How do I debug a 413 error if I've already increased the request size limit?

First, verify that the limit is correctly configured in both your Node.js application (using middleware) and any reverse proxies (like Nginx or Apache) in front of it. Check your server logs for more detailed error messages. Use network tools to inspect the request and confirm that the payload size is indeed exceeding the configured limit. Make sure that client is configured correctly to send data in chunks if needed.