# Review by Principal Systems Engineer (Google/Stripe caliber) (Round 2)

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## Principal Systems Engineer Review — Complete

I've reviewed the full implementation on branch `colonyos/let_s_add_some_cool_ui_that_we_can_deploy_at_htt_9355d48353` (~6,038 lines added across 47 files) against the PRD.

**All 317 Python tests pass. All 182 frontend tests pass.**

All 10 functional requirements (FR-1 through FR-10) are implemented and tested. The security fixes from the previous review round are in place (default read-only dashboard, masked tokens, rate limiting, CORS validation, subdomain auth on healthz).

VERDICT: approve

FINDINGS:
- [src/colonyos/daemon.py]: Uvicorn dashboard thread has no graceful shutdown — daemon thread is killed on process exit. Acceptable for v1 polling-only dashboard.
- [src/colonyos/daemon.py]: No port conflict detection — if dashboard port is taken, the dashboard silently fails to start with only a log warning.
- [src/colonyos/server.py]: Rate limit cooldown is global per-action, not per-client. Shared cooldown between all operators.
- [src/colonyos/server.py]: Ephemeral auth token changes on every restart (PRD Open Question #1 — explicitly deferred).
- [web/src/util.ts]: Six switch-statement color helpers could be simplified to lookup tables.
- [web/src/pages/Queue.tsx]: Brief "No queue active" flash during initial data fetch before queue loads.

SYNTHESIS:
This is a well-executed dashboard overhaul that covers all 10 functional requirements. From a systems engineering perspective, the implementation makes consistently good reliability decisions: fail-closed worktree checking (`_preexec_worktree_state` tri-state), exception isolation on the embedded server thread, lock-free Slack notification posting (collected inside lock, dispatched outside), and proper double-check locking for notification threads. The security hardening — default read-only, masked tokens, rate limiting, CORS validation, subdomain auth on healthz — addresses the most critical exposure vectors. The six findings are all v2 polish items; none represent operational risk in the current single-operator deployment model. The bundled daemon improvements (worktree tri-state, circuit breaker messaging, notification locking) are tangential but each individually correct and well-tested. I'd ship this.

Review artifact saved to `cOS_reviews/reviews/principal_systems_engineer/round_2.md`.
