This is a Next.js project to demonstrate a bug with dynamic routes.

Important

The issue is now fixed in Next.js 15.3.1-canary.2

Description

Under certain conditions, for a page with dynamic route an incorrect params are passed to the page

The error is reproducing for me when the following conditions are met:

• the page in question has a dynamic route
• the parent route of the dynamic route has PPR (Partial Prerendering) enabled
• a middleware is used to rewrite an original URL to patch a route (prepend a locale in my case)
• the project is deployed on Vercel

Important

Note #1: The issue is not reproducible locally.

Important

Note #2: The parameters are passed correctly when navigating to the page from another route. The issue reproduces only when the page is loaded directly, or by refreshing the page.

Steps to Reproduce

I have a deployed version of the project on Vercel, where you can see the issue in action.

Reproduce 1: with page refresh

1. Go to the deployed site

2. Click the Go to the test page link

   • the page has correct params (OK)

3. Refresh the page

   • the page has incorrect params, first segment of rest is missing and is incorrectly recognized as locale (BUG)

Reproduce 2: with a direct link

1. Go to the test page directly

   • the page has incorrect params, first segment of rest is missing and is incorrectly recognized as locale (BUG)