Astro Info

Astro                    v5.16.6
Node                     v22.18.0
System                   Windows (x64)
Package Manager          unknown
Output                   server
Adapter                  @astrojs/node
Integrations             @astrojs/react

If this issue only occurs in one browser, which browser is a problem?

No response

Describe the Bug

When creating an Astro SSR multilanguage website with the following config:

export default defineConfig({
    adapter: node({
        mode: 'standalone',
    }),

    output: 'server',

    i18n: {
        locales: ["en", "de"],
        defaultLocale: "en",

        routing: {
            prefixDefaultLocale: true,
        },
    },
});

And directory structure:

• src
  • pages
    • [locale]
      • index.astro
    • 404.astro

Then making requests to: http://localhost:4321/en/ or http://localhost:4321/de/ results into an HTTP response with code 200, returning /pages/[locale]/index.astro in the response body as expected.

However, if the user tries to make an HTTP request with an invalid language code (not specified in config), for example: http://localhost:4321/asdf/, it results into an HTTP response with code 404, returning /pages/[locale]/index.astro in the response body, instead of /pages/404.astro

Example in this repository:
https://github.com/jonas-s-s-s/astro-not-404
https://stackblitz.com/github/jonas-s-s-s/astro-not-404

What's the expected result?

Making an HTTP request containing an invalid locale code in the URL (for example http://localhost:4321/asdf/ instead of http://localhost:4321/en/) should always result into an HTTP response with code 404, containing the 404.astro page in its body - current implementation does NOT return the 404 page in the response body.

Link to Minimal Reproducible Example

https://stackblitz.com/github/jonas-s-s-s/astro-not-404

Participation

• I am willing to submit a pull request for this issue.