`pnpm build` takes forever then exits with error when `config.kit.prerender.handleHttpError` is set

[Mr-M1M3]

Describe the bug

Hi, I just made a static site and set config,kit.prerender.handleHttpError according to the docs. However, the build command takes a lot of time and then just exits with an error (see logs below)

Reproduction

in the root +layout.svelte, add the following:

<svelte:head>
	<meta property="og:title" content={dynamic_title} />
	<meta property="og:description" content={dynamic_desc} />
	<meta property="og:url" content={page.url.origin} />
	<meta property="og:image" content="{page.url.host}/{a_path_to_svelte_kit_static_content}" />
</svelte:head>

Then, my config looks just like this:

const config = {
	preprocess: vitePreprocess(),
	kit: {
		adapter: static_adapter({
			precompress: true
		}),
		prerender: {
			handleHttpError: (det) => {
				const { status, message } = det;
				console.log(`error from svelte.config.js -> config.kit.prerender.handleHttpError(): \n`);
				console.log(inspect(det, true, null, true));
				if (status >= 400 && status < 500) {
					return 'warn';
				}
				throw new Error(message);
			}
		}
	}
};

Logs

after running `pnpm build`, output looks like this:


vite v7.1.7 building SSR bundle for production...
✓ 213 modules transformed.
vite v7.1.7 building for production...
✓ 161 modules transformed.
.svelte-kit/output/client/_app/version.json                        0.03 kB │ gzip:  0.05 kB
.svelte-kit/output/client/.vite/manifest.json                      3.61 kB │ gzip:  0.72 kB
.svelte-kit/output/client/_app/immutable/assets/2.DSfxk8o2.css     1.50 kB │ gzip:  0.57 kB
.svelte-kit/output/client/_app/immutable/assets/0.CMpaBS7g.css    41.20 kB │ gzip:  7.82 kB
.svelte-kit/output/client/_app/immutable/chunks/DsnmJJEf.js        0.07 kB │ gzip:  0.08 kB
.svelte-kit/output/client/_app/immutable/entry/start.RRW9TG_7.js   0.08 kB │ gzip:  0.09 kB
.svelte-kit/output/client/_app/immutable/chunks/c7DZMM8V.js        0.18 kB │ gzip:  0.14 kB
.svelte-kit/output/client/_app/immutable/chunks/50G2RjtE.js        0.30 kB │ gzip:  0.22 kB
.svelte-kit/output/client/_app/immutable/nodes/1.mwG7EJ2z.js       0.42 kB │ gzip:  0.29 kB
.svelte-kit/output/client/_app/immutable/chunks/L6wIdL0K.js        0.45 kB │ gzip:  0.31 kB
.svelte-kit/output/client/_app/immutable/chunks/N9lAo_Pj.js        0.52 kB │ gzip:  0.33 kB
.svelte-kit/output/client/_app/immutable/nodes/0.CnpseRnQ.js       1.92 kB │ gzip:  0.94 kB
.svelte-kit/output/client/_app/immutable/chunks/CwY099cG.js        2.15 kB │ gzip:  1.15 kB
.svelte-kit/output/client/_app/immutable/entry/app.CbiFaNZM.js     5.62 kB │ gzip:  2.70 kB
.svelte-kit/output/client/_app/immutable/chunks/L23dAPVL.js        8.85 kB │ gzip:  4.17 kB
.svelte-kit/output/client/_app/immutable/chunks/KPqfODo3.js       29.39 kB │ gzip: 11.59 kB
.svelte-kit/output/client/_app/immutable/chunks/Ccp16_zV.js       31.71 kB │ gzip: 12.38 kB
.svelte-kit/output/client/_app/immutable/nodes/2.u4DBBnek.js      41.27 kB │ gzip: 15.74 kB
✓ built in 579ms
SvelteKitError: Not found: /sveltekit-prerender//me.jpg
  ...
    at AsyncLocalStorage.run (node:internal/async_local_storage/async_context_frame:63:14) {
  [stack]: [Getter/Setter],
  [message]: 'Not found: /sveltekit-prerender//me.jpg',
  status: 404,
  text: 'Not Found'
}
node:events:485
      throw er; // Unhandled 'error' event
      ^

Error [ERR_WORKER_OUT_OF_MEMORY]: Worker terminated due to reaching memory limit: JS heap out of memory
    at [kOnExit] (node:internal/worker:314:26)
    at Worker.<computed>.onexit (node:internal/worker:230:20)
Emitted 'error' event on Worker instance at:
    at [kOnExit] (node:internal/worker:314:12)
    at Worker.<computed>.onexit (node:internal/worker:230:20) {
  code: 'ERR_WORKER_OUT_OF_MEMORY'
}

Node.js v24.5.0

System Info

OS: Manjaro Linux x86_64
Kernel: Linux 6.12.48-1-MANJARO
Node: v24.5.0

Severity

serious, but I can work around it

Additional Information

No response

[Conduitry]

What's me.jpg? We need a proper and complete reproduction.

[Mr-M1M3]

@Conduitry Shoot, I forgot. Its just an image stored inside static/

[justingolden21]

I was trying to reproduce a different seemingly unrelated error and made a new repo, and in that new repo I got this error:

"Error [ERR_WORKER_OUT_OF_MEMORY]: Worker terminated due to reaching memory limit: JS heap out of memory"

More context:

.svelte-kit/output/client/_app/immutable/chunks/DCziGpnG.js               29.78 kB │ gzip: 10.72 kB
.svelte-kit/output/client/_app/immutable/chunks/DYpfYK7r.js               33.89 kB │ gzip: 12.99 kB
.svelte-kit/output/client/_app/immutable/nodes/20.v4TGHaIy.js             39.30 kB │ gzip: 11.12 kB
.svelte-kit/output/client/_app/immutable/chunks/MFsMVkYx.js               67.12 kB │ gzip: 24.59 kB
.svelte-kit/output/client/_app/immutable/chunks/DOpgCHb_.js               74.95 kB │ gzip: 30.71 kB
.svelte-kit/output/client/_app/immutable/chunks/D1hoDXJn.js              100.00 kB │ gzip: 63.32 kB
.svelte-kit/output/client/_app/immutable/chunks/BzpUzCiM.js              110.94 kB │ gzip: 34.90 kB
.svelte-kit/output/client/_app/immutable/nodes/0.DZAkH6Qt.js             213.81 kB │ gzip: 59.13 kB
✓ built in 4.25s
node:events:496
      throw er; // Unhandled 'error' event
      ^

Error [ERR_WORKER_OUT_OF_MEMORY]: Worker terminated due to reaching memory limit: JS heap out of memory
    at [kOnExit] (node:internal/worker:313:26)
    at Worker.<computed>.onexit (node:internal/worker:229:20)
Emitted 'error' event on Worker instance at:
    at [kOnExit] (node:internal/worker:313:12)
    at Worker.<computed>.onexit (node:internal/worker:229:20) {
  code: 'ERR_WORKER_OUT_OF_MEMORY'
}

Node.js v22.18.0
 ELIFECYCLE  Command failed with exit code 1.

It hung for a very long time and did this. Was able to reproduce multiple times. It's a lazy attempt to reproduce a different bug, so maybe in this repo a linked file is missing and the svelte compiler instead of warning about it, under these circumstances, memory leaks? When copying in the correct assets, it seems to go away.

For @Mr-M1M3 , I'd say see if removing references to me.jpg fixes it, and if so it's a file path/linking issue, and for @Conduitry I'd say that perhaps svelte kit isn't handling missing files as expected. In his case it at least says the file is missing, but still leaks memory and crashes, and in mty case it completely destroys the PC for a while and then crashes without so much as a helpful error about a missing file. Just my two cents here. Thanks in advance.

[Mr-M1M3]

@justingolden21 Hi. Thanks for taking your time.
I couldn't fix that error so I switched to a different adapter ( adapter-vercel ). Then, it stops taking forever to build and I stopped getting the ERR_WORKER_OUT_OF_MEMORY error. However, I did face another issue tho. It was because of the fact that I had added an extra / if you look closely. So, I doubt that it is an error related to path/linking issue. My guess is that, it is an error with adapter-static which is not handling promises well.

[Mr-M1M3]

I inspected a bit, and I think I kind of found the issue.

I think @justingolden21 is correct. While prerendering with adapter-static if a static content is not found, then the adapter takes tooo long to comnplete only to fail with an error.

What happened:

<meta property="og:image" content="{page.url.host}/{a_path_to_svelte_kit_static_content}" />

Notice, here I used {page.url.host}? That would resolve to sveltekit-prerender/ while building. If I instead used, page.url.origin, that would resolve to http://sveltekit-prerender/ while building. Because I used .host, sveltekit mistakes it as a local file and tries to resolve it and fails. (using .origin builds the site as expected). To conclude, that path is invalid.

My guess

Sveltekit defines a vite plugin named vite-plugin-sveltekit-compile. As it is a vite plugin, It has a closeBundle hook which isn't running properly. I changed the closeHandle hook to look like this:

closeBundle: {
			sequential: true,
			async handler() {
				console.log('runing handler')
				if (!vite_config.build.ssr) return;
				console.log('finalizing')
				try{
					await finalise?.();
				}catch(e){
					console.error('an error occurred')
					console.error(inspect(e, true, null, true))
				}
			}
		}

After that, I tried pnpm build and then got the following output:

> portfolio@0.0.1 build /home/mr-m1m3/Documents/portfolio
> vite build

vite v7.1.7 building SSR bundle for production...
✓ 222 modules transformed.
vite v7.1.7 building for production...
✓ 164 modules transformed.
.svelte-kit/output/client/_app/version.json                        0.03 kB │ gzip:  0.05 kB
.svelte-kit/output/client/.vite/manifest.json                      3.32 kB │ gzip:  0.63 kB
.svelte-kit/output/client/_app/immutable/assets/2.DSfxk8o2.css     1.50 kB │ gzip:  0.57 kB
.svelte-kit/output/client/_app/immutable/assets/0.CMpaBS7g.css    41.20 kB │ gzip:  7.82 kB
.svelte-kit/output/client/_app/immutable/chunks/DsnmJJEf.js        0.07 kB │ gzip:  0.08 kB
.svelte-kit/output/client/_app/immutable/entry/start.D4jg06oS.js   0.08 kB │ gzip:  0.09 kB
.svelte-kit/output/client/_app/immutable/chunks/D3846YtU.js        0.18 kB │ gzip:  0.15 kB
.svelte-kit/output/client/_app/immutable/chunks/50G2RjtE.js        0.30 kB │ gzip:  0.22 kB
.svelte-kit/output/client/_app/immutable/nodes/1.y_vfyHh7.js       0.42 kB │ gzip:  0.29 kB
.svelte-kit/output/client/_app/immutable/chunks/L6wIdL0K.js        0.45 kB │ gzip:  0.31 kB
.svelte-kit/output/client/_app/immutable/chunks/N9lAo_Pj.js        0.52 kB │ gzip:  0.33 kB
.svelte-kit/output/client/_app/immutable/nodes/0.CvxcQTyn.js       2.10 kB │ gzip:  0.98 kB
.svelte-kit/output/client/_app/immutable/chunks/CwY099cG.js        2.15 kB │ gzip:  1.15 kB
.svelte-kit/output/client/_app/immutable/entry/app.CWEL35nN.js     5.62 kB │ gzip:  2.70 kB
.svelte-kit/output/client/_app/immutable/chunks/CkPUv60Y.js        8.85 kB │ gzip:  4.17 kB
.svelte-kit/output/client/_app/immutable/chunks/KPqfODo3.js       29.39 kB │ gzip: 11.59 kB
.svelte-kit/output/client/_app/immutable/chunks/Br7G5R-Q.js       31.71 kB │ gzip: 12.38 kB
.svelte-kit/output/client/_app/immutable/nodes/2.t5ymjqeM.js      41.18 kB │ gzip: 15.70 kB
✓ built in 516ms
runing handler

And here, it gets stucked and doesn't move forward.
Mentioning @Conduitry to check this out.

[Rich-Harris]

This is nothing to do with <meta> tags or page.url.host or any of that. As long as you have a handleHttpError that doesn't throw (not that returning 'warn' does nothing; you must use 'warn' instead of a function, rather than returning it from the function), this is sufficient to reproduce it:

<!-- layout.svelte -->
<script>
  let { children } = $props();
</script>

<a href="bad/link">bad link</a>

{@render children()}

I'm at a loss as to why it's hanging though.

[Mr-M1M3]

@Rich-Harris Hi. From my guess, I think it is an issue with rollup and not sveltekit. After inspecting a bit, I noticed that closeBundle hook ran before writeBundle hook finished running. Maybe, rollup is running those hooks in parallel causing the issue. I'm not sure tho.

[Rich-Harris]

It's nothing to do with Rollup.

I see what's happening — it crawls /, includes <a href="bad/link">bad link</a> which resolves to /bad/link. It tries to crawl that, but it's a 404, which — because the offending <a> is in the root layout — includes the same link, which this time resolves to /bad/bad/link. That also 404s, resulting in /bad/bad/bad/link, and so on until we OOM.

Not 100% sure what the ideal solution is, but maybe we should avoid crawling 404 responses more than one level deep

[Rich-Harris]

Actually it's simpler than that — we don't save error responses, so we don't need to crawl them