I’m developing a Next.js application with API routes. In one of my routes, I need to perform some pre-processing on the incoming request body (e.g., authentication, validation, parsing). However, after this processing, the request body becomes unavailable, making it impossible to handle the request in the main route logic.

Here’s a simplified example of my API route:

import { NextRequest, NextResponse } from 'next/server';

export const POST = async (request: NextRequest) => {
  // 1. Attempt to read the body
  const requestBody = await request.json(); 

  // 2. Perform some processing on the body (e.g., validation, transformation)
  const processedBody = { ...requestBody, additionalData: "some extra info" };

  // 3. (Main handler logic)
  // ... this is where I need to access the original OR processed body
  // but request.body is now empty/consumed

  return NextResponse.json({ message: 'Request processed!', body: processedBody });
};

How can I preprocess the request body in a Next.js API route while ensuring the original body data remains available for the main handler logic? Are there recommended approaches or best practices for achieving this in Next.js?

I’d prefer not to use external libraries like next-connect and would like to implement this functionality myself.

I’ve tried parsing the body and rebuilding it, but none of these approaches have been successful so far.