# BRIEFING — 2026-10-01T20:47:02Z

## Mission
Empirical stress-testing of procedural tile map cache, culling, and rendering performance to detect thrashing, memory leaks, and performance regressions.

## 🔒 My Identity
- Archetype: EMPIRICAL CHALLENGER
- Roles: critic, specialist
- Working directory: c:\Projects\FreeExile\.agents\teamwork\challenger_m2_fix_1
- Original parent: 1cc48fc5-ce57-4f48-8964-24cab4bfcacc
- Milestone: Milestone M2 Fix 1 (Cache & Thrashing Stress Challenger)
- Instance: 1 of 1

## 🔒 Key Constraints
- Review-only — do NOT modify implementation code
- Must run verification and stress harnesses empirically; zero blind trust in worker logs
- If cannot reproduce a bug empirically, it does not count
- Verdict must be explicitly APPROVE or REQUEST_CHANGES

## Current Parent
- Conversation ID: 1cc48fc5-ce57-4f48-8964-24cab4bfcacc
- Updated: 2026-10-01T20:47:02Z

## 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_challenger_lru_thrashing_stress.js`
- **Interface contracts**: `c:\Projects\FreeExile\.agents\teamwork\ORIGINAL_REQUEST.md` (R2), `c:\Projects\FreeExile\GEMINI.md`
- **Review criteria**: 0 re-bakes on static camera, <=8 draw calls peak / <=6 avg, FPS >= 30, RAM within budget, 10,000 rapid pan stress stability, dirty chunk invalidation integrity.

## Attack Surface
- **Hypotheses tested**:
  - Does stationary camera at (30, 30) or (50, 50) trigger any evictions or re-bakes? Confirmed: 0 re-bakes over 50 static frames.
  - Does rapid panning (10,000 frames) thrash the LRU pool or cause memory bloat? Confirmed: 0 canvas leaks, 5.21 avg blits, max 8 blits.
  - Does dynamic dirty marking (`markChunkDirty`) properly trigger re-bake without cascade thrashing? Confirmed: dirty chunks re-bake once and immediately stabilize.
  - Are draw calls strictly bounded by SAT diamond culling? Confirmed: peak draw calls = 8 blits.
- **Vulnerabilities found**: None in target scope. 8-slot cache is fully invariant and stable across mobile portrait/landscape.
- **Untested angles**: Large desktop viewports (1024x768) have 10 visible chunks, which is out-of-scope for the mobile 390x844 target but noted in caveats.

## Loaded Skills
- None loaded.

## Key Decisions Made
- [2026-10-01T20:47:02Z]: Initialized challenger briefing.
- [2026-10-01T20:49:05Z]: Authored and executed dedicated empirical stress harness `tests/unit/test_challenger_lru_thrashing_stress.js` covering stationary (30,30), (50,50), boundaries, 10,000 pan frames, dirty invalidations, and viewports.
- [2026-10-01T20:50:00Z]: Verified all benchmark metrics and test suites pass with 100% success. Rendered verdict: APPROVE.

## Artifact Index
- `c:\Projects\FreeExile\.agents\teamwork\challenger_m2_fix_1\DISPATCH.md` — Dispatch assignment
- `c:\Projects\FreeExile\.agents\teamwork\challenger_m2_fix_1\BRIEFING.md` — Situational awareness
- `c:\Projects\FreeExile\.agents\teamwork\challenger_m2_fix_1\progress.md` — Liveness & execution progress
- `c:\Projects\FreeExile\tests\unit\test_challenger_lru_thrashing_stress.js` — Empirical challenger stress suite
- `c:\Projects\FreeExile\.agents\teamwork\challenger_m2_fix_1\handoff.md` — Final handoff report