# commands every session command is one definition with three faces: the CLI menu, user invocation, and the model's typed `commands` bindings. adding a command adds all three; nothing about a command is reimplemented per surface. ## the catalog `GET /sessions/:id/commands` lists the materialized catalog: name (the slash spelling), description, the minted python `method`, its `usage` line, declared `arguments`, and the `modelCallable`, `userTurn`, and `skill` flags. The `skill` flag marks a selected skill with a preparation function. The CLI submits these through the durable events route. Other command handlers keep their existing uncertainty policy. The CLI menu renders the catalog, merged with its presentation-only entries like `/login` and `/sessions`. The list mints the kernel bindings at boot, and the prompt's `<session_commands>` block summarizes it. `POST /sessions/:id/commands` runs one command. the body is `{name, arguments}` with raw invocation text (`{"name": "/model", "arguments": "gpt-5 anthropic"}`) or `{name, args}` with declared names (`{"name": "/model", "args": {"model": "gpt-5"}}`); `clientId` labels a submitted turn. the answer is `{"result": ...}` with the command's JSON value or `{"submitted": true}` when a user invocation submitted its turn. The Go client returns `daemon.APIError` for HTTP failures, retaining the status, daemon error code, and message. Use `errors.As` to inspect it. Workspace failures also unwrap to `daemon.WorkspaceMissingError` so the chat can offer a replacement folder. Capability checks return `daemon.UpgradeRequiredError`; the TUI recognizes that type when displaying catalog upgrade failures. Error wording does not control this routing. ## contributing commands `CommandPlugin` in an extension declares static commands; a `ManagedPlugin` contributes dynamic ones through `Managed.commands` (this is how skills registers its slash commands). the type lives in [`command.gleam`](../src/albedo/harness/command.gleam): ```gleam Command( "/usage", "Show token and cost …