How to fix Error: Bad chunked encoding (invalid transfer-encoding format) in Node.js

# Set NODE_DEBUG environment variable
NODE_DEBUG=http node your-app.js

const http = require('http');

// Log raw response data
const req = http.request(options, (res) => {
  console.log('Status:', res.statusCode);
  console.log('Headers:', res.headers);

  res.on('data', (chunk) => {
    console.log('Chunk received:', chunk.length, 'bytes');
  });

  res.on('end', () => {
    console.log('Response complete');
  });
});

req.on('error', (err) => {
  console.error('Request error:', err.message);
  console.error('Error code:', err.code);
});

req.end();

const http = require('http');

http.get('http://problematic-server.com/api', (res) => {
  const contentLength = res.headers['content-length'];
  const transferEncoding = res.headers['transfer-encoding'];

  if (contentLength && transferEncoding === 'chunked') {
    console.error('ERROR: Both Content-Length and Transfer-Encoding present!');
    console.error('Content-Length:', contentLength);
    console.error('This violates HTTP spec and causes parsing errors');
  }
});

# Test with curl to see raw response
curl -v http://your-api.com/endpoint

# Check for Transfer-Encoding header
curl -I http://your-api.com/endpoint | grep -i transfer-encoding

import requests
response = requests.get('http://your-api.com/endpoint')
print(response.headers)
print(response.status_code)

# Check current Node.js version
node --version

# Update Node.js (using nvm)
nvm install --lts
nvm use --lts

# Update dependencies that might handle chunked encoding
npm update axios node-fetch got undici

// Express.js example
app.get('/api/data', (req, res) => {
  // Don't set Content-Length when using chunked encoding
  res.removeHeader('Content-Length');

  // Explicitly set Transfer-Encoding if needed
  res.setHeader('Transfer-Encoding', 'chunked');

  res.write('chunk1');
  res.write('chunk2');
  res.end();
});

// Send complete response with Content-Length
app.get('/api/data', (req, res) => {
  const data = JSON.stringify({ result: 'data' });
  res.setHeader('Content-Type', 'application/json');
  res.setHeader('Content-Length', Buffer.byteLength(data));
  res.end(data);
});

# Test direct connection vs proxied
curl -v http://server-ip:port/endpoint  # Direct
curl -v http://load-balancer.com/endpoint  # Through proxy

location /api {
    proxy_pass http://backend;
    proxy_http_version 1.1;
    proxy_buffering off;  # Important for chunked encoding
    chunked_transfer_encoding on;
}

// Option 1: Use undici with lenient mode (Node.js 18+)
const { request } = require('undici');

const { statusCode, headers, body } = await request('http://api.com/endpoint', {
  strictContentLength: false  // More lenient with Content-Length
});

// Option 2: Use axios with custom adapter
const axios = require('axios');
const http = require('http');

const instance = axios.create({
  httpAgent: new http.Agent({
    // Customize agent if needed
  })
});