# Progress — explorer_m1_fix_1

Last visited: 2026-10-01T19:51:30Z

## Status
- [x] Initialized DISPATCH.md and BRIEFING.md
- [x] Analyzed challenger feedback from `challenger_m1_2/handoff.md` and user requirements from `ORIGINAL_REQUEST.md` (2026-10-01T19:19:13Z)
- [x] Inspected `client/webapp/js/engine/tile_grid_loader.js`, `server/world/map_binary_serializer.py`, and test suites
- [x] Empirically reproduced and analyzed all 3 defects:
  1. `getTileAt` returning `undefined` on `NaN`/`undefined`/`null`/`string`
  2. `ReferenceError: window is not defined` on un-shimmed Node.js require
  3. Buffer truncation silent acceptance on 0x0 map with fake POI count
- [x] Formulated mathematical root causes and logic chain
- [x] Designed exact remediation implementation in `proposed_tile_grid_loader.js` (162 lines <= 350 soft cap)
- [x] Verified independent Node.js harness passing all assertions
- [x] Benchmarked lookup throughput (39.75 MQPS, 40x requirement) and memory footprint
- [x] Writing comprehensive 5-component `handoff.md`
- [ ] Send completion message to parent