# Review — Principal Systems Engineer (Round 5)

**Branch:** `colonyos/recovery-7cc0851d44`
**PRD:** `cOS_prds/20260402_054259_prd_colonyos_daemon_py_recovery_context_previous_branch_colonyos_colonyos_daemon_py.md`

## Checklist

### Completeness
- [x] FR-1: `daemon.py` → `daemon/__init__.py` with identical behavior
- [x] FR-2: `DaemonError`, `_CombinedUI`, `_DaemonMonitorEventUI` extracted to `_ui.py`, re-exported
- [x] FR-3: Watchdog methods in `_WatchdogMixin` (`_watchdog.py`)
- [x] FR-4: Recovery methods in `_ResilienceMixin` (`_resilience.py`)
- [x] FR-5: `Daemon(_WatchdogMixin, _ResilienceMixin, _HelpersMixin)` — clean MRO
- [x] FR-6: `from colonyos.daemon import Daemon, DaemonError` works unchanged
- [x] FR-7: Zero test modifications — all 152 tests pass (3 pre-existing failures on main)
- [x] FR-8: No circular imports — confirmed by successful import chain

### Quality
- [x] 152 passed, 3 failed (pre-existing on main: `TestDailyThreadLifecycle` rotation tests)
- [x] Code follows existing conventions (lazy imports, logger per module, docstrings)
- [x] No unnecessary dependencies added
- [x] No unrelated changes included
- [x] Zero changes to `tests/test_daemon.py` and `src/colonyos/cli.py`

### Safety
- [x] No secrets or credentials in committed code
- [x] `subprocess.run` uses list args, no `shell=True`, 10s timeout
- [x] Error handling preserved identically from monolith

## Findings

- [src/colonyos/daemon/_watchdog.py]: `_get_daemon_module()` lazy import is the operationally critical pattern. It ensures `patch("colonyos.daemon.active_phase_controller_count")` and `patch("colonyos.daemon.request_cancel")` land correctly at test time. Without it, the watchdog would call the real functions even when tests patch them at the daemon module namespace. This is the kind of 3-line function that prevents 3am pages.
- [src/colonyos/daemon/_resilience.py]: All 7 recovery methods byte-for-byte identical to monolith. Lazy in-method imports (`from colonyos.recovery import ...`, `from colonyos.orchestrator import ...`) prevent circular deps. `subprocess.run` uses list args with 10s timeout — no shell injection vector.
- [src/colonyos/daemon/_helpers.py]: Beyond PRD scope (PRD specified 3 submodules, this is a 4th). Net positive — extracts pure helper/formatting methods that reduce `__init__.py` further. Follows the identical mixin pattern.
- [src/colonyos/daemon/_ui.py]: Zero Daemon coupling. Standalone classes with their own `__init__`. Clean extraction.
- [src/colonyos/daemon/__init__.py]: MRO is `Daemon → _WatchdogMixin → _ResilienceMixin → _HelpersMixin → object`. No diamond inheritance, no `__init__` conflicts (mixins define no `__init__`). All 4 public names re-exported.
- [tests/test_daemon.py]: Zero modifications. This is the strongest possible evidence of a correct refactoring.

## 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 file where I can read the stall-detection → cancel → grace-period → force-cancel → state-reset sequence in 180 lines without scrolling past 2,400 lines of unrelated code. The `_get_daemon_module()` pattern ensures mock substitutions land correctly, which means the existing 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. The _HelpersMixin addition (beyond PRD scope) is a net positive: it pulls out pure formatting functions that have zero blast radius. Zero test changes, zero import surface changes, zero regressions. The 3 failing tests are pre-existing on `main` and unrelated to this branch. Ship it.
