dsh-tool-call-timeout-policy

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Tool-call timeout enforcer: a single tools/execute around-dispatch listener that arms a per-call cooperative deadline on exec.signal for a tool declaring timeoutMs on its ToolDefinition and returns a structured TOOL_TIMEOUT result when that deadline wins. The budget is read from the tool's own declaration (ToolDefinition.timeoutMs, set by the owning tool plugin), so this plugin is zero-config. It is the reference tools/execute wrapper and the enforcement home for model-facing tool-call budgets (timeout-library Agent Note).

Plugin (namespace: timeout-policy)

A function/namespace plugin (name / inject / apply), not a service. It registers no tool and takes no config — it consumes ctx.tools's tools/execute waterfall (which the dsh-tools registry always provides) and reads each dispatched tool's declared timeoutMs from the registry (ctx.tools.get(exec.name)).

- id: timeout-policy
  name: '@deepseek-ai/dsh-tool-call-timeout-policy'

The per-tool budget is declared by the tool plugin (e.g. dsh-tool-web's fetchTimeoutMs/searchTimeoutMs config, attached as ToolDefinition.timeoutMs); this plugin only enforces it, so a mistyped tool name is not possible.

Behavior

For a tool that declares a timeoutMs the listener:

1. Reads the budget from the tool's own declaration in the registry (ctx.tools.get(exec.name)?.timeoutMs) and arms deadline(exec.signal, timeoutMs, 'TOOL_TIMEOUT') — one signal fusing the caller's abort with this plugin's timer (@deepseek-ai/dsh-timeout).
2. Swaps that derived signal onto exec for the downstream dispatch, then restores the caller's own signal afterward (cordis next() ignores passed arguments, so the wrapper mutates the shared exec in place; restoring keeps tools/post-execute seeing the caller's signal).
3. After dispatch, if timeoutOf(d.signal, 'TOOL_TIMEOUT') matches — this plugin's own timer fired — replaces the result with a structured TOOL_TIMEOUT tool result: { isError: true, error: { message, info: { name: 'ToolTimeoutError', code: 'TOOL_TIMEOUT' } }, content: 'Error: tool call timed out after <ms>ms' }.

A tool that declares no budget delegates untouched (no deadline).

The base next() of tools/execute is the registry's dispatch-with-normalization thunk, so when the timeout signal reaches a provider that throws its own upstream-abort error, dispatch first turns it into a normal error result, and this wrapper then replaces that with TOOL_TIMEOUT. That ordering is why the replacement is keyed off the signal (timeoutOf), not off the dispatched result's shape.

Cooperative, not a hard kill

The derived signal only notifies; termination stays with the tool and the capability it forwards exec.signal to (the dsh-timeout library owns no kill). Declaring timeoutMs therefore means "cooperative with exec.signal": a tool that ignores the signal will not stop on timeout. Only signal-forwarding tools should declare it — the shipped web_fetch/web_search (which forward through ctx.web to providers) are the reference. TOOL_TIMEOUT needs no session event for reconstructability: it is the final model-facing tool/result, already logged by the loop.

Composing with other tools/execute wrappers

Multiple tools/execute listeners compose by cordis registration order. Combined with a future retry/sandbox/metrics wrapper, registration order chooses the semantics — "timeout covers the whole retry operation" (timeout registered outer) versus "timeout covers each attempt" (timeout registered inner).

Model Experience

Conditional tool result

What the model sees

This plugin adds no prompt or schema. If a declared deadline wins, it replaces the provider's outcome with Error: tool call timed out after <ms>ms plus structured TOOL_TIMEOUT; otherwise the original result passes through unchanged.

Token effect

Zero tokens on non-timeout calls. A timeout adds one small retained error result and can prevent a larger late provider result from entering context.

KV Cache effect

Append-only; newly visible content follows the reusable request prefix and does not invalidate existing KV-cache entries.

Known Limitations and Deferred Work

• Cooperative, never a hard kill — the deadline only notifies via exec.signal; a tool that ignores the signal does not stop on timeout (see § Cooperative, not a hard kill).
• No blanket budget — only tools that declare timeoutMs on their ToolDefinition get a deadline; there is no registry-wide default for undeclared tools (the shipped bash/read/write/edit deliberately declare none).