nextjs - 💡(How to fix) Fix Turbopack: empty middleware-manifest for proxy.ts on Next 16.2.4 (Windows; both root and src/ placement) [1 comments, 2 participants]

Verify canary release

I verified the bug exists in the latest stable (16.2.4). Have not yet retested on canary 16.3.0-canary.3.

Provide environment information

Operating System:
  Platform: win32
  Arch: x64
  Version: Windows 11 Home
Binaries:
  Node: 25.9.0
  npm: 11.12.1
Relevant Packages:
  next: 16.2.4
  react: 19.2.5
  react-dom: 19.2.5
  typescript: 6.0.2
Next.js Config:
  output: N/A

Which area(s) are affected?

Middleware, Turbopack

Which stage(s) are affected?

next build (local), next start (local), production deploy on Vercel

Current vs. expected behavior

When the project's middleware/proxy file is named proxy.ts (the Next 16 convention) at either the project root or inside src/, next build produces an empty middleware manifest:

{
  "version": 3,
  "middleware": {},
  "sortedMiddleware": [],
  "functions": {}
}

The build summary still prints ƒ Proxy (Middleware), so Next sees the file — but Turbopack's Rust-side manifest writer never registers it. At runtime the proxy is silently skipped: no matcher rules fire, no auth redirects, no request rewrites.

Renaming the file to middleware.ts at the project root (with export async function middleware) immediately produces a populated manifest with the matcher entry, and proxy logic runs correctly in both next build && next start and production Vercel deploys.

Reproduction

1. Fresh Next 16.2.4 project on Windows 11 with src/ directory.
2. Create proxy.ts (or src/proxy.ts) with a default proxy export and a non-trivial matcher config.
3. npm run build.
4. Inspect .next/server/middleware-manifest.json — "middleware": {} and "sortedMiddleware": [].
5. Rename the file to root middleware.ts and rename the export to middleware. Rebuild — manifest now contains the entry under /.

Prior art

• Same symptom as #85243, which was closed citing fix in #85443 and is now locked. The github-actions bot in that thread instructs new reporters to open a fresh issue.
• Comments on #85243 suggest src/proxy.ts resolves it for some users — we tested both placements on 16.2.4 and both produce empty manifests on Windows 11 + Turbopack.

Workaround

Keep the file at the project root as middleware.ts (export middleware). Deploys to Vercel work correctly with this layout but emit a deprecation-style log expecting proxy.ts.