Symptoms: Page Unresponsive on poster grid, posters missing then black
backdrops, 'Abspielen' German Play button surviving Traefik+force-english
chases, video black-screen on play.
Root causes (different from initial guesses):
- Browser hangs: deployed index.html drifted ahead of repo; uncommitted
forceEnglishUI() text-walker MutationObserver froze main thread on poster
lazy-load. Reverted to repo HEAD.
- 'Abspielen': Cineplex theme HARDCODES German via 'content:' ::after rule
-- not a Jellyfin locale issue. Doc 25 already proved per-user UICulture
is theatre. Override CSS with content: 'Play'.
- Backdrops black: BLACK-PASS CustomCss block paints #000 !important on
.layout-desktop / .pageContainer -- occludes backdrop layer (z-index:-1).
Existing transparent-scope rule used body.itemDetailPage selector that
doesn't match in 10.10.3 (body class is libraryDocument). Replaced with
:has(.itemDetailPage) ancestor scoping.
- HLS 499: encoding.xml had EnableThrottling+EnableSegmentDeletion=true,
segments reaped before browser re-request. Disabled both.
Verified via new bin/headless-test.py (playwright Chromium login + screenshot
+ computed-style probe). Fixes idempotent and re-runnable via new
bin/apply-26-incident-fixes.sh.
Open: AV1+Opus items still black-screen in Chrome due to DirectStream
codec-tag mislabel bug. Tracked for 10.11.8 migration.
