Only the first import of an async chunk waits for the CSS #23652

Describe the bug

My SvelteKit website loads pages asynchronously, but I can see a flash of unstyled content when navigating to some pages. It seems that it tries to preload the page, do some stuff and then import the chunk again. But the second import does not wait for the CSS?

Found this random PR on a random fork which seems to try fixing the same bug: marko-js/vite#320.

AI says this:

The preload helper marks a dependency as seen when it inserts the <link>, not when the link has loaded, and returns early for seen dependencies (if (dep.href in seen) return). Only the call that inserted the link awaits its load event.

Reproduction

https://drop-5a75d175-5d4.kiwixz.workers.dev/

repro.zip

Steps to reproduce

F5 the page multiple time, you will see second import resolving before CSS is loaded.

System Info

Binaries:
    Node: 24.21.0
    npm: 9.2.0
  npmPackages:
    vite: ^8.3.2 => 8.3.2

Used Package Manager

npm

Logs

No response

Validations

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• The provided reproduction is a minimal reproducible example of the bug.