Handling Notifications

JSON-RPC notifications do not contain an id and must not receive a response. During initialization, the client sends notifications/initialized; both the stdio and SSE server transports suppress output for that notification.

Use onNotification(method, handler) to register callbacks for progress, resource-update, logging, and list-change notifications. Resource, resource-template, and prompt caches are invalidated automatically when the corresponding list-change notification arrives.

The client can also answer server-initiated requests with onServerRequest(...). The convenience methods setRoots(...) and setSamplingHandler(...) configure the standard roots/list and sampling/createMessage handlers before initialize() advertises those capabilities.

If a server-request handler throws a runtime exception, the client catches it at the common transport boundary and sends JSON-RPC INTERNAL_ERROR (-32603) with the original request ID. The exception is logged but does not terminate the stdio or SSE receive loop. Returning null means that no handler result is available and produces METHOD_NOT_FOUND.

When an SSE channel closes or fails, or when a transport is closed, all pending request futures are completed exceptionally. Likewise, an unexpected stdio subprocess exit fails pending requests immediately, including when requestTimeout is zero.

Cancellation is scoped by both session and JSON-RPC request ID on the server. Two clients may safely use the same request ID; cancelling one session does not interrupt the other. Closing a session interrupts only that session's running tools.