Uploaded images (SVGs rasterized, GIFs excepted) are stored as the
original (hash.orig.ext, internal only, never served) plus AVIF primary
and WebP/JPEG fallback derivatives re-encoded from it. Pages link the
bare hash; the server serves a format only when Accept lists it
explicitly (image/avif -> AVIF, image/webp -> WebP, else JPEG) with
vary: accept, while an explicit extension pins the format. Favicons go
through the same pipeline at 192px. migrate_v2 rewrites old
/_f/{hash}.avif article links, a startup backfill creates missing
derivatives, and twitter:image pins the .webp variant for X's scraper.
LeoVasanko
f793d21c5e