# Review by Principal Systems Engineer (Google/Stripe caliber) (Round 1)

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## Review Complete — Principal Systems Engineer

**VERDICT: approve**

### Summary

All 10 functional requirements from the PRD are fully implemented and tested across 45 changed files (~5,800 lines). **26 backend tests + 182 frontend tests all pass.**

### Key Strengths (from a systems reliability perspective)

1. **Fail-closed worktree check** — The `_preexec_worktree_state` refactor is the single best change in this diff. The old code swallowed `git status` errors and assumed clean. The new code returns `indeterminate`, auto-pauses the daemon, writes an incident report, and posts to Slack. This is exactly what you want at 3am.

2. **Notification thread race fix** — Double-check locking pattern with per-item locks prevents duplicate Slack intro messages. Validated with a 16-thread concurrency test.

3. **Daemon-embedded server isolation** — `daemon=True` thread, `try/except` around all uvicorn ops, graceful `ImportError` fallback. Blast radius of server crash is zero.

4. **CORS locked down** — No middleware unless explicitly configured. Unknown origins rejected (tested). No wildcard `*` origins.

### Minor Findings (non-blocking)

| File | Issue |
|---|---|
| `web/src/pages/Queue.tsx` | Redundant `!error` condition on line 74 |
| `web/src/__tests__/` | Duplicate test files for CostChart and PhaseBreakdownChart |
| `daemon.py:448` | Auth token logged at INFO level — consider DEBUG for prod |
| `DaemonHealthBanner.tsx` | Pause/resume errors silently swallowed (acceptable given 5s poll) |

Full review written to `cOS_reviews/reviews/principal_systems_engineer/round_1.md`.
