if/else rendering in webkit-box (18.4 (20621.1.15.11.10))

[andriuwe4ka]

Describe the bug

with latest Safari update we encountered strange behavior

• we have one tag with display: -webkit-box
• inside it we have svelte if/else block
• inside default visible part of if/else (no metter if or else) we have 2+ tags (even empty)
• when it is time to rerender based on if condition - only first default visible tag is hidden, its space is reused, however second tag is still there

seems like happens only on first rerender, however should be additionaly checked
only second and following tags affected
repro in Safari only (for now)

Reproduction

https://svelte.dev/playground/82c0ba79c6a84c5d97d21ac2317160e2?version=5.25.12

Logs

System Info

Safari 18.4 (20621.1.15.11.10)

Severity

blocking an upgrade