Preloading query with page param on hover breaks the app

[aintnewtathis]

Describe the bug

I display a simple list of products

//+page.svelte
{#each await getProducts() as product (product.id)}
	<a href="/{product.id}">
              ...
	</a>
{/each}

//data.remote.ts
export const getProducts = query(async () => {
	const products = db.select().from(product);

	return products;
});

that links to /[id] route, +page.svelte has top level await with remote query that gets product by id

//+page.svelte
<script lang="ts">
	import { page } from '$app/state';
	import { getProduct } from './data.remote';
</script>
<pre>{JSON.stringify(await getProduct(page.params.id!), null, 2)}</pre>


//data.remote.ts
export const getProduct = query('unchecked', async (id) => {
	return await db
		.select()
		.from(product)
		.where(eq(product.id, Number(id)));
});

After you hover over more than one link - it fires query with undefined param, on click query payload in Network tab is correct, but it doesn't navigate you to the page. Temporary fixes - data-sveltekit-preload-data="false" or full page reload after navigation.

Reproduction

Added basic code blocks in example.

Logs

getProduct on hover res:
{
    "type": "result",
    "result": "[[]]"
}

getProduct on click res:
{
    "type": "result",
    "result": "[[1],{\"id\":2,\"thumbnail\":3,\"title\":4,\"description\":5,\"size\":6,\"price\":7,\"quantity\":8,\"categoryId\":9,\"createdAt\":10,\"updatedAt\":11},4,\"https://picsum.photos/seed/product4/400\",\"Bluetooth Earbuds\",\"Noise-cancelling wireless earbuds with charging case.\",\"One Size\",7999,150,3,[\"Date\",\"2025-10-22T22:46:42.209Z\"],[\"Date\",\"2025-10-22T22:46:42.209Z\"]]"
}

System Info

System:
    OS: Linux 6.17 Arch Linux
    CPU: (12) x64 AMD Ryzen 5 8600G w/ Radeon 760M Graphics
    Memory: 6.55 GB / 14.74 GB
    Container: Yes
    Shell: 5.3.3 - /usr/bin/bash
  Binaries:
    Node: 22.18.0 - /home/yy/.local/share/mise/installs/node/22.18.0/bin/node
    npm: 10.9.3 - /home/yy/.local/share/mise/installs/node/22.18.0/bin/npm
    pnpm: 10.15.0 - /home/yy/.local/share/mise/installs/node/22.18.0/bin/pnpm
    bun: 1.3.0 - /home/yy/.bun/bin/bun
  Browsers:
    Chromium: 141.0.7390.122
  npmPackages:
    @sveltejs/adapter-auto: ^7.0.0 => 7.0.0
    @sveltejs/adapter-node: ^5.4.0 => 5.4.0
    @sveltejs/kit: ^2.48.0 => 2.48.0
    @sveltejs/vite-plugin-svelte: ^6.2.1 => 6.2.1
    svelte: ^5.42.2 => 5.42.2
    vite: ^7.1.12 => 7.1.12

Severity

serious, but I can work around it

Additional Information

Thanks in advance!

[sillvva]

This is a long shot, but try this instead:

<script lang="ts">
	import { getProduct } from './data.remote';

	let { params } = $props();
</script>

<pre>{JSON.stringify(await getProduct(params.id), null, 2)}</pre>

It's not recommended to use $app/state for page.params or page.data. Unlike the params and data props, it doesn't have route-awareness for types.

[aintnewtathis]

Tried, but still the same problem - multiple hovers\preloads cause app break.

[sillvva]

I wonder if this is the same issue: sveltejs/svelte#17079

Possibly also related to #14851

Both issues introduced in svelte@5.42.0. Downgrading to svelte@5.41.4 fixes both issues.

[teemingc]

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

[sillvva]

Still getting a significant amount of errors on 5.43.3 related to forking. Downgrading to 5.41.4 again. Will try to make MREs, but no promises.

This is the one I'm seeing right now: sveltejs/svelte#17090
I think I also saw another.

[teemingc]

Should I re-open this issue or are the errors you're running into a different issue?

[sillvva]

sveltejs/svelte#17090 is a different issue. There's also this one, which seems to be related to this one (preloading on hover issues), and still unfixed. I'm experiencing both of them on the latest version.

[acoyfellow]

i can confirm downgrading to svelte@5.41.4 fixes this hover preloading issue.

i only noticed it because the tab title changes on hover, which is an odd UX. Other than that I haven't noticed any other issues.