This is the bug report on Webkit's tracker: https://bugs.webkit.org/show_bug.cgi?id=297779 Might be worth chiming in there to get their attention.

Behavior bugs don't only occur when opening/closing the keyboard. It's the overall behavior of elements in sticky/absolute/fixed positions that are broken because of this new weird viewport. For example, if you go to Apple's website (https://www.apple.com/) and scroll down, the header will be sticky, but if you look closely, part of the header will extend a few pixels above the viewport.

I often integrate pop-ups/drawers that cover 100% of the width and 100% of the height of the screen. Since iOS 26, the behavior on Safari has changed and it is no longer a true 100% height because of this floating bar. The overlays of these pop-ups/drawers no longer cover 100% of the height, which looks very ugly.

Hi, This is the worst Safari update in years. The use of elements with 100% height in fixed/absolute position is completely broken. It's really unacceptable that this is live.