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CFL400 - Invalid Response From Cloudflare

Agent error code #CFL400 indicates that Cloudflare answered with something the agent could not use. A response arrived, and it was neither a success nor a status the agent maps to a specific code.

Common causes include:

  • A proxy or captive portal between the agent and Cloudflare returned its own HTML error page
  • Cloudflare returned a 5xx server error
  • The response body was truncated
  • TLS interception in the path rewrote the response

Steps to Resolve

Confirm You Are Reaching Cloudflare Directly

curl -sS -i https://api.cloudflare.com/client/v4/user/tokens/verify | head -20

The response should be JSON from the Cloudflare API. An HTML page, a redirect to a login portal or a corporate error page means something in the path is answering instead.

Check for TLS Interception

If your network terminates and re-signs TLS, confirm the agent host trusts the intercepting certificate authority, and that the proxy is not modifying the response body.

Check the Cloudflare Status Page

A run of 5xx responses is usually an incident on Cloudflare's side and clears without any change at your end.

Check the Agent Log

The raw response body is written to the agent log and never to this message. Inspect the log entry recorded with the failed operation to see exactly what came back.

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