# Codex Module Contract — QA/QC Foundation

Build deterministic QA/QC using fixture GeoJSON files before real AI integration.

## Input

- predicted polygon layer
- reference polygon layer
- IoU threshold, default 0.5

## Required Metrics

- true positives
- false positives
- false negatives
- precision
- recall
- f1
- mean_iou for matched pairs

## Required Outputs

- summary metrics JSON
- matched pairs list
- false positives GeoJSON
- false negatives GeoJSON

## Required Backend

- QA service with pure functions
- API endpoint to run QA for two stored layers or fixture mode
- persisted quality_check record

## Required Frontend

- QA run form
- threshold input
- metrics cards
- map layers for FP/FN
- explanation of IoU threshold

## Required Tests

- golden fixture test with deterministic counts
- zero denominator test
- invalid geometry test

## Forbidden

- presenting confidence as accuracy
- changing IoU formula
- computing area in EPSG:4326 degrees