# Review by Staff Security Engineer (Round 1)

I now have a complete picture of the implementation. Let me write the review.

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## Staff Security Engineer Review — Stuck Daemon Detection

### Completeness Assessment

All 7 functional requirements from the PRD are implemented:

| FR | Status | Notes |
|----|--------|-------|
| FR-1: Watchdog Thread | ✅ | `daemon=True` thread, 30s wake interval, independent of `_agent_lock` |
| FR-2: Auto-Recovery | ✅ | Graceful cancel → 30s grace → force cancel → reset state → mark FAILED |
| FR-3: Slack Alert | ✅ | Posts via `_post_slack_message()`, wrapped in try/except |
| FR-4: `started_at` on QueueItem | ✅ | Field added, schema v5, set atomically under `_lock` |
| FR-5: Enhanced `/healthz` | ✅ | `pipeline_started_at`, `pipeline_duration_seconds`, `pipeline_stalled` |
| FR-6: Monitor Event | ✅ | `watchdog_stall_detected` event with correct fields |
| FR-7: Configurable Threshold | ✅ | `watchdog_stall_seconds` with 120s floor, logged at startup |

All 377 tests pass. No linter errors observed. 7 clean commits, one per task.

### Security-Specific Analysis

**1. Heartbeat file spoofing (PRD §6 Security Consideration)**

The PRD explicitly flagged that a malicious instruction template could keep touching the heartbeat file to mask a hang. The implementation uses a **dual-gate** check: `elapsed >= stall_seconds` AND `time_since_heartbeat >= stall_seconds`. Both must be true. However, this dual-gate still has a weakness: if the heartbeat is continuously touched (spoofed), the second condition never fires, and the pipeline can run indefinitely up to the `pipeline_timeout_seconds` (2hr) ceiling. The PRD's Open Question #1 asked about a hard wall-clock ceiling independent of the heartbeat file — **this was not implemented**. This is a known, documented gap that the PRD left as an open question, so it's not a blocking finding, but it should be tracked.

**2. Information leakage via `/healthz`**

The new healthz fields expose: `pipeline_started_at` (ISO timestamp), `pipeline_duration_seconds` (float), `pipeline_stalled` (bool). These are **operational metadata only** — no queue item contents (`source_value`, prompt text) are leaked. The `item.id` and `source_type` appear only in the Slack alert (sent to the operator's own channel), not in `/healthz`. This is correctly scoped.

**3. Slack alert content**

The alert message includes `item.id` and `item.source_type` — both are opaque identifiers, not user content. `source_value` is **not** included in the alert. This is correct from a data minimization perspective.

**4. No explicit timeout on `_post_slack_message` call**

The `_post_slack_message()` helper swallows exceptions but doesn't enforce a socket-level timeout. If the Slack API hangs, the watchdog thread itself blocks. The implementation wraps the Slack call in `try/except` (line ~236), which catches exceptions but not a TCP-level hang. PRD Open Question #3 called for a 10-second timeout. The try/except is a partial mitigation — the watchdog won't crash — but it could block for the system's TCP timeout (typically 60-120s). **Non-blocking** because the watchdog is a daemon thread and won't prevent shutdown, but it delays recovery.

**5. Race condition analysis**

The `_pipeline_running`, `_pipeline_started_at`, and `_current_running_item` fields are read by the watchdog without holding `_lock`. This is intentional per the PRD (§6: "safe to read without lock"). In CPython, these are single-pointer reads protected by the GIL, so torn reads are impossible. The force-reset in `_watchdog_recover` step 4 correctly acquires `_lock` for the write-side. The only risk would be the watchdog reading a partially-updated state between the RUNNING transition and `_pipeline_started_at` assignment — but these are adjacent assignments under `_lock`, so the watchdog sees either both old or both new values. **No issue.**

**6. No secrets in committed code**

Verified: the diff touches only `config.py`, `daemon.py`, `models.py`, and test files. No `.env` files, no credentials, no API keys. The Slack token is read from `os.environ` (existing pattern), not hardcoded.

**7. Principle of least privilege**

The watchdog thread has access to the full `Daemon` instance (`self`), which is broad. However, it only reads `_pipeline_running`, `_pipeline_started_at`, `_current_running_item`, `daemon_config.watchdog_stall_seconds`, and calls `request_active_phase_cancel`, `request_cancel`, `_post_slack_message`. This is a reasonable surface for an in-process thread. Extracting it to a separate class with a narrow interface would be a v2 refinement.

**8. Configurable threshold floor enforcement**

The 120-second minimum is enforced via clamping (not rejection). This means invalid configs silently succeed — which is the right UX choice (warn + clamp, don't crash). Test coverage confirms this behavior.

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VERDICT: approve

FINDINGS:
- [src/colonyos/daemon.py]: Heartbeat file spoofing allows a malicious instruction to mask a hang indefinitely (up to `pipeline_timeout_seconds`). PRD Open Question #1 flagged this; recommend tracking as a v2 hardening task to add a hard wall-clock ceiling independent of heartbeat freshness.
- [src/colonyos/daemon.py]: `_post_slack_message()` in `_watchdog_recover` has no explicit socket/request timeout; a hanging Slack API could block the watchdog thread for 60-120s (TCP timeout). PRD Open Question #3 recommended 10s. Non-blocking because the thread is a daemon thread and recovery still completes after the TCP timeout, but delays the recovery window.
- [src/colonyos/daemon.py]: `/healthz` correctly avoids leaking `source_value` or prompt content — only exposes `pipeline_started_at` (ISO timestamp), `pipeline_duration_seconds`, and `pipeline_stalled` boolean. No information leakage.

SYNTHESIS:
From a security perspective, this implementation is sound for v1. The core invariants are preserved: the watchdog operates independently of the lock that stuck pipelines hold, the Slack alert doesn't leak sensitive queue item content, the `/healthz` additions expose only operational metadata, and the config floor enforcement prevents misconfiguration-induced false positives. The two non-blocking findings — heartbeat spoofing tolerance and missing Slack timeout — were both explicitly identified as open questions in the PRD and represent reasonable v2 hardening opportunities. The dual-gate stall detection (elapsed time AND heartbeat staleness) is a defense-in-depth pattern that reduces false positives at the cost of slightly delayed detection when the heartbeat is being spoofed. The auto-recovery path uses the existing cooperative cancellation infrastructure rather than unsafe thread killing, which is the right conservative choice. 377 tests pass with comprehensive coverage of the watchdog check, recovery, Slack alerting, monitor events, and false-positive prevention. Approve.