## Review Complete — Principal Systems Engineer (Google/Stripe caliber)

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

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### Checklist Assessment

#### Completeness
- [x] **FR-1**: `daemon.py` → `daemon/__init__.py` — confirmed, 1,975 lines (target ~2,100, actually better)
- [x] **FR-2**: `DaemonError`, `_CombinedUI`, `_DaemonMonitorEventUI` extracted to `_ui.py` (238 lines), re-exported from `__init__.py`
- [x] **FR-3**: Watchdog methods → `_watchdog.py` as `_WatchdogMixin` (179 lines)
- [x] **FR-4**: Recovery methods → `_resilience.py` as `_ResilienceMixin` (217 lines)
- [x] **FR-5**: `class Daemon(_WatchdogMixin, _ResilienceMixin, _HelpersMixin)` — clean MRO, no diamond
- [x] **FR-6**: `from colonyos.daemon import Daemon, DaemonError` — backward compat preserved
- [x] **FR-7**: 149 tests pass, 3 fail (pre-existing on `main`, confirmed)
- [x] **FR-8**: No circular imports — mixins import from `colonyos.*`, never from `daemon/`
- [x] **Bonus**: `_helpers.py` (153 lines) extracts formatting/incident methods — beyond PRD scope but follows identical pattern

#### Quality
- [x] All tests pass (149/152; 3 failures pre-existing on `main` — verified by checkout)
- [x] No linter errors introduced
- [x] Code follows existing project conventions (docstrings, logging patterns, type hints)
- [x] No unnecessary dependencies added
- [x] No unrelated changes included
- [x] Zero changes to `tests/test_daemon.py`
- [x] Zero changes to `src/colonyos/cli.py`

#### Safety
- [x] No secrets or credentials in committed code
- [x] No destructive database operations
- [x] Error handling preserved identically from monolith
- [x] `subprocess.run` in `_resilience.py` uses list args (no shell injection)

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### Operational Analysis

**What happens when this fails at 3am?**
Nothing changes. The watchdog loop, crash recovery, and dirty-worktree handling are method-for-method identical to the monolith. The `_get_daemon_module()` lazy import in `_watchdog.py` is the only novel runtime codepath — it's a 3-line function that does `import colonyos.daemon as mod; return mod`. If it somehow fails (impossible unless the package itself is broken), the existing `except Exception` in `_watchdog_loop` catches it and logs the traceback. Blast radius: zero.

**Where are the race conditions?**
Same as before. All shared mutable state is on `self`, protected by `self._lock`. Mixins don't introduce new state or new locks. The `_notification_thread_locks_guard` pattern is unchanged.

**Is the API surface minimal and composable?**
The public API is identical: `Daemon`, `DaemonError`, `_CombinedUI`, `_DaemonMonitorEventUI`. The 4 new files are all internal (`_` prefixed). No new public interfaces.

**Can I debug a broken run from the logs alone?**
Yes. Logger names use `__name__` which resolves to `colonyos.daemon._watchdog`, `colonyos.daemon._resilience`, etc. — actually *better* than the monolith where everything was `colonyos.daemon`. You can now filter logs by submodule.

**What's the blast radius of a bad agent session?**
Unchanged. The mixin pattern means every method is still on `self`, every mock target is unchanged, every error path is identical.

### Commit History

6 clean, incremental commits:
1. `ea4b637` — Convert to package, extract standalone UI classes
2. `b311c1d` — Extract watchdog methods into `_WatchdogMixin`
3. `1ee1f0b` — Extract recovery methods into `_ResilienceMixin`
4. `b16eaf6` — Extract helper/formatting methods into `_HelpersMixin`
5. `9d5ba21` — Final verification of package structure
6. `5602b9a` — Add call-site comments explaining lazy module lookups

Each commit is independently revertable. Good discipline.

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VERDICT: approve

FINDINGS:
- [src/colonyos/daemon/_helpers.py]: Beyond PRD scope (PRD specified 3 submodules, implementation has 4). Acceptable — further reduces `__init__.py` to 1,975 lines vs. the ~2,100 target. Follows identical mixin pattern.
- [src/colonyos/daemon/_watchdog.py]: `_get_daemon_module()` lazy import is the correct engineering decision for preserving `patch("colonyos.daemon.request_active_phase_cancel")` test targets. Well-documented with call-site comments.
- [src/colonyos/daemon/__init__.py]: MRO `Daemon(_WatchdogMixin, _ResilienceMixin, _HelpersMixin)` is clean — no diamond inheritance, no `__init__` conflicts, no `super()` chain issues.
- [tests/test_daemon.py]: Zero modifications. 3 `TestDailyThreadLifecycle` rotation failures confirmed pre-existing on `main` via checkout-and-run.

SYNTHESIS:
This is operationally invisible refactoring — exactly what you want from a structural change to a critical daemon. After 6 failed attempts that broke mock targets, introduced circular imports, or changed public API, attempt 7 does the boring, correct thing: mixins that keep methods on `self`. The `_get_daemon_module()` pattern in the watchdog deserves attention as a reusable technique — it solves the "test patches a module-level name but the mixin imports it directly" problem with zero complexity. Logger namespaces are actually improved (per-submodule filtering). The commit history is clean, incremental, and individually revertable. 149/152 tests pass; 3 failures are pre-existing on `main`. No regressions, no new runtime codepaths beyond a lazy import, no changes to tests or CLI. Ship it.
