Metadata duplication in <head> when using next-intl middleware with locale redirects #80529
Description
Link to the code that reproduces this issue
Live: https://job-board-chi-indol.vercel.app/
To Reproduce
- Set up next-intl middleware for internationalization.
- Configure locale routing with redirects from
/to/[locale]. - Export a
generateMetadatafunction in a page component. - Navigate from
/to a locale path (e.g.,/en). - Inspect the HTML output in browser DevTools.
Example code:
// middleware.ts
import createMiddleware from 'next-intl/middleware';
import { routing } from './src/i18n/routing';
export default createMiddleware(routing);
export const config = {
matcher: ['/', '/(en|el)/:path*']
};// src/i18n/routing.ts
export const routing = {
locales: ['en', 'el'],
defaultLocale: 'en',
localePrefixMode: 'always'
} as const;// app/[locale]/page.tsx
export async function generateMetadata({
params,
searchParams,
}: Props): Promise<Metadata> {
const { locale } = await params;
const t = await getTranslations({ locale, namespace: "meta" });
return {
title: t('title'),
description: t('description'),
openGraph: {
title: t('title'),
description: t('description'),
type: "website",
locale,
},
};
}Current vs. Expected behavior
Following the steps from the previous section, I expected the metadata to appear only once in the <head> section when redirecting between routes. However, metadata tags (title, description, Open Graph, etc.) are duplicated in the HTML output after locale redirects.
<!-- Expected: Single metadata -->
<head>
<title>Job Board</title>
<meta name="description" content="Find jobs..." />
</head>
<!-- Actual: Duplicated metadata -->
<head>
<title>Job Board</title>
<title>Job Board</title>
<meta name="description" content="Find jobs..." />
<meta name="description" content="Find jobs..." />
</head>Provide environment information
Operating System:
Platform: darwin
Arch: arm64
Version: Darwin Kernel Version 24.4.0
Binaries:
Node: 21.6.2
npm: 10.2.4
Yarn: N/A
pnpm: N/A
Relevant Packages:
next: 15.3.2
eslint-config-next: N/A
react: 19.1.0
react-dom: 19.1.0
typescript: 5.8.3
next-intl: 4.1.0
Next.js Config:
output: N/A
Which area(s) are affected?
- 'Metadata'
- 'Middleware'
- 'Redirects'
Which stage(s) are affected?
- 'Vercel (Deployed)'
Additional context
- Issue does NOT occur with static metadata exports.
- Only happens with
generateMetadatafunction during locale redirects. - Metadata merging behavior seems inconsistent with documented behavior.
- The issue is reproducible on deployed (Vercel) environments.