Struct StdioTransport 

pub struct StdioTransport { /* private fields */ }

MCP stdio transport proxy.

Spawns the upstream MCP server as a child process and proxies MCP messages between the client (our stdin/stdout) and the server (child process stdin/stdout), applying policy evaluation on tool calls.

Implementations

impl StdioTransport

pub fn new( engine: Engine, audit: AuditLogger, command: String, args: Vec<String>, fail_open: bool, ) -> Self

Creates a new stdio transport proxy.

pub fn with_shared_engine( engine: Arc<RwLock<Engine>>, audit: AuditLogger, command: String, args: Vec<String>, fail_open: bool, ) -> Self

Creates a new stdio transport proxy with a shared engine reference.

Use this when hot-reload is enabled — the caller retains a clone of the Arc<RwLock<Engine>> and can swap the engine atomically while the proxy is running.

pub fn with_approval_backend(self, backend: Arc<dyn ApprovalBackend>) -> Self

Sets the approval backend for handling RequireApproval decisions.

pub fn engine(&self) -> &Arc<RwLock<Engine>>

Returns a reference to the shared engine (for hot-reload wiring).

pub async fn run(&self) -> Result<(), Box<dyn Error>>

Runs the stdio proxy with graceful shutdown.

Spawns the upstream MCP server as a child process, then proxies all MCP messages through the policy engine. This function blocks until the client disconnects (stdin EOF), the child process exits, or a shutdown signal (SIGTERM/SIGINT) is received.

On shutdown signal:

1. Active proxy loop is allowed to drain (up to 30s by default)
2. Audit log is flushed
3. Upstream child process is terminated cleanly