Next.js 15 breaks alternate links

[amannn]

Recent canary versions of Next.js 15 as well as the stable version that was released yesterday break alternate links if you're using next/font or next/image with priority.

This header is important for apps that use i18n routing and the alternateLinks feature (which is turned on by default). Failing to return this header can result in content being marked as duplicate by search engines.

Upstream bug report: vercel/next.js#69000 (comment)

I'm currently waiting for this to be resolved upstream before updating the examples and the bug repro to use Next.js 15.

As a workaround, you can use a sitemap to instruct search engines about multiple variants of your pages.

[Wiibleyde]

Hello, I think it's a part of the problem enounced here (if it's not i'm sorryyy), I have this error :

Error: Route "/[locale]" used `headers().get('X-NEXT-INTL-LOCALE')`. `headers()` should be awaited before using its value. Learn more: https://nextjs.org/docs/messages/sync-dynamic-apis
    at createHeadersAccessError (turbopack://[project]/node_modules/next/src/server/request/headers.ts:487:9)
    at getMessage (turbopack://[project]/node_modules/next/src/server/create-deduped-by-callsite-server-error-logger.ts:46:20)
    at warnForSyncAccess (turbopack://[project]/node_modules/next/src/server/request/headers.ts:473:2)
    at syncIODev (turbopack://[project]/node_modules/next/src/server/request/headers.ts:376:8)
    at <unknown> (turbopack://[project]/node_modules/next-intl/dist/esm/server/react-server/RequestLocaleLegacy.js:1:278)
    at apply (file:///home/wiibleyde/Alternance/lex-port-cartel/node_modules/next/dist/compiled/next-server/dist/compiled/react/cjs/react.react-server.development.js:888:26)
    at s (turbopack://[project]/node_modules/next-intl/dist/esm/server/react-server/RequestLocaleLegacy.js:1:996)
    at get locale [as locale] (turbopack://[project]/node_modules/next-intl/dist/esm/server/react-server/getConfig.js:1:874)
    at <unknown> (turbopack://[project]/src/i18n/request.ts:5:41)
    at <unknown> (turbopack://[project]/node_modules/next-intl/dist/esm/server/react-server/getConfig.js:1:939)
    at apply (file:///home/wiibleyde/Alternance/lex-port-cartel/node_modules/next/dist/compiled/next-server/dist/compiled/react/cjs/react.react-server.development.js:888:26)
    at <unknown> (turbopack://[project]/node_modules/next-intl/dist/esm/server/react-server/getConfig.js:1:1446)
    at apply (file:///home/wiibleyde/Alternance/lex-port-cartel/node_modules/next/dist/compiled/next-server/dist/compiled/react/cjs/react.react-server.development.js:888:26)
    at r (turbopack://[project]/node_modules/next-intl/dist/esm/react-server/useConfig.js:1:436)
    at o (turbopack://[project]/node_modules/next-intl/dist/esm/react-server/useTranslations.js:1:168)
    at Loading (turbopack://[project]/src/app/[locale]/loading.tsx:6:30)
> 1 | import{headers as e}from"next/headers";import{notFound as t}from"next/navigation";import{cache as n}from"react";import{HEADER_LOCALE_NAME as o}from"../../shared/constants.js";import{getCachedRequestLocale as r}from"./RequestLocaleCache.js";const i=n((function(){let n;try{n=e().get(o)}catch(e){throw e instanceof Error&&"DYNAMIC_SERVER_USAGE"===e.digest?new Error("Usage of next-intl APIs in Server Components currently opts into dynamic rendering. This limitation will eventually be lifted, but as a stopgap solution, you can use the `setRequestLocale` API to enable static rendering, see https://next-intl-docs.vercel.app/docs/getting-started/app-router/with-i18n-routing#static-rendering",{cause:e}):e}return n||(console.error("\nUnable to find `next-intl` locale because the middleware didn't run on this request. See https://next-intl-docs.vercel.app/docs/routing/middleware#unable-to-find-locale. The `notFound()` function will be called as a result.\n"),t()),n}));function s(){return r()||i()}export{s as getRequestLocale};

With this packages :
"dependencies": {
"axios": "^1.7.7",
"next": "^15.0.2",
"next-intl": "^3.24.0",
"react": "19.0.0-rc-69d4b800-20241021",
"react-bootstrap-icons": "^1.11.4",
"react-dom": "19.0.0-rc-69d4b800-20241021",
"react-google-recaptcha-v3": "^1.10.1"
},

Any ideas if it's my fault ? (it's possible, I'm a junior developper)

[amannn]

Hey @Wiibleyde, nope—that's a different story. You're looking for this: await requestLocale.

[Wiibleyde]

Oh okay ! Thanks ! and sorry...

[amannn]

I opened a PR yesterday over at the Next.js repo to address this: vercel/next.js#73431