# Progress — Explorer M1 Fix 2

**Last visited**: 2026-10-01T19:52:00Z
**Current status**: Investigation complete, empirical verification complete, writing handoff report.

## Completed Steps
1. Appended new dispatch message to `DISPATCH.md`.
2. Verified `ORIGINAL_REQUEST.md` (section `## 2026-10-01T19:19:13Z`) and `challenger_m1_2/handoff.md`.
3. Executed baseline test suites:
   - `pytest tests/unit/test_wilderness_map_generator.py` (20 passed in 0.60s)
   - `pytest tests/unit/test_challenger_m1_2_binary_compat.py` (15 passed in 27.03s)
   - `node tests/unit/test_challenger_tile_grid_stress.js` (45 passed, 3 failed)
4. Identified root causes for why `test_wilderness_map_generator.py` had false confidence (masked window ReferenceError via `global.window = {}`, missed `NaN`/OOB queries, missed truncation and in-place mutation tests).
5. Implemented standalone verification test harness `test_complementary_cases_draft.py`.
6. Verified negative baselines against current `tile_grid_loader.js` (4 failures).
7. Created proposed remediation `proposed_tile_grid_loader.js` and verified positive baseline (6/6 tests passed in 0.70s).
8. Formulated clean, compact additions to `tests/unit/test_wilderness_map_generator.py` (keeping file length at 341 lines <= 350 soft cap).
9. Generated `.patch` files and replacement artifacts.
10. Updated `BRIEFING.md`.
11. Preparing final 5-component `handoff.md`.