Async Svelte breaks reactivity when using `preloadData`

[hmnd]

Describe the bug

I'm not entirely sure what's going on yet, but when I enable compilerOptions.experimental.async, reactivity in my dialog breaks. Oddly, when the preloaded data is already cached from a previous attempt, it works fine.

Reproduction

https://stackblitz.com/edit/sveltejs-kit-template-default-rtqnsjzu?file=svelte.config.js

First, try with Preload data checked, then refresh and try with it disabled. When preloadData is used, reactivity is broken in the dialog and the svelte query gets stuck on Loading....

Logs

System Info

System:
    OS: Linux 5.0 undefined
    CPU: (8) x64 Intel(R) Core(TM) i9-9880H CPU @ 2.30GHz
    Memory: 0 Bytes / 0 Bytes
    Shell: 1.0 - /bin/jsh
  Binaries:
    Node: 20.19.1 - /usr/local/bin/node
    Yarn: 1.22.19 - /usr/local/bin/yarn
    npm: 10.8.2 - /usr/local/bin/npm
    pnpm: 8.15.6 - /usr/local/bin/pnpm
  npmPackages:
    @sveltejs/adapter-auto: ^7.0.0 => 7.0.0 
    @sveltejs/kit: ^2.47.1 => 2.48.4 
    @sveltejs/vite-plugin-svelte: ^6.2.1 => 6.2.1 
    svelte: ^5.41.0 => 5.43.2 
    vite: ^7.1.10 => 7.1.12

Severity

blocking an upgrade

Additional Information

No response

[hmnd]

May be related or dupe of #14827

[teemingc]

This should have been fixed by sveltejs/svelte#17098 . I can re-open if it hasn't been fixed after upgrading to Svelte 5.43.3