# Codex Phase 6 Prompt — QA/QC Engine

Implement detection/reference QA.

## Goals

- Compare detection polygons against reference polygons.
- Compute IoU-based matches.
- Calculate precision, recall, F1.
- Persist quality check result.
- Return false positives and false negatives.

## Rules

- Default IoU threshold: 0.5.
- One detection can match at most one reference.
- Use greedy matching by highest IoU for V1.
- Document limitations.

## Done when

- Deterministic fixture test passes.
- QA endpoint returns metrics and findings.
- Frontend QA panel can display the result.