led2/.planning/phases/06-ai-sync/06-01-SUMMARY.md

phase, plan, subsystem, tags, dependency_graph, tech_stack, key_files, decisions, metrics, requirements_satisfied

phase	plan	subsystem	tags	dependency_graph	tech_stack	key_files	decisions	metrics	requirements_satisfied
06-ai-sync	01	audio-input	youtube yt-dlp sse streaming frontend transport-bar	requires provides affects youtube-audio-download sse-progress-stream yt-dlp-dependency lightsync/api/audio.py lightsync/frontend	added patterns yt-dlp>=2025.0.0 anthropic>=0.40.0 asyncio subprocess SSE ReadableStream terminal progress bar	created modified pyproject.toml docker-compose.prod.yml lightsync/api/audio.py lightsync/frontend/index.html lightsync/frontend/app.js lightsync/frontend/style.css	sys.executable -m yt_dlp used to avoid PATH issues in Docker --newline flag required for line-by-line progress parsing from yt-dlp yt_%(id)s.%(ext)s output template ensures predictable filenames ANTHROPIC_API_KEY wired with empty default so container starts without it Beat analysis runs post-download (same as upload path) for identical audio pipeline entry	duration completed tasks_completed files_changed ~8 min 2026-04-07 3 6	AUD-02

Phase 06 Plan 01: YouTube Audio Loading via yt-dlp Summary

One-liner: YouTube URL download via yt-dlp subprocess with SSE progress streaming, terminal-style block progress bar, and automatic audio pipeline entry after download.

What Was Built

Added full YouTube audio loading capability to the LightSync transport bar:

1. Dependencies (Task 1): Added yt-dlp>=2025.0.0 and anthropic>=0.40.0 to pyproject.toml. Wired ANTHROPIC_API_KEY env var (empty default) in docker-compose.prod.yml. Both packages are importable inside the running container.

2. Backend endpoint (Task 2): New POST /api/audio/fetch endpoint in lightsync/api/audio.py that:

   • Accepts {url: string} JSON body
   • Spawns yt-dlp subprocess via sys.executable -m yt_dlp (avoids PATH issues in Docker)
   • Parses progress with PROGRESS_RE = re.compile(r'\[download\]\s+([\d.]+)%') using --newline flag
   • Streams SSE progress events with media_type="text/event-stream"
   • Runs beat analysis on completion and caches in app.state.beats
   • Returns {type: "done", path, filename} event on success

3. Frontend UI (Task 3): Added to transport bar in index.html:

   • Text input #yt-url with placeholder "YOUTUBE URL"
   • #btn-fetch button
   • #yt-progress span for terminal-style progress display

   In app.js:

   • fetchWithProgress() function using fetch ReadableStream reader for SSE
   • renderProgressBar() rendering DOWNLOADING ████████░░░░░░░░░░░░ 42% style
   • FETCH button handler with D-02 disable-during-download
   • Auto-load into #player after download (identical to upload pipeline)

   In style.css: .yt-url-input and .yt-progress styles using existing CSS variables, flat/monospace/no border-radius.

Commits

Task	Commit	Description
1	165cdb6	feat(06-01): add yt-dlp and anthropic dependencies
2	d58ea8c	feat(06-01): add YouTube download endpoint with SSE progress streaming
3	dca1cb8	feat(06-01): add YouTube URL input with terminal progress bar

Deviations from Plan

None - plan executed exactly as written.

Known Stubs

None - YouTube download is fully wired end-to-end.

Self-Check: PASSED

• pyproject.toml contains yt-dlp>=2025.0.0 and anthropic>=0.40.0
• docker-compose.prod.yml contains ANTHROPIC_API_KEY
• lightsync/api/audio.py contains async def fetch_youtube, PROGRESS_RE, media_type="text/event-stream", class YouTubeFetchRequest, analyze_async(filename)
• lightsync/frontend/index.html contains id="yt-url", id="btn-fetch", id="yt-progress"
• lightsync/frontend/app.js contains fetchWithProgress, renderProgressBar, /api/audio/fetch, urlInput.disabled = true, audio.src
• lightsync/frontend/style.css contains .yt-url-input, .yt-progress
• All 3 task commits exist: 165cdb6, d58ea8c, dca1cb8