# Review by Principal Systems Engineer (Google/Stripe caliber) (Round 3)

## Review Complete — Principal Systems Engineer (Round 1)

**377 tests pass, 0 failures.** All 7 functional requirements implemented across ~162 lines of production code in 4 files, with 664 lines of tests.

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VERDICT: approve

FINDINGS:
- [src/colonyos/daemon.py]: Watchdog thread correctly avoids `_agent_lock`, reading only GIL-safe primitives — cannot deadlock with stuck pipeline
- [src/colonyos/daemon.py]: Dual-gate detection (elapsed AND heartbeat staleness) is conservative and correct — false positives are structurally prevented
- [src/colonyos/daemon.py]: Benign race between watchdog Step 4 and normal pipeline completion exists but is acceptable — both paths converge on consistent terminal state, and the 1920s+30s window makes collision probability negligible
- [src/colonyos/daemon.py]: `_post_slack_message()` lacks explicit socket timeout; relies on SDK internals + try/except. Non-blocking for v1
- [src/colonyos/daemon.py]: `_stop_event.wait(30)` grace period correctly integrates with daemon shutdown — recovery doesn't block graceful exit
- [src/colonyos/config.py]: Clamping invalid threshold to 120s with warning is the right fail-open behavior for a daemon
- [tests/test_daemon.py]: 664 lines of tests at ~4:1 ratio with excellent failure-mode coverage including Slack isolation and end-to-end integration

SYNTHESIS:
From a distributed systems perspective, this implementation gets the hard part right: the watchdog thread is architecturally independent of the lock held by the stuck pipeline. This is the single most important design constraint and it's correctly enforced — the watchdog reads only GIL-safe primitives (bool, float, reference) and filesystem stats, never touching `_agent_lock`. The dual-gate detection requiring both elapsed time AND heartbeat staleness to exceed the threshold is the conservative classifier design you want for auto-recovery where false positives are catastrophic. The escalation ladder (graceful cancel → grace period → force cancel → state reset) is the standard pattern for cooperative cancellation with a hard backstop. The 162 lines of production code across 4 files is appropriately minimal. The one area I'd improve in v2 is adding explicit socket timeouts to the Slack alert call, but the try/except wrapper makes this non-blocking. All 377 tests pass with thorough coverage of edge cases. This is production-ready.
