prefetchQuery initial data not available on mount after invalidateAll() in SvelteKit

[mdanilakis]

Describe the bug

Hello tanstackers, we're using @tanstack/svelte-query with SvelteKit and followed the prefetching approach (ssr) as outlined here:
https://tanstack.com/query/latest/docs/framework/svelte/ssr#prefetching-data

We have a parent layout as in the docs:

import { browser } from '$app/environment'
import { QueryClient } from '@tanstack/svelte-query'

export async function load() {
  const queryClient = new QueryClient({
    defaultOptions: {
      queries: {
        enabled: browser,
      },
    },
  })

  return { queryClient }
}

Everything seems to work fine, until we recently discovered that if we call SvelteKit's invalidateAll method (https://svelte.dev/docs/kit/$app-navigation#invalidateAll), the prefetched data is no longer available on mount.

This may sound confusing or expected (maybe?) but here's what we find problematic:

Expected behavior

The +page.svelte should immediately have access to the prefetched data from the cache. The createQuery should read from the cache that was populated by prefetchQuery as described in the docs:

<script lang="ts">
  import { createQuery } from '@tanstack/svelte-query'

  // This data is cached by prefetchQuery in +page.ts so no fetch actually happens here
  const query = createQuery(() => ({
    queryKey: ['posts'],
    queryFn: async () => (await fetch('/api/posts')).json(),
  }))
</script>

Even after an invalidateAll someone would expect the prefetch data to be available as initial data so the client doesn't have to fetch/is not in a stale state effectively causing a client-side load.

src/routes/+page.ts

export async function load({ parent, fetch }) {
  const { queryClient } = await parent()

  // You need to use the SvelteKit fetch function here
  await queryClient.prefetchQuery({
    queryKey: ['posts'],
    queryFn: async () => (await fetch('/api/posts')).json(),
  })
}

Actual behavior

The query.data is empty/undefined for a split of a second after mount, and then the client refetches.

Again, this only happens after a SvelteKit invalidateAll call.

Reproduce

https://stackblitz.com/edit/sveltejs-kit-template-default-f4juyo11

Your minimal, reproducible example

https://stackblitz.com/edit/sveltejs-kit-template-default-f4juyo11

Steps to reproduce

Follow: https://stackblitz.com/edit/sveltejs-kit-template-default-f4juyo11

Expected behavior

query.data should have the prefetchQuery data on mount after the navigation

How often does this bug happen?

Every time

Screenshots or Videos

No response

Platform

MacOS, Chrome, SvelteKit

Tanstack Query adapter

svelte-query

TanStack Query version

6.0.17

TypeScript version

No response

Additional context

No response