feat(events): interception seams — the typed-Decision surface for hooks
Reshape the agent's interception surface so every seam returns a small, typed
Decision union, and the set covers the hook points a CC/Codex bridge (and a
native plugin) needs. "Native hooks" are not a package — a native hook is just a
cordis plugin on these canonical events; the bridges (a later PR) only translate
an external protocol onto the same surface.
dsh-agent:
- NEW agent/session-start(agent, source) emit (once before turn 1; SessionStartSource
startup|resume|clear|compact) — a pure notification, seeds context via inject().
- NEW agent/prompt-submit waterfall → PromptDecision (allow, optionally rewriting the
prompt or attaching additionalContext, or block).
- RESHAPE agent/turn-continuation boolean → ContinuationDecision ({action:'stop'} |
{action:'continue', reason?}; a continue reason is recorded as next-step steering).
- New HookContext envelope (required source — inject() would mislabel a missing one).
dsh-tools: split the single tools/execute waterfall into tools/pre-execute
(PreToolDecision allow/deny/ask gate) and tools/post-execute (PostToolDecision
accept/block, optionally replacing content or attaching additionalContext). Core
dispatch sits between as plain code; the tool body keeps its inner try/catch so a
thrown tool still reaches post-execute as an isError. ToolExecutionResult gains
additionalContext (ferried to the loop's per-step buffer). Input rewrite is
deliberately NOT offered (a proposed RFC designs it consistently).
dsh-session: new `rejected` TurnEndReason — a turn whose whole prompt batch was
blocked by prompt-submit.
agent-loop firing points: session-start emitted at create (source threaded —
startup for create/fork, resume for resume()); prompt-submit per drained message
with the always-open-turn rule (a fully-blocked batch is a zero-step rejected
turn); the continuation reshape; post-tool additionalContext buffered and appended
after all tool/results (adjacency). ACP codec maps rejected→cancelled.
A worked native-plugin example (interception.spec.ts) proves all four seams compose
end-to-end through the real loop with NO hook/* events (those belong to the bridge
lib). All existing tools/execute + turn-continuation tests migrated. The
tool-subagent abort test now aborts after a microtask so it still exercises the
live onAbort bridge (execute() awaits pre-execute before the body runs).
RFCs: implemented/feature/2026-06-30-interception-seams.md (the reshape) +
proposed/feature/2026-06-30-pre-tool-input-rewrite.md (the deferred rewrite design).
This commit is contained in:
@@ -69,7 +69,7 @@ Swappable capabilities are split into **three packages** so each part evolves in
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The LLM seam has the same topology folded differently: `dsh-llm` carries the interface (`LlmAdapter`) AND the consumer surface (`ctx.llm.stream()`), with adapters as implementation packages — there the consumer is the loop itself, not a swappable schema surface. Use the full three-package split when the consumer is independently replaceable; keep interface + consumer together when they are one concern. Don't split preemptively: a capability with one conceivable implementation and one consumer stays one package until proven otherwise.
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> **"Capability" — two unrelated meanings.** (1) The *seam pattern* above ("one plugin provides a capability, another needs it") is realized by plain Cordis **services + `inject`**: a provider registers a service (`ctx.bash`, declared in `interface Context`); a consumer declares `inject: ['bash']` and its fiber stays pending until the service exists, tearing down via HMR if it later vanishes. No extra library is needed. (2) `@cordisjs/plugin-capability` is a different axis entirely — a **permission/capability-security** service (named permissions with inheritance/dependency, tested against a session via `ctx.capability.test`). It is a candidate for the deferred permissions/sandbox work (the `tools/execute` veto seam), NOT a mechanism for swapping implementations.
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> **"Capability" — two unrelated meanings.** (1) The *seam pattern* above ("one plugin provides a capability, another needs it") is realized by plain Cordis **services + `inject`**: a provider registers a service (`ctx.bash`, declared in `interface Context`); a consumer declares `inject: ['bash']` and its fiber stays pending until the service exists, tearing down via HMR if it later vanishes. No extra library is needed. (2) `@cordisjs/plugin-capability` is a different axis entirely — a **permission/capability-security** service (named permissions with inheritance/dependency, tested against a session via `ctx.capability.test`). It is a candidate for the deferred permissions/sandbox work (the `tools/pre-execute` deny/ask gate), NOT a mechanism for swapping implementations.
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## The vocabulary (dsh-llm)
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@@ -102,7 +102,7 @@ Tool schemas are deliberately **part of the assembly**: "what the model is told
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`ToolRegistry.register()` takes schema + `execute()`. The registry feeds its schemas into the system-prompt assembly automatically.
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`execute()` runs through the **`tools/execute` waterfall** — the single seam where sandbox, permission, hooks, and plan-mode plugins wrap or veto a call. This collapses Claude Code's validate → PreToolUse → permission → execute → PostToolUse pipeline into ordered waterfall listeners.
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`execute()` runs through a **two-waterfall pipeline** — `tools/pre-execute` (the allow/deny/ask gate) → core dispatch → `tools/post-execute` (inspect/replace the result, attach context) — the seams where sandbox, permission, hooks, and plan-mode plugins gate or transform a call. This maps Claude Code's validate → PreToolUse → permission → execute → PostToolUse pipeline onto two ordered waterfalls: `pre-execute` returns a `PreToolDecision` (allow/deny/ask), `post-execute` a `PostToolDecision` (accept/block, optionally replacing content or attaching `additionalContext`). Core dispatch sits between them as plain code, inside `execute`'s outer try/catch, with the tool body's own try/catch preserved so a thrown tool still reaches `post-execute` as an `isError`.
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**TODO**: tool shapes get revisited now that real tools exist (the bash suite landed; the `TODO(review)` in dsh-tools is still open) — e.g. a concurrency-safety hint for parallel execution; phase 1 executes tool calls sequentially.
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@@ -126,11 +126,16 @@ Tool schemas are deliberately **part of the assembly**: "what the model is told
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- **Step**: one model request + its tool executions.
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```
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create agent → emit agent/session-start(source) ⟵ once, before turn 1 (startup|resume)
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forever:
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wait for queued messages (idle)
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emit agent/status(running)
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TURN (error-contained — a throwing plugin ends the turn, never the loop):
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drain queued → 'turn/start' → session('user/message'…) → emit agent/turn-start
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'turn/start'
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each queued msg: waterfall agent/prompt-submit ⟵ allow (rewrite/+context) | block
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allow → session('user/message'…); inject additionalContext
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every prompt blocked → 'turn/end'(rejected), 0 steps ⟵ zero-step turn, model never called
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emit agent/turn-start
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STEP loop:
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drain steering (late steering from previous step's listeners)
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session('step/start') ⟵ durable step boundary (no agent/* mirror)
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@@ -145,15 +150,19 @@ forever:
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msg = waterfall agent/step-result ⟵ runs BEFORE the log append, so the
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session('assistant/message' {content, usage?}) log records what tool dispatch uses
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each tool-call (sequential, abort-checked between calls):
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session('tool/call'); ctx.tools.execute() ⟵ waterfall tools/execute
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session('tool/call'); ctx.tools.execute() ⟵ waterfall tools/pre-execute (allow/
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deny/ask gate) → dispatch → tools/post-execute (accept/block, replace, +context)
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tool execution may append tool-owned session events, e.g. `todo/write`
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session('tool/result')
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append buffered post-execute additionalContext → session('context/message')(s)
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⟵ after ALL tool/results (adjacency)
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drain steering → session('steering/message'); emit agent/steering
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session('step/end') ⟵ durable step boundary (no agent/* mirror)
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cont = waterfall agent/turn-continuation(default = hadToolCalls || steered)
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steering pending forces cont = true (from continuation listeners OR from
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step/end session-event listeners — the /goal pattern; hasSteering override)
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if !cont: break
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cont = waterfall agent/turn-continuation(default = {action: hadToolCalls||steered
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? 'continue' : 'stop'}) → ContinuationDecision
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a continue's reason is recorded as next-step steering (same turn); steering pending
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also forces continue (continuation OR step/end listeners — the /goal pattern)
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if action==stop: break
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session('turn/end'); emit agent/turn-end
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await ctx.parallel('session/flush', session) ⟵ durability checkpoint (failure
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reported via agent/error, not fatal)
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@@ -163,7 +172,7 @@ forever:
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Error containment: a throwing `agent/turn-continuation` listener or a broken step ends the **turn** with `turn/end { reason: { kind: 'error', step, message, code? } }` — the failure's step number rides on the durable turn reason (there is no separate session `error` event); live diagnostics fire via `agent/error`. Never the driver loop. An adapter that ends its stream with a `finish {kind:'error'}` or `{kind:'aborted'}` chunk (the in-band error path, for adapters that can't throw mid-stream) is likewise translated into a step error, so the turn ends `error`/`aborted` instead of logging a normal `completed` assistant message. A `cancel()` is honored mid-stream **and** between tool calls; disposal mid-turn ends the turn with reason `disposed` and emits `agent/status('disposed')`.
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Turn-end reasons: a turn ends with one `TurnEndReason` — `completed`, `aborted`, `error`, `disposed`, or `max-tokens`. `max-tokens` mirrors the model-call `FinishReason` of the same name (DeepSeek's `length`): a step that hit the output-token ceiling makes the turn end `max-tokens` rather than `completed`, by the rule *any `max-tokens` step in the turn surfaces as `max-tokens`* (a continuation plugin may run further steps after one, but the cut-short fact wins; the `disposed`/`aborted`/`error` outcomes still take precedence). This lets a consumer distinguish a clean stop from a truncated one (the ACP bridge maps it to the `max_tokens` stop reason). `TurnEndReason` is merge-extensible; `refusal` and `max_turn_requests` are the next variants to add when an adapter/loop first emits them.
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Turn-end reasons: a turn ends with one `TurnEndReason` — `completed`, `aborted`, `error`, `disposed`, `max-tokens`, `rejected`, or `interrupted`. `max-tokens` mirrors the model-call `FinishReason` of the same name (DeepSeek's `length`): a step that hit the output-token ceiling makes the turn end `max-tokens` rather than `completed`, by the rule *any `max-tokens` step in the turn surfaces as `max-tokens`* (a continuation plugin may run further steps after one, but the cut-short fact wins; the `disposed`/`aborted`/`error` outcomes still take precedence). `rejected` is a zero-step turn whose entire prompt batch was blocked by an `agent/prompt-submit` hook (the turn still opens and closes balanced; the ACP bridge maps it to `cancelled`). `interrupted` is synthesized by a persistence backend closing a crash-orphaned turn on reload. This lets a consumer distinguish a clean stop from a truncated/blocked one (the ACP bridge maps `max-tokens` to the `max_tokens` stop reason). `TurnEndReason` is merge-extensible; `refusal` and `max_turn_requests` are the next variants to add when an adapter/loop first emits them.
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A failure that happens once the turn is already closed has no in-turn position for a turn-end error reason (the turn already ended). So a rejecting `session/flush` (the post-`turn/end` durability checkpoint) and a throwing `agent/turn-end` listener are reported via `agent/error` + the logger only, NOT as a session event; the turn stays balanced and the persistence backend keeps its buffered events for the next flush.
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@@ -189,7 +198,7 @@ Every MVP feature (including the TODO-marked ones), with the mechanism that impl
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| MVP feature | Plugin mechanism |
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|---|---|
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| Hook system (user + project level) | listeners on `agent/request`, `agent/step-result`, `tools/execute`, `agent/turn-continuation`; a hooks plugin bridges config files to shell commands |
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| Hook system (user + project level) | listeners on `agent/session-start`, `agent/prompt-submit`, `agent/request`, `agent/step-result`, `tools/pre-execute`, `tools/post-execute`, `agent/turn-continuation` (each interception waterfall returns a typed Decision); a hooks bridge plugin maps config files / shell commands onto those seams, a native hook plugin uses them directly |
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| `/goal` | force-continue via `agent/turn-continuation` + `steer()` reminders |
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| `/loop` | on `agent/turn-end`, `send()` the next iteration; or force-continue |
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| Dynamic workflow | orchestrator plugin on `agent/turn-end` (or the `step/end` session event) driving `send`/`steer` (+ sub-agents later) |
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@@ -200,9 +209,9 @@ Every MVP feature (including the TODO-marked ones), with the mechanism that impl
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| AGENTS.md (subdir, on-touch) + file-change notices | `agent.inject()` from a watcher / tool-result listener |
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| Built-in tools (Read/Write/Edit/Bash/…) | `ctx.tools.register()`; schemas flow into the assembly automatically. **Bash: implemented** — `dsh-bash` (seam) + `dsh-bash-local` (subprocesses) + `dsh-tool-bash` (`bash`/`bash_output`/`bash_kill`, incl. background tasks). **`todo_write`: implemented** — `dsh-tool-todo` writes the whole task list to the session log (`todo/write`), rendered as a stdio checklist / ACP `plan` |
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| ToolSearch / progressive disclosure | wrap `agent/request`, filter `req.tools` |
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| Tool sandbox (landlock / sandbox-exec) | wrap `tools/execute`, or implement a sandboxing `BashExecutor` (the dsh-bash seam) |
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| Permission system / AskUserQuestion | wrap `tools/execute` (veto or ask); register an ask tool |
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| Plan mode | wrap `tools/execute` (deny writes) + `agent/request` (inject mode prompt) |
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| Tool sandbox (landlock / sandbox-exec) | `tools/pre-execute` (deny), or implement a sandboxing `BashExecutor` (the dsh-bash seam) |
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| Permission system / AskUserQuestion | `tools/pre-execute` (deny/ask); register an ask tool |
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| Plan mode | `tools/pre-execute` (deny writes) + `agent/request` (inject mode prompt) |
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| Sub-agents (spawn / fork / steer) | TODO seam on `AgentLoop.create()`; fork = seed Session with parent events; `steer()` on the child handle |
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| MCP | one plugin per server: discover tools → `ctx.tools.register()` |
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| Skills | section + tool registration; `inject()` skill content on invocation |
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@@ -8,24 +8,20 @@ A tool registers on `ctx.tools`. The annotated `defineTool` example (typed `exec
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## A hook plugin (permission gate)
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A hook wraps the `tools/execute` waterfall to veto or rewrite a call — the seam where sandbox, permission, and plan-mode plugins live.
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A hook returns a typed decision from the `tools/pre-execute` gate to allow or deny a call — the seam where sandbox, permission, and plan-mode plugins live. (A "native hook" is just this: an ordinary cordis plugin on the interception seams, returning typed decisions — no external protocol needed.)
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```ts
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import type { Context } from 'cordis'
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import type { ToolExecution } from '@deepseek-ai/dsh-tools'
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import type { PreToolDecision, ToolExecution } from '@deepseek-ai/dsh-tools'
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declare function isAllowed(exec: ToolExecution): Promise<boolean>
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export const name = 'permission-gate'
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export function apply(ctx: Context) {
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ctx.on('tools/execute', async (exec, next) => {
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ctx.on('tools/pre-execute', async (exec, next): Promise<PreToolDecision> => {
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if (!(await isAllowed(exec))) {
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return {
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callId: exec.callId,
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content: [{ type: 'text', text: 'Denied by policy.' }],
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isError: true,
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}
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return { kind: 'deny', reason: 'Denied by policy.' }
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}
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return next()
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})
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@@ -25,7 +25,7 @@ An agent was registered in the AgentRegistry and is ready to receive messages.
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Types: [Agent](../core-data-structures/core.md)
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Source: [`packages/core/agent/src/types.ts:165`](../../packages/core/agent/src/types.ts)
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Source: [`packages/core/agent/src/types.ts:228`](../../packages/core/agent/src/types.ts)
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#### `agent/disposed` — emit
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@@ -37,7 +37,7 @@ An agent was disposed and removed from the registry; its fiber and any in-flight
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Types: [Agent](../core-data-structures/core.md)
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Source: [`packages/core/agent/src/types.ts:171`](../../packages/core/agent/src/types.ts)
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Source: [`packages/core/agent/src/types.ts:234`](../../packages/core/agent/src/types.ts)
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#### `agent/error` — emit
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@@ -49,7 +49,19 @@ A step or turn errored. The loop reports a failure here (plus the logger) even w
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Types: [Agent](../core-data-structures/core.md)
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Source: [`packages/core/agent/src/types.ts:245`](../../packages/core/agent/src/types.ts)
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Source: [`packages/core/agent/src/types.ts:334`](../../packages/core/agent/src/types.ts)
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#### `agent/prompt-submit` — waterfall
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Waterfall: decide what happens to ONE drained queued message before it becomes a `user/message` — allow (optionally rewriting the prompt bytes or attaching `additionalContext`) or block it. Fires inside the already-open turn, per drained message. Maps onto Claude Code's `UserPromptSubmit` hook. Call `next()` to delegate to the default (allow unchanged), or return a PromptDecision without calling `next()` to short-circuit.
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```ts cordis-catalog
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'agent/prompt-submit'(agent: Agent, content: ContentBlock[], source: MessageSource, next: () => Promise<PromptDecision>): Promise<PromptDecision>
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```
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Types: [Agent](../core-data-structures/core.md) · [ContentBlock](../core-data-structures/core.md) · [MessageSource](../core-data-structures/core.md)
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Source: [`packages/core/agent/src/types.ts:293`](../../packages/core/agent/src/types.ts)
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#### `agent/queued` — emit
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@@ -61,7 +73,7 @@ A message entered the agent's inbox (queued or steering). `source` is the resolv
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Types: [Agent](../core-data-structures/core.md) · [ContentBlock](../core-data-structures/core.md) · [MessageSource](../core-data-structures/core.md)
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Source: [`packages/core/agent/src/types.ts:184`](../../packages/core/agent/src/types.ts)
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Source: [`packages/core/agent/src/types.ts:247`](../../packages/core/agent/src/types.ts)
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#### `agent/request` — waterfall
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@@ -73,7 +85,19 @@ Waterfall: mutate the fully-assembled GenerateOptions before the model call (hoo
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Types: [Agent](../core-data-structures/core.md) · [GenerateOptions](../core-data-structures/core.md)
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Source: [`packages/core/agent/src/types.ts:214`](../../packages/core/agent/src/types.ts)
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Source: [`packages/core/agent/src/types.ts:300`](../../packages/core/agent/src/types.ts)
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#### `agent/session-start` — emit
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The agent's session lifecycle began, fired once before its first turn. `source` says why (SessionStartSource: fresh startup, a resumed persisted session, …). A pure NOTIFICATION (emit, not waterfall): it carries no veto — a session-start listener that wants to seed context does so via `agent.inject()` (a `context/message` the first request sees), not by returning a decision. Cannot block the session from starting; that gap is deliberate (a bridge logs/injects, it does not gate startup).
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```ts cordis-catalog
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'agent/session-start'(agent: Agent, source: SessionStartSource): void
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```
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Types: [Agent](../core-data-structures/core.md)
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Source: [`packages/core/agent/src/types.ts:260`](../../packages/core/agent/src/types.ts)
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#### `agent/status` — emit
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@@ -85,7 +109,7 @@ Agent status changed (`idle` ⇄ `running`, or → `disposed`). Drive lifecycle
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Types: [Agent](../core-data-structures/core.md)
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Source: [`packages/core/agent/src/types.ts:178`](../../packages/core/agent/src/types.ts)
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Source: [`packages/core/agent/src/types.ts:241`](../../packages/core/agent/src/types.ts)
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#### `agent/steering` — emit
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@@ -97,7 +121,7 @@ Steering content was injected into a running turn.
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Types: [Agent](../core-data-structures/core.md) · [ContentBlock](../core-data-structures/core.md) · [MessageSource](../core-data-structures/core.md)
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|
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Source: [`packages/core/agent/src/types.ts:239`](../../packages/core/agent/src/types.ts)
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Source: [`packages/core/agent/src/types.ts:328`](../../packages/core/agent/src/types.ts)
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#### `agent/step-result` — waterfall
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@@ -109,7 +133,7 @@ Waterfall: post-process the assembled assistant Message before tool dispatch (va
|
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|
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Types: [Agent](../core-data-structures/core.md) · [Message](../core-data-structures/core.md)
|
||||
|
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Source: [`packages/core/agent/src/types.ts:220`](../../packages/core/agent/src/types.ts)
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Source: [`packages/core/agent/src/types.ts:306`](../../packages/core/agent/src/types.ts)
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|
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#### `agent/stream-chunk` — emit
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@@ -121,19 +145,19 @@ A raw StreamChunk arrived from the model (token-level UI/log feed).
|
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|
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Types: [Agent](../core-data-structures/core.md) · [StreamChunk](../core-data-structures/llm-streaming.md)
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|
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Source: [`packages/core/agent/src/types.ts:234`](../../packages/core/agent/src/types.ts)
|
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Source: [`packages/core/agent/src/types.ts:323`](../../packages/core/agent/src/types.ts)
|
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|
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#### `agent/turn-continuation` — waterfall
|
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|
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Waterfall: override the turn-continuation decision. The default (computed by the loop) is `hadToolCalls || steeringInjected`. Listeners can force-continue (/goal, /loop) or force-stop (budget guards).
|
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Waterfall: override the turn-continuation decision via a typed ContinuationDecision. The loop's `defaultDecision` is `continue` when the step had tool calls or steering was injected, else `stop`. Listeners force-continue (`/goal`, `/loop` — optionally attaching a `reason` recorded as next-step steering) or force-stop (budget guards). Call `next()` to delegate to the default, or return a decision to override.
|
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|
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```ts cordis-catalog
|
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'agent/turn-continuation'(agent: Agent, turn: number, defaultDecision: boolean, next: () => Promise<boolean>): Promise<boolean>
|
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'agent/turn-continuation'(agent: Agent, turn: number, defaultDecision: ContinuationDecision, next: () => Promise<ContinuationDecision>): Promise<ContinuationDecision>
|
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```
|
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|
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Types: [Agent](../core-data-structures/core.md)
|
||||
|
||||
Source: [`packages/core/agent/src/types.ts:227`](../../packages/core/agent/src/types.ts)
|
||||
Source: [`packages/core/agent/src/types.ts:316`](../../packages/core/agent/src/types.ts)
|
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|
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#### `agent/turn-end` — emit
|
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|
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@@ -145,7 +169,7 @@ A turn ended. `reason` distinguishes a clean stop from a truncated, aborted, fai
|
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|
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Types: [Agent](../core-data-structures/core.md) · [TurnEndReason](../core-data-structures/session.md)
|
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|
||||
Source: [`packages/core/agent/src/types.ts:205`](../../packages/core/agent/src/types.ts)
|
||||
Source: [`packages/core/agent/src/types.ts:281`](../../packages/core/agent/src/types.ts)
|
||||
|
||||
#### `agent/turn-start` — emit
|
||||
|
||||
@@ -157,7 +181,7 @@ A turn began. `turn` is the 1-based turn number within the session.
|
||||
|
||||
Types: [Agent](../core-data-structures/core.md)
|
||||
|
||||
Source: [`packages/core/agent/src/types.ts:197`](../../packages/core/agent/src/types.ts)
|
||||
Source: [`packages/core/agent/src/types.ts:273`](../../packages/core/agent/src/types.ts)
|
||||
|
||||
### `llm/*`
|
||||
|
||||
@@ -261,19 +285,31 @@ A tool was registered or unregistered (the available tool set changed).
|
||||
'tools/change'(): void
|
||||
```
|
||||
|
||||
Source: [`packages/core/tools/src/index.ts:48`](../../packages/core/tools/src/index.ts)
|
||||
Source: [`packages/core/tools/src/index.ts:66`](../../packages/core/tools/src/index.ts)
|
||||
|
||||
#### `tools/execute` — waterfall
|
||||
#### `tools/post-execute` — waterfall
|
||||
|
||||
Waterfall around every tool execution — the single seam where sandbox, permission, hook, and plan-mode plugins wrap or veto a call. Listeners receive `(exec, next)`: call `next()` to proceed (possibly around your own logic), or return a ToolExecutionResult without calling `next()` to short-circuit (veto).
|
||||
Waterfall AFTER a tool runs — where hook plugins inspect the result and accept it (optionally REPLACING the model-facing content, and/or attaching `additionalContext` for the next request) or block it with corrective `feedback` (Claude Code's `PostToolUse`). Listeners receive `(exec, result, next)`: call `next()` to delegate to the default (accept unchanged), or return a PostToolDecision to override. The core tool dispatch sits between the two waterfalls as plain code, all inside `execute`'s outer try/catch (and the tool body keeps its own inner try/catch, so a thrown tool still reaches `post-execute` as an `isError` result).
|
||||
|
||||
```ts cordis-catalog
|
||||
'tools/execute'(this: ToolRegistry, exec: ToolExecution, next: () => Promise<ToolExecutionResult>): Promise<ToolExecutionResult>
|
||||
'tools/post-execute'(this: ToolRegistry, exec: ToolExecution, result: ToolExecutionResult, next: () => Promise<PostToolDecision>): Promise<PostToolDecision>
|
||||
```
|
||||
|
||||
Types: [ToolExecution](../core-data-structures/tools.md) · [ToolExecutionResult](../core-data-structures/tools.md)
|
||||
|
||||
Source: [`packages/core/tools/src/index.ts:43`](../../packages/core/tools/src/index.ts)
|
||||
Source: [`packages/core/tools/src/index.ts:61`](../../packages/core/tools/src/index.ts)
|
||||
|
||||
#### `tools/pre-execute` — waterfall
|
||||
|
||||
Waterfall BEFORE a tool runs — the gate where sandbox, permission, and hook plugins allow or deny a call (Claude Code's `PreToolUse`). Listeners receive `(exec, next)`: call `next()` to delegate to the default (allow), or return a PreToolDecision without calling `next()` to short-circuit. A `deny` skips dispatch and yields an `isError` result; the tool body never runs. Input rewrite is deliberately NOT offered here (see PreToolDecision); `ask` degrades to deny until the permission system lands (`FIXME(permissions)`).
|
||||
|
||||
```ts cordis-catalog
|
||||
'tools/pre-execute'(this: ToolRegistry, exec: ToolExecution, next: () => Promise<PreToolDecision>): Promise<PreToolDecision>
|
||||
```
|
||||
|
||||
Types: [ToolExecution](../core-data-structures/tools.md)
|
||||
|
||||
Source: [`packages/core/tools/src/index.ts:47`](../../packages/core/tools/src/index.ts)
|
||||
|
||||
## Services
|
||||
|
||||
@@ -446,7 +482,7 @@ async execute(exec: ToolExecution): Promise<ToolExecutionResult>
|
||||
|
||||
Types: [ToolDefinition](../core-data-structures/tools.md) · [ToolExecution](../core-data-structures/tools.md) · [ToolExecutionResult](../core-data-structures/tools.md)
|
||||
|
||||
Source: [`packages/core/tools/src/index.ts:277`](../../packages/core/tools/src/index.ts)
|
||||
Source: [`packages/core/tools/src/index.ts:341`](../../packages/core/tools/src/index.ts)
|
||||
|
||||
## Inherited tier (cordis core + loader/hmr/timer)
|
||||
|
||||
|
||||
@@ -306,7 +306,42 @@ interface Agent {
|
||||
}
|
||||
```
|
||||
|
||||
`AgentStatus` is `'idle' | 'running' | 'disposed'`. `AgentId` is a branded string. `AgentOptions` (`model?`, `systemPrompt?`) is merge-extensible — plugins add creation options by declaration merging. The `agent/*` event taxonomy (lifecycle, turn/step boundaries, the `agent/request`/`agent/step-result`/`agent/turn-continuation` waterfalls) is in [architecture.md § Event taxonomy](../architecture.md#event-taxonomy).
|
||||
`AgentStatus` is `'idle' | 'running' | 'disposed'`. `AgentId` is a branded string. `AgentOptions` (`model?`, `systemPrompt?`) is merge-extensible — plugins add creation options by declaration merging. The `agent/*` event taxonomy (lifecycle, turn/step boundaries, the `agent/prompt-submit`/`agent/request`/`agent/step-result`/`agent/turn-continuation` waterfalls) is in [architecture.md § Event taxonomy](../architecture.md#event-taxonomy).
|
||||
|
||||
## Interception decisions
|
||||
|
||||
Each `agent/*` interception waterfall returns a small, seam-specific typed union — the unified Decision idiom (the tool seams' `PreToolDecision`/`PostToolDecision` in [tools.md](tools.md) follow the same shape). A CC/Codex hook bridge maps its `permissionDecision`/`decision`/`continue`/`additionalContext` fields onto these; a native plugin returns them directly. They share one envelope for model-facing context, `HookContext`, which is `inject()`ed as a `context/message` and so carries a REQUIRED `source` (a missing source would default to `{kind:'user'}` and mislabel plugin context as a user prompt).
|
||||
|
||||
Source: [`packages/core/agent/src/types.ts`](../../packages/core/agent/src/types.ts)
|
||||
|
||||
```ts type-equiv
|
||||
interface HookContext {
|
||||
content: ContentBlock[]
|
||||
source: MessageSource
|
||||
}
|
||||
```
|
||||
|
||||
`agent/prompt-submit` returns a `PromptDecision` (allow a drained queued message — optionally rewriting its `content` or attaching `additionalContext` — or block it; a batch whose every prompt is blocked opens a zero-step turn that ends `rejected`):
|
||||
|
||||
```ts type-equiv
|
||||
type PromptDecision =
|
||||
| { kind: 'allow'; content?: ContentBlock[]; additionalContext?: HookContext }
|
||||
| { kind: 'block'; reason: string }
|
||||
```
|
||||
|
||||
`agent/turn-continuation` returns a `ContinuationDecision` (the loop's default is `continue` when the step had tool calls or steering was injected, else `stop`; a `continue` `reason` is recorded as next-step steering in the same turn — the typed `/goal` pattern):
|
||||
|
||||
```ts type-equiv
|
||||
type ContinuationDecision =
|
||||
| { action: 'stop' }
|
||||
| { action: 'continue'; reason?: HookContext }
|
||||
```
|
||||
|
||||
`agent/session-start` carries a `SessionStartSource` (why the session lifecycle began; a bridge keys its SessionStart matcher on it):
|
||||
|
||||
```ts type-equiv
|
||||
type SessionStartSource = 'startup' | 'resume' | 'clear' | 'compact'
|
||||
```
|
||||
|
||||
## `ToolDefinition`
|
||||
|
||||
|
||||
@@ -181,6 +181,16 @@ interface TurnEndReasonMap {
|
||||
error: { kind: 'error'; step: number; message: string; code?: string }
|
||||
disposed: { kind: 'disposed' }
|
||||
'max-tokens': { kind: 'max-tokens' }
|
||||
/**
|
||||
* The turn's entire prompt batch was BLOCKED before any step ran — every
|
||||
* drained queued message was vetoed by an `agent/prompt-submit` listener (a
|
||||
* hook). The turn still opened (so the boundary stays balanced and the block
|
||||
* is a durable in-turn fact), but ran zero steps. `reason` carries the block
|
||||
* message from the vetoing decision. Distinct from `aborted` (a user-driven
|
||||
* cancel) and `error` (a failure): the prompt was rejected by policy, not
|
||||
* interrupted or broken. A UI renders it as "prompt blocked by hook".
|
||||
*/
|
||||
rejected: { kind: 'rejected'; reason: string }
|
||||
/**
|
||||
* The turn never ended on its own: the process crashed mid-turn and a
|
||||
* persistence backend later closed the orphaned (open) turn on reload so the
|
||||
@@ -195,7 +205,7 @@ interface TurnEndReasonMap {
|
||||
}
|
||||
```
|
||||
|
||||
`max-tokens` mirrors the model-call `FinishReason` of the same name: any `max-tokens` step in a turn makes the whole turn end `max-tokens` (the cut-short fact wins over a later continuation), so a consumer can tell a clean stop from a truncated one. `interrupted` is the one reason no loop emits — it is synthesized by crash recovery (see [persistence.md](persistence.md)). Both maps are merge-extensible.
|
||||
`max-tokens` mirrors the model-call `FinishReason` of the same name: any `max-tokens` step in a turn makes the whole turn end `max-tokens` (the cut-short fact wins over a later continuation), so a consumer can tell a clean stop from a truncated one. `rejected` is a zero-step turn whose whole prompt batch an `agent/prompt-submit` hook blocked (the ACP bridge maps it to `cancelled`). `interrupted` is the one reason no loop emits — it is synthesized by crash recovery (see [persistence.md](persistence.md)). Both maps are merge-extensible.
|
||||
|
||||
## The turn-enclosure invariant
|
||||
|
||||
|
||||
@@ -73,7 +73,7 @@ type InferArgs<S extends SchemaSpec> = Simplify<
|
||||
|
||||
## Execution: the `tools/execute` waterfall shapes
|
||||
|
||||
`ctx.tools.execute()` runs each call through the `tools/execute` waterfall — the single seam where sandbox, permission, hook, and plan-mode plugins wrap or veto. The pending call is a `ToolExecution`; the outcome is a `ToolExecutionResult`.
|
||||
`ctx.tools.execute()` runs each call through a two-waterfall pipeline — `tools/pre-execute` (the allow/deny/ask gate) → core dispatch → `tools/post-execute` (inspect/replace the result, attach context) — the seams where sandbox, permission, hook, and plan-mode plugins gate or transform a call. The pending call is a `ToolExecution`; the outcome is a `ToolExecutionResult`.
|
||||
|
||||
```ts type-equiv
|
||||
interface ToolExecution {
|
||||
@@ -98,10 +98,36 @@ interface ToolExecutionResult {
|
||||
* text in `content` is always present; this is extra structure for code.
|
||||
*/
|
||||
error?: ToolErrorInfo
|
||||
/**
|
||||
* Extra model-facing context a `tools/post-execute` listener attached for the
|
||||
* NEXT request (Claude Code's PostToolUse `additionalContext`). It is NOT part
|
||||
* of this call's `content` — `content`/`feedback` shape the tool RESULT, but
|
||||
* `additionalContext` is a SEPARATE `context/message`. A step can carry
|
||||
* multiple tool calls, so the loop BUFFERS every call's `additionalContext`
|
||||
* and appends them only AFTER all `tool/result`s for the step, keeping
|
||||
* tool-call/result adjacency intact. Carried on the result purely to ferry it
|
||||
* from `execute()` up to the loop's per-step buffer.
|
||||
*/
|
||||
additionalContext?: HookContext
|
||||
}
|
||||
```
|
||||
|
||||
A waterfall listener receives `(exec, next)`: call `next()` to proceed (possibly around your own logic), or return a `ToolExecutionResult` without calling `next()` to veto. An unregistered tool routes through the same catch as a tool-thrown error, so both failure classes get a structured `{ name, code }` (`ToolNotFoundError` → `UNKNOWN_TOOL`) — the loop records a failed tool call instead of failing the whole turn.
|
||||
Each interception waterfall returns a typed **Decision** (the idiom shared with the `agent/*` seams). `tools/pre-execute` listeners receive `(exec, next)` and return a `PreToolDecision`; `tools/post-execute` listeners receive `(exec, result, next)` and return a `PostToolDecision`:
|
||||
|
||||
```ts type-equiv
|
||||
type PreToolDecision =
|
||||
| { kind: 'allow' }
|
||||
| { kind: 'deny'; reason: string }
|
||||
| { kind: 'ask'; reason?: string }
|
||||
```
|
||||
|
||||
```ts type-equiv
|
||||
type PostToolDecision =
|
||||
| { kind: 'accept'; content?: ContentBlock[]; additionalContext?: HookContext }
|
||||
| { kind: 'block'; feedback: ContentBlock[]; additionalContext?: HookContext }
|
||||
```
|
||||
|
||||
Call `next()` to delegate to the default (allow / accept-unchanged), or return a decision to short-circuit. A `pre-execute` `deny` (or `ask`, which degrades to deny until the permission system lands) skips dispatch and yields an `isError` result; input rewrite is deliberately NOT offered on `PreToolDecision` (it would desync the pre-execution audit/history/UI from what ran — its own proposed RFC). A `post-execute` `accept` may replace the model-facing `content` (clean, because `tool/result` is logged after `execute()` returns); a `block` turns the call into an `isError` whose content is the corrective `feedback`. Core dispatch sits between the waterfalls as plain code; the tool body keeps its own try/catch so a thrown tool still reaches `post-execute` as an `isError`. An unregistered tool routes through the same catch as a tool-thrown error, so both failure classes get a structured `{ name, code }` (`ToolNotFoundError` → `UNKNOWN_TOOL`) — the loop records a failed tool call instead of failing the whole turn.
|
||||
|
||||
## Tool-presentation UI vocabulary
|
||||
|
||||
|
||||
@@ -45,6 +45,7 @@ Do NOT write one for a mechanical or local choice (a variable name, a one-file r
|
||||
| [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 |
|
||||
| [Compaction as a capability seam (abstract contract + basic backend)](proposed/feature/2026-06-18-compaction-capability-seam.md) | 2026-06-18 |
|
||||
| [Pre-tool input rewrite — a consistent design](proposed/feature/2026-06-30-pre-tool-input-rewrite.md) | 2026-06-30 |
|
||||
|
||||
### Simplification
|
||||
|
||||
@@ -86,6 +87,7 @@ Do NOT write one for a mechanical or local choice (a variable name, a one-file r
|
||||
| [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 |
|
||||
|
||||
### Simplification
|
||||
|
||||
|
||||
@@ -0,0 +1,45 @@
|
||||
# RFC: Interception seams — the typed-Decision surface a hook programs against
|
||||
|
||||
Status: implemented (accepted 2026-06-30)
|
||||
|
||||
<!-- XXX: legacy ADR/RFC body format, not yet normalized to a unified RFC template. -->
|
||||
|
||||
## Context
|
||||
|
||||
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 (a later stack PR) 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).
|
||||
|
||||
Before this change the interception surface was incomplete and inconsistent for that goal: there was no per-prompt seam (CC's `UserPromptSubmit`), no session-start signal (CC's `SessionStart`), the single `tools/execute` waterfall conflated the pre-gate and post-inspect phases (CC splits `PreToolUse`/`PostToolUse`), and `agent/turn-continuation` returned a bare `boolean` with no room for a force-continue *reason*. The [event-domain-semantics RFC](../architecture/2026-06-30-event-domain-semantics.md) (the stack's first change) pinned down the three-domain rule and the typed-Decision idiom as the interception convention; this RFC builds the actual seams on top of it.
|
||||
|
||||
## Decision
|
||||
|
||||
Add/reshape the interception seams so every one returns a small, seam-specific **typed Decision union**, and the set covers the hook points in scope (`session-start`, `prompt-submit`, `pre-tool`, `post-tool`, `stop`-via-continuation).
|
||||
|
||||
**New `agent/*` events** (`dsh-agent`):
|
||||
- `agent/session-start(agent, source)` — emit, once before turn 1, carrying a `SessionStartSource` (`startup` for a fresh/forked create, `resume` for a reloaded persisted session; `clear`/`compact` reserved). A pure notification — it CANNOT block startup (a deliberate gap: a bridge logs/injects, it does not gate startup). A listener seeds context via `agent.inject()`.
|
||||
- `agent/prompt-submit(agent, content, source, next) → PromptDecision` — waterfall, fired per drained queued message inside the open turn, before the `user/message` append. `allow` (optionally rewriting the prompt `content` or attaching `additionalContext`) or `block`.
|
||||
|
||||
**Reshaped** `agent/turn-continuation` from `(…, defaultDecision: boolean) → boolean` to `(…, defaultDecision: ContinuationDecision) → ContinuationDecision`. A `{action:'continue', reason?}` may carry model-facing context recorded as next-step steering in the same turn — the typed twin of the existing `/goal` step-end-steer pattern.
|
||||
|
||||
**Split** the single `tools/execute` waterfall into `tools/pre-execute` (→ `PreToolDecision` allow/deny/ask gate) and `tools/post-execute` (→ `PostToolDecision` accept/block, optionally replacing content or attaching `additionalContext`). Core dispatch sits between them as plain code inside `ToolRegistry.execute`'s outer try/catch, and the tool body keeps its own inner try/catch so a thrown tool still becomes an `isError` result that `post-execute` listeners can inspect.
|
||||
|
||||
**New `TurnEndReason` variant** `rejected` (`dsh-session`): a turn whose entire prompt batch was blocked by `prompt-submit`.
|
||||
|
||||
### Three load-bearing loop decisions
|
||||
|
||||
1. **Always open the turn first; a fully-blocked batch is a zero-step `rejected` turn.** `prompt-submit` fires AFTER `turn/start`, per message. A batch whose every prompt is blocked does NOT skip the turn — it opens a zero-step turn that closes with `rejected`. This one move resolves three problems at once: (1) turn-enclosure holds (every event has an open turn to live in); (2) `agent/turn-end` fires and the ACP bridge settles normally (mapping `rejected`→`cancelled`) instead of hanging; (3) the block reason is a durable in-turn fact. An `allow`'s `additionalContext` is `inject()`ed into this now-open turn.
|
||||
|
||||
2. **Post-tool `additionalContext` is buffered and appended AFTER all `tool/result`s.** `content`/`feedback` shape the result `execute()` returns, but `additionalContext` is a SEPARATE `context/message`, and a single step can carry multiple tool calls. Appending context right after each result would interleave `result(c1) → context → result(c2)` and break tool-call/result adjacency. So `execute()` surfaces `additionalContext` on its `ToolExecutionResult`, and the loop buffers every per-call context for the step and appends them as `context/message`(s) only after every `tool/result` is appended.
|
||||
|
||||
3. **A forced `continue` `reason` is enqueued through the steering channel**, so the next step's top-of-loop drain records it as steering for the continued turn — next-*step* steering within the SAME turn, not a next-*turn* prompt (matching the existing `hasSteering` force-continue override).
|
||||
|
||||
### Pre-tool INPUT rewrite is DEFERRED (the over-reach signal)
|
||||
|
||||
`PreToolDecision` is allow/deny/ask only — **no `arguments` rewrite**. Output replacement (`PostToolDecision.accept.content`) is safe because `tool/result` is logged AFTER execution (one source of truth). Input rewrite is NOT safe today: `assistant/message` (the model-history source) and `tool/call` (the audit record) are both logged BEFORE execution, and live consumers READ `tool/call.arguments` for presentation (the ACP bridge remembers them for `presentResult`; `dsh-tool-bash` derives the title/cwd/terminal-vs-background from them). A rewrite that changed only execution would make the UI show one command while another RAN. Designing that consistently (rewriting the audit + history + presentation as one unit) is a real consistency-design problem CC itself warns is racy — so it gets its own [proposed RFC](../../proposed/feature/2026-06-30-pre-tool-input-rewrite.md), and `TODO(pre-tool-input-rewrite)` anchors it at the loop's pre-execute call site. This does not regress any production consumer (no production `tools/execute` listener mutated `exec.arguments`). The low-level capability to mutate `exec` in a `pre-execute` listener still exists (unadvertised — a test shim uses it to thread a generated id), but it is not a first-class advertised contract.
|
||||
|
||||
### 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 (a later stack PR), 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).
|
||||
|
||||
## Consequences
|
||||
|
||||
The canonical interception surface is now complete and uniformly typed: a native plugin returns typed decisions directly, and a CC/Codex bridge maps its protocol fields onto the same unions. The loop gained four firing points (session-start emit, prompt-submit waterfall, the post-tool context buffer, the continuation reshape) and the `dsh-tools` registry runs a two-waterfall pipeline; both are documented in [architecture.md](../../../architecture.md) and the package READMEs, and the decision types in [core-data-structures](../../../core-data-structures/core.md#interception-decisions) + [tools.md](../../../core-data-structures/tools.md). All existing `tools/execute` and `turn-continuation` listeners (tests, docs) migrated to the new seams. The ACP bridge maps the new `rejected` reason to `cancelled` (its codec). A pure internal change with no editor-visible transcript shift for the existing scenarios — the new behavior only fires when a hook is registered — so the snapshot goldens are unchanged; a hook-driven snapshot scenario lands with the bridges (the PR that makes a hook observable end-to-end through ACP).
|
||||
@@ -0,0 +1,39 @@
|
||||
# RFC: Pre-tool input rewrite — a consistent design (proposed)
|
||||
|
||||
Status: proposed (2026-06-30)
|
||||
|
||||
<!-- XXX: legacy ADR/RFC body format, not yet normalized to a unified RFC template. -->
|
||||
|
||||
## Context
|
||||
|
||||
The [interception-seams RFC](../../implemented/feature/2026-06-30-interception-seams.md) added `tools/pre-execute` returning a `PreToolDecision` (allow/deny/ask) — but deliberately NOT input rewrite (a hook changing a tool call's `arguments` before it runs). Claude Code's `PreToolUse` hook offers an `updatedInput`, so a faithful CC bridge wants the same. This RFC designs that, separately, because doing it consistently is a real problem — not a field to bolt onto the allow decision.
|
||||
|
||||
## The problem: three readers of pre-execution arguments
|
||||
|
||||
In the loop, a tool call's arguments are committed to the log and read by live consumers BEFORE the tool executes:
|
||||
|
||||
1. **`assistant/message`** is appended before tool dispatch — it is the model-history source `deriveMessages()` replays, so it carries the tool-call arguments the model itself emitted.
|
||||
2. **`tool/call`** is the durable AUDIT record, appended before `ctx.tools.execute()`.
|
||||
3. **Live presentation reads `tool/call.arguments`**: the ACP bridge remembers them and passes them to `presentResult`; `dsh-tool-bash` derives the card title, the rawInput, the cwd, and the terminal-vs-background treatment from them.
|
||||
|
||||
So an "input rewrite" that changes ONLY what executes would make the UI show one command while another RAN, and render result state against the wrong arguments — a real inconsistency, not a documentable gap. (The existing low-level capability to mutate `exec.arguments` in a listener has exactly this latent inconsistency; it is unadvertised precisely because of this.)
|
||||
|
||||
## Proposed design (sketch — to validate against the code when built)
|
||||
|
||||
Treat input rewrite as a consistency unit: when a `pre-execute` hook supplies `updatedInput`, the rewrite must be reflected in ALL three readers, atomically, before execution:
|
||||
|
||||
- The `tool/call` audit event records the REWRITTEN arguments (with the original retained in a sidecar field for the audit trail — a hook changed the call, and both the original and the effective arguments are facts worth keeping).
|
||||
- The `assistant/message` in derived history must agree with what executed — options to evaluate: rewrite the assistant message's tool-call block in place (changes what the model "sees it said"), or record a separate correction the next request carries. The CC model is that the model sees the rewrite took effect.
|
||||
- Presentation (`presentCall`/`presentResult`) reads the rewritten arguments, so the UI shows what actually ran.
|
||||
|
||||
The shape would extend `PreToolDecision` with an allow-variant `arguments` (or a dedicated `{kind:'rewrite', arguments}`), and the loop would thread the rewrite through the three readers above rather than only into `ctx.tools.execute()`.
|
||||
|
||||
## Why not now
|
||||
|
||||
The interception-seams RFC notes input rewrite "fought the code across two review rounds" — the signal AGENTS.md names for an over-reaching change. Shipping allow/deny/ask first keeps the seam honest (no advertised contract that silently desyncs the UI), and a CC/Codex bridge that receives an `updatedInput` logs it and surfaces a faithful-but-degraded warning (like `ask`→deny) until this lands. This RFC is the home for the consistent design; `TODO(pre-tool-input-rewrite)` in the loop's pre-execute call site anchors it.
|
||||
|
||||
## Open questions
|
||||
|
||||
- Does rewriting the `assistant/message` tool-call block corrupt any provider's expectation on replay, or is a separate correction safer?
|
||||
- Should the original arguments be preserved on the `tool/call` event (audit) and, if so, under what field?
|
||||
- How does this interact with a future permission `ask` flow (a user approving a rewritten call)?
|
||||
Reference in New Issue
Block a user