flip/crossfade animation regression in 5.43.8

[gyzerok]

Describe the bug

Observe how new items are sliding from the top. In the 5.43.7 they are just added at the bottom.

Screen.Recording.2025-11-18.at.10.25.01.mov

Reproduction

Compare 5.43.7 and 5.43.8 in the REPL

Logs

System Info

irrelevant

Severity

blocking an upgrade

[gyzerok]

There are couple more issues, that look relevant and might be either results of the same bug, or could be tackled together during the fix: #17166, #17180

[mustafa0x]

My app hangs, but in 5.43.9 (edit: it seems to be indeed .8).

[gyzerok]

My app hangs, but in 5.43.9 (edit: it seems to be indeed .8).

It looks like hanging problem was fixed with the latest release

[mustafa0x]

Tested and working, thanks for the tip @gyzerok

[pekeler]

My crossfade was also broken by 5.43.8. Probably the same underlying issue. Getting lot's of these warnings in the browser console now:

 Invalid keyframe value for property transform: matrix(0, 0, 0, 0, -114.726, -701.708) translate(83.08177185058594px,326.88427734375px) scale(Infinity, Infinity)

[pekeler]

Compare the crossfade 5.43.7, 5.43.8, and latest.

[dummdidumm]

Another reprodution: https://svelte.dev/playground/a9f3aca528e94927bcdbab96046db781?version=5.43.8