# Review by Staff Security Engineer (Round 3)

## Staff Security Engineer — Review Complete

**VERDICT: approve** ✅

### Key Security Findings

**No blocking issues.** The implementation is security-sound:

1. **Access control invariant preserved**: `should_process_message()` — the single chokepoint for all 5 access control filters (channel allowlist, bot rejection, edit rejection, thread rejection, sender allowlist) — is **completely untouched** by this diff. Passive messages pass through the exact same gate as @mentions.

2. **Information leakage prevented**: The `is_passive` flag correctly suppresses all user-visible side effects (👀 reactions, queue-full warnings) for passive messages. The bot is truly invisible until triage confirms actionability. Dedicated test coverage (`test_triage_queue_full_passive_message_no_warning`) confirms this.

3. **No bypass vectors**: `is_passive` is derived from a deterministic `has_bot_mention()` check on the raw text — there's no user-controllable way to manipulate it.

4. **Expanded prompt injection surface is mitigated**: Yes, `trigger_mode: "all"` routes more messages to the triage LLM. But this is gated by channel allowlist + optional sender allowlist + the triage LLM itself. The startup warnings (FR-6, FR-7) alert operators to tighten these controls.

5. **No secrets in committed code**, no destructive operations, proper error handling throughout.

6. **318 tests pass**, including dedup race conditions, queue-full privacy scenarios, and end-to-end integration tests.

**Non-blocking (v2)**: Hard enforcement of `allowed_user_ids` in "all" mode and explicit `message_subtype` filtering remain reasonable v2 hardening opportunities.

Review artifact written to `cOS_reviews/reviews/staff_security_engineer/20260401_150000_round1_you_are_a_code_assistant_working_on_behalf_of_the_engineering_team_the_following.md`.
