Astro Info

Astro                    v4.5.12
Node                     v20.12.0
System                   Linux (x64)
Package Manager          pnpm
Output                   hybrid
Adapter                  @astrojs/node
Integrations             none

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

No response

Describe the Bug

i want to use Astro.preferredLocale to redirect the "/" root route to the user's preferred locale (or the default locale). i am using hybrid output mode, and have set export const prerender = false in src/pages/index.astro, and configured redirectToDefaultLocale: false in astro.config.mjs.

When logging both Astro.preferredLocale and Astro.request.headers.get("Accept-Language"), i see that Astro.preferredLocale is undefined, even though the Accept-Language headers are logged correctly.

how to reproduce

0. clone the repo at https://github.com/stefanprobst/issue-astro-i18n-preferredlocale-hybrid
1. pnpm run build
2. pnpm run preview
3. open http://localhost:3000
4. see server logs:

Preferred locale: undefined
Accept-Language header: de,en-US;q=0.7,en;q=0.3

observations

• when changing "output" mode from hybrid to server, it correctly prints: "Preferred locale: de"
• when not using any import from astro:i18n, i.e. commenting out this line, it also works correctly in hybrid mode
• changing src/pages/index.astro to a src/pages/index.ts GET route does not make a difference

What's the expected result?

see above

Link to Minimal Reproducible Example

https://github.com/stefanprobst/issue-astro-i18n-preferredlocale-hybrid

Participation

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