# Progress: Challenger Chat M3-2

Last visited: 2026-10-01T03:03:00Z

## Status: COMPLETE

### Completed Steps:
- [x] Initialized BRIEFING.md and DISPATCH.md.
- [x] Read ORIGINAL_REQUEST.md, worker handoff.md, orchestrator plan.md.
- [x] Inspected source code of `tools/stress/chat_load_benchmark.py` and `tests/unit/test_chat_load_benchmark.py`.
- [x] Designed, implemented, and executed empirical adversarial test suite in `tests/security_fuzzing/test_chat_load_benchmark_adversarial.py` (9 tests, 100% pass in 1.82s).
- [x] Evaluated all 4 empirical challenge dimensions:
  1. CLI parameter boundary handling (0 CCU, negative CCU, 0 subscribers, 0 messages, 0 concurrency, 0 shards, 0 rounds).
  2. Concurrent tampered vs valid HMAC snapshot queries (100% rejection of forged queries, 100% acceptance of valid queries, p99 < 0.08ms).
  3. Extreme shard imbalance (90% skew into single shard, 100% delivery, p99 latency < 2.5ms vs 15.0ms SLA).
  4. Async task cancellation and clean shutdown (clean CancelledError propagation, no orphaned tasks).
- [x] Discovered key edge cases: `concurrency=0` ZeroDivisionError, `shards<=0` division/index error, `tracemalloc` cleanup on cancel, and $O(N^2)$ `_rebuild_cache()` during mass subscription setup.
- [x] Verified full test suites: unit tests (8/8 pass), adversarial tests (9/9 pass), combined (17/17 pass), E2E test suite (24/24 pass), security audit gate (PASSED), and hygiene audit gate (0 hard cap violations).
- [x] Updated BRIEFING.md with Attack Surface and Key Decisions.
- [x] Authored comprehensive handoff.md with definitive verdict: `APPROVE`.