# Implementation Tasks

## 1. Backend Configuration
- [x] 1.1 Add `DIFY_STT_API_KEY` to `backend/app/config.py`
- [x] 1.2 Add `DIFY_STT_API_KEY` to `backend/.env.example`

## 2. Sidecar VAD Segmentation
- [x] 2.1 Add `segment_audio` action handler in `sidecar/transcriber.py`
- [x] 2.2 Implement VAD-based audio segmentation using Silero VAD
- [x] 2.3 Support max chunk duration (default 5 minutes)
- [x] 2.4 Support minimum silence threshold (default 500ms)
- [x] 2.5 Export chunks as WAV files to temp directory
- [x] 2.6 Return segment metadata (paths, timestamps)

## 3. Backend API Endpoint
- [x] 3.1 Create `POST /api/ai/transcribe-audio` endpoint in `backend/app/routers/ai.py`
- [x] 3.2 Implement multipart file upload handling (max 500MB)
- [x] 3.3 Validate audio file format (MP3, WAV, M4A, WebM, OGG)
- [x] 3.4 Save uploaded file to temp directory
- [x] 3.5 Call sidecar `segment_audio` for VAD chunking
- [x] 3.6 For each chunk: call Dify STT API (`/v1/audio-to-text`)
- [x] 3.7 Implement retry with exponential backoff for Dify errors
- [x] 3.8 Concatenate chunk transcriptions
- [x] 3.9 Clean up temp files after processing
- [x] 3.10 Return final transcript with metadata

## 4. Frontend UI
- [x] 4.1 Add "Upload Audio" button in meeting-detail.html (next to recording controls)
- [x] 4.2 Implement file input with accepted audio formats
- [x] 4.3 Add upload progress indicator (upload phase)
- [x] 4.4 Add transcription progress indicator (chunk X of Y)
- [x] 4.5 Show confirmation dialog if transcript already has content
- [x] 4.6 Display transcription result in transcript area
- [x] 4.7 Handle error states (file too large, unsupported format, API error)

## 5. API Service
- [x] 5.1 Add `transcribeAudio()` function to `client/src/services/api.js`
- [x] 5.2 Implement FormData upload with progress tracking
- [x] 5.3 Handle streaming response for chunk progress

## 6. Testing
- [ ] 6.1 Test sidecar VAD segmentation with various audio lengths
- [ ] 6.2 Test with various audio formats (MP3, WAV, M4A, WebM, OGG)
- [ ] 6.3 Test with large file (>100MB) to verify chunking
- [ ] 6.4 Test error handling (invalid format, Dify timeout, API error)
- [ ] 6.5 Verify transcript displays correctly after upload
- [ ] 6.6 Test chunk concatenation quality (no missing content at boundaries)