.
- [The web capability seam RFC](../architecture/2026-06-24-web-capability-seam.md) converted from spec-speak to shipped reality (drop the migration plan and test enumeration, "should" → "is").
- `docs/core-data-structures/core.md`: drop the JSDoc walls from the `Agent`/`GenerateOptions` type-equiv pastes per that page's own stated rule.
- [Postmortem 0001](../../../postmortem/0001-acp-default-export-drops-inject.md): merge the overlapping Executive summary and Summary sections.

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# RFC: Generate the RFC index tables
Status: implemented
## Problem
The RFC index's per-lifecycle/per-class tables list facts that are fully derivable: an RFC's path encodes lifecycle and class, its filename encodes the first-proposed date, and its H1 carries the title. A hand-maintained copy of those facts is also the repo's highest-contention docs hotspot: every proposal wave appends rows to the same few lines, so concurrent RFC branches conflict precisely there while agreeing everywhere else, and each conflict is resolved by hand-merging rows whose content the filesystem already knows. [The classification RFC](2026-06-20-rfc-classification.md) originally kept the index hand-written for curation's sake — but the curated part of the README is the prose, and the prose never conflicts; only the mechanical tables do.
## Decision
Keep the curated prose; generate the list. The tables live in [`docs/rfc/INDEX.md`](../../INDEX.md), a **fully generated file** — the curated prose stays in README.md, which carries no index rows at all. [`scripts/rfc-index.ts`](../../../../scripts/rfc-index.ts) is the shared source of truth — the tree walker (owning the closed lifecycle/class sets and the structure rules, including a parseable-H1 requirement) and the renderer (rows from H1 title with any `RFC: ` prefix stripped, plus the filename date, sorted by date then filename, grouped as `### {Class}` sections in canonical class order). Two thin consumers share it:
- [`scripts/gen-rfc-index.ts`](../../../../scripts/gen-rfc-index.ts) (`pnpm run gen-rfc-index`) rewrites INDEX.md in full from the tree.
- [`scripts/verify-rfc-classification.ts`](../../../../scripts/verify-rfc-classification.ts) (a `doc-sync` member) checks structure, asserts the committed INDEX.md byte-matches a fresh render — the `gen-cordis-catalog`/`verify-cordis-catalog` pattern — and rejects an index-shaped row in the curated README. Freshness subsumes the index-completeness check: a generated-from-disk table is definitionally complete and correctly headed.
Adding, moving, or deleting an RFC means editing only the RFC file and running the generator; the classification RFC's rejected-alternatives record carries the supersession cross-link.
## Alternatives considered
### Why not marker-delimited regions inside README.md?
The first landed shape: the generator spliced the tables into README.md between `gen-rfc-index` marker comments, under each `## {Lifecycle}` heading. Superseded by the whole-file INDEX.md once the README also absorbed the in-file format contract ([the uniform-format RFC](2026-07-05-uniform-rfc-format.md)): a front-door README hosting hundreds of generated rows dwarfed its curated prose, and splice mechanics (marker pairs, heading checks, outside-region row detection) exist only to protect curated text that a dedicated generated file simply doesn't contain.
### Why not the verifier-only model?
It catches mistakes but still makes every proposal edit a shared hotspot in a hand-maintained table, and a failed verifier is strictly more annoying than a generator for a purely mechanical row: the author has already named and placed the file; the index copy adds no information. This is the same hand-list-versus-derivation judgment the [package-inventory proposal](../../proposed/process/2026-06-20-discover-package-inventory.md) applies to tsconfig references and knip stanzas — applied to the one list that demonstrably conflicts.
## Consequences
- The generated file is explicit: its banner names the generator, there is no curated region to protect inside it, and the generator refuses to run on a structurally invalid tree.
- A malformed or missing H1 is a hard error in both the generator and the gate — the H1 is now load-bearing as the index title source.
- Concurrent RFC branches resolve index conflicts by rerunning the generator, never by hand-merging rows.

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# RFC: Generated persistence log event catalog
Status: implemented
## Problem
The session event log is the harness's on-disk contract: every `SessionEventMap` member is a record a persistence backend writes verbatim and a replay reconstructs from, and adding one that breaks the durability rules is a breaking change to the on-disk format. Yet the vocabulary had no single reference. The declarations are split across three files — the owning interface in `@deepseek-ai/dsh-session` plus declaration merges in `@deepseek-ai/dsh-compact` and `@deepseek-ai/dsh-hook-protocol` — and the doc surfaces covered it with hand-copies: a `hook/*` payload table in [session.md](../../../core-data-structures/session.md), a `compact/*` payload table in the compact README, payload bullets in the hook-protocol README, and a name-list in the session README. The name-list's merge note had already drifted (it named the compaction merge and omitted the hook merge entirely), and nothing could catch the next merge going undocumented: a hand-copy only checks the names someone already wrote down. This is the same gap the [cordis catalog](2026-06-20-generated-cordis-catalog.md) closed for bus events and the [tool catalog](2026-07-02-tool-schema-catalog.md) closed for model-facing tools — and log events are covered by neither: a `SessionEventMap` member is not a cordis `Events` declaration (it reaches listeners via the single `session/event` emit), so it has no cordis-catalog row by design.
## Decision
Generate `docs/persistence-catalog.md` from source, with a freshness gate, as the fourth reference surface: the *records* a persisted session log can contain, complementing the cordis catalog (wiring), core-data-structures (vocabulary), and the tool catalog (tools).
`scripts/gen-persistence-catalog.ts` is a pure TypeScript-AST pass, like `gen-cordis-catalog.ts` — log events ARE statically knowable: every member is a string-literal-named property with a static type annotation, so the AST is the whole truth. The walk collects every `interface SessionEventMap` declaration under `packages/*/*/src` — the owning top-level interface and every `declare module '@deepseek-ai/dsh-session'` merge — so a brand-new event, core or merged, appears in the next regenerate and an un-regenerated file fails `--check` (`verify-persistence-catalog`, a `doc-sync` member, so pre-push and CI both run it). Each entry renders the member's JSDoc prose, its payload (printed through the TypeScript printer, so a newline-separated multi-line type literal still yields a valid one-line fragment), a surface badge, cross-links into core-data-structures, and the declaration's source pointer, grouped by scope.
Specific choices:
- **JSDoc completeness, enforced.** Every member must carry description prose — the JSDoc becomes the catalog entry, the same forcing function the cordis catalog applies to bus events. An `@mode` tag on a member is a hard error: dispatch modes belong to cordis bus events, and a log event has none — the tag would misread as "this fires on the bus with mode X". Violations aggregate into one error listing every offender.
- **The surface badge is derived, not hand-listed.** `SurfaceEventType` — the subset that produces LLM messages and may carry `surfaceOp` — is parsed from its union declaration in the owning package; a union member naming no declared event is a hard error (a stale union member would otherwise silently badge nothing). Everything else renders **log-only**.
- **A dedicated fence.** Payload blocks use a ` ```ts persistence-catalog ` info string that `doc-typecheck` recognizes and skips, excluded from the opt-out ratio — the same treatment as `ts cordis-catalog` (a bare payload fragment is not standalone-compilable).
- **Repo scope.** The catalog enumerates the packages in this repo, matching the siblings' packages-only scope; a downstream plugin can merge further event types, which are outside the catalog by construction. The walk defends its own assumptions with hard errors: the owning top-level `interface SessionEventMap` must be the single exported declaration in `@deepseek-ai/dsh-session` (an unrelated, local, or duplicate same-named interface cannot be catalogued as the on-disk vocabulary), no declaration may carry `extends` (inherited keys would join `keyof SessionEventMap` without a catalog row), every member must be a property signature with an explicit payload type (a method-form member would join `keyof` yet slip past a silent walk), and a duplicate member across declarations fails.
This supersedes the hand-copies: the session.md `hook/*` table, the compact README's event table, the hook-protocol README's payload bullets, and the session README's name-list now link the catalog instead of restating payloads (the surrounding semantics prose stays where it was). The two stray `@mode emit` tags on the hook-protocol merge members are removed — the new gate rejects them as the category error they were.
## Alternatives considered
- **A boot-based generator, like the tool catalog's** — the log vocabulary is fully static, so the AST pass reads the whole truth without booting anything.
- **Keeping the hand-copies** — a hand-copy only checks the names someone already wrote down; the session README's merge note had already drifted when the catalog landed.
## Consequences
- The catalog cannot drift: a vocabulary change the committed file doesn't reflect fails `verify-persistence-catalog` in the pre-push hook and CI, and a new merged event with no JSDoc fails the generator outright — a plugin can no longer add an undocumented on-disk record type.
- Event prose has a single home, the JSDoc at the declaration; thin JSDoc yields a thin catalog entry, pressuring authors to document at the source.
- The `SurfaceEventType` union is now structurally load-bearing for docs: renaming an event without updating the union (or vice versa) fails the generator, not just the compiler.
- The badge derivation assumes the union stays a closed set of string literals with exactly one owner; a refactor away from that shape must update the generator in the same change.

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# RFC: One gated in-file format for RFCs
Status: implemented
## Problem
The tree's layout is uniform — [the classification scheme](2026-06-20-rfc-classification.md) path-encodes lifecycle and class and gates both — but the file insides never were. The corpus the format decision faced had two H1 spellings; some twenty-seven `Status:` line spellings once free-text rejection reasons are collapsed — bare enums, dated parentheticals duplicating what the filename and git already carry — plus three English files (and the zh counterpart of one of them) with no status at all; two body genres side by side (ADR-style `Context`/`Decision`/`Consequences` beside proposal-style `Problem`/`Proposal`/`Risks`), so every new RFC guessed its shape from whichever neighbor its author opened; thirty-nine files carrying a debt comment that flagged them as "legacy ADR/RFC body format" awaiting a unified template that was never actually defined; and nineteen implemented RFCs still carrying thirty occurrences of the proposal-era headings (`Acceptance criteria`, `Plan`, `Migration plan`, `Proposal`) that the [documentation standard's slop checklist](../../../AGENTS.md) outlaws for `implemented/` — outlawed, but enforced by nothing, so the `proposed/` → `implemented/` move could silently skip the rewrite [implemented/AGENTS.md](../AGENTS.md) requires.
## Decision
[README.md § The file format](../../README.md#the-file-format) is the in-file contract — the header block (`# RFC: <title>` plus a dateless, folder-agreeing `Status:` enum whose only content is the rejection reason), the per-lifecycle body skeleton (`Problem` opener everywhere; `Proposal`/`Acceptance criteria`/`Risks` in `proposed/`; present-tense `Decision`/`Consequences` with proposal-era headings banned in `implemented/`; frozen proposal shape in `rejected/`), a mandatory `Alternatives considered` section, and the canonical section vocabulary between which bespoke technical sections stay free-form. `pnpm run verify-rfc-format` ([scripts/verify-rfc-format.ts](../../../../scripts/verify-rfc-format.ts)) enforces every mechanical clause as part of `doc-sync`, so a lifecycle move that skips its rewrite now fails CI instead of review memory.
The whole corpus was normalized in the same change that defined the format — the pre-release stance: no transition period, no dual-format tolerance. The one grandfather is content, not format: alternatives are recorded, never invented, so a pre-format RFC whose alternatives are not reconstructible from the record carries the exact `rfc-format: alternatives-not-recorded` comment, which the gate accepts only for files dated before this RFC.
## Alternatives considered
- **A full rigid template** (one fixed section sequence per lifecycle, every RFC restructured to fit) — rejected: the big design RFCs carry eight to fifteen bespoke technical sections (package topology, wire contracts, schemas) that are load-bearing content, not drift; a rigid sequence would force destructive rewrites now and template-fighting forever.
- **Header-only normalization** (H1 and Status, bodies untouched) — rejected: the debt markers flagged the *body* genre split, and leaving `Context`/`Decision` beside `Problem`/`Proposal` indefinitely resolves nothing.
- **No Status line** (the folder already is the status; the three newest pre-format RFCs (and the zh counterpart of one) omitted the line) — rejected in favor of keeping a self-describing file: the drift risk that motivated dropping it is neutralized by gating the line against the folder instead.
- **Dated status** (`Status: implemented (accepted YYYY-MM-DD)`) — rejected: the acceptance date is narrated history the writing rules keep out of docs; the filename carries first-proposed, git carries the rest, and the gate could check a date's format but never its truth.
- **A bare `# <title>` H1** — rejected: the `RFC: ` prefix is the corpus-majority form and self-describes the genre when a file is read outside its tree; the index generator strips it, so index rows are identical either way.
- **`## What we give up` as the implemented closer** (the README's own phrase for what an RFC records) — rejected: it names only costs, and an honest consequences section records what the trade-off bought as well.
- **Convention without a gate** (write the contract down, enforce by review) — rejected: the slop checklist already outlawed spec-speak in `implemented/` by convention, and nineteen files show what convention alone achieves here.
- **A standalone `FORMAT.md` contract file** — the first landed home; folded into README.md once the generated index moved out to [INDEX.md](../../INDEX.md): with the tables gone the README regained the room, and one front door carrying layout, classification, and format beats splitting the contract across two files.
## Consequences
Every RFC now costs slightly more structure, and the mandatory `Alternatives considered` section is deliberate friction: a decision recorded without what it beat invites the re-litigation RFCs exist to prevent. Pre-format RFCs whose alternatives were not reconstructible carry the grandfather comment permanently — an honest gap on the record rather than fabricated rationale. `doc-sync` gains one gate, and moving an RFC between lifecycle folders is now real work at move time (the body rewrite the move always owed) instead of deferred cleanup nothing tracked. The thirty-nine debt markers are gone, resolved by the template they were waiting for.

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# RFC: Export-surface JSDoc gate
Status: implemented
## Problem
The [cordis JSDoc completeness gate](2026-07-04-cordis-jsdoc-completeness-gate.md) made undocumented parameters and results impossible on the cordis surface — `interface Events` members and `ctx.<key>` service classes — but that surface is a fraction of what a plugin author imports. The AGENTS.md rule "every export (and non-obvious method) has a JSDoc explaining semantics" stayed prose-checkable only by review everywhere else, and nothing at all asked for `@param`/`@returns` on ordinary exported functions. A survey at adoption found 203 under-documented module-level exports across 34 packages: seam-adjacent helpers (`runBash`, `readForEdit`, `htmlToMarkdown`), format codecs, whole undocumented interfaces and type aliases — exactly the names an IDE consumer hovers.
## Decision
A new gate, `scripts/verify-export-jsdoc.ts` (`pnpm run verify-export-jsdoc`, wired into `doc-sync` beside `verify-cordis-catalog`), walks every module-level exported name under each `packages/<group>/<pkg>/src/` tree. The parsing and check helpers moved from `gen-cordis-catalog.ts` into a shared `scripts/jsdoc.ts`, so "documented" means the same thing on both surfaces: description prose ends at the first block tag, every checkable parameter needs a non-empty `@param`, a non-void ANNOTATED return needs a non-empty `@returns`, a stale `@param` errors, and violations aggregate into one report.
The contract by declaration kind:
- Every exported name needs JSDoc with non-empty description prose.
- Function-like exports (function declarations; consts with function initializers or an INLINE callable annotation; non-identifier function default exports) follow the full function contract, with wrapper expressions (parentheses, `as`/`satisfies` casts, non-null assertions) peeled before classifying. A const whose declarator is annotated with a NAMED type (`export const f: Handler = …`) defers the signature contract to that type's own declaration and `@returns` stays optional; an inline `(x: T) => U` annotation or single-call-signature literal is the surface signature itself and gets the full contract, and a literal mixing call/construct signatures with anything else is refused outright (no single signature to hold the tags against — extract a named type).
- Exported classes need class-level prose; public methods (statics included — reachable on the exported name) follow the function contract; public properties and accessors need prose (a get/set pair is covered by the getter). Overload implementations are exempt — the signatures carry the docs.
- Exported interfaces, type aliases, and enums need prose on the declaration; member-level enforcement is deliberately deferred (the highest-value member surface — seam service classes — is already under the cordis gate).
- Exported namespaces recurse (inside an ambient `declare` namespace every member exports implicitly); the namespace itself needs prose only when it does not merge with a documented same-name declaration (the Config-namespace idiom documents the plugin once).
- `declare module` / `declare global` bodies and `export … from` re-export statements are skipped: an augmentation is not an export of the package, and a re-exported definition is checked where it is defined. An `export import X = N.member` alias documents ITSELF — its target may be a non-exported namespace member no walk visits — and only prose-only target kinds are gate-supported: a callable, class, or namespace target carries signature/member contracts the alias prose cannot hold, so the gate refuses it and demands the declaration be exported directly.
- Everything else fails CLOSED: `export =` is refused outright, parameters the base never names keep their `@param` duty even as binding patterns, and an exported statement kind the dispatch does not recognize is itself a violation — no export form can pass unchecked by omission.
Three exemption families keep the gate from demanding boilerplate, in the spirit of the cordis gate's `this`/`next` exemptions (documenting an exempt name anyway is allowed; only absence goes unchecked):
- **Heritage members.** A class member whose name exists on an `extends`/`implements` heritage type is exempt: the seam declaration is the doc's one home, and the IDE inherits it on hover — re-documenting every `LocalBashExecutor.run` invites drift. The exemption stops where the override grows surface the base never documented: a protected-only base member does not exempt a public override, parameters the base never names keep their `@param` duty (an underscore-prefixed rename of a base parameter — the deliberately-unused marker — is the same parameter), and a concrete result above a void base return keeps its `@returns` duty (an unannotated override's inferred return is classified by the checker, so a faithful void override needs no boilerplate annotation). Heritage lookups and that one return classification are the walk's only TYPE CHECKER questions (heritage types live across package boundaries, resolved through the repo `paths` map); everything else stays pure AST, and the annotated-return requirement is kept for symmetry with the cordis gate (it bound nothing at adoption — every exported function was already annotated).
- **Plugin-protocol slots.** Top-level `name` / `inject` / `reusable` / `Config` consts and the `apply` entry, plus the same slots as statics on a plugin class, are framework protocol: their shape is fixed by cordis, and the module doc comment plus the `interface Config` carry the plugin's real semantics.
- **Constructors**, mirroring the cordis gate: plugin classes are framework-constructed, and the class doc owns the story.
`collectExportJsdocViolations()` returns the violation list (the CLI exits 1 on non-empty) so the negative-path tests in `packages/core/agent/tests/verify-export-jsdoc.spec.ts` assert on findings directly, driving fixture packages through every rejection and every exemption.
## Alternatives considered
- **eslint-plugin-jsdoc** (`require-jsdoc`/`require-param`/`require-returns`) — covers the mechanical core but cannot express the repo's contract: the heritage-member exemption needs cross-package type resolution, the protocol-slot and namespace-merge idioms are cordis-specific, and the completeness semantics (prose-above-tags, stale-tag errors, aggregate reporting) already have one home in `scripts/jsdoc.ts` shared with the catalog generator. Two subtly different definitions of "documented" is the failure mode this repo's one-home rule exists to prevent.
- **Extending `gen-cordis-catalog.ts`** — the catalog generator renders a curated surface and gates its freshness; a repo-wide walk has no catalog to render. Sharing the helpers while keeping the walks separate keeps each gate's scope legible.
- **Enforcing interface/type-alias member docs** — deferred: it would multiply the checked surface for members that are largely self-describing fields, while the seam classes carrying the load-bearing member contracts are already gated. Revisit if member-doc drift shows up in review.
## Consequences
- A new export cannot land undocumented: `verify-export-jsdoc` fails `doc-sync`, which pre-push and CI already run. The 203 gaps found at adoption were filled in the same change, so the gate landed green.
- Exported functions must annotate return types (universal at adoption, now load-bearing) and use identifier parameters where `@param` must name them.
- Seam docs are canonical: an implementation inherits its heritage docs, and behavior notes worth keeping on the implementation are additions, not requirements.
- The gate builds a `ts.Program` (~6s) — the one doc gate that pays for type resolution; acceptable inside `doc-sync`, which already compiles doc snippets.
- The protocol-slot names are reserved by convention at module top level; a non-protocol export coincidentally named `apply` or `Config` would go unchecked — accepted, documented here.

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# RFC: Generated plugin config catalog
Status: implemented
## Problem
The config surface — the exact set of fields a `cordis.yml` entry's `config:` block can set for each plugin, with types, defaults, and semantics — had no reference page. A deployment author assembling a config tree had to open every plugin's source (or trust its README) to learn what is settable. The per-package README `## Config` sections cover parts of it by hand, in formats that diverged package-by-package (a key/default table here, an annotated YAML snippet there) and with no gate tying them to source. Nothing enumerated which packages are loadable at all — plugin vs abstract seam vs plain library — and nothing verified that the runtime schemastery schema and the documented `Config` interface agree, so a schema-validated field could exist with no documentation anywhere.
## Decision
Generate the catalog from source: `scripts/gen-config-catalog.ts` emits [docs/config-catalog.md](../../../config-catalog.md), one section per configurable package containing the VERBATIM config declaration — the `export interface Config` (or equivalently named type) with its JSDoc, pasted as-is in a ` ```ts config-catalog ` fence — plus a `Requires:` line (the plugin's `inject`), a `Depends on:` line resolving every type name the paste references, and a source pointer. The paste is the plugin's full declared config type: a field the runtime schema deliberately excludes is a runtime-only seam, marked as such by its own JSDoc, not a `cordis.yml`-settable knob. Package-local referenced types are pasted transitively into the same fence; another plugin's config type links to that plugin's section; names in the cordis catalog's shared `LINK_MAP` link to core-data-structures; any other workspace type links to its source; an external type is named with its module. It mirrors the `gen-cordis-catalog` pattern exactly: `--write` regenerates, `--check` (`verify-config-catalog`, inside `doc-sync`) fails if the committed file is stale, output is deterministic, the file is a build artifact never hand-edited.
Pure AST generation is correct here for the same reason it is for the events/services catalog and NOT for the tool catalog: a config type is a static declaration and every schemastery schema in the repo is a static `z.object`/`z.intersect` literal, so the source is the whole truth — nothing about the config surface is runtime-composed.
Specific choices:
- **The config type is the second-parameter type.** What the catalog documents is the declared type of `apply(ctx, config)` / the service constructor's `(ctx, config)` — the value cordis actually passes — not a `Config` export located by naming convention. This is what makes the walk total: it works for interfaces named `AcpConfig` or `BasicCompactConfig`, for types declared in a sibling file, and for plugins with no validating schema at all.
- **Classification is total.** Every `packages/<group>/<pkg>` entry resolves, mirroring the Loader's `unwrapExports` (`exports.default ?? exports`), to a configurable plugin, a config-free plugin, an abstract seam class, or a library — each rendered in its own section — and an unclassifiable entry hard-errors. A new package cannot be silently undocumented.
- **Per-field JSDoc is enforced.** Every property of a pasted declaration (nested type literals included) needs non-empty JSDoc prose, or generation fails. The paste IS the documentation, so this is the same forcing function the events catalog applies via `@mode`: thin source docs fail the gate rather than yielding a thin catalog.
- **The schema is cross-checked, one-directionally, nested keys included.** When a plugin declares a schemastery schema (`export const Config` / `static Config`), the generator walks it statically — object-literal keys and their nested object/array compositions as key paths (`agents[].id`), chained refinements, and `z.intersect` composition across workspace packages — and every schema-validated key path must be locatable on the declared config type, resolving package-local and workspace-imported types (re-export chains included), intersections, unions, utility wrappers, and indexed access. So the paste cannot hide a loader-accepted field, top-level or nested. The check is presence-only and fails loud only on a definite miss: a path crossing a type the walk cannot enumerate (an external package's type) is skipped rather than mis-reported, and dynamic-key shapes (`z.dict`) or union alternatives contribute no nested paths. The reverse direction is deliberately unchecked: a declared field may be a runtime-only seam the schema excludes (the ACP bridge's test-injected `stream`).
- **A dedicated fence.** Pasted declarations use a ` ```ts config-catalog ` info string that `doc-typecheck` skips (a lone declaration referencing imported types is not standalone-compilable), excluded from the opt-out ratio — the same treatment the `cordis-catalog` and `persistence-catalog` fences get.
- **A single file at `docs/config-catalog.md`**, not a one-file directory: the page serves one audience (the `cordis.yml` author) with one axis, unlike `cordis-catalog/`, which holds two sibling pages.
The package README `## Config` sections stay. The overlap is accepted deliberately: the README is the curated per-package contract (config semantics in deployment context, alongside limitations and extension points), the catalog is the exhaustive generated enumeration. Because the catalog is generated, a disagreement between the two indicts the README, and the fix is a README edit — the catalog cannot drift.
## Alternatives considered
- **Synthesized per-field rendering** — a bullet list, table, or annotated-YAML snippet per field, assembled from parsed JSDoc plus schema metadata. Rejected for the verbatim paste: the interface with its JSDoc is already the authored contract in its authored form, and a synthesizing renderer re-formats prose it does not own, adding a rendering layer that can misrepresent it.
- **Runtime boot + schema introspection, as the tool catalog does** — rejected: nothing here is runtime-composed, and the schema alone under-documents the surface (prose-documented defaults, runtime-only fields, plugins with no schema at all). Booting would add fragility without adding truth.
- **Two-directional schema/interface equality** — rejected for the subset check: the declared type legitimately carries members the schema refuses to accept from config (runtime-only seams).
- **Retiring the README `## Config` sections in the same change** — rejected: the accepted duplication keeps the per-package contract readable in place, and a sweep would have to fold each README's extra facts into field JSDoc first — separable work the catalog does not depend on.
## Consequences
- The catalog cannot drift: a source change the committed file does not reflect fails `verify-config-catalog` in pre-push and CI. An undocumented config field, an unresolvable referenced type name, or a schema key missing from the config type fails the generator outright.
- Config prose now has a forcing function at the declaration: writing a new config field means writing its JSDoc, which becomes the catalog entry verbatim.
- The generator hard-errors on shapes it cannot walk statically — an aliased package-local config import, a schema built by anything other than `object`/`intersect` composition, an unlisted global type name. Introducing such a shape includes teaching the generator (or the shape stays out of the repo), which is the point: the catalog stays the whole truth.
- `gen-cordis-catalog.ts` exports its JSDoc/pointer helpers and `LINK_MAP` for reuse, so the two catalogs cross-link types identically and a link-map addition serves both.

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# RFC: Raise the Node LTS engine floor to 22.19
Status: implemented
## Problem
The Node 22 branch of the root `engines.node` range is a contract for the installed workspace, not only for the runtime APIs the harness source calls directly. It must be no lower than package `engines.node` declarations for dependencies the workspace installs on that branch; otherwise `pnpm install --engine-strict` fails at an advertised LTS version, and non-strict installs run outside a dependency's supported runtime.
## Decision
Set `engines.node` to `^22.19.0 || >=24.0.0` and test the keyless CI compatibility matrix on `['22.19', 24, 26]`. The real-API e2e workflow stays on Node 24 because it exercises API integration rather than the runtime floor.
Two Node features gate the source runtime:
- **`node:sqlite`** — `packages/session-persistence/session-persistence-sqlite` does a top-level `import { DatabaseSync } from 'node:sqlite'`. The module dropped its `--experimental-sqlite` flag requirement at **22.13** (LTS) and **23.4** (Current); before those, importing it throws at load.
- **Native TypeScript type-stripping** — the `packages/ui/stdio-agent/tests/built-bin.e2e.ts` smoke boots the published `lib/bin.js` under plain `node` (no tsx) and loads the example's `.ts` plugins (`mock-llm.ts`, `echo-tool.ts`). Type-stripping is the default from **22.18** (LTS) and **23.6** (Current); before those it needs `--experimental-strip-types`.
Those source features clear on the 22.x line at **22.18**, but the installed Pi adapter dependency raises the advertised LTS floor. `@deepseek-ai/dsh-llm-pi-ai` depends on `@earendil-works/pi-ai@0.79.3`, whose package declares `engines.node >=22.19.0`, so the LTS floor is **22.19**. The 24.x branch remains `>=24.0.0`. The disjoint range excludes Node 23 entirely: Node 23.0–23.5 still has at least one flagged source feature, and the 23 line is non-LTS/EOL, so advertising `>=23.6` would add a dead release line and a CI leg no deployment should use.
`@types/node` remains pinned to the 22.x line (`^22.20.0`) to match the LTS support line: reaching for a Node 23+/24+/25+ API fails `tsc` on every machine and in the typecheck gate, rather than compiling clean and surviving to a runtime failure only a floor matrix leg could catch. The whole tree typechecks clean against the Node 22 type surface today, so the pin costs nothing.
## Consequences
- The advertised LTS branch no longer undercuts the Pi adapter dependency floor.
- CI proves the Node 22 LTS floor directly with Node 22.19, keeps the Node 24 branch on `node: 24`, and keeps Node 26 for the next even line.
- The built-bin smoke needs no version-conditional flag: at 22.19 type-stripping is already the default, so the test stays the plain `node lib/bin.js` path it documents.
- A future dependency or source API that raises the runtime floor must move `engines.node`, the compatibility matrix, and this RFC in the same change.
## Alternatives considered
- **Keep `^22.18.0 || >=24.0.0`.** Rejected: it advertises an LTS version lower than the Pi adapter dependency floor. `@earendil-works/pi-ai@0.79.3` requires `>=22.19.0`.
- **Downgrade or pin `@earendil-works/pi-ai` to preserve the 22.18 advertised range.** Rejected: the current Pi adapter dependency is part of the intended workspace, and 22.19 is still inside the Node 22 LTS line.
- **Floor `>=22.13` (the `node:sqlite` boundary) plus `--experimental-strip-types` in the built-bin smoke on 22.13–22.17.** Rejected: it adds a version-conditional test flag for one narrow range and dresses up an experimental-flag dependency as first-class support. The Pi adapter dependency already requires a higher LTS floor.
- **Open-ended `>=22.19`.** Rejected: it advertises support for Node 23.0–23.5, where `node:sqlite` (until 23.4) or type-stripping (until 23.6) is still flagged.
- **Include Node 23.6+ (`^22.19.0 || >=23.6.0`).** Rejected: 23.6+ does run both source features unflagged, but Node 23 is end-of-life; advertising a dead release line adds a range term and a CI leg for a runtime no deployment should use.
- **Matrix `[22, 24, 26]` instead of pinning `22.19`.** Rejected: floating major-version entries drift upward over time and silently stop exercising the declared LTS floor.
- **Keep `@types/node` ahead of the floor (`^25`).** Rejected: types ahead of the runtime floor let a Node 24/25-only API compile clean and fail only at runtime on 22.x. Pinning `@types/node` to the 22.x line turns that into a compile error everywhere.

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# RFC: Parallel GitHub CI gates
Status: implemented
## Problem
The keyless GitHub CI gates are mostly orthogonal: typecheck, lint, documentation freshness, coverage, snapshot replay, build, package-publication hygiene, demo smoke, and built-bin smoke fail for different reasons and do not need each other's runtime state. Running them as one ordered command chain makes the workflow wall clock equal the sum of those gates, while splitting every leaf gate into its own GitHub job repeats checkout, Node setup, pnpm restore, and install work until orchestration overhead becomes the bottleneck.
The hard part is the artifact boundary. `publint`, `verify-node-next-types`, and built-bin smoke tests need the built `lib/` outputs, while most gates only need source and dependencies. A blind fan-out either races those artifact consumers before `pnpm run build` has emitted declarations and bundles, or repeats the build in every artifact-dependent job.
## Decision
[CI](../../../../.github/workflows/ci.yml) keeps the keyless workflow to a few broad jobs instead of one job per gate. The Node 24 matrix has five lanes: static gates (`pnpm run check:ci:static`), lint (`pnpm run check:ci:lint`), coverage (`pnpm run check:ci:coverage`), snapshot replay (`pnpm run check:ci:snapshot`), and artifact gates (`pnpm run check:ci:artifacts`). The Node 26 compatibility job installs once and runs `pnpm run check:node-compat`.
Each lane delegates to [scripts/run-gates.ts](../../../../scripts/run-gates.ts), an in-process scheduler with bounded concurrency (`DSH_GATE_CONCURRENCY`). The static lane fans out constraints, the echo-agent demo smoke, `doc-sync` leaf gates, module-graph freshness, and `knip`; the lint lane runs ESLint with its own Node heap cap and a content-strategy ESLint cache; the coverage lane runs Vitest coverage with bounded file workers (`DSH_COVERAGE_MAX_WORKERS`); the snapshot lane isolates replay; the artifact lane builds once and then fans out the artifact consumers; the Node 26 compatibility job owns the TypeScript typecheck. The scheduler buffers each gate's output and prints a named result block with duration, so independent failures stay attributable inside each broad job log.
Generated `.sessions/` logs and `.doc-typecheck-*` temp directories are ignored by lint. The aggregate local CI mode still runs demo smoke after lint, while the split GitHub static lane can run demo smoke directly because lint is isolated in its own lane.
Build output is produced once inside the Node 24 artifact lane. The artifact consumers (`publint`, `verify-node-next-types`, and built-bin smoke) declare a dependency on `build`, so there is no upload/download handoff and no consumer can race ahead of declarations or bundles. The CI coverage reporter is text-only while local coverage keeps the HTML report.
Both CI workflows cache the pnpm store after enabling Corepack. The real-API e2e workflow also uses the shared `vitest.e2e.config.ts` bounded file pool (`DSH_E2E_MAX_WORKERS=14` in CI), so its speedup comes from dependency-cache reuse plus lower-level test-file fan-out instead of a separate GitHub job split.
## Alternatives considered
- **Keep the full serial chain in a Node matrix** - simplest to reason about, but it duplicates repo-wide gates that do not produce Node-version-specific signal and leaves every PR waiting for the sum of all gates.
- **Run every gate as a separate GitHub job** - maximizes GitHub-visible fan-out, but it creates too many checks and pays repeated setup/install overhead for gates whose runtime is shorter than the runner preparation.
- **Upload build artifacts to artifact-dependent jobs** - preserves correctness across many jobs, but it adds artifact upload/download time and keeps the workflow wide when the artifact consumers can run behind a local dependency in the primary job.
- **Run `typecheck` and `build` concurrently** - exposes more work to the scheduler, but both commands invoke `tsc -b`; sharing incremental build state between them is a needless race for a small wall-clock gain.
- **Use unbounded real-API e2e parallelism** - rejected because the suite includes many live model/tool scenarios; the worker pool needs an explicit `DSH_E2E_MAX_WORKERS` cap so CI and local runs can fan out without hiding quota or resource problems behind flaky rate-limit failures.
## Consequences
PR feedback arrives as a few GitHub checks with structured per-gate log blocks inside each broad job. That keeps runner setup overhead bounded and the Actions UI compact, at the cost of losing one status check per leaf gate.
The broad-lane split repeats checkout, setup, and install more often than a single primary job. That setup cost is intentional: on GitHub's hosted runner, running lint, coverage, and snapshot replay in one process pool oversubscribes CPU badly enough that the single-job critical path is longer than the repeated setup.
The split introduces a maintenance obligation: when `package.json` adds or removes a gate that belongs in CI, [scripts/run-gates.ts](../../../../scripts/run-gates.ts) needs the matching leaf. That obligation is intentional because the runner is the parallel execution plan for the same gate vocabulary, not a separate quality policy.
The Node 26 signal is narrower than the primary Node 24 signal. It proves the source graph on the newer runtime without doubling documentation, coverage, publication, snapshot, and smoke checks whose failures are not expected to vary by Node minor version.

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# RFC: Parallel pre-push gates
Status: implemented
## Problem
The pre-push hook is the last local checkpoint before a branch leaves the machine, so its wall clock directly shapes whether contributors keep it enabled and trust its signal. Lefthook already runs top-level jobs in parallel, but aggregate jobs such as `pnpm run hygiene` and `pnpm run doc-sync` hide long sequential chains inside one job. The hook can therefore be configured as parallel while still waiting on serial subcommands whose members are independent.
Flattening those members directly into `lefthook.yml` solves the local hook only. CI has the same scheduling problem, and duplicating a long leaf list in YAML gives future script changes two places to drift.
`publint` has the same shape one level lower. Each package is linted independently against its own manifest and built output, but the runner loops through every package in order. On this repo that makes one package-publication gate consume time proportional to the number of packages even though the checks do not share mutable state.
## Decision
[lefthook.yml](../../../../lefthook.yml) keeps one pre-push job named `full check` and runs `pnpm run check:pre-push`. That package script delegates to [scripts/run-gates.ts](../../../../scripts/run-gates.ts), the same bounded scheduler CI uses.
The `pre-push` mode expands into leaf gates for the unit suite, snapshot suite, build, `hygiene` members, `doc-sync` members, and module-graph freshness. The leaf list keeps the same gate vocabulary as the package scripts, including RFC classification and RFC format, while the runner schedules independent checks concurrently and prints one timing/output block per gate.
The build gate makes the hook self-contained from a clean worktree. `publint` and `verify-node-next-types` wait for that build output, while source-only gates continue in parallel.
[scripts/publint-all.ts](../../../../scripts/publint-all.ts) discovers the package list from `packages/<group>/<pkg>` and runs `publint` with a worker pool sized from `availableParallelism()`. `DSH_PUBLINT_CONCURRENCY` can cap or raise the worker count for local machines and CI runners with different resource profiles. Results are buffered per package and printed in deterministic package order, so parallel execution does not scramble each package's log block.
The aggregate package scripts remain the source of truth for ad hoc local runs. The scheduler is a parallel execution plan over their member gates, not a replacement vocabulary.
## Alternatives considered
- **Keep aggregate `hygiene` and `doc-sync` jobs in the hook** - simpler config, but it leaves most of the pre-push wall clock inside serial command chains that lefthook cannot see or schedule.
- **Declare one lefthook job per leaf gate** - exposes parallelism through lefthook's native job model, but it makes the hook file carry a long member list that CI cannot reuse.
- **Require developers to build before pushing** - avoids one hook gate, but it makes `publint` fail in a clean worktree and turns the final local checkpoint into a convention instead of a runnable check.
- **Background subcommands inside shell scripts** - can parallelize work, but it loses lefthook's job names, per-job timing, and failure grouping, and makes signal handling harder to reason about.
- **Declare one publint lefthook job per package** - exposes maximum parallelism, but it turns the hook into a hand-maintained package inventory that drifts exactly when new packages are added.
- **Run publint with unbounded concurrency** - minimizes elapsed time on small machines only by gambling with process count, memory pressure, package tarball creation, and readable logs.
## Consequences
The hook's critical path becomes the slowest real gate instead of the sum of hidden gate chains. Lefthook reports one `full check` job, and the runner reports per-gate timing inside that job, so a slow local checkpoint still points at the gate that dominates the run.
The hook file stays short, and the duplicated member list lives in [scripts/run-gates.ts](../../../../scripts/run-gates.ts), where CI and pre-push can share it. The cost is a custom scheduler script instead of pure lefthook configuration, plus a build in the local pre-push path.
`publint-all.ts` becomes asynchronous code and buffers command output instead of inheriting stdio live. The payoff is package-level parallelism with stable output order and one environment variable for resource tuning.

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# RFC: Drop the mutable session summary
Status: implemented (proposed and accepted 2026-06-19)
Status: implemented
## Context
## Problem
The [session-persistence seam](../architecture/2026-06-14-session-persistence.md) split a session's out-of-log metadata into two types owned by `dsh-session`: an immutable `SessionHeader` (`version`, `id`, `createdAt`, `cwd?`, `parentSession?`) written once at creation, and a mutable `SessionSummary` (`updatedAt`, `title?`, `firstPrompt?`) "updateable without touching the append-only log". Their union was `SessionMeta = SessionHeader & SessionSummary`, and the abstract `SessionPersistence` service carried a seventh method — `update(id, summary)` — for rewriting the summary. Each backend implemented the mutable store its own way: JSONL wrote a separate atomic `.summary.json` **sidecar** beside the log (temp-write + rename, best-effort), SQLite kept `updated_at`/`title`/`first_prompt` **columns** bumped inside the append transaction.
@@ -26,6 +26,8 @@ This is recorded as a decision because it is **durable** (it narrows a public se
This is unreleased software (see [root AGENTS.md](../../../../AGENTS.md) § "Pre-release stance: foundation over blast radius"), so there are no on-disk databases or logs to preserve. SQLite does not migrate a v1 database: the `openDatabase` guard now rejects any non-current on-disk `user_version` (`onDisk !== 0 && onDisk !== SCHEMA_VERSION`) — older *or* newer — so a stale v1 DB is cleanly rejected rather than half-read against the new column set. A fresh database stamps the current version; that is the only path that needs to work.
## What we gave up
## Consequences
A future session picker now has to derive its preview/ordering from the log (or reintroduce a typed field) rather than reading a ready-made summary row. That is the correct cost: a cache for a feature that does not exist is dead weight that every backend pays to maintain and every contract test pays to assert. The principle — **a passing test pins current behavior, not necessarily correct behavior; behavior can be an artifact of a past compromise** — is now recorded as a standalone convention in [root AGENTS.md](../../../../AGENTS.md), with this change as its worked example.
<!-- rfc-format: alternatives-not-recorded (pre-format RFC) -->

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# RFC: Fold trace-only session facts into load-bearing events
Status: implemented (proposed and accepted 2026-06-20)
Status: implemented
## Problem
@@ -8,27 +8,26 @@ The session event vocabulary includes first-class events that are not part of re
These events make the canonical transcript look more useful as telemetry than it currently is. They add event variants, invariants, tests, snapshots, and persistence cases, but they are not load-bearing as separate records. The facts they carry can still be useful: token usage should remain available for accounting, and an error's step number should not silently disappear. The simplification is to fold those facts into nearby events consumers already must understand, not to record less information.
## Proposal
## Decision
Remove standalone trace-only events only where their information can be preserved without a parallel record:
Standalone trace-only events are removed exactly where their information is preserved without a parallel record:
- Fold successful-step usage into the matching `assistant/message`, e.g. `assistant/message { turn, step, content, usage? }`, so the assembled model output and its accounting travel together.
- For a failed or aborted step that has usage but no `assistant/message`, carry the usage on the terminal turn reason or another load-bearing failure record in the same turn. The implementing design must prove no usage chunk that is currently persisted becomes unrepresented.
- Fold the step number from the standalone `error` event into `turn/end.reason` for `kind: 'error'`, e.g. `{ kind: 'error', step, message, code? }`. `turn/end` is the durable turn outcome ACP and resume already consume.
- Keep `agent/error` and logging for live diagnostics; do not add a second session-log error record after `turn/end`.
- Successful-step usage folds into the matching `assistant/message` (`assistant/message { turn, step, content, usage? }`), so the assembled model output and its accounting travel together.
- A failed or aborted step that has usage but no assistant content carries the usage on an empty-content `assistant/message` (the implementation note below carries the no-information-loss proof) — no persisted usage chunk goes unrepresented.
- The step number from the standalone `error` event folds into `turn/end.reason` for `kind: 'error'` (`{ kind: 'error', step, message, code? }`) — `turn/end` is the durable turn outcome ACP and resume already consume.
- `agent/error` and logging stay for live diagnostics; there is no second session-log error record after `turn/end`.
If analytics become real, add a projection helper or a dedicated telemetry store with its own retention policy. The user conversation log should contain what is needed to render, resume, audit, and account for the interaction without requiring consumers to reconcile duplicate trace rows.
The user conversation log contains what is needed to render, resume, audit, and account for the interaction without consumers reconciling duplicate trace rows.
## Acceptance criteria
## Alternatives considered
- `SessionEventMap` drops standalone `usage` and `error` only after their fields are represented on load-bearing session events.
- The loop no longer appends a separate `usage` event for a usage chunk.
- The loop records durable failures through `turn/end { kind: 'error', step, message, code? }` or an equivalent no-information-loss shape and reports live diagnostics through `agent/error`.
- ACP snapshots and persistence tests stop asserting trace-only lines.
- Documentation explains exactly where token usage and operational errors are observed.
- Recorded fixtures are refreshed for the new event shape; the session format version stays pinned at `0` (unstable/pre-release) and backends reject any non-`0` stored log per the pre-release format policy.
**Keep the standalone rows as telemetry** — the events made the canonical transcript look more useful as telemetry than it was, at the cost of event variants, invariants, tests, snapshots, and persistence cases nothing consumed. If analytics become real, the shape is a projection helper or a dedicated telemetry store with its own retention policy — not duplicate trace rows in the conversation log.
## What we give up
## Verification
`SessionEventMap` carries no standalone `usage` or `error`; the loop appends no separate usage event and records durable failures through `turn/end { kind: 'error', step, message, code? }`; ACP snapshots and persistence tests assert no trace-only lines; recorded fixtures are on the new event shape with the session format version pinned at `0` (backends reject any non-`0` stored log per the pre-release format policy); and the docs state where token usage and operational errors are observed.
## Consequences
A consumer can no longer filter the canonical log for standalone `usage` or step-level `error` rows. It must read those facts from the assistant/failure events that carry them. That is a reasonable simplification only if the implementing PR proves the same facts remain present; otherwise the standalone events should stay.

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# RFC: Drop the unconsumed `llm/adapter-change` event
Status: implemented (proposed and accepted 2026-06-20)
Status: implemented
## Problem
@@ -10,32 +10,23 @@ This differs from `tools/change` and `system-prompt/change`. Those two events ar
The event is not free. `registerAdapter()` yields its rollback disposer before emitting `llm/adapter-change` so a throwing listener unwinds the mutation instead of leaking an adapter entry, and the package carries tests for that listener-throw path. That defensive ordering protects a failure mode only tests can trigger.
## Proposal
## Decision
Remove only `llm/adapter-change`:
Only `llm/adapter-change` is removed: the declaration in `dsh-llm`'s `interface Events`, the `ctx.emit('llm/adapter-change')` calls, and the "Emits `llm/adapter-change` on registration and disposal" sentence in `LlmService.registerAdapter`'s JSDoc. `registerAdapter()`'s effect generator keeps the mutation and rollback disposer for HMR/disposal but sheds the listener-throw rollback ordering that existed only for the removed event. The adapter-disposer test asserts the returned disposer removes the adapter without subscribing to the event; the listener-throw rollback test is gone with its subject. The event taxonomy in [docs/architecture.md](../../../architecture.md) and [packages/llm/llm/README.md](../../../../packages/llm/llm/README.md) is updated in the same change.
- Delete the `llm/adapter-change` declaration from `dsh-llm`'s `interface Events`.
- Delete the `ctx.emit('llm/adapter-change')` calls.
- Simplify `registerAdapter()`'s effect generator: keep the mutation and rollback disposer for HMR/disposal, but drop the listener-throw rollback ordering that exists only for the removed event.
- Remove the "Emits `llm/adapter-change` on registration and disposal" sentence from `LlmService.registerAdapter`'s JSDoc.
- Rewrite the adapter-disposer test to assert the returned disposer removes the adapter without subscribing to `llm/adapter-change`; delete the listener-throw rollback test that exists solely for the removed event.
- Update the event taxonomy table in [docs/architecture.md](../../../architecture.md) and [packages/llm/llm/README.md](../../../../packages/llm/llm/README.md). The [doc-sync-enforcement RFC](../../implemented/process/2026-06-11-doc-sync-enforcement.md) should avoid using `llm/adapter-change` as an example once the event is gone.
## Alternatives considered
## Why not remove every registry change event?
### Why not remove every registry change event?
A microkernel where registries announce mutations is a coherent convention. `tools/change` and `system-prompt/change` may become useful when a UI can live-refresh available tools or prompt sections. This RFC leaves that convention intact where it has a plausible user-facing consumer and cuts only the adapter-change event whose current and likely future consumer is unclear.
If an LLM adapter browser or dynamic model-picker needs this signal later, reintroduce it with that consumer and a clearer payload than "something changed."
## Acceptance criteria
## Verification
- `llm/adapter-change` and its emits are gone; `pnpm run verify-cordis-catalog` passes against the regenerated catalog.
- HMR-safety tests still pass: disposing a contributing fiber still removes the adapter.
- `tools/change` and `system-prompt/change` remain documented and tested.
- `pnpm run test:coverage` stays 100% per-file.
- No production code path changes observable behavior (verified by unchanged ACP snapshot goldens and the echo-agent smoke test).
`llm/adapter-change` and its emits are gone and the regenerated cordis catalog is fresh; HMR-safety holds (disposing a contributing fiber removes the adapter); `tools/change` and `system-prompt/change` remain documented and tested; and no production path changed observable behavior — the ACP snapshot goldens and the echo-agent smoke are byte-unchanged.
## Risks
## Consequences
- **Removing a documented emit event is a public-surface change.** It is in the taxonomy table, so it reads as deliberate API. But "declared and emitted" is not "consumed" — the same distinction that justified dropping the mutable summary. The taxonomy table is updated in the same change, so the docs do not drift.
- **The registry-change convention becomes uneven.** That is acceptable because LLM adapter registration is not the same user-facing concept as tools or prompt sections. Uneven but honest beats uniform but dead.

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@@ -1,6 +1,6 @@
# RFC: Drop unconsumed assembled LLM convenience surfaces
Status: implemented (proposed and accepted 2026-06-20)
Status: implemented
## Problem
@@ -16,27 +16,19 @@ This is the [drop-mutable-session-summary](../../implemented/simplification/2026
`streamBlocks()` drags a dedicated slice of `BlockAssembler` behind it: `flushReady()` and `flushRemaining()` ([packages/llm/llm/src/assembler.ts:138-168](../../../../packages/llm/llm/src/assembler.ts)) plus the `flushed` cursor field exist only to support incremental in-order yield. `generate()` drags `GenerateResult`, `BlockAssembler.result()`, and the `llm/generate` waterfall as a second interception surface over the same underlying stream. The loop's assembler usage is `push()` / `message()` / `usage` / `finish` — not streaming flush or one-shot service assembly.
## Proposal
## Decision
Make `stream()` the only public LLM call surface:
`stream()` is the only public LLM call surface. Removed with their JSDoc and doc references: `LlmService.streamBlocks()`; `LlmService.generate()`, the `llm/generate` waterfall event, and `GenerateResult`; `BlockAssembler.flushReady()`/`flushRemaining()` and the `flushed` cursor field; and `BlockAssembler.result()`, which only served the deleted `generate()` path. Adapter tests drive `ctx.llm.stream()` through a small helper that pushes chunks into `BlockAssembler` and returns the assembled message, usage, and finish reason — keeping the [twin-adapter design](../../implemented/architecture/2026-06-13-twin-llm-adapters.md) intact without a public method whose only callers are tests. The assembler invariants that apply to `push()` / `blocks()` / `message()` keep their tests; the flush-API pins went with the API. The `ctx.llm` service-map row in [docs/architecture.md](../../../architecture.md) is `stream()` only, the event taxonomy carries no `llm/generate`, and the [property-based-testing RFC](../../implemented/testing/2026-06-11-property-based-testing.md) names block-assembly invariants without the removed convenience methods.
- Remove `LlmService.streamBlocks()` and its JSDoc.
- Remove `LlmService.generate()`, the `llm/generate` waterfall event, and `GenerateResult` if no surviving API needs that named result shape.
- Remove `BlockAssembler.flushReady()`, `BlockAssembler.flushRemaining()`, and the `flushed` cursor field.
- Remove `BlockAssembler.result()` if it is only a helper for the deleted `generate()` service path and tests.
- Replace adapter-test use of `ctx.llm.generate()` with a small test helper that calls `ctx.llm.stream()`, pushes chunks into `BlockAssembler`, and returns the assembled message, usage, and finish reason needed by that test. That keeps the [twin-adapter design](../../implemented/architecture/2026-06-13-twin-llm-adapters.md) intact while avoiding a public method whose only callers are tests.
- Remove or rework the `flushReady`/`flushRemaining`-dependent tests. Keep assembler invariants that still apply to `push()` / `blocks()` / `message()`; delete behavior that only pins the removed flush API.
- Update every doc/comment reference to `streamBlocks`, `generate`, `GenerateResult`, and `llm/generate` across `docs/`, package READMEs, and source comments. The `ctx.llm` service-map row in [docs/architecture.md](../../../architecture.md) becomes `stream()` only, the event taxonomy drops `llm/generate`, and the [property-based-testing RFC](../../implemented/testing/2026-06-11-property-based-testing.md) names block-assembly invariants without referring to removed convenience methods.
## Alternatives considered
## Acceptance criteria
**Keep `generate()` as a test-only convenience** — rejected: adapter tests hand-draining `stream()` through the shared assembler exercise the same streaming path production uses, and a public method whose only callers are tests is exactly the dead-surface shape [the drop-mutable-summary precedent](2026-06-19-drop-mutable-session-summary.md) retired. A future consumer that wants assembled blocks without deltas reintroduces a focused helper with that consumer.
- `streamBlocks`, `generate`, `llm/generate`, and the assembler helpers they alone require are gone; `pnpm run knip` reports no new dead exports.
- `pnpm run test:coverage` stays at 100% per-file (the deleted methods take their dedicated tests with them; no remaining line goes uncovered).
- Adapter tests still exercise both real adapters through `stream()` and the shared assembler, not through a test-only public shortcut.
- The loop behaves identically — verified by unchanged ACP snapshot goldens.
- `packages/llm/llm/README.md`, [docs/architecture.md](../../../architecture.md), and module docs no longer mention the removed convenience surfaces.
## Verification
## Risks
`streamBlocks`, `generate`, `llm/generate`, and the assembler helpers they alone required are gone with no new dead exports; both real adapters are exercised through `stream()` and the shared assembler; the loop behaves identically (ACP snapshot goldens unchanged); and the README, architecture doc, and module docs carry no mention of the removed surfaces.
## Consequences
- **It removes public methods from a core vocabulary package.** A future plugin that wants assembled blocks without deltas would need to call `stream()` and use `BlockAssembler` directly or reintroduce a focused helper with a real consumer. Given the pre-release "foundation over speculative future" stance ([AGENTS.md](../../../../AGENTS.md)), this is the right time to cut test-only public shape.
- **Adapter tests get a little more explicit.** They lose the ergonomic `generate()` wrapper, but that is useful pressure: tests exercise the same streaming path production uses.

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@@ -1,6 +1,6 @@
# RFC: Prune dead methods from the persistence seam
Status: implemented (proposed and accepted 2026-06-20)
Status: implemented
> **Implementation note (scope narrowed from the original proposal).** This RFC proposed pruning dead methods from BOTH the persistence seam (`SessionPersistence.has()`/`.delete()`) and the bash seam (`BashExecutor.get()`/`.list()`). Only the **persistence** removal shipped. The bash `get()`/`.list()` removal was reverted before merge: each is a one-line accessor over the executor's already-tracked `tasks` map, and removing them forced `dsh-tool-bash`'s tests onto a ~35-line `onTaskDone`-based completion-tracking harness to replace the one-line `ctx.bash.get(id)` lookup — the migration cost dwarfed the surface removed. Per the [AGENTS.md "RFCs are proposals, not golden truth"](../../../../AGENTS.md) principle, that friction is evidence the method earns its keep (a test harness IS a consumer that programs against the seam), so `get()`/`list()` stay. The bash-seam analysis below is retained for the record but was NOT acted on; `BashTaskId`-branding those methods lands in the [branded-ids RFC](../architecture/2026-06-20-branded-ids.md) instead. The persistence removal stands: `has()`/`delete()` had only contract-test callers and no test-ergonomics cost to remove.
@@ -14,27 +14,26 @@ The abstract service declared its operations beyond create/append: `load`, `list
`has()` was not just unused — it was the most intricate branch in the shared coordinator: a tracked-vs-untracked dual-probe (`loadLive(id, cwd)` for a live-tracked session vs `loadStored(id)` for an untracked one) with a multi-line rationale. `delete()` dragged the `deleteStored` backend hook that every backend had to implement. This is the [drop-mutable-session-summary](../../implemented/simplification/2026-06-19-drop-mutable-session-summary.md) pattern: a contract test exercised both, but no shipping code asks "is this session persisted?" or removes one.
## Proposal
## Decision
Remove the methods nothing consumes, from the abstract seam, the implementation, and the contract/spec suites that exist only to exercise them:
The methods nothing consumes are removed — from the abstract seam, the implementation, and the contract/spec suites that existed only to exercise them:
- `SessionPersistence.has()` / `.delete()`: delete the abstract declarations, the coordinator's `has`/`delete`/`deleteCore`, and the `PersistenceBackend.deleteStored` hook. Remove the `has`/`delete` rows from the contract suite and the per-backend specs (jsonl + sqlite each implemented `deleteStored` only to satisfy the hook — that implementation goes too). The backends are the [dual-backend](../../implemented/architecture/2026-06-14-session-persistence.md) design and otherwise out of scope, but removing a hook they implement for no consumer is part of removing the hook, not a backend redesign.
- Update every doc and source-comment reference to the removed methods — not only literal `has(`/`delete(`/`deleteStored` call spellings, but also `{@link has}`/`{@link delete}` JSDoc links and prose that counts the methods (removing 2 of the persistence service's 6 public methods makes any "six public methods" phrasing wrong). The implementing PR greps `has`/`delete`/`deleteStored`/`{@link `/`six ` across `docs/`, `packages/*/README.md`, and source comments, and fixes each. The known doc sites: the seam README ([packages/session-persistence/session-persistence/README.md](../../../../packages/session-persistence/session-persistence/README.md)'s `has(id)`/`delete(id)` API row and its "delegates its six public service methods" prose → four), the backend READMEs that describe `has`/`list` semantics ([packages/session-persistence/session-persistence-sqlite/README.md](../../../../packages/session-persistence/session-persistence-sqlite/README.md), [packages/session-persistence/session-persistence-jsonl/README.md](../../../../packages/session-persistence/session-persistence-jsonl/README.md) — reword "absent from `has()`/`list()`" to just `list()`), the service-map / seam docs in [docs/architecture.md](../../../architecture.md), and the persistence prose in the [session-persistence RFC](../../implemented/architecture/2026-06-14-session-persistence.md) and [shared write-coordinator RFC](../../implemented/architecture/2026-06-18-shared-persistence-write-coordinator.md). The known source-comment sites: the abstract `create()` JSDoc's `{@link has}/{@link list}` link ([packages/session-persistence/session-persistence/src/index.ts](../../../../packages/session-persistence/session-persistence/src/index.ts) — drop the `has` link), the coordinator's "six public methods"/"six public service methods" module + class JSDoc and its lazy-materialization JSDoc justifying the `materialized` flag by "the signal `has`/`list` rely on" ([packages/session-persistence/session-persistence/src/coordinator.ts](../../../../packages/session-persistence/session-persistence/src/coordinator.ts)), the JSONL backend's `loadStored`/`deleteStored` comment, and the SQLite backend's `schema.ts` and `index.ts` comments that mention "absent from `has`/`list`" — all reworded to the surviving four-method, `list()`-only contract.
- `SessionPersistence.has()` / `.delete()` are gone: the abstract declarations, the coordinator's `has`/`delete`/`deleteCore`, and the `PersistenceBackend.deleteStored` hook (jsonl + sqlite each implemented `deleteStored` only to satisfy the hook — those implementations went too). The backends are the [dual-backend](../../implemented/architecture/2026-06-14-session-persistence.md) design and otherwise out of scope; removing a hook they implemented for no consumer is part of removing the hook, not a backend redesign.
- Every doc and source-comment reference is updated to the surviving four-method, `list()`-only contract — not only literal `has(`/`delete(`/`deleteStored` spellings but `{@link has}`/`{@link delete}` JSDoc links and "six public methods" counts — across the seam and backend READMEs, [docs/architecture.md](../../../architecture.md), the [session-persistence](../../implemented/architecture/2026-06-14-session-persistence.md) and [write-coordinator](../../implemented/architecture/2026-06-18-shared-persistence-write-coordinator.md) RFCs, and the coordinator/backends JSDoc.
## Why not keep them as "the seam should be complete"?
## Alternatives considered
### Why not keep them as "the seam should be complete"?
The instinct that a persistence seam "should" offer delete is real — and it is exactly the speculative-completeness the pre-release stance warns against ([AGENTS.md](../../../../AGENTS.md): optimize for the correct foundation, not for hypothetical callers you do not have). `delete()` is one method to re-add the day a consumer needs it: a session-management UI that deletes old sessions will want it — add it then, designed against that UI's real needs (soft-delete? cascade? confirmation?), not guessed now.
Re-adding a seam method with a live consumer is cheap and better-designed than the speculative version, because the consumer pins the contract. Carrying it unused means every implementation (and every future backend) must implement and test a method that does nothing.
## Acceptance criteria
## Verification
- `has`/`delete`/`deleteStored` are gone from the persistence seam, impl, and contract suites; `pnpm run knip` reports no new dead exports.
- The remaining persistence operations (`create`/`append`/`load`/`list`) are untouched; ACP `session/list` and crash-recovery behave identically.
- `pnpm run test:coverage` stays 100% per-file (the contract/spec rows for the removed persistence methods are deleted with them).
- The persistence seam README and `docs/architecture.md` no longer list the removed `has`/`delete` methods.
`has`/`delete`/`deleteStored` are gone from the persistence seam, impl, and contract suites with no new dead exports; the remaining operations (`create`/`append`/`load`/`list`) are untouched, with ACP `session/list` and crash-recovery behaving identically; and the seam README and `docs/architecture.md` list only the surviving methods.
## Risks
## Consequences
- **`delete()` is the kind of operation a product eventually wants.** True — but "eventually" is the point. Deleting it now and re-adding it against a real consumer is strictly better than shipping a guessed contract. The dual backends each shed a `deleteStored` impl, which is a bounded edit in otherwise-out-of-scope packages.
- **Low coupling.** The removal is confined to the persistence seam + impl + tests; no cross-package consumer references the removed methods, so there is no ripple beyond the docs.

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@@ -1,6 +1,6 @@
# RFC: Keep one public stop primitive
Status: implemented (proposed 2026-06-20; accepted in amended form — `whenIdle()` retained)
Status: implemented
> **Implementation note (scope narrowed from the original proposal).** This RFC proposed removing BOTH `abort()` and `whenIdle()` from the public `Agent` handle. Only `abort()` was removed. Validating the premise against the code ([AGENTS.md "RFCs are proposals, not golden truth"](../../../../AGENTS.md)) found `whenIdle()` to be a **load-bearing quiescence primitive**, not dead surface: it is the settle signal in several ACP tests (`packages/ui/acp/tests/{edges,turns,dispose}.spec.ts`) and is backed by a deliberate loop contract (settle waiters without a status transition; handle the replacement-turn race). The RFC's suggested migration — have consumers observe the `running`→`idle` transition by hand — is exactly the brittle hand-rolled path [the defensive patterns](../../../defensive-patterns.md) warns against ("Async state is not synchronous state"). Deleting a clean primitive to push every consumer onto that is a net loss, so `whenIdle()` stays. `abort()` was genuinely dead public surface (no production caller; the loop aborts its own `AbortController` directly), so it was removed as proposed. The text below is amended to describe what shipped.
@@ -12,22 +12,23 @@ The `abort()`/`cancel()` distinction is real — `abort()` preserves queued prom
The extra surface area made the loop carry a public verb that is mostly a teardown internal: `abort()` had to be documented as distinct from queue-aware cancellation even though a UI cancellation almost always wants the broader operation.
## Proposal
## Decision
Keep `cancel()` as the only public *stop* primitive on `Agent`. Lifecycle owners use `AgentHandle.dispose()` to stop and unregister an agent; non-owners use `cancel()` to abandon current and queued work. The implementation keeps a private abort controller, but it is not part of the plugin-facing `Agent` contract.
`cancel()` is the only public *stop* primitive on `Agent`. Lifecycle owners use `AgentHandle.dispose()` to stop and unregister an agent; non-owners use `cancel()` to abandon current and queued work. The implementation keeps a private abort controller, but it is not part of the plugin-facing `Agent` contract.
`whenIdle()` is **retained** as the public quiescence-observation primitive (resolve once the agent settles out of `running`, resolve immediately when already idle, await the loop exit when disposed). It is not a stop verb; it is how a non-owner observes the stop *completing* without disposing the agent. Its live consumers are ACP and agent tests that await settlement through this public seam (`packages/ui/acp/tests`, `packages/core/agent-loop/tests`); the production ACP bridge owns its agents and tears them down through `AgentHandle.dispose()`, so `packages/ui/acp/src` itself has no `whenIdle()` call.
Delete public `abort()`, the tests that exercise it as standalone API, and the docs that describe step-only abort as an embedding feature. Empty-queue abort tests migrate to `cancel(reason)` where they still prove cancellation behavior; tests whose subject is the loop's internal `AbortController` behavior drive that controller directly via an in-package typed cast to the private field; tests that only pin the removed no-arg `abort()` default go away with the method. The disposer remains async and still waits for the loop to stop.
Public `abort()` is deleted, with the tests that exercised it as standalone API and the docs that described step-only abort as an embedding feature. Empty-queue abort tests migrated to `cancel(reason)` where they still prove cancellation behavior; tests whose subject is the loop's internal `AbortController` drive that controller directly via an in-package typed cast to the private field; tests that only pinned the removed no-arg `abort()` default went with the method. The disposer remains async and still waits for the loop to stop.
## Acceptance criteria
## Alternatives considered
- `Agent` exposes no public `abort()`; `cancel()`, `whenIdle()`, and `steer()` remain part of the surface.
- ACP cancellation continues to call `cancel()`.
- Agent teardown continues to await quiescence through handle disposal, and `whenIdle()` still resolves on quiescence for non-owner observers.
- Tests cover cancellation and disposal as the two supported stop paths.
**Removing `whenIdle()` too** — the original proposal's shape, reversed on validating the premise against the code (the implementation note above carries the full record): it is a load-bearing quiescence primitive, and pushing consumers onto hand-observed `running`→`idle` transitions is exactly the brittle path the defensive patterns warn against.
## What we give up
## Verification
`Agent` exposes no public `abort()` while `cancel()`, `whenIdle()`, and `steer()` remain; ACP cancellation calls `cancel()`; teardown awaits quiescence through handle disposal, with `whenIdle()` resolving on quiescence for non-owner observers; and the suites cover cancellation and disposal as the two supported stop paths.
## Consequences
A future plugin cannot abort only the current model/tool step while preserving queued prompts through the public interface. If that use case becomes real, it should return with a named consumer and a narrower contract. Today it is latent generality that keeps a private loop mechanic public.

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@@ -1,14 +1,15 @@
# RFC: Stop mirroring durable boundaries as agent events
Status: implemented (accepted 2026-07-01)
Status: implemented
<!-- Shipped in AMENDED, narrowed form: the four turn/step BOUNDARY mirrors are
removed; `agent/steering` and `agent/stream-chunk` were RETAINED here (they
are not durable-boundary mirrors — see "Scope: what is and isn't removed").
The original proposal bundled `agent/steering` into the removal; validating
against the code showed it is a distinct live-only signal, so it stayed.
`agent/stream-chunk` was later removed by its own decision — see
[Stop mirroring the token stream as an agent event](2026-07-02-remove-stream-chunk-mirror.md). -->
The original proposal bundled `agent/steering` into the removal; keeping it
out kept this RFC's scope to boundaries. Each retained event was later
removed by its own decision — see
[Stop mirroring the token stream as an agent event](2026-07-02-remove-stream-chunk-mirror.md)
and [Remove the `agent/steering` mirror emit](2026-07-04-remove-agent-steering-mirror.md). -->
## Problem
@@ -30,10 +31,15 @@ Removed (durable-boundary mirrors — the session log is authoritative for each)
RETAINED — NOT durable-boundary mirrors, so out of scope for this decision:
- `agent/steering` — a live control signal, not a boundary. (The original proposal bundled it into the removal; validating against the code, it is not a duplicate of a durable boundary, so removing it here would have been scope creep. Its fate is a separate future decision.)
- `agent/steering` — not a boundary, so out of scope for THIS decision (the original proposal bundled it into the removal; that would have been scope creep here). It mirrors the durable `steering/message` control record rather than a boundary, and was removed by its own follow-up: [Remove the `agent/steering` mirror emit](2026-07-04-remove-agent-steering-mirror.md).
- `agent/stream-chunk` — the live token stream. Out of scope for THIS decision (a mirror of the durable `assistant/chunk`, not a boundary), it was removed by its own follow-up: [Stop mirroring the token stream as an agent event](2026-07-02-remove-stream-chunk-mirror.md).
- `agent/created`, `agent/disposed`, `agent/status`, `agent/error`, `agent/queued` — lifecycle/control events that are not transcript data. `agent/queued` in particular is an inbox acknowledgement that fires before any durable event exists (cancelled queued work may never enter the log), so it is deliberately live-only.
## What we give up
## Alternatives considered
- **Bundling `agent/steering` into the removal** — the original proposal's shape; narrowed out as scope creep: it mirrors the durable `steering/message` control record, not a boundary, and was removed by [its own later decision](2026-07-04-remove-agent-steering-mirror.md) (as was `agent/stream-chunk`, by [the stream-chunk-mirror RFC](2026-07-02-remove-stream-chunk-mirror.md)).
- **Keeping the turn mirrors for the stdio UI** — [the event-domain-semantics RFC](../architecture/2026-06-30-event-domain-semantics.md)'s original stance; rejected here because `dsh-ui-stdio` is a disposable test REPL, not a load-bearing consumer, and it renders boundaries from `session/event` + the id map instead.
## Consequences
A plugin can no longer observe turn/step boundaries from a convenient `Agent`-first event. It must either subscribe to `session/event` or maintain a session-to-agent association. That is an acceptable trade: boundary consumers should not depend on a second event feed that can drift from the durable log.

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@@ -105,24 +105,24 @@ This RFC reverses two decisions from [filesystem-capability-seam](../../implemen
It keeps the interface/implementation/consumer discipline, consumer-never-imports-backend rule, backend-defined target/version/display metadata, atomic local writes, and the shared `FsError` taxonomy.
## Acceptance Criteria
## Verification
- `dsh-fs` exposes exactly `resolve`/`stat`/`readText`/`streamText`/`writeText`/`editText`; `stat` returns `FsInfo | undefined`; `writeText` uses `FsWriteIntent` (`createIfAbsent` or `replaceIfVersion`); removed types/primitives are gone, and the old `applyEdit` API is replaced by `editText`.
- `dsh-fs-policy` adds the observed-state + `read`/`write`/`edit` freshness policy and has HMR/disposal coverage. (It does so as a gate PLUGIN on the `fs/*` events with no `ctx.fileContext` service, per [the event-gate RFC](../architecture/2026-06-26-file-context-as-event-gate.md) — the original service form this RFC proposed was reworked.)
- `dsh-tool-fs` reaches the policy decisions and model-facing schemas stay byte-for-byte unchanged; the observation contract (a read records observed-state; a direct `ctx.fs` read does not) is documented and tested. (The tool injects `fs` and dispatches the `fs/*` events rather than injecting a `fileContext` service, per the event-gate RFC.)
- Windowed read authorizing edit is shown to fail on the pre-refit code and pass after the refit. Existing version-CAS behavior is preserved with a regression test; it is not claimed as a pre-refit failure. An edit based on a stale read must report `FS_STALE_VERSION` before attempting literal matching.
- `dsh-fs-local` carries no line, view, or `formatReadBody` logic; it does carry provider-level `editText` logic.
- Docs and generated artifacts are updated: `docs/architecture.md`, `packages/README.md`, fs package READMEs, `docs/core-data-structures/filesystem.md`, affected `type-equiv` blocks and `scripts/type-equiv.manifest.json`, Cordis catalog, module graph, and doc references.
- Gates stay green: normal `doc-sync`, `pnpm run knip`, and `pnpm run test:coverage` with 100% per-file coverage.
`dsh-fs` exposes exactly `resolve`/`stat`/`readText`/`streamText`/`writeText`/`editText` (`stat` returning `FsInfo | undefined`, `writeText` taking `FsWriteIntent`), with the removed types/primitives gone; `dsh-fs-local` carries no line, view, or `formatReadBody` logic; model-facing schemas stayed byte-for-byte unchanged. Tests pin that a windowed read authorizes a later edit of an unchanged file, that an edit based on a stale read reports `FS_STALE_VERSION` before attempting literal matching, that version-CAS behavior is preserved, and that the observation contract holds (a `read`-tool read records observed-state; a direct `ctx.fs` read does not); `dsh-fs-policy` has HMR/disposal coverage.
## Later extension
The seam was later extended with direct directory listing by [Add direct directory listing to the filesystem seam](../architecture/2026-07-03-filesystem-directory-listing-seam.md). That follow-up is tracked separately so this RFC's acceptance criteria continue to describe the fsspec-style refit that originally shipped.
## Risks
## Alternatives considered
- Adds a fourth fs package and a new service. This is intentional: it is the previously deferred policy layer, not a second abstract backend seam.
- **Byte-level fsspec (`cat`/`open` handing back raw bytes)** — rejected: the seam is deliberately text-storage, half a level up, so UTF-8 decoding, binary/NUL rejection, and guarded text mutations live once in the provider and the policy layer never touches raw bytes or separates stale checks from the mutation critical section.
- **A concrete `ctx.fileContext` method service** — this RFC's original policy shape; reworked by [the event-gate RFC](../architecture/2026-06-26-file-context-as-event-gate.md) into the gate plugin, so the tool is never method-coupled to the policy.
- **Keeping `readPage` and `full`/`partial` view authorization on the provider** — the pre-refit shape the Supersedes section reverses: view completeness is not what edit safety needs, version freshness is, and the view rule made large files past the read cap impossible to edit.
## Consequences
- Adds a fourth fs package and a new plugin layer. This is intentional: it is the previously deferred policy layer, not a second abstract backend seam.
- Direct `ctx.fs` use bypasses the policy: a direct `ctx.fs.readText` emits no `fs/observed`, so under the default policy a later `edit` rejects with `FS_NOT_OBSERVED` until the file is read through the `read` tool. The failure is explicit and documented.
- Large-file line windowing moves from the backend to the `read` tool in `dsh-tool-fs`; text decoding and binary rejection stay in `ctx.fs.streamText`, so this is relocation of windowing only, not a second text-IO implementation.
- Keeping `editText` in the provider seam means every backend must implement the literal replacement contract. This is intentional: the operation is not pure storage, but stale guard + literal match + atomic rewrite is the unit that must stay together for correct error attribution and concurrency behavior. The contract should stay narrow and text-only so future backends can implement it natively or by whole-file rewrite.
- Freshness permits full-file `write` after a windowed read. That is weaker than the old view check, but avoids making large files impossible to edit; prompt guidance should still discourage blind full replaces.
- Freshness permits full-file `write` after a windowed read. That is weaker than the old view check, but avoids making large files impossible to edit; prompt guidance still discourages blind full replaces.

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@@ -1,6 +1,6 @@
# RFC: Stop mirroring the token stream as an agent event
Status: implemented (accepted 2026-07-02)
Status: implemented
## Problem
@@ -33,9 +33,13 @@ Removed: `agent/stream-chunk`.
Not touched:
- `assistant/chunk` (the durable session event) — the authoritative token stream, kept exactly as-is. This RFC removes the LIVE MIRROR, not the persistence (the persistence-removal proposal was separately rejected — see above).
- `agent/steering` — a live control signal with no durable twin, retained (its fate remains a separate future decision, per the boundary RFC).
- `agent/steering` — not touched by THIS decision (a control signal, not the token stream). Its durable twin is `steering/message`, and the mirror emit was removed by its own follow-up: [Remove the `agent/steering` mirror emit](2026-07-04-remove-agent-steering-mirror.md).
- `agent/status`, `agent/error`, `agent/created`/`agent/disposed`, `agent/queued`, `agent/session-start` — lifecycle/control events that are not transcript data and have no durable duplicate.
## What we give up
## Alternatives considered
**Remove the persistence and keep only a transient live stream** — the inverse cut, [rejected separately](../../rejected/simplification/2026-06-20-assembled-assistant-messages-only.md): high-fidelity replay, partial failed streams, and snapshot replay all depend on the persisted `assistant/chunk` feed. With that settled, the live emit is the redundant half of the pair.
## Consequences
A plugin can no longer observe token deltas from an `Agent`-first event. It subscribes to `session/event` and filters `assistant/chunk` (the `Agent` handle, if needed, is recovered from a session-id→agent map built from `agent/created`/`agent/disposed`, exactly as boundary consumers already do). No production consumer needed the live `Agent` at chunk time; this is the same acceptable trade the boundary-mirror removal made.

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# RFC: Drop the `image` content block until a path can honor it
Status: implemented
## Problem
`ImageBlock` (`packages/llm/llm/src/types.ts`) had no production producer, and every consumer on every path DROPPED it: the deepseek adapter's serializer skipped image blocks (a documented MVP limitation), the pi-ai converter skipped them as unrepresentable, the ACP codec neither advertises image prompt capability nor forwarded image blocks outbound and REJECTS image prompt content inbound, and the compaction estimator charged a flat token constant and rendered `[image]`. An `ImageBlock` constructed then would silently vanish from the wire — the vocabulary advertised a capability no path honored, which is the silent-data-loss shape AGENTS.md's defensive patterns warn against. The only constructors anywhere were tests pinning the skip/drop/estimate branches.
## Decision
Remove `ImageBlock`, its `ContentBlockMap` entry (and its `cache?: CacheHint` field with it), the explicit `image` estimate/placeholder arms in compact-basic, and the image-naming comments in the deepseek serializer's, pi-ai converter's, and ACP codec's default arms — those default arms absorb the case the way they absorb any unknown block type. Updated in the same change: the vocabulary line in [architecture.md](../../../architecture.md), the block list in `packages/llm/llm/README.md`, the deepseek README's image-skip row, the pi-ai README's images-not-representable row, the compact-basic README's image-estimation and `[image]`-placeholder rows, the pastes in [core.md](../../../core-data-structures/core.md) and [llm-streaming.md](../../../core-data-structures/llm-streaming.md), and the [content-block vocabulary RFC](../architecture/2026-06-11-content-block-vocabulary.md)'s block list and multimodal-home consequence per [implemented/AGENTS.md](../AGENTS.md); the tests that constructed image blocks to exercise the removed branches were dropped (the estimate pin) or retargeted onto the merge-extensible default arms (plugin-added block types). The ACP codec's inbound rejection of image PROMPT content is unaffected — that guard is about protocol content a client can send regardless of our vocabulary, and it stays.
## Alternatives considered
### Why not keep it?
This was the most contested cut in the batch. Multimodal input (screenshots) is a plausible near-term coding-agent feature, and the [content-block vocabulary RFC](../architecture/2026-06-11-content-block-vocabulary.md) reserved the slot deliberately. Two responses. First, `ContentBlockMap` is merge-extensible by design: a real multimodal feature reintroduces `image` in core in the same coordinated change that maps it in the adapters, advertises and renders it in ACP, and prices it in compaction — the producer and its consumers arrive together, which is how the map is meant to grow. Second, the middle option — keep the type but make adapters throw UNSUPPORTED instead of silently dropping — converts this into exactly the shape the sibling request-knobs proposal (`2026-07-04-drop-inert-request-knobs`) argues against: surface whose only implementation is rejection. Absence (a compile error at the would-be producer) is strictly clearer than either silent loss or universal throw.
The recorded fallback, had review landed on keeping the slot: keep `ImageBlock` but replace every silent skip with a loud rejection, and document that policy in the vocabulary — the silent drop was the one state with no defender. Review landed on removal; the fallback stands as the documented alternative should the slot ever return ahead of a full feature.
## Verification
No `ImageBlock` / harness `type: 'image'` block is constructed anywhere outside RFC records; the codec's inbound ACP-image rejection keeps its tests; and the adapter/codec/compaction switches handle the case through their unknown-block default arms, pinned by the plugin-added-block tests.
## Consequences
Re-adding a core vocabulary type later touches several packages at once — but that coordinated change is the shape a real multimodal feature needs anyway (adapter mapping, ACP advertisement, compaction pricing), and none of it existed to preserve.

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# RFC: Drop `GenerateOptions.prefill` and `ToolSchema.strict` — request knobs with no working end-to-end path
Status: implemented
## Problem
Two request-contract knobs rode the whole request pipeline, yet neither could do anything:
- **`prefill`** (`packages/llm/llm/src/types.ts`) had no production setter — the loop assembles `model`/`system`/`tools`/`messages` plus `sessionId`/`signal`, and the compaction backend adds only `maxTokens` — and BOTH adapters rejected it: `packages/llm/llm-deepseek/src/serialize.ts` and `packages/llm/llm-pi-ai/src/adapter.ts` each threw `LlmError('UNSUPPORTED')` on a non-undefined `prefill`. The field's entire observable behavior was two throws, each pinned by one adapter test. DeepSeek's chat-prefix completion is a Beta feature on a base URL neither adapter targets.
- **`strict`** (`ToolSchema`, same file) was threaded through `DefineToolOptions`/`defineTool` (`packages/core/tools/src/schema.ts`), the registry's `schemas()` allowlist (`packages/core/tools/src/index.ts`), the deepseek wire mapping (`packages/llm/llm-deepseek/src/serialize.ts`, whose wire-type note recorded that strict mode requires the `/beta` base URL the adapter does not use), a per-tool payload-patching pass in `packages/llm/llm-pi-ai/src/adapter.ts`, and a conditional `Strict:` row in the tool-catalog renderer (`scripts/gen-tool-catalog.ts`). No shipped tool set it — `rg` across every `tool-*` package src and `examples/` found zero `strict:` producers; the only setters were dsh-tools unit tests.
Both knobs were adapter-symmetric, so removal shed them from both twins together — the [twin-adapter design](../architecture/2026-06-13-twin-llm-adapters.md) is untouched.
## Decision
- `prefill` is removed from `GenerateOptions`, along with both adapters' UNSUPPORTED guards, the tests pinning the throws, the paste line in [core.md](../../../core-data-structures/core.md), and the adapter README rows documenting the rejection. The cookbook's UNSUPPORTED guidance ([adding-an-llm-adapter.md](../../../cookbook/adding-an-llm-adapter.md)) states the rule generically — a `GenerateOptions` field your provider cannot honor throws `LlmError(..., 'UNSUPPORTED')` — instead of using prefill as the example. The [content-block vocabulary RFC](../architecture/2026-06-11-content-block-vocabulary.md)'s consequences record prefill as producer-gated rather than as having a home, per [implemented/AGENTS.md](../AGENTS.md).
- `strict` is removed from `ToolSchema`, `DefineToolOptions`, `defineTool`, the `schemas()` allowlist, the deepseek serializer branch and its wire-type field, and the tool-catalog renderer's `Strict:` row. The pi-ai payload fixup is simplified to the unconditional scrub of pi-ai's own per-tool strict default (pi-ai stamps `strict: false` on every serialized tool; the hand-rolled twin sends no such field, so the scrub survives for wire parity, pinned by its serializer test). The setter tests and the core.md paste line are gone; both `GenerateOptions` and `ToolSchema` keep their rows in `scripts/type-equiv.manifest.json`, since each type survives minus a field.
This RFC deliberately does NOT touch `temperature`, `stop`, or `maxTokens`: those are honored end-to-end by both adapters and are the natural first targets of a request-mutating hook plugin on `agent/request`.
## Alternatives considered
### Why not keep them?
"An explicit UNSUPPORTED throw is honest contract behavior" — but a knob whose only implementation across both twins is rejection promises nothing, and deleting it upgrades the failure mode: an accidental setter becomes a compile error instead of a runtime throw. "Strict schema adherence is an officially documented provider feature with complete plumbing" — but a knob is not product surface until a shipped tool sets it AND an endpoint honors it; today neither is true. Each returns with its first real producer: `prefill` together with an adapter that implements chat-prefix completion (and a stated policy for adapters that do not), `strict` together with a tool that wants it and a beta-endpoint story.
## Verification
`rg prefill` returns only RFC records (this one and the [content-block vocabulary RFC](../architecture/2026-06-11-content-block-vocabulary.md)'s producer-gated consequence); a tool-schema-scoped `rg strict` returns only this RFC, the surviving pi-ai scrub, and unrelated prose such as `strictEqual`. Both adapters' contract tests pass without the guards, and the pi-ai fixup still scrubs the library's strict default — wire parity pinned by its serializer tests.
## Consequences
The shipped hook bridges set no request fields at all, and a request-mutating plugin (an `agent/request` waterfall listener) reaches for `temperature`/`stop` (kept, working), not a field adapters reject. If chat-prefix completion or strict mode become product features, the re-add lands with the adapter/endpoint work, where the contract can say what actually happens rather than "everyone throws".

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# RFC: Drop the unconsumed web observation surface — the `providers-change` event and the status methods
Status: proposed
Status: implemented
## Problem
`WebService` exposes an observation surface no production code observes:
- **`web/providers-change`** (`packages/web/web/src/index.ts`) is declared and emitted on every provider registration and disposal, and each registration effect's rollback yield is ordered BEFORE the emit solely so a throwing change listener unwinds the registration. No listener exists outside the package's own two unit tests (one of which exists to pin that rollback ordering).
- **`searchStatus()` / `fetchStatus()` and the `WebCapabilityStatus` union** (same package) have zero production callers: `dsh-tool-web` executes directly through `ctx.web.search()`/`fetch()` and surfaces unavailability as the structured `WebError` codes the seam throws at execution time (`packages/web/tool-web/src/search.ts`, `packages/web/tool-web/src/fetch.ts`); the only status callers are the web packages' own tests. The prose in `packages/web/tool-web/README.md` and [architecture.md](../../../architecture.md) still claims the tool "reads only the aggregated `searchStatus()`/`fetchStatus()`" — drift that survives only because nothing checks prose against call sites.
- **`searchStatus()` / `fetchStatus()` and the `WebCapabilityStatus` union** (same package) have zero production callers: `dsh-tool-web` executes directly through `ctx.web.search()`/`fetch()` and surfaces unavailability as the structured `WebError` codes the seam throws at execution time (`packages/web/tool-web/src/search.ts`, `packages/web/tool-web/src/fetch.ts`); the only status callers are the web packages' own tests. The prose in `packages/web/tool-web/README.md` and [architecture.md](../../../architecture.md) claims the tool "reads only the aggregated `searchStatus()`/`fetchStatus()`" — drift that survives only because nothing checks prose against call sites.
The seam's own design starves both surfaces of consumers: tool registration follows product ENABLEMENT, not provider availability (`packages/web/tool-web/src/index.ts`), and provider selection resolves at execution time, never cached — so there is no cache to invalidate, no registration set to recompute, and no caller that needs an availability probe distinct from executing and routing the structured error. HMR cleanup is carried by the effect disposers themselves.
This mirrors [drop the unconsumed `llm/adapter-change` event](../../implemented/simplification/2026-06-20-drop-unconsumed-llm-adapter-change-event.md), which removed the same notification shape, the same rollback-before-emit machinery, and the same listener-throw test from `LlmService`. That RFC's keep/cut criterion — keep `tools/change` for its plausible user-facing tool-list consumer, cut the boot-time backend-registry signal — puts a web-provider registry squarely on the cut side; the status methods are the same judgment applied to a pull surface instead of a push one.
## Proposal
## Decision
Delete the event declaration, both emits, and the rollback-before-emit ordering (the plain `ctx.effect` disposer keeps HMR cleanup). Delete `searchStatus()`/`fetchStatus()`/`WebCapabilityStatus` — the provider-private `status()` stays, since it feeds execution-time selection. Delete the two event tests and rewrite the status-based test assertions onto the behavior a real caller observes (a successful `search()`/`fetch()`, or the structured `WebError` codes for unavailable/ambiguous/misconfigured provider sets). Run `pnpm run gen-cordis-catalog`; update `packages/web/web/README.md`, `packages/web/tool-web/README.md` (the drifted reads-status sentence), [web.md](../../../core-data-structures/web.md), and the web paragraph in [architecture.md](../../../architecture.md). The implementing PR amends the [web capability seam RFC](../../implemented/architecture/2026-06-24-web-capability-seam.md)'s facts (it specifies the event and the status aggregation) per [implemented/AGENTS.md](../../implemented/AGENTS.md).
The event declaration, both emits, and the rollback-before-emit ordering are deleted (the plain `ctx.effect` disposer carries HMR cleanup). `searchStatus()`/`fetchStatus()`/`WebCapabilityStatus` are deleted — the provider-private `status()` stays, since it feeds execution-time selection. The listener-throw rollback test that existed solely for the removed event is gone, and the emission assertions and every status-based assertion are rewritten onto the behavior a real caller observes: a successful `search()`/`fetch()`, or the structured `WebError` codes for unavailable/ambiguous/misconfigured provider sets. The cordis catalog is regenerated; `packages/web/web/README.md`, `packages/web/tool-web/README.md` (the drifted reads-status sentence), [web.md](../../../core-data-structures/web.md), and the web paragraph in [architecture.md](../../../architecture.md) describe the shipped contract; the [web capability seam RFC](../../implemented/architecture/2026-06-24-web-capability-seam.md)'s facts (it specified the event and the status aggregation) are amended per [implemented/AGENTS.md](../AGENTS.md).
## Why not keep it?
## Alternatives considered
### Why not keep it?
The web seam RFC specified both deliberately — the event as a minimal HMR-visibility signal, the status methods as the tool's aggregated diagnostics — and a future provider-status panel is imaginable. But the same RFC's other choices starved them: derived-on-call selection and enablement-based registration leave no consumer that CAN need either, the shipped tool demonstrates the real pattern (execute and route the structured error), and the drifted README sentence shows the promised consumer never materialized. Per AGENTS.md "RFCs are proposals, not golden truth", these are the parts of that proposal the code has since shown to over-reach; a future observer reintroduces the smallest signal or query it actually consumes, shaped by that consumer.
## Acceptance criteria
## Verification
- No `providers-change`, `searchStatus`, `fetchStatus`, or `WebCapabilityStatus` spelling outside RFC history; the catalog is regenerated and fresh (`verify-cordis-catalog` green).
- Registration/disposal HMR-safety tests prove cleanup through execution behavior rather than the removed surfaces.
- `packages/web/tool-web/README.md` and the architecture paragraph describe the execution-time error-routing contract the tool actually has.
No `providers-change`, `searchStatus`, `fetchStatus`, or `WebCapabilityStatus` spelling survives outside RFC history; the catalog is fresh (`verify-cordis-catalog` green); registration/disposal HMR-safety tests prove cleanup through execution behavior; and the tool-web README plus the architecture paragraph describe the execution-time error-routing contract the tool actually has.
## Risks
## Consequences
A future provider-picker UI or diagnostics panel wants change notifications or a status query — it re-adds the smallest surface it consumes; the identical judgment, and its reversal condition, is already recorded on the llm precedent.
A future provider-picker UI or diagnostics panel that wants change notifications or a status query re-adds the smallest surface it consumes; the identical judgment, and its reversal condition, is already recorded on the llm precedent.

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# RFC: Fold the stdio UI helper into the stdio app
Status: implemented
## Problem
The readline UI was a whole package (`@deepseek-ai/dsh-ui-stdio` under `packages/support/`) whose only runtime importer was the app package `@deepseek-ai/dsh-stdio-agent`. The examples reach the readline UI by loading the app, never by composing the helper themselves; every other repo reference was mechanical or descriptive surface that existed BECAUSE the package boundary existed — manifest and tsconfig entries, generated module-graph rows, dependency-graph and README rows, and doc comments naming the package. The ui group README recorded the support placement rationale ("exists chiefly for the examples and the coverage gate — `ui/` is reserved for surfaces shipped as product"), which left a standing tension: a shipped product app depending on a support package documented as NOT product surface.
The boundary bought package metadata, workspace and tsconfig references, module-graph rows, README entries, and publint surface for a helper that is not independently swappable: the stdio app's front-door cluster always includes the readline UI, and nothing else can meaningfully consume it.
## Decision
The helper lives inside `@deepseek-ai/dsh-stdio-agent` as the in-package `stdio-chat` module (`packages/ui/stdio-agent/src/stdio-chat.ts`): `createStdioChat`, its `StdioRuntime` test seam, and its unit tests (`packages/ui/stdio-agent/tests/stdio-chat.spec.ts`, `readline.spec.ts`) moved with it, so EOF handling, rendering, disposal, and piped-vs-TTY behavior stay unit-covered under the per-file coverage gate without hijacking process globals. The module keeps the named `name`/`inject`/`Config`/`apply` export shape — the contract the app's `ctx.plugin(uiStdio, …)` mount consumes — and the keyless Loader-path smokes in `examples/echo-agent` and `examples/coding-agent` keep proving the composed tree boots through the real Loader (the app's export SHAPE is pinned by the stdio-agent unit suite's explicit `unwrapExports` assertion, since a bundle without `inject` would boot past a stray default rather than crash).
The `packages/support/ui-stdio` package is gone: manifest, tsconfig references, module-graph rows, and README rows deleted; the doc comments that named the package (the example e2e module docs, `packages/README.md`, the support and todo READMEs, [the ui group README](../../../../packages/ui/README.md)) describe the in-package module.
## Alternatives considered
### Why not promote it to `ui/` instead?
Promotion would have resolved the support-vs-product mismatch while keeping the boundary — the right call only if the readline UI were an independently swappable integration or had a second composer, and the consumer census said neither. The structured ACP bridge stays its own package because it is the product protocol surface with its own contract and snapshot tiers; the readline helper is scaffolding for one app's front door. Re-extraction stays cheap pre-release: if a second product app wants the readline UI, split it back out then, with that consumer shaping the package contract.
## Consequences
- The stdio app owns its whole front door; a leaf `cordis.yml` still loads one app package and nothing changed shape for the demos.
- A future standalone terminal UI that wants the helper as a package reintroduces it with that second consumer, rather than the repo keeping a boundary for hypothetical reuse.

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# RFC: Prune producer-less vocabulary variants (block cache hints, the `agent` message source, the `continuation` turn trigger)
Status: implemented
## Problem
The merge-extensible vocabulary maps are designed to grow by declaration merging, and the codebase already states the admission policy on `TurnEndReasonMap` (`packages/core/session/src/types.ts`): a variant like `refusal` is "deliberately omitted until" an adapter or loop first emits it. Three declared vocabulary items violated that policy — each had no producer and no consumer, and two had not even a test:
- **`CacheHint` and its `cache?: CacheHint` block fields** on `TextBlock`/`ToolResultBlock` (`packages/llm/llm/src/types.ts`; the image block carried a third such field, which left with it — see [the drop-image RFC](2026-07-04-drop-image-content-block.md)). Nothing constructed a block with `cache:` anywhere — src, tests, and doc pastes all came up empty — and neither adapter read `.cache`: DeepSeek prompt caching is automatic, so the adapters map `prompt_cache_hit_tokens` OUT of responses without ever sending a hint IN. This was Anthropic-style `cache_control` surface with no provider that could honor it.
- **`MessageSourceMap.agent`** (`{ kind: 'agent'; agentId: string }`, same file). Zero constructors, tests included. Its intended producer shipped without it: the subagent backends send the parent's prompt to the child with no `source`, so it logs as `{ kind: 'user' }`, and the generic envelope renderer interpolates `source.kind` without ever routing on it.
- **`TurnTriggerMap.continuation`** (`packages/core/session/src/types.ts`). The loop structurally cannot emit it — continuation happens *within* a turn as further steps, never as a new turn — and it constructs only `message` and `injection` triggers. The only writer was one hand-built test fixture needing an arbitrary non-message trigger (`packages/support/llm-replay/tests/llm-replay.spec.ts`), which an `injection` trigger serves equally; the only production trigger reader, the ACP bridge, filters on `kind === 'message'`.
## Decision
`CacheHint`, its `cache?` block fields, the `agent` message-source variant, and the `continuation` turn-trigger variant are deleted: the shipped vocabulary carries none of them. The llm-replay fixture uses an `injection` trigger (any non-`message` trigger serves its purpose). The type-equiv pastes in [core.md](../../../core-data-structures/core.md) and [session.md](../../../core-data-structures/session.md) match the pruned maps — both symbols keep their rows in `scripts/type-equiv.manifest.json`, since each map survives minus a member — and the [content-block vocabulary RFC](../architecture/2026-06-11-content-block-vocabulary.md)'s consequences record cache hints as producer-gated rather than as having a home, per [implemented/AGENTS.md](../AGENTS.md).
Each variant returns the day it gains a real producer, exactly as the maps are designed to grow: a caching feature re-adds `cache` together with the adapter that transmits it; subagent attribution re-adds `agent` together with the backend that stamps it and a consumer that routes on it; an auto-continue feature that genuinely starts new turns re-adds `continuation` with the plugin that emits it.
## Alternatives considered
### Why not keep them?
The [content-block vocabulary RFC](../architecture/2026-06-11-content-block-vocabulary.md) listed "cache hints … have a home" as a design consequence, and reserved slots do advertise intent. But an empty slot is contract surface every implementation and consumer must consider (must my adapter honor `cache`? must my renderer route `agent` sources?), and the sibling map's own JSDoc already rejects reservation-without-emitter — `refusal` and `max_turn_requests` are named as variants to add *when something first emits them*, not declared in advance. Holding already-declared dead variants to the same standard makes the vocabulary mean something: if it is in the map, something produces it.
## Verification
`rg` for `CacheHint`, the `agent` message-source spelling, and the `continuation` trigger spelling returns only RFC records (this one, and [the drop-image RFC](2026-07-04-drop-image-content-block.md)'s account of the image block's own `cache` field); the llm-replay fixture asserts the same replay behavior with an `injection` trigger; the core-data-structures pastes and the type-equiv manifest are in sync.
## Consequences
Nothing operational changed — nothing could construct these values. The mirror-event removals ([the boundary-mirror RFC](2026-06-20-remove-agent-boundary-mirror-events.md), [the stream-chunk RFC](2026-07-02-remove-stream-chunk-mirror.md)) touch only transient `agent/*` events, never the durable vocabulary, so there is no collision. Elsewhere the admission policy already holds: `rejected`, `prompt/blocked`, and `hook/invoked`/`hook/result` each have live producers — this RFC extends the same bar to the three variants that lacked one. The image block's own `cache?` field belongs to [the drop-image RFC](2026-07-04-drop-image-content-block.md), which removed it together with the block; this RFC covers the two fields on the block types that remain.

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# RFC: Prune write-only fields and a dead routing knob from the fs seam
Status: implemented
## Problem
The [fs seam split](2026-06-26-fsspec-style-fs-seam.md) moved read routing and policy out of the backend into `dsh-tool-fs` and `dsh-fs-policy`. Four pieces of surface kept the pre-split shape — populated on every call, read by nobody:
1. **`STREAM_MIN_SIZE` + `FsIoInternals.streamMinSize` in `dsh-fs-local`** — *removed ahead of this change by the no-hardcoded-tunables audit, which made the routing bound `dsh-tool-fs`'s `readStreamMinSize` config; recorded here as part of the full prune.* Originally (`packages/fs/fs-local/src/fsio.ts`, re-exported from `packages/fs/fs-local/src/index.ts`): zero readers anywhere, including fs-local's own source and tests. The backend has no read routing — `readWholeText`/`streamWholeText` are separate primitives the caller chooses between — and the real routing constant lives in the consumer (`packages/fs/tool-fs/src/read.ts`, compared against `info.size`). Two mirrors of the 10 MiB fact; the backend's was dead, and the knob's JSDoc claimed a "read routing" override that did not exist.
2. **`FsTarget.inputPath`** (`packages/fs/fs/src/types.ts`): every backend and every test fake had to fabricate a "diagnostics only" value with zero production readers — the policy plugin and every error message use `targetKey`/`displayPath`. The `listDir` producer exposed the semantic wobble: directory children got the bare entry name, which was nobody's "input".
3. **`FsEditOutcome.replacements` + `.replaceAll`** (`packages/fs/fs/src/types.ts`): `replacements` had zero production readers (the single-match policy itself stays — it is enforced by the `FS_AMBIGUOUS_EDIT`/`FS_EDIT_NOT_FOUND` throws inside the backend, whose error message keeps the internal count); `replaceAll` was read only by `formatEditOutput` in `packages/fs/tool-fs/src/edit.ts` — as an echo of the `replace_all` argument the tool already holds. Shrunk, `FsEditOutcome` is `{ version, before, after }`, parallel to `FsWriteOutcome`'s genuinely backend-discovered fields.
4. **`FileReadOutcome.limit` + `.version`** (`packages/fs/tool-fs/src/read-render.ts`): populated by the read tool, but `formatReadOutput` renders `offset`/`lines`/`totalLines`/`truncatedByBytes` only, and the `fs/observed` emit uses `info.version` directly rather than an outcome copy.
## Decision
Delete the fs-local constant, its re-export, and the `streamMinSize` knob (the remaining `FsIoInternals` knobs are genuinely used by the atomic-write tests); drop `inputPath` from `FsTarget`; shrink `FsEditOutcome` to `{ version, before, after }` and pass `replaceAll` to `formatEditOutput` from the parsed args; drop `limit`/`version` from `FileReadOutcome`. The [filesystem.md](../../../core-data-structures/filesystem.md) pastes, `packages/fs/fs/README.md`, and the test fakes that had to fabricate the removed fields shrink with the types.
## Alternatives considered
### Why not keep them?
A future permission/containment layer might want the pre-resolution path for error text — but it would want the *request*, which every call site still holds. "N occurrences replaced" might become model-facing text — a behavior change to design when wanted, and the backend-internal count survives for its error message. A read footer might display `limit` — everything the footer shows already derives from `lines`/`totalLines`. Meanwhile every current and future backend (remote, native) would have to fabricate wire fields nobody consumes, and every test fake would have to satisfy them.
## Verification
The removed surfaces are gone — `STREAM_MIN_SIZE`/`streamMinSize` in `dsh-fs-local`, `FsTarget.inputPath`, `FsEditOutcome.replacements`/`.replaceAll`, and `FileReadOutcome.limit`/`.version` — while the request-side `replaceAll` (`FsEditRequest`) and the version fields on the other outcome types are untouched; the test fakes shrank with the types. `formatEditOutput`'s emitted text is unchanged for both `replace_all` branches, so no snapshot golden churned.
## Consequences
Backends gain no new obligations; they shed four fields nobody consumed. The fs discovery work (glob/grep tools) touches the same `dsh-fs` type files — a textual, not design, overlap that reconciles mechanically.

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# RFC: Remove the `agent/steering` mirror emit
Status: implemented
## Problem
`agent/steering` was the last remaining transient mirror of a durable session event. The loop's steering drain appends the durable `steering/message { turn, content, source }` and, on the very next line, emitted `agent/steering(agent, turn, content, source)` — the identical fact as a fire-and-forget event (`packages/core/agent-loop/src/loop.ts`, `drainSteering`). It had zero production listeners: the only subscriber anywhere was a loop regression test asserting the emit carried `source` — the same fact the durable event already records one line above.
Both mirror-removal RFCs retained it while explicitly deferring the decision this RFC makes. The [boundary-mirror removal](2026-06-20-remove-agent-boundary-mirror-events.md) kept it as a live control signal rather than a boundary; the [stream-chunk removal](2026-07-02-remove-stream-chunk-mirror.md) retained it on the reading that it had no durable twin. The second rationale did not survive the code: the durable twin is `steering/message`, appended immediately before the emit with the same payload. The mirrored-vs-live-only line the taxonomy actually draws puts it on the mirror side: `agent/queued` is genuinely live-only (it fires at enqueue time, before any durable event exists, and already carries a `steering: boolean` flag — cancelled queued work never enters the log), while `agent/steering` fired at the exact moment its durable twin landed, carrying nothing the log does not.
Steering carries real production traffic — the hook bridges' turn-continuation decisions inject their reasons through `inbox.steer()`, landing as durable `steering/message` events that the hook-matrix goldens pin — and every one of those consumers observes the durable event. Nothing observed the mirror.
## Decision
`agent/steering` is removed from the agent event taxonomy: the declaration in `packages/core/agent/src/types.ts` (and its mention in the live-events JSDoc list there), the emit in `drainSteering` (whose then-unused `ctx` parameter went with it), the row in `packages/core/agent/README.md`, and the emit line in the loop-pseudocode blocks (the `packages/core/agent-loop/src/loop.ts` module doc and [architecture.md](../../../architecture.md)); the cordis catalog is regenerated without it. The one regression test pins source preservation on the durable `steering/message` event — the fact it pins lives on the log.
Three implemented RFCs stated the retention, and each is amended per [implemented/AGENTS.md](../AGENTS.md) to point here as the record of the removal: the [boundary RFC](2026-06-20-remove-agent-boundary-mirror-events.md)'s retained-list entry, the [stream-chunk RFC](2026-07-02-remove-stream-chunk-mirror.md)'s scope clause, and the [event-domain-semantics RFC](../architecture/2026-06-30-event-domain-semantics.md)'s transient-emit enumeration.
## Alternatives considered
### Why not keep it?
"It is a control signal, not a boundary" — but the taxonomy's operative distinction is mirrored-vs-live-only, not control-vs-boundary, and this event mirrored. A consumer that wants enqueue-time notification has `agent/queued` (with its steering flag); a consumer that wants drain-time notification is by definition asking for the moment `steering/message` is appended, which `session/event` delivers with the same payload plus durability. The rejected [retire-mid-turn-steering RFC](../../rejected/simplification/2026-06-20-retire-mid-turn-steering.md) defended the steering *capability* — `steer()`, the durable event, continuation forcing — all of which this removal keeps untouched.
## Verification
The `agent/steering` spelling survives only in RFC prose (this RFC, the three amended RFCs above, and the frozen [rejected steering-capability RFC](../../rejected/simplification/2026-06-20-retire-mid-turn-steering.md), whose text records the proposal it declined); the catalog is regenerated; the retargeted test pins source preservation on `steering/message`.
## Consequences
Zero production listeners existed to migrate, and both live-notification needs keep surviving homes: enqueue-time on `agent/queued` (with its `steering` flag), drain-time on `session/event` as the durable `steering/message` lands.

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# RFC: Share the app bins' boot glue instead of maintaining twin copies
Status: implemented
## Problem
`packages/ui/stdio-agent/src/bin.ts` and `packages/ui/acp-agent/src/bin.ts` carried four near-twin helpers — `loadEnv`, `installFailLoud`, `assertEntriesLoaded`, `boot` — whose bodies differed essentially in the diagnostic prefix, plus two copies of the hardest-won boot lore in the repo: the `Promise.allSettled` swallow inside `loader.await()`, the silent-exit-0 import-failure guard, and the `--expose-internals` resolution note. The copies had drifted (`boot(configPath)` resolved the path internally in one bin but required a pre-resolved absolute path in the other, with forked JSDoc prose), and all of it sat outside the per-file 100% gate — `vitest.config.ts` excludes `packages/*/*/src/bin.ts` because importing a self-executing bin runs it — which also made the helpers' `export` keywords decorative: no spec could import them, so the only exercisers were subprocess smokes.
## Decision
The helpers live once, in [`@deepseek-ai/dsh-app-boot`](../../../../packages/ui/app-boot) (`packages/ui/app-boot`, in the `ui` group because the bins are published artifacts whose runtime dependency must itself be published, not `support/`): `resolveConfigPath` (snapshot-aware, the single path resolver for both bins), `loadEnv`, `installFailLoud`, `assertEntriesLoaded`, and `boot`, each parameterized by the bin's diagnostic prefix and injectable at its side-effect seams (the warn sink, the process slice) so the unit suite covers every branch — including `boot()` driven in-process against the real Loader with relative-specifier configs, both the settled-tree happy path and the fiber-less-entry rejection. The package carries the per-file 100% coverage gate; the loader-failure lore has one home.
Each `bin.ts` is a thin self-executing composition over the shared helpers plus its app-specific lifecycle (the ACP bin: replay-mode env skipping and the stdin-EOF dispose; the stdio bin: nothing extra). The bins stay coverage-excluded and export nothing; the published-artifact guards are unchanged — the built-bin smokes still run each bin under plain node in a node_modules-shaped temp dir (now symlinking `ui/app-boot` too) and still assert the missing-config non-zero exit, per the "real entry path means the published artifact" defensive pattern. The [extract-example-app-packages RFC](../architecture/2026-06-20-extract-example-app-packages.md)'s bin-ownership facts are amended accordingly.
## Alternatives considered
### Why not keep the duplication?
The bins were framed as independently-owned published artifacts, and a new package carries fixed overhead (manifest, README, tsconfig reference, publint surface) comparable to the deduplicated line count. But app-vs-app sharing was never weighed by the RFC that created the bins — it consolidated three example `start.ts` copies INTO the bins and stopped there; the drift was observed fact; and the coverage-gap argument is independent of the dedup argument: this was the only nontrivial runtime logic in the repo exempt from the per-file 100% gate. The recorded fallback (extracting only the pure logic into per-app modules) would have ended the exemption but kept two homes for the lore.
## Consequences
- A boot-glue change (a new guard, a resolution fix) lands once and both published bins inherit it; the bins cannot drift apart again.
- `dsh-app-boot` stays dependency-light (cordis + the loader/include pair) — it is boot machinery, not app surface.
- The bins' own files are near-trivial compositions; everything with branches lives under the coverage gate.

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