Five sibling agents converged on root cause:
jellyfin-asset-immutable Traefik router (priority 90) was matching
/web/serviceworker.js (Jellyfin PWA's actual SW filename), pinning it
with Cache-Control: public, max-age=31536000, immutable. The
priority-100 jellyfin-html-nocache router only excluded the literal
path /web/sw.js, missing serviceworker.js.
Stale SWs from earlier ARRFLIX iterations intercepted /Videos/* and
/web/* fetch events, returning cached/empty bytes. Result:
MediaSource appendBuffer got bad data -> black <video>. INC6's
Clear-Site-Data: "cache" couldn't fix it (per MDN spec, "cache"
excludes SW registrations; "storage" would have worked).
Fix: added jellyfin-sw-nocache router at priority 250 in
/opt/docker/traefik/config/dynamic.yml on nullstone, forcing
cache-no-store@file on /web/serviceworker.js + /web/sw.js. Hot-reload
via Traefik file provider, no docker restart.
Verified at the wire (curl -I /web/serviceworker.js now returns
no-cache, no-store, must-revalidate; main.jellyfin.bundle.js still
immutable as intended) and via headless Chromium probe of MNS S1E4
(33s of currentTime advance, readyState 4, videoWidth 1920x1080,
no errors, both s8n admin and guest user).
bin/prod-vs-dev-compare.py also lands as a one-shot diff helper used
during the investigation.
