localePrefix: "as-needed" not working as expected for default locale routes

[cagdaser]

The localePrefix: "as-needed" configuration is not behaving as expected for default locale routes. According to the documentation, this setting should allow the default locale to be accessed without a prefix, but currently it only works for the root path (/) and not for other routes like /contact.

Expected Behavior

With localePrefix: "as-needed" and defaultLocale: "tr", the following URLs should work:

• ✅ / → Turkish homepage (default locale, no prefix)
• ✅ /contact → Turkish contact page (default locale, no prefix)
• ✅ /en → English homepage (non-default locale, prefix required)
• ✅ /en/contact → English contact page (non-default locale, prefix required)

This is the standard behavior seen on major international websites like [CoinMarketCap] https://coinmarketcap.com/currencies/xrp/ (English default, no prefix) vs [CoinMarketCap Turkish]https://coinmarketcap.com/tr/currencies/xrp/ (Turkish with /tr/ prefix).

Current Behavior

Currently with localePrefix: "as-needed":

• ✅ / → Works (Turkish homepage)
• ❌ /contact → 404 (should work for default locale)
• ✅ /tr/contact → Works (explicit prefix)
• ✅ /en/contact → Works (non-default locale)

Reproduction

Minimal reproduction setup:

src/i18n/routing.ts:

import { defineRouting } from "next-intl/routing";

export const routing = defineRouting({
  locales: ["en", "tr"] as const,
  defaultLocale: "tr",
  localePrefix: "as-needed",
  localeDetection: false,
  localeCookie: false,
});

middleware.ts:

import createMiddleware from 'next-intl/middleware';
import { routing } from '@/i18n/routing';

const intlMiddleware = createMiddleware(routing);

export async function middleware(request: NextRequest) {
  return intlMiddleware(request);
}

export const config = {
  matcher: ['/((?!api|_next|_vercel|.*\\..*).*)',]
};

File structure:

src/app/
├── [locale]/
│   ├── page.tsx (works with prefix)
│   ├── layout.tsx
│   └── contact/
│       └── page.tsx (works with prefix)
├── page.tsx (root page - works without prefix)
└── layout.tsx

Steps to reproduce:

1. Visit / → ✅ Works (Turkish default)
2. Visit /contact → ❌ 404 error
3. Visit /tr/contact → ✅ Works
4. Visit /en/contact → ✅ Works

Workaround Attempted

Created duplicate pages at root level (e.g., src/app/contact/page.tsx) that import and render the locale-specific components, but this creates:

• Code duplication
• Potential SEO issues (duplicate content)
• Maintenance overhead
• Not scalable for larger applications

Environment

• next-intl version: 4.1.0
• Next.js version: 15
• React version: 19

Request

Could you please provide guidance on how to properly configure localePrefix: "as-needed" to work for all routes of the default locale, not just the root path?

The goal is to have a clean URL structure where:

• Default locale routes have no prefix (/, /contact, /about)
• Non-default locale routes have prefixes (/en/contact, /fr/about)

This would align with common international website patterns and provide better UX for the primary audience.

---

[amannn]

Hmm, can't see an obvious problem, but if you start with the code from example-app-router and add localePrefix: 'as-needed' to the config, the default locale works correctly for nested pathnames without a prefix.