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

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VERDICT: approve

FINDINGS:
- [src/colonyos/cli.py:2018]: Fix round increment and fix item creation are correctly inside the `state_lock` critical section — no TOCTOU race on `fix_rounds`.
- [src/colonyos/cli.py:2663-2682]: HEAD SHA staleness correctly addressed — new SHA propagated to parent item after successful fix round.
- [src/colonyos/orchestrator.py:run_thread_fix]: `finally` block restores original branch, critical for watch process stability.
- [src/colonyos/sanitize.py]: Two-pass Slack link stripping correctly ordered before XML tag stripping in sanitization pipeline.
- [src/colonyos/orchestrator.py:1750]: Verify phase system prompt is inline rather than template-loaded — minor divergence from pattern, non-blocking.
- [src/colonyos/slack.py:should_process_thread_fix]: Clean separation from `should_process_message()` (FR-2 preserved), all guard conditions present (bot mention, allowlist, completed parent, channel allowlist).

SYNTHESIS:
This is a well-executed implementation. All 21 functional requirements from the PRD are addressed with appropriate defense-in-depth. The concurrency model is sound — `state_lock` protects all shared mutable state transitions, the `fix_rounds` check-and-increment is atomic, and `QueueItem` snapshots avoid holding locks during I/O. The security posture is strong: git ref validation occurs at three trust boundaries (triage parse, enqueue, execution), Slack link sanitization strips the `<URL|text>` injection vector, and HEAD SHA verification defends against force-push tampering. From an operability perspective, the `finally` branch restoration, circuit breaker integration, max round caps, and comprehensive logging at decision points mean a 3am incident can be diagnosed from logs alone. 508 tests pass. The minor observations (inline verify prompt, implicit budget enforcement delegation) are non-blocking and appropriate for future cleanup.