I spent a bit of time debugging why Firefox mobile is so annoying to use with the new Assistant. I believe the main problem is the logic that detects if the scroll-down button should be hidden doesn't take into account dynamic viewport resizing (e.g when the document is scrolled, the browser expands the viewport instead of scrolling the actual document):
The code that Kagi uses is basically this (in the scroll event handler):
1 <= document.documentElement.scrollHeight - document.documentElement.clientHeight - document.documentElement.scrollTop
Under mobile Firefox (with a device touch screen, this does not occur when emulating Firefox/the viewport), this calculation is off by 56px (on my device and pixel density). This number is coming from the difference between 100lvh and 100svh, or the size of the address bar on my setup (that is scrolled before the document is scrolled).
This causes the sources to be covered up by the sticky .bottom-box:
Ideally, as on desktop or desktop emulating mobile/touch, the scroll down button (and friends) would be hidden, preventing touch inputs from being eaten by the wrong element.
