MCP TypeScript SDK (V2) / @modelcontextprotocol/server / server/serveStdio

server/serveStdio

Interfaces

ServeStdioOptions

Defined in: packages/server/src/server/serveStdio.ts:85

Options for serveStdio.

Properties

legacy?

optional legacy?: "reject" | "serve"

Defined in: packages/server/src/server/serveStdio.ts:98

How a 2025-era opening (an initialize request, or any claim-less message) is handled:

• 'serve' (default) — the connection is pinned to a 2025-era instance from the same factory and served exactly as a hand-wired stdio server serves it today.
• 'reject' — the opening request is answered with the unsupported-protocol-version error naming the supported modern revisions (claim-less notifications are dropped); the connection stays open for a modern opening.

maxSubscriptions?

optional maxSubscriptions?: number

Defined in: packages/server/src/server/serveStdio.ts:116

Reject a new subscriptions/listen with -32603 'Subscription limit reached' (in-band, before the ack) when this many subscriptions are already open on this connection.

Default

1024

onerror?

optional onerror?: (error) => void

Defined in: packages/server/src/server/serveStdio.ts:109

Callback for out-of-band errors (reporting only; it never alters what is written to the wire).

Parameters

error

Error

Returns

void

transport?

optional transport?: Transport

Defined in: packages/server/src/server/serveStdio.ts:107

Bring your own transport (for example a StdioServerTransport constructed over a Unix domain socket or TCP stream, per the stdio binding's custom-transport guidance). Defaults to a StdioServerTransport over the current process's stdio. The entry owns the transport: it starts it, receives every inbound message, and closes it when the connection ends.

---

StdioServerHandle

Defined in: packages/server/src/server/serveStdio.ts:120

The handle returned by serveStdio.

Methods

close()

close(): Promise<void>

Defined in: packages/server/src/server/serveStdio.ts:122

Tears the connection down: closes the pinned instance (if any) and the underlying transport.

Returns

Promise<void>

Functions

serveStdio()

serveStdio(factory, options?): StdioServerHandle

Defined in: packages/server/src/server/serveStdio.ts:375

Serves MCP over stdio from a server factory, owning the era decision for the connection: the opening exchange selects the era, ONE instance from the factory is pinned for the connection lifetime, and everything after passes straight through to it. See the module documentation for the opening rules.

import { serveStdio } from '@modelcontextprotocol/server/stdio';

serveStdio(() => {
    const server = new McpServer({ name: 'my-server', version: '1.0.0' }, { capabilities: { tools: {} } });
    // register tools/resources/prompts once — the same factory serves both eras
    return server;
});

Parameters

factory

McpServerFactory

options?

ServeStdioOptions = {}

Returns

StdioServerHandle