Svelte 5: Sibling elements with different out:transition durations makes the content flash

[brianschwabauer]

Describe the bug

When there are two elements in an #if block and they both have out transitions applied (but different durations), the element with the shorter duration will flash back on screen while the element with the longer duration finishes its animation.

In other words, the short duration transition's final style is not holding on the last frame of its animation.

This wasn't an issue until I upgraded to svelte 5 next 220. It was working in ~next210.

Reproduction

https://svelte-5-preview.vercel.app/#H4sIAAAAAAAACq2RX2_bIBTFv8odW9VESma3U1-IbWnfoW9zHwhcHFQCFlynjRDfvcLun01qtD3sCXHOPYcfkJg2FiPjvxJz4oiMs5_jyDaMzmPZxBNaQrZh0U9BFqWJMpiRut71ZI6jDwQJohQWN6CFQsiggz_C9RKtKAgXDRnvrnclY5EgHvwTtPAtkiBcaWEjrne9a6qPbtfsJyLvwDtpjXxs02oNbfcW_VLW3N37YbDYVMvsnEtfjZ6ncjmtUeYE0ooY254dvRJ2ux96BsbxGdZPxGf4NiU1BVE4Ofyo65y7plLm1F1q8er8156bu9Jzj5HeulJldJ6vF-lscW7__tEIqQg97YV8HIKfnNpKb33gEFDtFm_0y3Ny0Ob5XX0yig4cbup6fH6VDmiGA_2pkR85SGHl6q6-gu3irV9Ni5ouufl30uEy595O-C-gt5-A3v4n0KZaHpdtymcZbVAxTmHC_JBfAJLtlhbxAgAA

Logs

No response

System Info

N/A

Severity

blocking an upgrade

[trueadm]

Is there any chance you could isolate which version caused the issue? That would help tremendously - thanks!

[harrisi]

Looks like 215.

215 (broken)

214 (working)

[trueadm]

Likely #12759 then. Thanks!