Function start_server_sidecar 

pub async fn start_server_sidecar(
    config_manager: Arc<ConfigManager>,
    listener: TcpListener,
    launch_token: SidecarLaunchToken,
    ready: Sender<SocketAddr>,
    http_shutdown: Option<CancellationToken>,
) -> Result<()>

Start the supervised sidecar on a caller-provided, already-bound listener.

The readiness sender fires only after configuration, persistence, routes, and the HTTP application are initialized. The listener remains owned by the server for the entire startup path, so no other process can claim its port.

launch_token authenticates the host that launched the sidecar. Every request must carry it, name 127.0.0.1:{port} or localhost:{port} as its authority, and carry no Origin. Sidecar mode also binds no companion or A2A gRPC listener, serves no operator SPA or CORS headers, keeps tool governance mandatory, and keeps the global MCP server list empty.

Errors

Returns an error when runtime initialization or serving fails, or when the supervising process drops the readiness receiver before startup completes.