# Implementation Report — Video Pre-Write Removal

**Date**: 2026-04-01
**Tasks**: 1
**Batches**: 1
**Total Complexity**: 2 points

## Summary

Removed redundant synchronous video pre-writes in the `/detect` endpoint. Videos are now written to disk exactly once by `inference.pyx`'s background writer thread, concurrently with frame detection.

## Tasks Completed

| Task | Name | Complexity | Status |
|------|------|-----------|--------|
| AZ-177 | remove_redundant_video_prewrite | 2 | Done |

## Changes

| File | Change |
|------|--------|
| src/main.py | Auth'd path: wrap file write with `if kind == "image"` so videos skip pre-write |
| src/main.py | Non-auth'd path: remove `open().write()` after `mkstemp` — inference handles the write |

## Test Results

18/18 tests passed. 4 new tests added:
- `test_auth_video_storage_path_opened_wb_once`
- `test_non_auth_temp_video_opened_wb_once_and_removed`
- `test_auth_image_still_writes_once_before_detect`
- `test_video_writer_runs_in_separate_thread_from_executor`