[mkaand]

FINAL FEATURE

Adds source-quality-preserving adaptive YouTube preparation. PR remains OPEN and UNMERGED pending sequential physical acceptance.

Behavior and security

• High-resolution adaptive outputs are detected through 2160p when the public source offers them. Existing progressive combined formats, including the 360p path, remain direct; adaptive outputs pair a compatible audio track and prepare asynchronously.
• FFmpeg uses validated local inputs and stream copy only; no default H.264 transcode, no silent truncation. MP4 is paired with AAC; WebM is paired with Opus/Vorbis.
• Updated yt-dlp 2026.07.04 to 2026.08.19 because current Android/Android VR adaptive URLs require a PO token and return 403 anonymously. The default client now supplies anonymous adaptive formats; Android is used only for the legacy progressive source. The selected source client is signed into the internal plan and revalidated on fresh resolution. No cookies, login, PO-token generation, DRM bypass, or raw upstream URL submission.
• Existing Redis jobs, signed tokens, pinned source validation, private artifacts, bounded two-job admission, 512 MiB preparation bound, deadlines, atomic ready state and cleanup are retained.
• Download and compatible Share / Save reuse one artifact. Existing Tap Again/OPFS behavior is unchanged; the 100 MiB Share / Save limit remains.

Validation

• PHP: 211 tests / 1636 assertions; Pint, Composer validate and Composer audit pass.
• Python: 334 passed / 3 existing skips; Ruff passes.
• JavaScript feature suite, Vite build, icon validation and npm audit pass; GitHub php/frontend/python/docker checks are green.
• Tiny MP4/WebM mux integration proves stream copy, video + audio, MIME/filename and cleanup.
• Isolated real public 1080p smoke: H.264 + AAC, 1080p, 84.4 MB MP4; no persistent artifact.

Production and acceptance

No migration, data reset, backup, or server cleanup. Candidate is deployed with only app, worker, scheduler and extractor recreated; nginx and Redis are untouched. First physical test is https://www.youtube.com/watch?v=dQw4w9WgXcQ at 1080p with audio. No merge in this task.