# Error Codes Runbook

Purpose: provide consistent, AI-readable error categories for faster autonomous debugging.

## Format

Use codes in this format: `<SUBSYSTEM>-<CATEGORY>-<ID>`

Examples:

- `BE-EXPORT-001`
- `FE-WAVEFORM-002`
- `HOST-BRIDGE-003`

## Backend (FastAPI / Services)

### Export

- `BE-EXPORT-001`: Export request validation failed.
  - Symptoms: HTTP 400, missing/invalid ranges.
  - Likely causes: malformed payload, empty segments.
  - First checks: request body shape, keep/mute/gain ranges.

- `BE-EXPORT-002`: FFmpeg command failed.
  - Symptoms: HTTP 500, stderr contains filter/codec error.
  - Likely causes: invalid filter chain, unsupported codec/container.
  - First checks: generated FFmpeg args, source media codec, target format.

- `BE-EXPORT-003`: Caption burn-in/subtitle generation failed.
  - Symptoms: burn-in export fails while plain export works.
  - Likely causes: ASS generation issue, subtitle path/temp file cleanup race.
  - First checks: ASS file generation, temp file lifecycle.

### Transcription

- `BE-TRANSCRIBE-001`: Model unavailable or download failure.
  - Symptoms: transcription never starts or exits early.
  - Likely causes: missing model, network/cache issue.
  - First checks: model cache path, ensure-model logs.

- `BE-TRANSCRIBE-002`: Inference pipeline runtime failure.
  - Symptoms: mid-run crash, partial output.
  - Likely causes: CUDA/CPU mismatch, unsupported media, resource exhaustion.
  - First checks: environment, GPU availability, media decoding logs.

### Audio / Waveform

- `BE-AUDIO-001`: Waveform endpoint failed.
  - Symptoms: waveform panel shows unavailable/error.
  - Likely causes: decode error, invalid file path, unsupported media input.
  - First checks: `audio/waveform` response body, file existence, FFmpeg decode path.

## Frontend (React)

### Timeline / Zones

- `FE-TIMELINE-001`: Zone interaction state inconsistency.
  - Symptoms: cannot drag/select/delete zones predictably.
  - Likely causes: stale selection/editing state, hidden/selected mismatch.
  - First checks: zone mode flags, selectedZone state transitions.

- `FE-TIMELINE-002`: Visibility filter mismatch.
  - Symptoms: hidden zones still interactive or selected.
  - Likely causes: hit-testing ignores visibility flags.
  - First checks: hit-test filters and selected-zone reset logic.

### Media UI

- `FE-WAVEFORM-001`: Waveform fetch failed.
  - Symptoms: warning banner with URL/error.
  - Likely causes: backend unavailable, bad path encoding, CORS/proxy issue.
  - First checks: backend health endpoint, waveform URL, network tab logs.

- `FE-PROJECT-001`: Project load mismatch.
  - Symptoms: loaded media/transcript differs from saved data.
  - Likely causes: schema drift, fallback URL mismatch.
  - First checks: project schema fields, loadVideo/loadProject URL parity.

## Host / Bridge (Tauri)

- `HOST-BRIDGE-001`: Desktop API bridge unavailable.
  - Symptoms: open/save/transcribe actions no-op or throw.
  - Likely causes: bridge init error, host command mismatch.
  - First checks: bridge initialization, command names, runtime environment.

- `HOST-WEBKIT-001`: Linux WebKit startup/render regression.
  - Symptoms: noisy startup errors, UI load issues.
  - Likely causes: CSP/font regressions, unsupported protocol calls.
  - First checks: CSP config, remote font usage, bridge fallback behavior.

## Logging Guidance

When raising errors, include:

1. Error code.
2. Human message.
3. Correlation/request id.
4. Relevant paths/ids (sanitized).
5. Suggested first-check hints.

Example structured payload:

```json
{
  "code": "BE-EXPORT-002",
  "message": "FFmpeg export failed",
  "requestId": "exp_20260415_001",
  "context": {
    "format": "mp4",
    "mode": "reencode"
  }
}
```