NextJS 15's `next/font` breaks alternate header injection.

[zenzen-sol]

Description

I notice that in the NextJS 15 release candidate, the "alternate" links that should appear in the response header are missing if next/font is used to optimize fonts. I'm not sure whether this issue belongs to NextJS or next-intl.

Verifications

• [X] I've verified that the problem I'm experiencing isn't covered in the docs.
• [X] I've searched for similar, existing issues on GitHub and Stack Overflow.
• [X] I've compared my app to a working example to look for differences.

Mandatory reproduction URL

https://github.com/zenzen-sol/next-reproduction-template/tree/sol/repro-001-next-15-broken

Reproduction description

Steps to reproduce:

1. Open reproduction
2. Run pnpm run dev
3. Reload http://localhost:3000 in a browser.
4. Check the response header links in dev tools.

✅ OK(Next 14): https://github.com/zenzen-sol/next-reproduction-template/tree/sol/repro-001-Next-14-working

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🙅🏻Broken (Next 15rc + next/font): https://github.com/zenzen-sol/next-reproduction-template/tree/sol/repro-001-next-15-broken

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✅ OK (Next 15rc without next/font): https://github.com/zenzen-sol/next-reproduction-template/tree/sol/repro-001-next-15-working

Expected behaviour

Both the next-intl and next/font links should be present in the response header.

[amannn]

Many thanks for the thoughtful bug report and reproduction! Do you think you could report this upstream in the Next.js repo? Seems like this is something to be addressed there. If you do, can you leave a link here so we can track the upstream issue?

[zenzen-sol]

@amannn Thanks. The upstream issue is here.

[amannn]

Thanks a lot, I'll keep an eye on the issue!