docs: align the agent-scope contracts

packages/core/tools/README.md

@@ -1,6 +1,6 @@
 # dsh-tools
 
-Tool registry and execution pipeline. Tool plugins register their schemas and executors; the agent loop executes each call through `tools/pre-execute` (the allow/deny gate) → `tools/execute` (an around-dispatch wrapper for timeout/retry/metrics plugins) → `tools/post-execute` (inspect/replace the result, attach context). The registry also owns HOW its tools are presented to the model — its `mode` config selects native function calling, [Code Mode](#code-mode), or both.
+Tool registry and execution pipeline. Tool plugins register their schemas and executors; the agent loop executes each call through `tools/pre-execute` (the extensible allow/deny gate) → monotonic registered guards → `tools/execute` (an around-dispatch wrapper for timeout/retry/metrics plugins) → `tools/post-execute` (inspect/replace the result, attach context) → the observe-only `tools/result` notification. The registry also owns HOW its tools are presented to the model — its `mode` config selects native function calling, [Code Mode](#code-mode), or both.
 
 ## Service: `ToolRegistry` (ctx key: `tools`)
 
@@ -11,44 +11,43 @@ tools:
   mode: native   # native (default) | code | both
 ```
 
-`native` contributes every registered tool as a wire function definition — the default, byte-for-byte the pre-config behavior. `code` contributes exactly ONE wire tool, `run_code`, plus the generated `tools:sdk` prompt section (see [Code Mode](#code-mode)). `both` contributes every native definition AND `run_code` + the SDK section. In non-native modes `run_code` is reserved presentation infrastructure rather than a filterable capability: allow/deny restrictions cannot remove it, and registering, shadowing, or explicitly filtering that name fails loudly. Non-native modes require a loaded `ctx.codeRuntime` with `language: 'typescript'`; a missing or mismatched runtime rejects every prompt assembly with an actionable error, and a `systemPrompt.toolOrder` naming tools the mode no longer contributes rejects the assembly the same way.
+`native` contributes the calling agent's visible end capabilities as wire function definitions. Under `code`, this registry's canonical contribution is the reserved `run_code` transport plus the generated `tools:sdk` prompt section (see [Code Mode](#code-mode)); an assembly listener may still deliberately add unrelated schemas. `both` contributes the visible native definitions, `run_code`, and the SDK section. In non-native modes both infrastructure pieces are protected rather than filterable capabilities: restrictions and assembly listeners cannot remove them, a scoped section cannot shadow the globally protected `tools:sdk`, and registering, shadowing, or explicitly filtering `run_code` fails loudly. Non-native modes require a loaded `ctx.codeRuntime` with `language: 'typescript'`; a missing or mismatched runtime rejects every prompt assembly with an actionable error, and a `systemPrompt.toolOrder` naming tools the mode no longer contributes rejects the assembly the same way.
 
 ### Public API
 
-- `ctx.tools.register(definition: ToolDefinition): () => Promise<void> | void` Register a tool. The layer is the CALLING context's scope (`dsh-scope`): a plain plugin context registers globally; an agent's `agent.ctx` registers for that agent alone, SHADOWING a same-named global tool there (per-agent tool variants). Duplicate names within one layer throw; non-native modes also reject the reserved `run_code` transport name. Disposed with the calling fiber (= the agent, for scoped registrations).
+- `ctx.tools.register(definition: ToolDefinition): () => Promise<void> | void` Register a tool as a frozen snapshot. Parameters must survive lossless-JSON validation before and after cloning; scalar fields are copied, and execute/presentation callbacks are bound once to the original definition as their method receiver, so later callback-property replacement cannot change dispatch. The layer is the CALLING context's scope (`dsh-scope`): a plain plugin context registers globally; an agent's `agent.ctx` registers for that agent alone, SHADOWING a same-named global tool there (per-agent tool variants). Duplicate names within one layer throw; non-native modes also reject the reserved `run_code` transport name. Disposed with the calling fiber (= the agent, for scoped registrations).
 - `ctx.tools.restrict(filter: ToolRestriction): () => Promise<void> | void` Scoped-only (throws on a plain context): mask the GLOBAL end-capability surface for the calling agent — `allow` keeps only the listed tools, `deny` removes them; multiple restrictions intersect; scoped registrations bypass restriction as explicit grants. The reserved `run_code` transport remains available automatically and cannot be named explicitly. Snapshot-at-registration, loud unknown-name validation, `restrict({})` rejects (the materialized-empty-config trap).
-- `ctx.tools.get(name: string, scope?: ScopeKey): ToolDefinition | undefined` Resolution as one scope sees it (shadowing applied; a restricted-away global reads as absent) — presenters pass the calling agent so the card matches what executed.
-- `ctx.tools.visible(scope?: ScopeKey): ToolDefinition[]` THE visibility function — restricted global layer ∪ the scope's own layer, plus the reserved transport in non-native modes — feeding prompt assembly, `get`, and `execute`, so what the model sees and what dispatches can never disagree.
+- `ctx.tools.get(name: string, scope?: ScopeKey): ToolDefinition | undefined` Resolution as one scope sees it (shadowing applied; a restricted-away global reads as absent) — presenters pass the calling agent so the card matches what executed. Returned definitions are the registry's frozen snapshots.
+- `ctx.tools.visible(scope?: ScopeKey): ToolDefinition[]` The canonical executable view — restricted global layer ∪ the scope's own layer, plus the reserved transport in non-native modes — feeding prompt assembly, `get`, and `execute`, so presentation and dispatch resolve the same frozen definitions.
 - `ctx.tools.knownNames(scope?: ScopeKey): string[]` The PRE-restriction end-capability name universe `restrict` validates against: a typo fails loud while a restricted-away tool stays a normal absence. Presentation providers add reserved transport names separately when validating `toolOrder`.
 - `ctx.tools.schemas(scope?: ScopeKey): ToolSchema[]` Schemas of everything the scope can see (without the `execute` functions). The shipped tools' schemas are catalogued in [docs/tool-catalog.md](../../../docs/tool-catalog.md), generated by booting each tool plugin and harvesting this method (see [the tool-schema-catalog RFC](../../../docs/rfc/implemented/process/2026-07-02-tool-schema-catalog.md)).
-- `ctx.tools.execute(exec: ToolExecution): Promise<ToolExecutionResult>` Execute one tool call through the `tools/pre-execute` → `tools/execute` → `tools/post-execute` pipeline.
+- `ctx.tools.guard(guard: ToolGuard): () => Promise<void> | void` Register a monotonic synchronous execution guard after `tools/pre-execute`: returning a reason denies the call, while `undefined` leaves it unchanged. A plain-context guard applies globally; an `agent.ctx` guard applies only to that agent. Later waterfall listeners cannot turn a guard denial back into permission. Disposed with the calling fiber.
+- `ctx.tools.execute(exec: ToolExecutionInput): Promise<ToolExecutionResult>` Snapshot one single-use call input into a pipeline-owned execution, assign its opaque correlation token, require `arguments` to be losslessly JSON-serializable before and after cloning, deep-freeze the detached arguments, and protect its identity before running `tools/pre-execute` → guards → `tools/execute` → `tools/post-execute`; optional `signal` is the only operational field an around-dispatch wrapper may add, replace, or remove. Validate the final result as losslessly JSON-serializable and freeze the complete execution before `tools/result` observers run. Invalid or unstable input—including cloneable mutable exotics—and malformed or non-JSON listener/tool results normalize to `isError` outcomes rather than bypassing policy or failing later at the session log.
 
 ### Injected services
 
 `SystemPrompt` — the registry automatically feeds its tool schemas into the system-prompt assembly via `ctx.systemPrompt.tools()`.
 
-### Events
+### Live events
 
-| Event | Mode | Purpose |
-|---|---|---|
-| `tools/pre-execute` | waterfall | Allow/deny gate BEFORE a tool runs (sandbox, permission, hooks); returns `PreToolDecision`. Scope-filtered by `exec.agent`: an `agent.ctx` listener gates only its own agent |
-| `tools/execute` | waterfall | Around-dispatch wrapper (timeout, retry, metrics): `(exec, next)` → the dispatched `ToolExecutionResult`; `next()` is dispatch-with-normalization (resolving through the caller's visible view). Scope-filtered by `exec.agent` like the gate |
-| `tools/post-execute` | waterfall | Inspect/replace the result AFTER a tool runs, attach context; returns `PostToolDecision` |
-| `tools/change` | emit | A tool or restriction was registered or unregistered (possibly for one scope); deliberately unfiltered |
+The live registry pipeline has three transformable waterfalls followed by the owner-final `tools/result` observation boundary; registry changes are deliberately unfiltered shared-state notifications. Exact signatures, dispatch modes, scope filtering, and failure-containment contracts live in the generated [Cordis event catalog](../../../docs/cordis-catalog/events.md), while the complete ordering is visualized in the generated [tool execution pipeline](../../../docs/tool-execution-pipeline.md). `tools/result` is live and observe-only; the similarly named `tool/result` is the durable session event the agent loop appends afterwards.
 
 ### Key types
 
-- `ToolDefinition` — `ToolSchema` + `execute(args, exec): Promise<ContentBlock[] | { content: ContentBlock[]; meta? }>` (the bare array is the model-facing content; the object form additionally attaches an opaque, JSON-serializable `meta` presentation payload persisted on the `tool/result` event and handed back to `presentResult`), plus optional `presentCall(args)` / `presentResult(args, result)` for tool-owned UI presentation (see below). It also carries an optional cooperative timeout budget `timeoutMs?: number` (ms) enforced by `@deepseek-ai/dsh-timeout-policy`, never sent to the model.
-- `ToolExecution` — one pending tool call: `{ callId, name, arguments, agent?, signal? }`.
-- `ToolExecutionResult` — outcome: `{ callId, content, isError, error?, additionalContext?, meta? }`. On failure with a `HarnessError`, `error: { name, code }` carries the structured failure class alongside the model-facing text (the loop forwards it onto the `tool/result` session event for retry/sandbox plugins and replay). `additionalContext` (a `HookContext`) ferries any `tools/post-execute` context up to the loop, which buffers it and appends it as a `context/message` after all `tool/result`s in the step. `meta` is the tool's opaque presentation payload from a successful `execute` (the object return form); the loop forwards it onto the `tool/result` session event for result-card rendering.
+- `ToolDefinition` — `ToolSchema` + `execute(args, exec): Promise<ContentBlock[] | { content: ContentBlock[]; meta? }>` (the bare array is the model-facing content; the object form additionally attaches an opaque, JSON-serializable `meta` presentation payload persisted on the `tool/result` event and handed back to `presentResult`), plus optional `presentCall(args)` / `presentResult(args, result)` for tool-owned UI presentation (see below). It also carries an optional cooperative timeout budget `timeoutMs?: number` (ms) enforced by `@deepseek-ai/dsh-timeout-policy`, never sent to the model. Registration stores a frozen snapshot with detached JSON parameters and once-bound callback identities.
+- `ToolExecutionInput` — the caller-supplied call description: `{ callId, name, arguments, agent?, parent?, signal? }`; `arguments` must be losslessly JSON-serializable, and callers may pass an enclosing execution's opaque token as `parent` but never choose the new execution's own token.
+- `ToolExecutionToken` — a frozen, property-free identity value assigned by the registry. It supports equality correlation only and exposes no live outer execution state.
+- `ToolExecution` — the pipeline-owned call: immutable `{ token, callId, name, arguments, agent?, parent? }` identity plus optional operational `signal`, which an around wrapper may add, replace, remove, and restore. A nested call's `parent` is a `ToolExecutionToken`, not an execution object.
+- `ToolExecutionResult` — losslessly JSON-serializable outcome: `{ callId, content, isError, error?, additionalContext?, meta? }`. The registry validates the complete post-policy value before final observation. On failure with a `HarnessError`, `error: { name, code }` carries the structured failure class alongside the model-facing text (the loop forwards it onto the `tool/result` session event for retry/sandbox plugins and replay). `additionalContext` (a `HookContext`) ferries any `tools/post-execute` context up to the loop, which buffers it and appends it as a `context/message` after all `tool/result`s in the step. `meta` is the tool's opaque presentation payload from a successful `execute` (the object return form); the loop forwards it onto the `tool/result` session event for result-card rendering.
 - `PreToolDecision` — `{kind:'allow'}` | `{kind:'deny', reason}` | `{kind:'ask', reason?}`. Input rewrite (changing `arguments`) is deliberately NOT offered (it would desync the pre-execution audit/history/UI from what ran — its own proposed RFC); `ask` degrades to `deny` until the permission system lands.
 - `PostToolDecision` — `{kind:'accept', content?, additionalContext?}` (keep the call successful, optionally replacing the model-facing content) | `{kind:'block', feedback, additionalContext?}` (turn it into an `isError` whose content is the corrective feedback). Output replacement is clean because `tool/result` is logged AFTER `execute()` returns.
+- `ToolGuard` — `(execution) => string | undefined`; the returned string is a final monotonic denial reason evaluated after the reorderable pre-execute waterfall and before dispatch.
 - `ToolCallView` / `ToolResultView` — provider-neutral `card`-tagged render intents a tool returns from `presentCall` / `presentResult` to own how a UI renders ITS calls (see "Tool-owned UI presentation").
 
 ### Extension points
 
 - Tool plugins call `ctx.tools.register()` — schemas flow into the assembly automatically.
-- `tools/pre-execute` is the allow/deny gate (sandbox, permission, hooks): listeners receive `(exec, next)` and call `next()` to delegate to the default (allow) or return a `PreToolDecision` to short-circuit; a `deny`/`ask` skips dispatch and yields an `isError` result. `tools/execute` is the around-dispatch seam (timeout, retry, metrics): listeners receive `(exec, next)` and call `next()` to delegate to core dispatch (returning its `ToolExecutionResult`, optionally wrapped), or return a replacement result to short-circuit dispatch; the base `next()` IS dispatch-with-normalization, so `await next()` already yields an `isError` result for a thrown/unknown tool (never a raw throw). A wrapper mutates `exec` in place before `next()` — e.g. replacing `exec.signal` with a per-call deadline — because cordis `next()` ignores passed arguments. `tools/post-execute` is the inspect/transform seam: `(exec, result, next)` → a `PostToolDecision` that can replace content, block with feedback, or attach `additionalContext`. Core dispatch is the base of the `tools/execute` waterfall; the tool body keeps its own try/catch so a thrown tool still reaches `post-execute` as an `isError`. All follow the typed-Decision idiom shared with the `agent/*` interception seams (see [`dsh-agent`](../agent/README.md)); `@deepseek-ai/dsh-timeout-policy` is the reference `tools/execute` wrapper.
+- `tools/pre-execute` is the reorderable allow/deny gate (sandbox, permission, hooks): listeners receive `(exec, next)` and call `next()` to delegate to the default (allow) or return a `PreToolDecision` to short-circuit; a `deny`/`ask` skips dispatch and yields an `isError` result. `ctx.tools.guard()` installs scope-aware monotonic policy after that waterfall when a denial must not be overridable by listener ordering. `tools/execute` is the around-dispatch seam (timeout, retry, metrics): listeners receive `(exec, next)` and call `next()` to delegate to core dispatch (returning its `ToolExecutionResult`, optionally wrapped), or return a replacement result to short-circuit dispatch; the base `next()` is dispatch-with-normalization, so `await next()` already yields an `isError` result for a thrown or unknown tool. A wrapper may change only `exec.signal` before `next()`—adding a per-call deadline, replacing a caller signal, or restoring absence afterwards—because call identity is protected before policy begins. `tools/post-execute` is the inspect/transform seam: `(exec, result, next)` → a `PostToolDecision` that can replace content, block with feedback, or attach `additionalContext`. Core dispatch is the base of the `tools/execute` waterfall; the tool body keeps its own error boundary so a thrown tool still reaches `post-execute` as an `isError`. Finally, `tools/result` observes the immutable authoritative result after every transform and error boundary. All follow the typed-decision idiom shared with the `agent/*` seams (see [`dsh-agent`](../agent/README.md)); `@deepseek-ai/dsh-timeout-policy` is the reference `tools/execute` wrapper.
 - MCP servers: one plugin per server, discover tools, call `ctx.tools.register()` with the server's schemas.
 
 ### Typed tool parameter schemas
@@ -135,13 +134,13 @@ const bash = defineTool({
 
 Under `mode: code` (or `both`) the registry turns the tool surface into a programming API, per the [Code Mode RFC](../../../docs/rfc/implemented/feature/2026-06-15-code-mode.md): the model writes a TypeScript program (the body of an async function) and passes it to the reserved wire transport `run_code`; the program runs in `ctx.codeRuntime` (the [code-execution seam](../../code-runtime/README.md) — the shipped backend is a worker thread) with one async binding per visible end-capability tool (`await tools.bash({...})`), and ONLY what it prints or returns re-enters the model's context. Scope restrictions change those SDK bindings but cannot remove or replace the transport itself.
 
-- **The SDK section** (`tools:sdk`, order 150): a lazy prompt section regenerating, at each assembly, a `declare const tools: {...}` TypeScript declaration of every registered tool except `run_code` (exotic names via quoted keys), plus fixed usage instructions. Deterministic — lexicographic tool order, byte-identical text for an unchanged tool set (prefix-cache-friendly). The codegen (`jsonSchemaToTs`, exported) is TOTAL: constructs outside the `defineTool` subset degrade to `unknown`, never throw.
-- **The dispatch bridge** (`run_code`'s execute): every binding call is JSON-normalized BEFORE dispatch (a value that does not survive — `BigInt`, circulars — rejects that one call, so the dispatched form and the logged form are the same JSON value by construction), serialized through a per-run queue (even `Promise.all` executes the underlying `ctx.tools.execute()` calls one at a time in submission order — the tool contract carries no concurrency-safety metadata yet), gated by `tools/pre-execute`/`tools/post-execute` like any native call (a deny reaches the program as a binding rejection), and logged as one `tool/code-dispatch` session event (log-only: `deriveMessages()` never surfaces it) with the deterministic sub-id `<parent>:code:<n>`. A failed sub-call REJECTS the program-side promise with the tool's error text — real code error handling, no bespoke envelope. A sub-call's `additionalContext` is deliberately DROPPED (no safe outlet mid-run without breaking tool-call/result adjacency; deferred until a real hook needs it through Code Mode).
+- **The SDK section** (`tools:sdk`, order 150): a lazy prompt section regenerating, at each assembly, a `declare const tools: {...}` TypeScript declaration of the calling scope's visible end capabilities (exotic names via quoted keys), plus fixed usage instructions. The registry protects this section and the `run_code` wire schema after the assembly waterfall, so Code Mode cannot silently lose either half of its transport. Deterministic — lexicographic tool order, byte-identical text for an unchanged tool set (prefix-cache-friendly). The codegen (`jsonSchemaToTs`, exported) is total: constructs outside the `defineTool` subset degrade to `unknown`, never throw.
+- **The dispatch bridge** (`run_code`'s execute): every binding call is JSON-normalized before dispatch (a value that does not survive — `BigInt`, circulars — rejects that one call, so the dispatched form and logged form are the same JSON value by construction), serialized through a per-run queue (even `Promise.all` executes underlying calls one at a time in submission order), given the outer execution's opaque token as `parent`, and run through the complete pre-execute → guards → execute → post-execute → result pipeline. A denial reaches the program as a binding rejection, and each sub-call is logged as a `tool/code-dispatch` session event with deterministic id `<parent>:code:<n>`; `deriveMessages()` does not surface that event. Token correlation lets commit-style observers defer an inner success until the final `run_code` result without exposing the live outer execution; ordinary tool side effects are not rolled back. A sub-call's `additionalContext` is deliberately dropped because inserting it inside a running parent call would break tool-call/result adjacency.
 - **Settlement discipline**: the bridge owns a run-scoped abort that follows the outer signal in and fires when the run settles for any reason, so a budget expiry aborts an in-flight sub-tool instead of orphaning it; the bridge then drains its queue BEFORE returning, so every `tool/code-dispatch` lands inside the open turn. A failed run throws `CodeRunFailedError` (`code: 'CODE_RUN_FAILED'`, message = the failure kind + captured logs), which the pipeline converts to a structured `isError` the model self-corrects from.
 
-The wire collapse is the registry's own contribution (`systemPrompt.tools()` is mode-aware), so the logged `request/header` records it for free — under `code`, the assembled tool list is exactly `[run_code]`, pinned by tests and the snapshot goldens. Try it: `pnpm run demo:code-mode` ([the coding-agent example's Code Mode overlay](../../../examples/coding-agent/README.md#code-mode)); `pnpm run demo:code-mode acp` serves the same mode over ACP instead of the REPL.
+The wire collapse is the registry's own contribution (`systemPrompt.tools()` is mode-aware), so the logged `request/header` records it for free. With no deliberate schema-adding assembly listener, `code` assembles exactly `[run_code]`, pinned by tests and the snapshot goldens; protection guarantees that `run_code` and `tools:sdk` remain present, not that unrelated listener additions are erased. Try it: `pnpm run demo:code-mode` ([the coding-agent example's Code Mode overlay](../../../examples/coding-agent/README.md#code-mode)); `pnpm run demo:code-mode acp` serves the same mode over ACP instead of the REPL.
 
 ### What is NOT here (TODO)
 
-- **Tool shapes review** — when real tools land (e.g. a concurrency-safety hint for parallel execution); phase 1 executes tool calls sequentially.
-- **Parallel execution** — the loop currently iterates tool calls sequentially.
+- **Concurrency metadata** — tool definitions do not declare whether executions are safe to overlap.
+- **Parallel execution** — the loop and Code Mode bridge execute tool calls sequentially until that metadata exists.