NS_ERROR_CORRUPTED_CONTENT with kit 2.65.0

[charlyoleg2]

Describe the bug

After upgrading sveltekit to 2.65.0, my website get broken with the following errors:

• NS_ERROR_CORRUPTED_CONTENT after entering the URL
• Loading module from “https://charlyoleg2.github.io/parame76/_app/immutable/entry/_app/immutable/chunks/DBrbuulb.js” was blocked because of a disallowed MIME type (“text/html”) if using a link

Tested with Chromium and Firefox.
At compilation time, no error, no warning.

Reproduction

npx sv create kitissue
# select SvelteKit minimal, Typescript, none, npm
cd kitissue
vim vite.config.ts
# add the line: paths: { relative: false }
npm run build
npm run preview
# open the browser, you see the issue in DevTool console

import adapter from '@sveltejs/adapter-auto';
import { sveltekit } from '@sveltejs/kit/vite';
import { defineConfig } from 'vite';

export default defineConfig({
	plugins: [
		sveltekit({
			compilerOptions: {
				// Force runes mode for the project, except for libraries. Can be removed in svelte 6.
				runes: ({ filename }) =>
					filename.split(/[/\\]/).includes('node_modules') ? undefined : true
			},

			// adapter-auto only supports some environments, see https://svelte.dev/docs/kit/adapter-auto for a list.
			// If your environment is not supported, or you settled on a specific environment, switch out the adapter.
			// See https://svelte.dev/docs/kit/adapters for more information about adapters.
			adapter: adapter(),
			paths: { relative: false }
		})
	]
});

Logs

Loading module from “https://charlyoleg2.github.io/parame76/_app/immutable/entry/_app/immutable/chunks/DBrbuulb.js” was blocked because of a disallowed MIME type (“text/html”). losange
Loading module from “https://charlyoleg2.github.io/parame76/_app/immutable/entry/_app/immutable/nodes/0.CTGQGwbp.js” was blocked because of a disallowed MIME type (“text/html”). losange
Uncaught (in promise) Error: Unable to preload CSS for https://charlyoleg2.github.io/parame76/_app/immutable/entry/_app/immutable/assets/0.Be5pTVV_.css
    Immutable 6
    async* https://charlyoleg2.github.io/parame76/desi76/losange:69
    promise callback* https://charlyoleg2.github.io/parame76/desi76/losange:68
DBrbuulb.js:3:8570
Loading module from “https://charlyoleg2.github.io/parame76/_app/immutable/entry/_app/immutable/chunks/C-5QfD1z.js” was blocked because of a disallowed MIME type (“text/html”). losange
Loading module from “https://charlyoleg2.github.io/parame76/_app/immutable/entry/_app/immutable/nodes/1.Dj998sHj.js” was blocked because of a disallowed MIME type (“text/html”). losange
Loading module from “https://charlyoleg2.github.io/parame76/_app/immutable/entry/_app/immutable/nodes/3.CyFmq4Op.js” was blocked because of a disallowed MIME type (“text/html”). losange
Loading module from “https://charlyoleg2.github.io/parame76/_app/immutable/entry/_app/immutable/chunks/xihTtKlq.js” was blocked because of a disallowed MIME type (“text/html”). losange
Loading module from “https://charlyoleg2.github.io/parame76/_app/immutable/entry/_app/immutable/chunks/CCm9NRYp.js” was blocked because of a disallowed MIME type (“text/html”). losange
Loading module from “https://charlyoleg2.github.io/parame76/_app/immutable/entry/_app/immutable/chunks/C1eJXQDC.js” was blocked because of a disallowed MIME type (“text/html”). losange
Loading module from “https://charlyoleg2.github.io/parame76/_app/immutable/entry/_app/immutable/chunks/DkYxdl8U.js” was blocked because of a disallowed MIME type (“text/html”). losange
Error: Unable to preload CSS for https://charlyoleg2.github.io/parame76/_app/immutable/entry/_app/immutable/assets/3.CYDkf_cO.css
    Immutable 9
    async* https://charlyoleg2.github.io/parame76/desi76/losange:69
    promise callback* https://charlyoleg2.github.io/parame76/desi76/losange:68
app.It4h8LkS.js:2:2184
Loading module from “https://charlyoleg2.github.io/parame76/_app/immutable/entry/_app/immutable/nodes/2.1TgUCM8q.js” was blocked because of a disallowed MIME type (“text/html”).

System Info

System:
    OS: Linux 6.17 Ubuntu 24.04.4 LTS 24.04.4 LTS (Noble Numbat)
    CPU: (22) x64 Intel(R) Core(TM) Ultra 7 155H
    Memory: 25.99 GB / 30.80 GB
    Container: Yes
    Shell: 5.2.21 - /bin/bash
  Binaries:
    Node: 24.16.0 - /usr/bin/node
    npm: 11.16.0 - /usr/bin/npm
    bun: 1.2.1 - /home/charles/.bun/bin/bun
    Deno: 2.8.2 - /home/charles/.deno/bin/deno
  Browsers:
    Chromium: 149.0.7827.53
    Firefox: 151.0.4
    Firefox Developer Edition: 151.0.4

Severity

blocking an upgrade

[teemingc]

We need a minimal reproduction. Not the entire project

[charlyoleg2]

Ok. I will work on that.
Notice that @svelte/kit@2.64.0 doesn't have the issue.

[charlyoleg2]

The issue occurs when a Svelte component library is used. At least with this Svelte component library: https://www.npmjs.com/package/geomui

[murayy]

Ran into the same thing and did a bit of digging that might save someone time :)

Repro / trigger: it specifically hits projects that set kit.paths.relative: false (served from the domain root). With the default (relative: true) everything is consistent and fine, which is probably why it isn't more widely reported.

Bisect: clean on 2.64.0, broken on 2.65.0 (every 2.55/2.61/2.63/2.64 build → 0 doubled requests; 2.65.0 → hundreds).

Likely cause: the renderBuiltUrl rework in #15936. The hostType === 'js' branch honors paths.relative:

if (hostType === 'js') {
  if (ssr) return base + filename;
  return { relative: kit.paths.relative !== false || !!kit.paths.assets };
}
// _app/immutable/assets (CSS) + static files:
if (filename.startsWith(root_to_assets)) return `./${filename.slice(root_to_assets.length)}`;
return assets_to_root + filename;

…but the CSS / static-asset branch always returns a relative path and never checks paths.relative. So with relative: false the JS modules come out absolute while the CSS preloads come out relative — and with the new global base: './' they resolve against the importing chunk's dir, producing the doubled /_app/immutable/entry/_app/immutable/... 404s (which Firefox surfaces as NS_ERROR_CORRUPTED_CONTENT). It only shows up on client-side navigation / lazily-loaded route chunks, since the initial page's assets come from the SSR <link modulepreload> (absolute, correct).

Workaround (no patching needed): set paths.relative: true — verified 0 doubled requests on 2.65.0, including deep routes.

Happy to put together a minimal reproduction repo if that's useful 🙏

[charlyoleg2]

The workaround works well for me:

               paths: {
                        base: dev ? '' : `/${basePath}`,
-                       relative: false
+                       relative: true
                }

[charlyoleg2]

I have updated the Reproduction steps.
Basically from the Sveltekit minimal project, just add paths: { relative: false } in vite.config.ts and you get the issue.

[teemingc]

Thanks for breaking down the reproduction. Really appreciate it. Sorry about this issue. I've added a test for it so that it doesn't regress again.

[kirso]

We hit this in production-bound work and bisected it fully. It is not related to component libraries — the trigger is kit.paths.relative: false alone. Minimal reproduction below (6 files, no plugins beyond sveltekit()).

Version matrix (clean installs, fresh lockfile each)

@sveltejs/kit	vite	result
2.59.1 / 2.62.0 / 2.64.0	7.3.5	✅ works
2.65.0	7.3.5	❌ broken
2.65.0	8.0.16	❌ broken
2.64.0	8.0.16 (+ plugin-svelte 7.1.2)	✅ works

Kit version is the only variable — Vite major is irrelevant.

Mechanism

With paths.relative: false, kit's renderBuiltUrl returns { relative: false } for hostType === 'js'. Through 2.64.0, the built client entry gets the absolute asset helper and root-relative dep maps:

// 2.64.0 — entry/app.*.js + helper chunk
const v = function(l){ return "/" + l }                    // assetsURL
__vite__mapDeps=[..."_app/immutable/nodes/0.xxx.js"...]    // no ./ prefix
S(() => import("../nodes/0.xxx.js"), __vite__mapDeps([0,1,2,3]))   // no importer arg

In 2.65.0 the same config produces the relative-base variant:

// 2.65.0
const t = function(e,t){ return new URL(e,t).href }        // importer-relative resolution
__vite__mapDeps=[..."./_app/immutable/nodes/0.xxx.js"...]  // ./-prefixed, root-shaped
T(() => import("../nodes/0.xxx.js"), __vite__mapDeps([0,1,2]), import.meta.url)

new URL('./_app/immutable/nodes/0.js', 'https://site/_app/immutable/entry/app.js') →
https://site/_app/immutable/entry/_app/immutable/nodes/0.js → 404 on every preload dep. CSS deps reject loudly (Unable to preload CSS … → vite:preloadError), JS modulepreloads fail silently. Matches the /_app/immutable/entry/_app/immutable/... URLs in the issue description exactly.

Playwright-verified: on 2.65.0 every route preload 404s with the nested path; on 2.64.0 + vite 8.0.16 the same app has zero failed requests and zero console errors.

Minimal reproduction

// package.json
{
  "name": "repro", "private": true, "type": "module",
  "scripts": { "build": "vite build", "preview": "vite preview" },
  "devDependencies": {
    "@sveltejs/adapter-auto": "latest",
    "@sveltejs/kit": "2.65.0",
    "@sveltejs/vite-plugin-svelte": "7.1.2",
    "svelte": "latest",
    "vite": "8.0.16"
  }
}

// svelte.config.js
import adapter from '@sveltejs/adapter-auto';
export default { kit: { adapter: adapter(), paths: { relative: false } } };

// vite.config.js
import { sveltekit } from '@sveltejs/kit/vite';
import { defineConfig } from 'vite';
export default defineConfig({ plugins: [sveltekit()] });

<!-- src/app.html -->
<!doctype html>
<html lang="en"><head>%sveltekit.head%</head><body><div>%sveltekit.body%</div></body></html>

<!-- src/routes/+page.svelte -->
<script>
	import { onMount } from 'svelte';
	let extra = '';
	onMount(async () => { const mod = await import('./heavy.js'); extra = mod.heavy(); });
</script>
<style> h1 { color: rebeccapurple; } </style>
<h1>home {extra}</h1>
<a href="/about">about</a>

// src/routes/heavy.js
export function heavy() { return 'heavy-' + Math.sqrt(144); }

<!-- src/routes/about/+page.svelte -->
<style> p { color: tomato; } </style>
<p>about page with its own css chunk</p>
<a href="/">home</a>

npm install && npm run build
grep -o '__vite__mapDeps=.\{0,160\}' .svelte-kit/output/client/_app/immutable/entry/app.*.js
# 2.65.0 → "./_app/immutable/nodes/0...js" (broken)
# change @sveltejs/kit to 2.64.0, reinstall, rebuild
# 2.64.0 → "_app/immutable/nodes/0...js" + "/"+dep helper (correct)

Suspected area (unconfirmed)

2.65.0's changelog has three changes; the only build-pipeline one is #15936 ("skip client build if all routes have CSR disabled"). We have not bisected at the commit level, so treat that as a pointer, not a conclusion.