Agent 6 applied SW-pin fix and marked verified via element state
(currentTime advancing, videoWidth=1920, readyState=4). Headless pixel
histogram still showed darkPct=100% — element decoded fine but CSS
overlay covered it.
Real cause: branding.xml BLACK-PASS paints .libraryPage with
#000 !important. Jellyfin OSD page renders <div id=videoOsdPage
class=libraryPage>; class match -> opaque black div above <video>.
Fix: extend transparent-scope using :has(.htmlVideoPlayer) +
#videoOsdPage selector. Post-fix darkPct=9.8% (was 100%), MNS S1E4
video frame visually paints.
Removed INC6 clear-cache-only middleware (no longer needed, was
burning HTTP cache every visit).
bin/apply-26-incident-fixes.sh extended with INC7 patch (idempotent
re-apply if branding.xml ever drifts back).
Lesson: video-element state alone is insufficient verification.
Always sample pixel histogram + canvas drawImage on the painted
viewport.
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.
