Reported from an iPhone, with a screenshot: tap the message box, the keyboard
comes up, and the whole app has slid off the top — header gone, only the bottom
edge of the composer left, black underneath it down to the keyboard.
That is the visual viewport being panned. WebKit shrinks it for the keyboard and
then moves it down inside the layout viewport (which it does not shrink) to
reveal the focused field. The shell had shrunk correctly, to the top --sb-vh of
the layout viewport; the window had simply moved off it. No CSS declines that
pan, and it is not a document scroll, so there is no scrollTop to put back.
So the shell is pinned to the visible rect: fixed to the layout viewport and
translated by visualViewport.offsetTop. The earlier objection to pinning is kept
where it was right — HEIGHT still moves on resize only, which is what stopped the
layout twitching under the finger, and the offset rides a transform rather than
`top`.
The first cut of this had a guard that silently disabled it: the pan was only
followed when window.innerHeight was much taller than the visual viewport, i.e.
"a keyboard is covering us". That assumes iOS never resizes the layout viewport,
which stopped being safe once WebKit started honouring interactive-widget. Only a
pinch-zoomed page switches the pan off now, by scale, and offsetTop is believed
whenever it is non-zero. The offset is also re-read across the keyboard's
animation on focusin/focusout: on iOS 26 the viewport is documented not to settle
back immediately on dismissal.
The message list stays at the newest message across a keyboard open or close,
instead of holding a scroll position from the taller layout and leaving the last
few messages under the composer.
Two smaller things on the same screen:
The QR code closes itself once the safety number appears. It was only dismissed
when both exchange flags cleared, and those stay set through verification, so a
one-time credential sat on top of the code the user was meant to be reading.
The disconnect button's label is hidden wherever the button becomes a 40px
square. Its own rule stopped at 560px while the square starts at 768px, so
between the two the word was still inside the box, pushing the icon off centre.
?vvdebug=1 paints the viewport numbers over the app — visible rect height,
offset, scale, what the shell resolved to. A phone cannot be put on a debugger
and none of those numbers show up in a screenshot of the result; this one is how
the guard above was caught. Off unless named in the URL.
Claude-Session: https://claude.ai/code/session_01R63J7dexujFQCJpDAeKxr9
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