toolbarbuttons_in_tabs_periphery.css makes some tabs jump several by pixels when hovered, resizing of tabs is weird

[e-t-l]

trafficstars

https://github.com/MrOtherGuy/firefox-csshacks/blob/master/chrome/toolbarbuttons_in_tabs_periphery.css Firefox v131.0 on Windows 11

There are a few weird behaviors I'm observing after updating Firefox to version 131.0; they're all visible in the video below, but I'll also try to enumerate them here:

1. Some tabs "jump" (expand?) by a couple pixels when hovered. It seems to happen specifically to tabs with titles that do NOT overflow (for example, "Google" does not overflow the tab width, while "DuckDuckGo ― Privacy, simplified." does overflow)
2. When a tab is opened with a title that DOES overflow the tab width, this resizes the width of all tabs (you can see this in the video when I open DuckDuckGo, and then it reverts when I close DuckDuckGo)
3. Tabs' overall widths start shrinking before reaching the limit of #tabbrowser-tabs (you can see this when I create more new tabs, all the tabs' widths start shrinking despite still having more empty space to their right)

https://github.com/user-attachments/assets/89d7e680-ba5f-4189-b448-9718de0da833