Known limits

What Caelus does not do, as of this version.

Commands

The registry does not validate args against parameters. Handlers check their own args. The CLI and MCP surfaces validate before the handler runs; a key chord, a button, and a forwarder do not.
Parameters have three types: string, integer, and boolean. There are no arrays, objects, or enumerations.
A string or integer parameter is always required by the CLI and MCP surfaces. Only boolean parameters are optional.
An outcome is a single value. There is no streaming or progress reporting.

No platform modifier (mod). Bind the cmd and ctrl chords separately.
No chord sequences, such as cmd+k cmd+s.
No focus context: the listener fires wherever focus is, text fields included.
No Electron menu accelerators.
alt chords are read by physical key position on a US layout.
The table resolves against the registry when it is built. Commands registered later need a reload().

The CLI has long options only, named after the parameters. There are no positional arguments or short flags.
An MCP server's tools are the commands registered when mcp() is called.