HierarchyRequestError: Failed to execute 'appendChild' on 'Node': This node type does not support this method.

[teemingc]

Describe the bug

When an error is thrown during hydration (such as from a SvelteKit universal load function), an uncaught "appendChild on Node" error occurs which prevents the error page from rendering successfully.

See sveltejs/kit#13054 (comment) for additional context.
Also related to sveltejs/kit#11057

Reproduction

https://stackblitz.com/edit/sveltejs-kit-template-default-umktkj?file=src%2Froutes%2F%2Bpage.svelte

Expected: Error page gets rendered.
Actual: Uncaught error during hydration.

In comparison, with Svelte 4, the error page is rendered.

Logs

Uncaught (in promise) HierarchyRequestError: Failed to execute 'appendChild' on 'Node': This node type does not support this method.

	in layout.svelte
	in root.svelte

    at Module.child (https://sveltejskittemplatedefaultumkt-o32a--5173--88b6dd69.local-credentialless.webcontainer.io/node_modules/.vite/deps/chunk-7AF2HH4B.js?v=9e2bab17:966:27)
    at Error (https://sveltejskittemplatedefaultumkt-o32a--5173--88b6dd69.local-credentialless.webcontainer.io/node_modules/@sveltejs/kit/src/runtime/components/svelte-5/error.svelte?v=9e2bab17:32:17)
    at https://sveltejskittemplatedefaultumkt-o32a--5173--88b6dd69.local-credentialless.webcontainer.io/node_modules/.vite/deps/chunk-JXW34V7O.js?v=9e2bab17:234:58
    at update_reaction (https://sveltejskittemplatedefaultumkt-o32a--5173--88b6dd69.local-credentialless.webcontainer.io/node_modules/.vite/deps/chunk-7AF2HH4B.js?v=9e2bab17:1723:23)
    at update_effect (https://sveltejskittemplatedefaultumkt-o32a--5173--88b6dd69.local-credentialless.webcontainer.io/node_modules/.vite/deps/chunk-7AF2HH4B.js?v=9e2bab17:1814:21)
    at create_effect (https://sveltejskittemplatedefaultumkt-o32a--5173--88b6dd69.local-credentialless.webcontainer.io/node_modules/.vite/deps/chunk-7AF2HH4B.js?v=9e2bab17:1194:7)
    at branch (https://sveltejskittemplatedefaultumkt-o32a--5173--88b6dd69.local-credentialless.webcontainer.io/node_modules/.vite/deps/chunk-7AF2HH4B.js?v=9e2bab17:1326:10)
    at https://sveltejskittemplatedefaultumkt-o32a--5173--88b6dd69.local-credentialless.webcontainer.io/node_modules/.vite/deps/chunk-JXW34V7O.js?v=9e2bab17:228:17
    at update_reaction (https://sveltejskittemplatedefaultumkt-o32a--5173--88b6dd69.local-credentialless.webcontainer.io/node_modules/.vite/deps/chunk-7AF2HH4B.js?v=9e2bab17:1723:23)
    at update_effect (https://sveltejskittemplatedefaultumkt-o32a--5173--88b6dd69.local-credentialless.webcontainer.io/node_modules/.vite/deps/chunk-7AF2HH4B.js?v=9e2bab17:1814:21)HierarchyRequestError: Failed to execute 'appendChild' on 'Node': This node type does not support this method.

	in layout.svelte
	in root.svelte

    at Module.child (https://sveltejskittemplatedefaultumkt-o32a--5173--88b6dd69.local-credentialless.webcontainer.io/node_modules/.vite/deps/chunk-7AF2HH4B.js?v=9e2bab17:966:27)
    at Error (https://sveltejskittemplatedefaultumkt-o32a--5173--88b6dd69.local-credentialless.webcontainer.io/node_modules/@sveltejs/kit/src/runtime/components/svelte-5/error.svelte?v=9e2bab17:32:17)
    at https://sveltejskittemplatedefaultumkt-o32a--5173--88b6dd69.local-credentialless.webcontainer.io/node_modules/.vite/deps/chunk-JXW34V7O.js?v=9e2bab17:234:58
    at update_reaction (https://sveltejskittemplatedefaultumkt-o32a--5173--88b6dd69.local-credentialless.webcontainer.io/node_modules/.vite/deps/chunk-7AF2HH4B.js?v=9e2bab17:1723:23)
    at update_effect (https://sveltejskittemplatedefaultumkt-o32a--5173--88b6dd69.local-credentialless.webcontainer.io/node_modules/.vite/deps/chunk-7AF2HH4B.js?v=9e2bab17:1814:21)
    at create_effect (https://sveltejskittemplatedefaultumkt-o32a--5173--88b6dd69.local-credentialless.webcontainer.io/node_modules/.vite/deps/chunk-7AF2HH4B.js?v=9e2bab17:1194:7)
    at branch (https://sveltejskittemplatedefaultumkt-o32a--5173--88b6dd69.local-credentialless.webcontainer.io/node_modules/.vite/deps/chunk-7AF2HH4B.js?v=9e2bab17:1326:10)
    at https://sveltejskittemplatedefaultumkt-o32a--5173--88b6dd69.local-credentialless.webcontainer.io/node_modules/.vite/deps/chunk-JXW34V7O.js?v=9e2bab17:228:17
    at update_reaction (https://sveltejskittemplatedefaultumkt-o32a--5173--88b6dd69.local-credentialless.webcontainer.io/node_modules/.vite/deps/chunk-7AF2HH4B.js?v=9e2bab17:1723:23)
    at update_effect (https://sveltejskittemplatedefaultumkt-o32a--5173--88b6dd69.local-credentialless.webcontainer.io/node_modules/.vite/deps/chunk-7AF2HH4B.js?v=9e2bab17:1814:21)

System Info

System:
    OS: Linux 5.0 undefined
    CPU: (8) x64 Intel(R) Core(TM) i9-9880H CPU @ 2.30GHz
    Memory: 0 Bytes / 0 Bytes
    Shell: 1.0 - /bin/jsh
  Binaries:
    Node: 18.20.3 - /usr/local/bin/node
    Yarn: 1.22.19 - /usr/local/bin/yarn
    npm: 10.2.3 - /usr/local/bin/npm
    pnpm: 8.15.6 - /usr/local/bin/pnpm
  npmPackages:
    svelte: ^5.0.0 => 5.2.7

Severity

blocking an upgrade

[dummdidumm]

This is actually a result of SvelteKit not behaving correctly, sveltejs/kit#13056 should fix this