Transport or independent RequestTransport, or call server.handle() directly. Protocol methods do not belong in the framing adapter.
Message transport
Transport has start(callbacks), send(response), and close() methods; optional mode is "message". On startup, retain callbacks for messages, parse failures, unexpected errors, and connection closure. Callbacks are synchronous; message processing runs independently.
Own UTF-8 framing, JSON decoding, write ordering/backpressure, and stream cleanup. Do not call the MCP dispatcher yourself. Message transports are unsuitable for servers with HTTP authorization configured.
Request transport
RequestTransport declares mode: "request". Its start(server, callbacks) receives the composed server plus onError and onClose; close() stops its listener. Each incoming request has its own validation, authorization scope, and cancellation signal. Never reuse a scope across requests.
The server claims one transport before startup, across compatible package copies. Reusing a transport or attaching a second one is rejected; the existing owner remains running. Closure is terminal, idempotent, and re-entrant.
Handle a complete protocol message
handle() returns a protocol response or undefined for notifications/cancelled work. It does not perform HTTP method, host, Origin, content-type, or body-size checks. Implement those boundaries before direct handling, or reuse an HTTP adapter.
For protected calls, obtain a server-bound scope with authorize(), pass it as { auth }, and dispose it in finally. Scopes are single-use. The detailed authorization guide shows that lifecycle.