nginx protocol_error ai_generated true

upstream sent invalid Transfer-Encoding: chunked with Content-Length while reading response header from upstream

ID: nginx/upstream-sent-invalid-transfer-encoding-chunked-with-content-length

Also available as: JSON · Markdown

90%Fix Rate

88%Confidence

1Evidence

2025-05-10First Seen

Version Compatibility

Version	Status	Introduced	Deprecated	Notes
nginx 1.24.0	active	—	—	—
nginx 1.25.3	active	—	—	—
nginx 1.26.0	active	—	—	—

Root Cause

Upstream server sends both Content-Length and Transfer-Encoding: chunked headers in the same response, which is invalid per HTTP/1.1.

generic

Official Documentation

https://nginx.org/en/docs/http/ngx_http_proxy_module.html#proxy_ignore_headers

Workarounds

85% success Use proxy_ignore_headers to ignore one of the conflicting headers. Example to ignore Content-Length: location / { proxy_pass http://upstream; proxy_ignore_headers Content-Length; }
```
Use proxy_ignore_headers to ignore one of the conflicting headers. Example to ignore Content-Length:
  location / {
      proxy_pass http://upstream;
      proxy_ignore_headers Content-Length;
  }
```
95% success Fix the upstream application to send only one of the headers. For example, in a Node.js Express app: app.get('/data', (req, res) => { res.removeHeader('Content-Length'); res.setHeader('Transfer-Encoding', 'chunked'); res.send('hello'); });
```
Fix the upstream application to send only one of the headers. For example, in a Node.js Express app:
  app.get('/data', (req, res) => {
      res.removeHeader('Content-Length');
      res.setHeader('Transfer-Encoding', 'chunked');
      res.send('hello');
  });
```

中文步骤

Use proxy_ignore_headers to ignore one of the conflicting headers. Example to ignore Content-Length:
  location / {
      proxy_pass http://upstream;
      proxy_ignore_headers Content-Length;
  }

Fix the upstream application to send only one of the headers. For example, in a Node.js Express app:
  app.get('/data', (req, res) => {
      res.removeHeader('Content-Length');
      res.setHeader('Transfer-Encoding', 'chunked');
      res.send('hello');
  });

Dead Ends

Common approaches that don't work:

Remove Content-Length header from nginx config using proxy_set_header 95% fail
proxy_set_header affects request headers to upstream, not response headers from upstream.
Enable chunked_transfer_encoding off; in nginx 80% fail
This directive controls nginx's own encoding, not upstream response validation.
Increase proxy_buffer_size 100% fail
Header size is not the issue; header validity is.