Two background yt-dlp processes were firing every time a video page loaded:
1. importChapters (called unconditionally via useEffect on mount) was calling
_upsert_video_from_yt with polite=False when chapters=NULL — no rate
limiter, no download-pause check, runs concurrently with active downloads.
Fix: return [] immediately when chapters=NULL and let the normal enrichment
pipeline (already polite=True) fill them in.
2. get_video_by_yt_id schedules a background _enrich task whenever description
or chapters are NULL. The frontend polls every 3 s while description is
null, so dozens of enrichment tasks would pile up for the same video.
Fix: deduplicate with _enriching set — only one background fetch per
video_id at a time; the set entry is cleared when the task finishes.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Mattias Thall
1179b53f2e