iOS fires visualViewport scroll events at 60fps during a pan with the
keyboard up. Routing those through React state and into the .chat-thread
translateY(--vv-offset-top) transform amplified the pan into a visible
judder + ~300px shift + body background exposure.
useMobileKeyboard now uses two listeners: a full update (resize +
focusin/focusout) that re-snapshots all metrics including offsetTop, and
a scroll-only update that updates only height/keyboardOpen. offsetTop
is therefore frozen between keyboard open/close events — the transform
correctly compensates for iOS's initial visualViewport shift on focus
without following pan-time movement.
Restores the translateY anchor (so the thread isn't off-screen on
first focus) while keeping the swipe-jitter fix.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
4708e453ae