fix(scope): harden final ownership boundaries

packages/core/tools/README.md

@@ -22,7 +22,7 @@ tools:
 - `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.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>` Read each caller-owned top-level field once, snapshot the single-use call into a pipeline-owned execution, assign its opaque correlation token, materialize `arguments` through one lossless-JSON traversal, deep-freeze them, and protect 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. After the required `callId`/`name` correlation identity is captured, the same captured optional fields build the normalized error shell if a later accessor or validation fails, so policy, dispatch, routing, and `tools/result` cannot observe different caller values. Every top-level result field is likewise captured once and the complete result or post-decision is losslessly materialized before final observation. Invalid 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. A throwing `callId` or `name` accessor rejects because no trustworthy result identity exists yet.
+- `ctx.tools.execute(exec: ToolExecutionInput): Promise<ToolExecutionResult>` Read each caller-owned top-level field once, require `callId` and `name` to yield strings, snapshot the single-use call into a pipeline-owned execution, assign its opaque correlation token, materialize `arguments` through one lossless-JSON traversal, deep-freeze them, and protect 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. After the required string correlation identity is captured, the same captured optional fields build the normalized error shell if a later accessor or validation fails, so policy, dispatch, routing, and `tools/result` cannot observe different caller values. Every top-level result field is likewise captured once and the complete result or post-decision is losslessly materialized before final observation. Invalid later 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. A throwing accessor or non-string value in `callId` or `name` rejects before `tools/result` because no trustworthy result identity exists yet.
 
 ### Injected services
 
@@ -35,7 +35,7 @@ The live registry pipeline has three transformable waterfalls followed by the ow
 ### 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. 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.
+- `ToolExecutionInput` — the caller-supplied call description: `{ callId, name, arguments, agent?, parent?, signal? }`; `callId` and `name` must be strings, `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.