# Codex Module Contract — Detection Boundary

Build the detection architecture so real YOLO can be added safely, but V1 may use deterministic fixture mode first.

## Required Concepts

- model registry entry
- analysis run
- detection result
- output layer
- model mode: `fixture`, `stub`, `real`

## Required Backend

- detection service interface
- fixture detection provider
- analysis run persistence
- detection persistence
- GeoJSON export of detections

## Required Frontend

- detection run form
- model selector
- confidence threshold
- mode indicator
- results table
- map overlay

## Required Tests

- fixture detection produces stable number of detections
- output includes class, confidence and geometry
- response clearly states mode

## Forbidden

- fake real model claims
- silent fallback from real to fixture
- detections without geospatial provenance