# Progress: Milestone M5 Encounter Zone Architecture

**Worker**: `worker_m5_1`
**Last visited**: 2026-10-01T22:34:00Z
**Status**: COMPLETED

## Steps:
- [x] Read DISPATCH.md, ORIGINAL_REQUEST.md (R5), explorer reports (1, 2, 3)
- [x] Initialize BRIEFING.md and progress.md
- [x] Implement `client/webapp/js/engine/grid_pathfinder.js` (300 lines <= 320 lines)
- [x] Update `client/webapp/js/data/wilderness_zone_packs.js` (298 lines <= 350 lines, preserved existing keys)
- [x] Update `client/webapp/js/engine/monster_pack_system.js` (277 lines <= 350 lines)
- [x] Update `client/webapp/js/engine/ambush_trigger_system.js` (143 lines <= 300 lines)
- [x] Update `client/webapp/js/engine/monster_system.js` (476 lines <= 480 lines target, strict <= 490 cap)
- [x] Update `client/webapp/js/engine/boss_gate_controller.js` (197 lines <= 200 lines)
- [x] Update `client/webapp/js/engine/world_renderer.js` (475 lines <= 490 lines)
- [x] Update `client/webapp/index.html` (198 lines <= 200 lines, mounted grid_pathfinder.js before monster_system.js)
- [x] Update `tests/unit/test_encounter_zones.py` (259 lines <= 300 lines, 12 genuine hybrid tests)
- [x] Run test suites and verify all passing with zero regressions:
  - `pytest tests/unit/test_encounter_zones.py -v`: 12/12 PASSED
  - `pytest tests/unit/test_waypoint_safe_radius.py -v`: 17/17 PASSED
  - `pytest tests/unit/test_fog_and_minimap.py -v`: 14/14 PASSED
  - `pytest tests/unit/test_tile_collision.py -v`: 11/11 PASSED
  - `pytest tests/unit/test_mobile_webapp_config.py -v`: 15/15 PASSED
  - `pytest tests/unit/test_monster_poise_and_leash.py -v`: 10/10 PASSED
  - `pytest tests/e2e/test_poe2_map_system_e2e.py -v`: 81/81 PASSED
  - `node tools/perf/map_render_benchmark.js`: PASSED (0 stationary re-bakes, 163K+ FPS, <16.01MB RAM)
  - `pytest tests/unit/ -q`: 1055/1055 PASSED
- [x] Run hygiene check (`python tools/lint/check_code_and_doc_hygiene.py --strict`): all modified files clean and strictly within caps
- [x] Produce handoff.md and notify parent