Hooks

Servers expose lifecycle hooks in the style of @johannes.latzel/llm-chat: server.hook() returns a fluent builder, and each builder's do(callback) registers the callback and returns a disposable Hook. Callbacks (sync or async) run fire-and-forget; errors are caught and logged, so a hook never breaks the server. Call hook.dispose() to unsubscribe.

started

Fires once the server has connected its transport (after start() completes). For HttpMcpServer, start() is idempotent and the event fires exactly once.

server
    .hook()
    .started()
    .do(() => {
        console.log('server ready');
    });

toolRegistered(name)

Fires for every tool registered via registerTool. Pass tool names to filter; with no names the hook fires for every tool.

server
    .hook()
    .toolRegistered('greet')
    .do((name) => {
        console.log(`tool registered: ${name}`);
    });

documentRegistered(info)

Fires when a document resource is registered (registerDocument, registerFolder, registerContentDocument). The payload is { kind: DocumentKind, name?: string }; name is omitted for folders (their resources are named per-file).

server
    .hook()
    .documentRegistered()
    .do(({ kind, name }) => {
        console.log(`registered ${kind}${name ? ` ${name}` : ''}`);
    });

sessionCreated(sessionId) / sessionDisposed(sessionId)

HTTP-only events, available on HttpMcpServer. sessionCreated fires when an initial POST /mcp yields a session id; sessionDisposed fires when a session is torn down via DELETE /mcp or when stop() closes all sessions.

const server = new HttpMcpServer({ name: 'demo', version: '1.0.0', port: 3000 });
server
    .hook()
    .sessionCreated()
    .do((sessionId) => console.log('created', sessionId));
server
    .hook()
    .sessionDisposed()
    .do((sessionId) => console.log('disposed', sessionId));

Error handling

Callbacks never break the server:

• A callback that throws synchronously is caught and logged.
• An async callback that rejects is caught and logged: no unhandled rejection.
• A throwing callback does not prevent other subscribers from firing.
• hook.dispose() is idempotent and unsubscribes from the underlying emitter.

Reference

Method	Event	Payload
hook().started().do(cb)	started	—
hook().toolRegistered(...names).do(cb)	toolRegistered	name: string
hook().documentRegistered().do(cb)	documentRegistered	info: DocumentRegisteredInfo
hook().sessionCreated().do(cb)	sessionCreated	sessionId: string
hook().sessionDisposed().do(cb)	sessionDisposed	sessionId: string

DocumentRegisteredInfo and the builder classes (McpServerHookBuilder, HttpServerHookBuilder) are exported from the package root. The HTTP session events are only reachable through HttpServerHookBuilder (returned by HttpMcpServer.hook()).