{@render ...} inside <svelte:head> causes "invalid_snippet_arguments" error

[NextLegacy]

Describe the bug

Using the {@render} directive within a <svelte:head> tag results in a "Svelte error: invalid_snippet_arguments".
This issue started occurring with version svelte@5.26.0. The code was working in previous versions.

Reproduction

1. Run npx sv create my-app
2. Replace the contents of src/routes/+page.svelte with the following:

{#snippet abc()}
    <p>
     abc
    </p>
{/snippet}

<svelte:head>
    {@render abc()}
</svelte:head>

3. Run npm install && npm run dev

Logs

Svelte error: invalid_snippet_arguments
A snippet function was passed invalid arguments. Snippets should only be instantiated via `{@render ...}`
https://svelte.dev/e/invalid_snippet_arguments
    at invalid_snippet_arguments (eval at runInlinedModule (file:///C:/Users/NextLegacy/Desktop/New%20folder/my-app/node_modules/vite/dist/node/module-runner.js:1049:11), <anonymous>:29:17)
    at Module.validate_snippet_args (eval at runInlinedModule (file:///C:/Users/NextLegacy/Desktop/New%20folder/my-app/node_modules/vite/dist/node/module-runner.js:1049:11), <anonymous>:114:54)
    at abc (eval at runInlinedModule (file:///C:/Users/NextLegacy/Desktop/New%20folder/my-app/node_modules/vite/dist/node/module-runner.js:1049:11), <anonymous>:11:24)
    at eval (eval at runInlinedModule (file:///C:/Users/NextLegacy/Desktop/New%20folder/my-app/node_modules/vite/dist/node/module-runner.js:1049:11), <anonymous>:23:3)
    at Module.head (eval at runInlinedModule (file:///C:/Users/NextLegacy/Desktop/New%20folder/my-app/node_modules/vite/dist/node/module-runner.js:1049:11), <anonymous>:130:2)
    at _page (eval at runInlinedModule (file:///C:/Users/NextLegacy/Desktop/New%20folder/my-app/node_modules/vite/dist/node/module-runner.js:1049:11), <anonymous>:21:24)
    at children (eval at runInlinedModule (file:///C:/Users/NextLegacy/Desktop/New%20folder/my-app/node_modules/vite/dist/node/module-runner.js:1049:11), <anonymous>:66:5)
    at _layout (eval at runInlinedModule (file:///C:/Users/NextLegacy/Desktop/New%20folder/my-app/node_modules/vite/dist/node/module-runner.js:1049:11), <anonymous>:19:2)
    at Root (eval at runInlinedModule (file:///C:/Users/NextLegacy/Desktop/New%20folder/my-app/node_modules/vite/dist/node/module-runner.js:1049:11), <anonymous>:61:3)
    at render (eval at runInlinedModule (file:///C:/Users/NextLegacy/Desktop/New%20folder/my-app/node_modules/vite/dist/node/module-runner.js:1049:11), <anonymous>:94:2)

System Info

System:
  OS: Windows 11 10.0.26100
  CPU: (28) x64 Intel(R) Core(TM) i7-14700K
  Memory: 6.92 GB / 31.75 GB
Binaries:
  Node: 22.13.0 - C:\Program Files\nodejs\node.EXE
  npm: 11.0.0 - C:\Program Files\nodejs\npm.CMD
  pnpm: 10.6.3 - ~\AppData\Local\pnpm\pnpm.EXE
  bun: 1.1.42 - ~\.bun\bin\bun.EXE
Browsers:
  Edge: Chromium (133.0.3065.69)
  Internet Explorer: 11.0.26100.1882

Severity

blocking an upgrade

[Ocean-OS]

This reproduction doesn't seem to have any issues, could you please make a REPL reproduction that demonstrates the issue?

[NextLegacy]

I couldn't reproduce the issue in the Svelte Playground either, but I was able to reproduce it using SvelteLab:
https://www.sveltelab.dev/5819y119sc28v1w

Additionally, I've created a minimal GitHub repository that demonstrates the issue using the exact steps mentioned above:
https://github.com/NextLegacy/svelte-issue-15753

It's also worth mentioning that the error only occurs in development environments, production builds don't seem to be affected.

[paoloricciuti]

The issue is that the validate snippet function on the server is checking for instance of Payload but inside the head we pass Payload.head which is just an object