CLI reference

The castiel launcher accepts the following flags. Unknown options and stray arguments fail fast with an error rather than being ignored.

Flag	Description
--port, -p	HTTP port to listen on (default: 8081).
--bind	Network address to bind (default: 127.0.0.1).
--auth	Require token authentication for every API call.
--show-token	Print the --auth access token and exit.
--reset-token	Replace the --auth access token; takes effect on the next start.
--debug	Enable debug logging for castiel and LLM/MCP traffic.
--log-file [FILE]	Also write logs to a file, rotated automatically. Without a value, uses castiel.log in the current directory.
--check-update	Compare this build with the latest GitHub release and install a newer one if available.
--help, -h	Show all flags.
--version, -V	Print the version and exit.

Exposing castiel beyond localhost

By default castiel binds to 127.0.0.1 and is reachable only from your own machine. Binding beyond localhost — putting the UI on your LAN or a tunnel — requires --auth: without a token, anyone who can reach the port could drive your harness. Together:

castiel --bind 0.0.0.0 --auth

--show-token prints the generated access token (for logging in from another device); --reset-token replaces it and takes effect on the next start.

Logging

--debug turns on debug logging for castiel itself and for all LLM and MCP traffic — useful when a model misbehaves or a server misconfigures. --log-file additionally mirrors logs into a rotating file:

castiel --debug
castiel --log-file castiel.log
castiel --log-file           # same, using castiel.log in the current directory