# Review by Principal Systems Engineer (Google/Stripe caliber) (Round 5)

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## Review — Principal Systems Engineer

**VERDICT: approve**

**FINDINGS:**
- [src/colonyos/daemon/_watchdog.py]: `_get_daemon_module()` lazy import is the operationally critical pattern — ensures `unittest.mock.patch` targets at `colonyos.daemon.<name>` land correctly. Without it, the watchdog calls real functions even when tests patch the daemon module namespace.
- [src/colonyos/daemon/_resilience.py]: All 7 recovery methods byte-for-byte identical to monolith. `subprocess.run` uses list args with 10s timeout. Lazy in-method imports prevent circular deps.
- [src/colonyos/daemon/_helpers.py]: Beyond PRD scope (4th mixin, PRD specified 3 submodules). Net positive — pure helper/formatting functions with zero blast radius.
- [src/colonyos/daemon/_ui.py]: Zero Daemon coupling. Clean standalone extraction.
- [src/colonyos/daemon/__init__.py]: Clean MRO: `Daemon → _WatchdogMixin → _ResilienceMixin → _HelpersMixin → object`. No diamond, no `__init__` conflicts. All 4 public names re-exported.
- [tests/test_daemon.py]: Zero modifications. Strongest possible evidence of correct refactoring.

**Test results:** 152 passed, 3 failed — identical to `main`. The 3 `TestDailyThreadLifecycle` rotation failures are pre-existing (confirmed across all review rounds). Zero regressions.

**SYNTHESIS:**
From an operational reliability perspective, this is exactly the refactoring I want to see: operationally invisible. The watchdog thread — the component most likely to wake me at 3am — is now in its own 180-line file where I can read the stall-detection → cancel → grace-period → force-cancel → state-reset sequence without scrolling past 2,400 lines of unrelated coordinator logic. The `_get_daemon_module()` pattern ensures mock substitutions land correctly, which means the existing 152-test suite remains a trustworthy regression oracle. The resilience mixin keeps all 7 recovery paths exactly as they were — same subprocess args, same timeouts, same incident recording. Zero test changes, zero import surface changes, zero regressions. Ship it.

Review artifact written to `cOS_reviews/reviews/principal_systems_engineer/20260402_064500_round5_colonyos_daemon_py_recovery_context_previous_branch_colonyos_colonyos_daemon_py.md`.
