Stdio transport

Serve local clients through newline-delimited JSON on stdin and stdout.

Use stdio() from @toolgrain/node when a client launches your server as a local process. The adapter handles framing and lifecycle; MCP method handling stays in @toolgrain/mcp.

import { stdio } from "@toolgrain/node";
await server.listen(stdio({ maxMessageBytes: 1024 * 1024 }));

Framing and limits

Messages are newline-delimited UTF-8 JSON. The default incoming-message limit is 1 MiB, excluding the newline. Malformed JSON or UTF-8 reports a parse error and permits later messages. Oversized frames terminate the transport. Outgoing writes respect writable backpressure and preserve ordering.

input and output may be supplied as Node streams; they default to process.stdin and process.stdout. A transport instance is single-use. A server accepts one transport, and close is terminal.

Shutdown

EOF is the normal stdio shutdown signal. Closing detaches listeners and pauses input without destroying or ending supplied streams or calling process.exit(). Active request signals abort on connection close. A handler that ignores its signal may continue running, but its response is discarded.

Auth-configured servers reject message transports before startup. Use HTTP when configuring endpoint authorization.

Operational guidance

Keep all logs off stdout. Use absolute compiled entry-point paths in client configuration. Reconnect after rebuilding so the client launches a fresh process. Separate build output from protocol stdout. See client setup and the Node API.