# BRIEFING — 2026-10-01T20:26:00Z

## Mission
Empirically challenge `client/webapp/js/engine/tile_map_renderer.js` and `tools/perf/map_render_benchmark.js`:
- Verify avg FPS >= 30, draw calls <= 4-6 chunk blits, canvas RAM <= 8.02 MB.
- Stress test LRU cache over 10,000 pan frames with dirty chunk invalidations.
- Run pytest tests/e2e/test_poe2_map_system_e2e.py -v.
- Provide definitive verdict (APPROVE or REQUEST_CHANGES) with rigorous empirical data.

## 🔒 My Identity
- Archetype: empirical-challenger
- Roles: critic, specialist
- Working directory: c:\Projects\FreeExile\.agents\teamwork\challenger_m2_1
- Original parent: 407bb748-17c2-4835-a44a-d76c8299151f
- Milestone: Milestone 2 (R2: Waypoint Safe Radius & Healing)
- Instance: 1 of 1
- Current parent: 1cc48fc5-ce57-4f48-8964-24cab4bfcacc
- Current mission: Milestone 2 (R2: Tile-Based Rendering & LRU Cache Stress)

## 🔒 Key Constraints
- Review-only — do NOT modify implementation code
- Empirical verification mandatory — run tests directly, do not trust claims
- .agents/teamwork/ holds only metadata (no code/tests/data files)
- Canvas RAM <= 8.02 MB hard limit for 120x90 grid
- Average FPS >= 30.0 under stress
- Draw calls <= 4-6 chunk blits per frame
- Zero allocations in hot path rendering loop

## Current Parent
- Conversation ID: 1cc48fc5-ce57-4f48-8964-24cab4bfcacc
- Updated: 2026-10-01T20:26:00Z

## Review Scope
- **Files to review**:
  - `client/webapp/js/engine/tile_map_renderer.js`
  - `tools/perf/map_render_benchmark.js`
  - `tools/perf/stress_test_lru_cache.js`
  - `tests/e2e/test_poe2_map_system_e2e.py`
  - `tests/unit/test_wilderness_map_generator.py`
- **Interface contracts**: `c:\Projects\FreeExile\.agents\teamwork\ORIGINAL_REQUEST.md` (section `## 2026-10-01T19:19:13Z` - R2)
- **Review criteria**: Empirical correctness, performance thresholds, LRU cache behavior, memory leak absence, test suite passes.

## Key Decisions Made
- Executed `tools/perf/map_render_benchmark.js`: observed synthetic pass due to camera oscillation restricted to corner (10, 10).
- Created empirical stress harness `tools/perf/stress_test_lru_cache.js` testing 10,000 frames across all 48 chunks, stationary camera caching, and adversarial inputs.
- Discovered critical LRU cache thrashing bug: at stationary camera (30, 30), 8 chunks are visible simultaneously, but only 4 slots exist in cache, causing 5.0 chunk re-bakes EVERY SINGLE FRAME.
- Discovered draw call ceiling violation: maximum draw calls reach 8 chunk blits per frame (target <= 4-6 blits).
- Ran Python test suites: `test_poe2_map_system_e2e.py` (37 tests) and `test_wilderness_map_generator.py` (24 tests) PASSED 100%.
- Formulated final verdict: **REQUEST_CHANGES**.

## Artifact Index
- `c:\Projects\FreeExile\.agents\teamwork\challenger_m2_1\DISPATCH.md` — Incoming dispatch log
- `c:\Projects\FreeExile\.agents\teamwork\challenger_m2_1\BRIEFING.md` — Agent state and briefing
- `c:\Projects\FreeExile\.agents\teamwork\challenger_m2_1\progress.md` — Liveness and progress heartbeat
- `c:\Projects\FreeExile\.agents\teamwork\challenger_m2_1\handoff.md` — Final empirical challenge report
- `c:\Projects\FreeExile\tools\perf\stress_test_lru_cache.js` — Automated empirical stress test harness

## Attack Surface
- **Hypotheses tested**:
  - Canvas pool invariance (exactly 4 canvas instances): CONFIRMED (PASS).
  - Canvas RAM budget <= 8.02 MB: CONFIRMED (8.010 MB, PASS).
  - Average FPS >= 30.0 under benchmark: CONFIRMED (43,468 FPS in Node mock context, PASS).
  - Python E2E & unit test suites pass: CONFIRMED (PASS).
  - LRU cache preserves cached chunks when camera is stationary: REJECTED (FAIL: 5 bakes/frame at (30, 30)).
  - Draw calls per frame <= 4-6 chunk blits: REJECTED (FAIL: peak 8 blits/frame).
- **Vulnerabilities found**:
  - Critical: LRU cache thrashing when >4 chunks visible (occurs across 86.6% of map on iPhone portrait and 79% on landscape).
  - Medium: Draw call spike to 8 blits per frame due to axis-aligned bounding box culling on isometric diamonds.
  - Medium: Benchmark bias in `map_render_benchmark.js` masking thrashing by only testing corner (10, 10).
- **Untested angles**: WebGL/Metal hardware rasterization on physical device (mock context validated).

## Loaded Skills
- None explicitly loaded.