Link header is not set in Next.js 15.1

[tobiashaefermann]

Description

In Next.js 15.1 the Link header with hreflang links is not set, it seems to be removed or overridden.

I provided a minimum reproducible example which contains a freshly installed Next app (create-next-app) with the basic setup of next-intl (start dev server). Alternatively you can use the example-app-router and just bump the Next.js version to 15.1.

Link headers in dev server before:

link:
<http://localhost:3001/en>; rel="alternate"; hreflang="en"
<http://localhost:3001/de>; rel="alternate"; hreflang="de
<http://localhost:3001/>; rel="alternate"; hreflang="x-default"

link:
</_next/static/media/a34f9d1faa5f3315-s.p.woff2>; rel=preload; as="font"; crossorigin=""; type="font/woff2"

Link headers in Next.js 15.1:

link:
</_next/static/media/a34f9d1faa5f3315-s.p.woff2>; rel=preload; as="font"; crossorigin=""; type="font/woff2"
</_next/static/css/app/layout.css?v=1734104148288>; rel=preload; as="style"
</_next/static/css/app/%5Blocale%5D/layout.css?

Verifications

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

Mandatory reproduction URL

https://github.com/tobiashaefermann/next-intl-link-header-bug

Reproduction description

Steps to reproduce:

1. Clone reproduction repo
2. Install dependecies (pnpm install)
3. Start dev server: pnpm dev
4. Open home page and inspect document request headers

Expected behaviour

I expect the link header to be properly set in the default setup (as it is described in the docs and works for Next.js 14). As the peer dependencies include Next.js 15, I consider this as a bug.

[tobiashaefermann]

I see this is already opened as an issue in the nextjs repo: vercel/next.js#69000 and there's already a PR provided, waiting to be merged: vercel/next.js#73431.

I leave this open for now for other people as reference :) thanks!

[amannn]

Yep, an issue is also already open in this repo: #1442. I'll close in favor of the existing one.