Looks like there's an issue with width computation and psuedoelements: With a 2-deep nested flex layout, with widths determined by the content sizes, adding a pseudo-element on hover breaks text-align: center on all but the 2 most recently hovered elements.

Example test file: align-bug.html
Tested with cargo run --release --package readme --features incremental ./align-bug.html

Behavior with incremental enabled: https://github.com/user-attachments/assets/3fb691a8-dc37-40a1-bfa3-2908d58af767
Behavior without incremental: https://github.com/user-attachments/assets/e5374ec2-f2ee-4c67-be5d-f178a5ea56bc

@Aeledfyr That is really bizarre behaviour. Thanks for the reproduction! I think I've managed to track down the issue.

This is a bit technical, but what was happening was that the "measure content width" stages of subsequent layout runs were "clobbering" the layout in order to measure the text (but were unable to correctly compute alignment as they didn't yet have the width to align to available at that stage). Normally the later "final layout" stage would overwrite that, but in this case that stage was hitting the cache and not running at all.

The fix I've pushed is a bit of hack which runs the "measure content width" stage on a clone of the layout. I would have expected this to be slow, but in practice it doesn't seem to make much difference. So I've put it in for now, and we can clean it up later.