Why does the AI Proxy plugin log content-type header does not match request body, and how do I resolve it?
This literal error message is dead code in current Kong Gateway releases and no longer appears — the same underlying issue now surfaces as request body doesn't contain valid inputs. Confirm the content type is application/json and that the request body matches the shape your configured LLM provider expects.
When attempting to use the AI-Proxy plugin we receive the below error:
Response Body:
{
"error": {
"message": "content-type header does not match request body"
}
}Kong Error log:
2024/05/27 13:09:33 [warn] 2160906#0: *2936 [kong] handler.lua:23 [ai-proxy] content-type header does not match request body, client: 192.168.10.10, server: kong, request: "POST /ai HTTP/1.1", host: "kong", request_id: "cbfefa2a2e15db3d91ce0224dea8fb1d"What causes this and how can it be resolved?
The exact error message shown above (content-type header does not match request body) is now unreachable dead code in current Kong Gateway releases — you will not see this literal message anymore. The underlying situation it used to describe (a genuine mismatch between the content-type header and the request body, or a request body the AI Proxy plugin cannot parse) still occurs, but now instead surfaces as a different error:
{
"error": {
"message": "request body doesn't contain valid inputs"
}
}If you encounter this error, check that the content type is application/json and use a validator to confirm the JSON payload is properly structured and matches the shape expected by the configured LLM provider format.
Note: an undersized nginx_http_client_body_buffer_size (causing the request body to be buffered to disk) does not, on its own, reproduce this error. Buffered-to-disk log lines near the time of the error are not the root cause and increasing this value is not a fix for this issue.