Async Svelte: Navigation with preload and conditional bind:this causes page to flash then revert

[jose-manuel-silva]

Describe the bug

I'm experiencing what appears to be a related issue to sveltejs/svelte#17118, but with different symptoms specific to SvelteKit navigation.

Setup:

• Route structure: /[test] with +page.svelte and +layout.svelte
• Layout contains a shadcn sidebar using conditional bind:this
• Main page has links to /a and /b

Bug behavior:

1. Hovering /a and clicking → works correctly
2. Hovering /a, then hovering /b, then clicking /b → page navigates to /b, then immediately navigates back to the previous page (less than a second), BUT the URL remains /b

Environment:

• Async: enabled (If disabled, it works correctly)

Workaround:
Disabling data-sveltekit-preload-data fixes the issue.

Question:
Will the fixes in sveltejs/svelte#17147 and #14865 address this navigation issue, or is this a separate problem?

Reproduction

If needed, heres minimum repro: https://github.com/jose-manuel-silva/svelte-repro.git
(probably could be smaller, sorry for that)

The conditional bind:this is in $lib/components/ui/sidebar/sidebar-menu-button.svelte

Logs

System Info

System:
    OS: macOS 15.5
    CPU: (10) arm64 Apple M4
    Memory: 68.34 MB / 24.00 GB
    Shell: 5.9 - /bin/zsh
  Binaries:
    Node: 24.9.0 - /opt/homebrew/bin/node
    npm: 11.6.0 - /opt/homebrew/bin/npm
    pnpm: 10.20.0 - /opt/homebrew/bin/pnpm
    bun: 1.3.1 - /opt/homebrew/bin/bun
  Browsers:
    Safari: 18.5
  npmPackages:
    @sveltejs/adapter-auto: ^7.0.0 => 7.0.0 
    @sveltejs/kit: ^2.48.4 => 2.48.4 
    @sveltejs/vite-plugin-svelte: ^6.2.1 => 6.2.1 
    svelte: ^5.43.6 => 5.43.6 
    vite: ^7.1.10 => 7.2.2

Severity

serious, but I can work around it

Additional Information

No response