# BRIEFING — 2026-10-01T21:05:00Z

## Mission
Investigate client-side tile-level collision checking and 2-axis sliding physics for Milestone 3 (R3: Tile-Level Collision & Boss Gate Logic).

## 🔒 My Identity
- Archetype: explorer
- Roles: investigation, synthesis
- Working directory: c:\Projects\FreeExile\.agents\teamwork\explorer_m3_1
- Original parent: bc45a740-aa86-45b5-8706-381960281bc6 (orchestrator_1 / af73d9ec-d3ff-4501-b986-47b632c5d073)
- Milestone: Milestone 3 (Pack Affixes & Modifiers Explorer)
- Current Dispatch Parent: 1cc48fc5-ce57-4f48-8964-24cab4bfcacc (orchestrator_11)
- Subtask: Explorer M3 1 (Collision Architecture & 2-Axis Sliding Physics)

## 🔒 Key Constraints
- Read-only investigation — do NOT implement
- Zero modification to project code files (only write inside .agents/teamwork/explorer_m3_1/)
- Follow 5-component handoff report structure
- Use send_message to report back to parent
- client/webapp/js/engine/collision_engine.js must stay <= 320 lines (Soft cap 350, Hard cap 500 lines)
- Zero dynamic allocations inside hot collision checks (hot path 120 FPS)
- Preserve 2-axis wall-sliding kinematics

## Current Parent
- Conversation ID: 1cc48fc5-ce57-4f48-8964-24cab4bfcacc
- Updated: 2026-10-01T21:05:00Z

## Investigation State
- **Explored paths**:
  - `client/webapp/js/engine/collision_engine.js` (current 218 lines: boundary clamp, water hazard, prop footprint checks, sliding)
  - `client/webapp/js/engine/tile_grid_loader.js` (binary map loader, `window.currentMapGrid`, `window.getTileAt(tx, ty)`)
  - `client/webapp/js/engine/tile_map_renderer.js` (tile palettes, chunk caching, rendering)
  - `client/webapp/js/engine/canvas_renderer.js` (game loop, `resolveMovementWithSliding` call site, dodge roll i-frame)
  - `client/webapp/js/engine/combat_skills.js` (blink / dash skill position validation)
  - `server/world/map_data_types.py` (canonical 20-code TileType enum and passability rules)
  - `server/world/wilderness_map_generator.py` (tile map generator and boss gate placement)
  - `server/world/zone_engine.py` (server-side spawn validation and boundary handling)
  - `docs/client/ISOMETRIC_COLLISION_BOUNDARIES_AND_PROP_SYSTEM.md` (collision architecture and bitmask specs)
  - `tests/e2e/test_poe2_map_system_e2e.py` (81 passing tests, passability assertions)
  - `tests/unit/test_challenger_tile_grid_stress.js` (out-of-bounds, mutation, and throughput tests)
- **Key findings**:
  - Code Discrepancy Identified: Dispatch mentions `WALL (1), CHASM (4), WATER (5), locked BOSS_GATE (15)`, whereas canonical repo schema (`map_data_types.py`, `tile_grid_loader.js`, `test_poe2_map_system_e2e.py`) defines `VOID=0, FLOOR=1, WALL=2, CHASM=9, BOSS_GATE=10, WATER=19`. If 1 was blocked in standard map, FLOOR would be impassable. Formulated dual-mode passability table resolving both standards.
  - Zero Dynamic Allocation: `resolveMovementWithSliding` currently creates new `{ wx, wy, isSliding }` objects every frame; formulated module-level static result cache `SLIDE_RESULT` to achieve 0-heap allocation at 120 FPS.
  - Continuous Circle-AABB Intersection: For radius $r \in [0.2, 0.4]$, player overlaps at most $2 \times 2 = 4$ tiles. Formulated closed-form circle-AABB clamping distance check that is faster and more accurate than 8-point radial sampling.
  - Dodge/Blink Chasm Bypass: Formulated mid-roll `isDodge` chasm passability and `canBypassChasm` endpoint verification ensuring player cannot land in chasm.
  - Boss Gate Integration: Seamlessly hooks into `window.bossGateBreached` / `setTileAt(gx, gy, 1)`.
- **Unexplored areas**: None within collision engine and 2-axis sliding scope.

## Key Decisions Made
- Reconciled tile ID discrepancies by providing high-performance $O(1)$ lookup table supporting standard 20-code schema with fallback/toggle for dispatch compact schema.
- Recommended Circle-AABB 4-tile clamping over 8-point sampling to prevent corner tunneling while cutting tile lookups by 50%.
- Proposed module-level reusable object `SLIDE_RESULT` for `resolveMovementWithSliding` to fulfill 0-allocation mandate.
- Designed `canBypassChasm` helper to prevent dodge rolls from getting stranded inside void/chasm.

## Artifact Index
- DISPATCH.md — incoming dispatch log
- BRIEFING.md — persistent situational awareness
- progress.md — liveness heartbeat
- report.md — comprehensive technical investigation report
- handoff.md — final 5-component handoff report (file:///c:/Projects/FreeExile/.agents/teamwork/explorer_m3_1/handoff.md)