[Turbopack] POST requests from client components to API routes never reach server in Next.js 16

[createdbymax]

Link to the code that reproduces this issue

https://github.com/createdbymax/nextjs-turbopack-post-bug

To Reproduce

1. Create a Next.js 16.1.4 app with App Router
2. Create an API route at src/app/api/test/route.ts:

import { NextResponse } from "next/server";

export async function POST(request: Request) {
  const body = await request.json();
  console.log('API route hit:', body);
  return NextResponse.json({ success: true });
}

Create a client component with a button that calls the API:

"use client";

export function TestComponent() {
const handleClick = async () => {
console.log('Fetching...');
const response = await fetch('/api/test', {
method: 'POST',
headers: { 'Content-Type': 'application/json' },
body: JSON.stringify({ test: 'data' }),
});
console.log('Response:', response.status);
};

return Test API;
}

Run next dev (Turbopack enabled by default in Next.js 16)
Click the button
Observe: Browser logs "Fetching..." but server terminal never logs the request

### Current vs. Expected behavior

Expected: POST request reaches the API route handler and server logs show:

POST /api/test 200 in XXms
Actual:

Browser console shows fetch is called with correct URL and payload
Request appears in browser Network tab as "pending" indefinitely
Server terminal shows NO log of the incoming request
Request never completes or times out
Browser Console:

Fetching...
# Request hangs here forever
Server Terminal:

▲ Next.js 16.1.4 (Turbopack)
- Local:         http://localhost:3000

✓ Ready in 548ms
GET /some-page 200 in 3.0s
# POST /api/test never appears

### Provide environment information

```bash
Operating System:
  Platform: darwin
  Arch: arm64
  Version: macOS
Node: 24.8.0
pnpm: (run pnpm -v to get version)
Relevant Packages:
  next: 16.1.4
  react: 19.2.3
  react-dom: 19.2.3
  typescript: 5.x

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

Turbopack

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

next dev (local)

Additional context

GET requests to API routes work fine
POST requests to the same route work intermittently when the server first starts, before Turbopack fully initializes
Middleware is configured to exclude /api routes:

export const config = {
  matcher: ["/((?!api|_next/static|_next/image|favicon.ico|login).*)"],
};

Workarounds attempted:

• TURBOPACK=0 next dev - Still uses Turbopack in Next.js 16
• Using absolute URL ${window.location.origin}/api/test - Still doesn't reach server
• rm -rf .next - No effect
• Downgrading to Next.js 15.1.3 - Resolves the issue

This appears to be a critical routing bug in Turbopack that prevents POST requests from client components from reaching API route handlers.

[vedanthnyk25]

I attempted to reproduce this issue using the provided reproduction steps, but the API route works correctly on my machine. The POST request completes and is logged by the server.

My Environment:

• OS: Ubuntu (Linux)

• Next.js: 16.1.4

• Node: v24.12.0

The original report mentions macOS + Node v24.8.0. Since it works flawlessly on my Linux setup with a newer Node version, this issue might be specific to:

• macOS-specific networking in Turbopack.
• A regression in Node v24.8.0 that was fixed in v24.12.0.

[Chibuike-web]

I cannot reproduce this in a window machine even with the code you shared