[Bug] agent-core v1 Agent tool description says "fixed 30-minute timeout", actual default is 2 hours

[starquakee]

Summary

In agent-core (v1), the Agent tool description tells the model that subagents use "a fixed 30-minute timeout", but the enforced default is 2 hours. The model-facing text and the runtime constant disagree, and a test assertion pins the stale text so nothing flags the drift.

Evidence

1. Stale description — packages/agent-core/src/tools/builtin/collaboration/agent.md:12:

   Subagents use a fixed 30-minute timeout. If one times out, resume the same agent instead of starting over.

   This file is embedded verbatim into the tool description (AGENT_DESCRIPTION_BASE via ?raw import in agent.ts), so every v1 session injects this text into the model's context.

2. Actual default is 2 hours — packages/agent-core/src/session/subagent-host.ts:33:

   export const DEFAULT_SUBAGENT_TIMEOUT_MS = 2 * 60 * 60 * 1000;

   Effective resolution: KIMI_SUBAGENT_TIMEOUT_MS (env) → [subagent] timeout_ms (config.toml) → this constant.

3. A test locks in the stale text — packages/agent-core/test/tools/agent.test.ts:131:

   expect(tool.description).toContain('fixed 30-minute timeout');

   Execution-side tests use the constant itself, so everything stays green while the two sides disagree.

4. v2 is aligned, v1 is not — packages/agent-core-v2/src/session/subagent/tools/agent.md:12 correctly reads "Subagents use a fixed 2-hour timeout".

Impact

• The model plans around a nonexistent 30-minute cap: it may split long delegations unnecessarily, or assume a subagent was killed at 30 minutes when it actually had 2 hours.
• The word "fixed" also hides that the timeout is configurable (KIMI_SUBAGENT_TIMEOUT_MS / [subagent] timeout_ms).
• No functional breakage: enforcement is 2 hours; only the LLM-facing description is wrong.

Suggested fix

1. Update packages/agent-core/src/tools/builtin/collaboration/agent.md:12 to match the constant (as v2 does), and update the assertion in packages/agent-core/test/tools/agent.test.ts:131.
2. Better still: render the timeout in the description from formatSubagentTimeoutDescription(resolveSubagentTimeoutMs(...)) so the text cannot drift from the code again.

[Correctover]

PR submitted: #2423 — Updated agent.md:12 from "30-minute timeout" to "2-hour timeout" and fixed corresponding test assertion.