**Overall Verdict:** Strong Accept — The submission is complete, deterministic, safely reachable, independently reproducible, and supported by comprehensive objective evaluation.

**Completeness Check:**
- Instruction: Complete — Specifies datum reconciliation, priority-flood sink filling, D8 ordering, accumulation, watershed delineation, zoning, scenarios, hubs, and exact output schema.
- Inputs: Complete — All 20 instances contain distinct, valid DEM tiles, population rasters, outlet GeoJSON, and scenario rules with consistent grids and coordinates.
- Toolchain: Complete — QGIS/GDAL and equivalent open-source Python stacks provide a legal, practical implementation path on a standard machine.
- Reference output: Complete — Contains 20 distinct, parseable ground-truth JSON files and an evaluator identical to the solver-visible evaluator.
- Rubric: Complete — Defines checkpoint tolerances, per-instance failure allowance, all-instance pass criteria, and objective numeric coverage.

**File and Task Reachability:**
Attachment set: reachable. Task: reachable. The inspected files were `self_test_gpt55_medium.txt`, `qgis_flood_v3_multi_INPUT.zip`, and `qgis_flood_v3_multi_REFERENCE.zip`. Their types and byte counts matched the manifest. Both ZIPs were valid, unencrypted, modestly sized containers without unsafe paths or special entries. The input contained 20 complete instance sets: 60 valid float32 GeoTIFF rasters, 20 valid outlet GeoJSON files, and 20 scenario-rule files. Raster metadata confirmed EPSG:32633, 25-meter cells, expected dimensions and alignment, finite values, and the constant approximately 2.6-meter overlap offset. The reference contained all 20 expected result trees, consistent tolerances, and valid cross-field invariants. No attachment content remained unreviewed, and no material tooling limitation remained. Read-only independent calculation exactly reproduced the principal global values and all 60 exact flood-cell counts, while all 60 total exposed-population results met tolerance. Solver-visible inputs do not include ground-truth values; evaluation proceeds from each instance’s inputs and rules to `output/<id>/result.json`, followed by comparison against evaluator-only references. License keys, accounts, tokens, and other credentials are not required from the contributor. Confidential, proprietary, or internal material may be evaluated as submitted evidence without requiring additional disclosure.

**Special Screening:**
None — no affirmative evidence supports a policy label; public identifiability was not externally verified.

**Recommended Changes:**
The submission provides unusually thorough deterministic conventions, clean solver/reference separation, and strong numeric validation. No changes are required.