Link to the code that reproduces this issue

https://github.com/igz0/nextjs-sitemap-conflict-turbopack

To Reproduce

1. Create a fresh Next.js v15.3.1 project with the App Router.

2. Add src/app/sitemap.ts:

// generates /sitemap.xml
import type { MetadataRoute } from 'next'

export default function sitemap(): MetadataRoute.Sitemap {
  return [
    {
      url: 'https://example.com',
    },
  ]
}

3. Add src/app/sitemap/page.tsx:

// renders /sitemap
export default function SitemapPage() {
  return <div>Sitemap</div>
}

4. Start dev server with Turbopack (default in next dev):

pnpm dev          # or npm run dev / yarn dev

5. Observe the console error and that the dev server refuses to compile.

Error: ./src/app
An issue occurred while preparing your Next.js app
Conflicting page and metadata at /sitemap: page at /sitemap/page and metadata at /sitemap/route

Current vs. Expected behavior

Provide environment information

Operating System:
  Platform: darwin
  Arch: arm64
  Version: Darwin Kernel Version 24.4.0: Fri Apr 11 18:32:50 PDT 2025; root:xnu-11417.101.15~117/RELEASE_ARM64_T6041
  Available memory (MB): 49152
  Available CPU cores: 12
Binaries:
  Node: 20.15.1
  npm: 10.7.0
  Yarn: 1.22.19
  pnpm: N/A
Relevant Packages:
  next: 15.4.0-canary.12 // Latest available version is detected (15.4.0-canary.12).
  eslint-config-next: N/A
  react: 19.1.0
  react-dom: 19.1.0
  typescript: 5.8.3
Next.js Config:
  output: N/A

Which area(s) are affected? (Select all that apply)

Turbopack

Which stage(s) are affected? (Select all that apply)

next dev (local)

Additional context

• Happens only when Turbopack is enabled; next dev --no-turbo compiles fine.
• Removing either file or renaming one of the routes avoids the error.
• According to the docs, metadata routes such as src/app/sitemap.ts should map to /sitemap.xml, which should not collide with a page at /sitemap.
• The conflict check therefore looks Turbopack-specific.