ERR_NGROK_3901: CEL interpolation in action ACTIONTYPE field FIELD did not result in a valid regex - ngrok documentation

What does ERR_NGROK_3901 mean?

ngrok returns ERR_NGROK_3901 with this message:

CEL interpolation in action <ACTIONTYPE> field <FIELD> did not result in a valid regex.
ERROR: <ERROR>

Troubleshoot ERR_NGROK_3901 with your AI agent. Connect it to the ngrok MCP server, then ask what caused the error and how to fix it.

Where can I get more help with ERR_NGROK_3901?

Email support@ngrok.com and include the error code.