A later streaming parse-cache change dropped the #MOBILESCROLL guard from
the live-stream render tick while leaving the helper and CSS in place.
On iOS PWA, Safari can paint a transient scrollTop=0 frame during streamed
DOM rebuilds, forcing the reader to the first/oldest message.
Re-add _fixMobileScrollJank() before streaming DOM work begins and pin it
with a regression test so the third layer of the mobile scroll fix cannot
be silently dropped again.
Root cause: .messages had overflow-anchor:none unconditionally. On mobile
touch devices (iOS Safari, Android Chrome), the compositor can paint a frame
with scrollTop=0 between innerHTML='' and snapshot restore, scroll-janking
the user to the top of the transcript.
Three-layer fix:
1. CSS (style.css): Use overflow-anchor:auto on touch devices (mobile),
keep overflow-anchor:none on desktop (mouse-driven) via
@media (hover:hover) and (pointer:fine) — preserves the existing
behavior where tool/card inserts don't yank a reading user.
2. JS guard (ui.js): Add window._fixMobileScrollJank() that temporarily
sets overflowAnchor='auto' on #messages before innerHTML='' and
clears it one rAF later — prevents the compositor frame with scrollTop=0.
3. Streaming protection (messages.js): Call _fixMobileScrollJank() at the
top of each _doRender() tick so streaming DOM growth doesn't jank the
viewport position.
Tests:
- Updated test_issue1360_streaming_scroll_hardening.py: split the
overflow-anchor test into desktop (none) and mobile (auto) variants.
- Added test_mobile_scroll_jank.html: interactive visual test that
simulates the scroll jank on a mobile-sized viewport.
#4584 (fixes#4295): scroll re-pin requires deliberate downward intent (deltaY<-30 unpin
threshold, re-pin only if not user-unpinned OR bottomDistance<=80, reset counter) so reading
mid-stream isn't hijacked back to bottom. ui.js only + 5 scroll-regression tests (4 existing
assertions adjusted, all green; new test_issue4295_scroll_pin_reentry).
#4583 (fixes#4553): mobile transcript overflow-x:hidden + max-width:100% + word-break so wide
content can't pan sideways. style.css only + own test. Disjoint files. 32 scroll-family tests pass.
Co-authored-by: nesquena-hermes <agent@nesquena-hermes>
Co-authored-by: rodboev <rodboev@users.noreply.github.com>
Brett Yelverton