Serves a Sake.Server over standard input and output, for a client that launches the server as a subprocess:

Sake.Stdio.run(MyApp.MCP)

run/2 blocks until standard input closes. In a supervision tree, start it as a child instead, after Sake:

{Sake.Stdio, server: MyApp.MCP}

From a Mix project, mix sake.stdio MyApp.MCP does the same.

Options: server: (the child's, required), scope: (the host's principal: a value, or a function of no arguments called for every request; default nil), secret: (binary or {m, f, a}; default the Sake configuration, else a random secret for the life of the process), reraise: (re-raise tool exceptions, for tests), grace: (ms that requests still running when standard input closes get to finish, default 2 000), halt: (the child's only: stop the VM once standard input closes, default true), input: and output: (IO devices, default standard input and output).

The server speaks both eras on the one connection. A request whose _meta names the modern revision is served statelessly; an initialize request opens the connection's legacy session, and requests without a protocol version in _meta then belong to it. Each request runs in its own process, so responses can arrive out of order; notifications/cancelled stops a request and suppresses its response.

There is no authorization on stdio: the client that launched the server already holds its credentials, and the server takes its own from its environment. Pass the principal as scope:.

Standard output carries MCP messages only. While serving it, Sake moves the default Logger handler to standard error and runs every request with standard error as its group leader, so IO.puts/1 in a tool cannot break the stream.