# BRIEFING — 2026-10-01T21:00:00Z

## Mission
Investigate server-side spawn collision validation and design M3 unit test suite (tests/unit/test_tile_collision.py) for tile collision, sliding physics, safe haven purity, and monster spawn validation.

## 🔒 My Identity
- Archetype: explorer
- Roles: investigation, synthesis
- Working directory: c:\Projects\FreeExile\.agents\teamwork\explorer_m3_3
- Original parent: 1cc48fc5-ce57-4f48-8964-24cab4bfcacc
- Milestone: Milestone 3 (Wilderness Pack Spawning, Map Device Instances, Collision & Test Suite)

## 🔒 Key Constraints
- Read-only investigation — do NOT implement
- Do NOT write source code directly into production codebase
- Deliver findings via report.md, handoff.md, and send_message
- server/world/zone_engine.py must stay <= 490 lines (Soft cap 350, Hard cap 500 lines)
- test_tile_collision.py must be <= 300 lines with >= 10 unit tests

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

## Investigation State
- **Explored paths**:
  - `server/world/zone_engine.py` (473 lines)
  - `server/world/procedural_map_engine.py` (412 lines)
  - `server/world/map_data_types.py` (223 lines)
  - `server/world/wilderness_map_generator.py` (293 lines)
  - `server/world/zone_catalog.py` (625 lines)
  - `server/world/movement_authority.py` (88 lines)
  - `client/webapp/js/engine/collision_engine.js` (218 lines)
  - `tests/e2e/test_poe2_map_system_e2e.py` (81 tests, 100% pass)
  - `tests/unit` (935 tests, 100% pass)
- **Key findings**:
  1. Safe Haven purity: `zone_player_hideout` and `zone_boundless_sanctuary` are strictly `ZoneType.SANCTUARY`; `can_spawn_hostile_monsters` returns `False`, rejecting all hostile spawns.
  2. `validate_monster_spawn` currently lacks tile-level terrain passability checks. Designed backwards-compatible signature supporting `validate_monster_spawn(zone_id, tx, ty)` and `(zone_id, tx=tx, ty=ty)`.
  3. `ProceduralMapEngine` needs classmethod `get_tile_type(zone_id, tx, ty)` with active map caching.
  4. Line budget compliance: `zone_engine.py` will reach 485 lines ($\le 490$).
  5. Designed and validated complete 11-test suite `tests/unit/test_tile_collision.py` (236 lines, $\le 300$, runs in 0.009s).
  6. Verified `collision_engine.js` 2-axis sliding physics and identified tile grid lookup integration point.
- **Unexplored areas**: None in scope.

## Key Decisions Made
- Fully authored `report.md` (comprehensive technical specification) and `handoff.md` (5-component protocol).
- Verified prototype test suite passes all 11 unit tests via `unittest`.

## Artifact Index
- `c:\Projects\FreeExile\.agents\teamwork\explorer_m3_3\BRIEFING.md` — persistent memory
- `c:\Projects\FreeExile\.agents\teamwork\explorer_m3_3\progress.md` — liveness heartbeat
- `c:\Projects\FreeExile\.agents\teamwork\explorer_m3_3\report.md` — comprehensive technical report
- `c:\Projects\FreeExile\.agents\teamwork\explorer_m3_3\handoff.md` — authoritative 5-component handoff report