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Lifecycle Hooks ​

Server-level hooks for reacting to startup and session events.

Setup ​

Pass hooks as options to createMCPServer:

ts
import { createMCPServer } from "@lynq/lynq";

const server = createMCPServer({
  name: "my-server",
  version: "1.0.0",
  onServerStart: () => {
    console.log("Server started");
  },
  onSessionCreate: (sessionId) => {
    console.log(`Session created: ${sessionId}`);
  },
  onSessionDestroy: (sessionId, data) => {
    console.log(`Session destroyed: ${sessionId}`);
    // data contains session KV pairs — e.g. data.get("user") for cleanup
  },
});

Hooks ​

HookSignatureWhen
onServerStart() => void | Promise<void>After stdio connect, or on first HTTP request
onSessionCreate(sessionId: string) => void | Promise<void>When a new session is first accessed
onSessionDestroy(sessionId: string, data: ReadonlyMap<string, unknown>) => void | Promise<void>When an HTTP session closes

All hooks are optional. All hooks are fire-and-forget -- errors (sync throws or async rejections) are silently caught and do not affect server operation.

onServerStart ​

Fires once after the server is ready to handle requests.

  • stdio: after server.connect(transport) completes
  • HTTP: on the first incoming request (since there is no explicit listen() call)
ts
createMCPServer({
  name: "my-server",
  version: "1.0.0",
  onServerStart: async () => {
    await db.connect();
    console.log("Database connected, server ready");
  },
});

onSessionCreate ​

Fires once per unique session ID, when the session is first accessed (lazily created).

ts
createMCPServer({
  name: "my-server",
  version: "1.0.0",
  onSessionCreate: async (sessionId) => {
    await analytics.track("session_start", { sessionId });
  },
});

For stdio transport, the default "default" session is created on the first tool call.

onSessionDestroy ​

Fires when a session is destroyed (HTTP session close or transport disconnect). The second argument contains the session's KV data, useful for cleanup (e.g. resolving the user ID to delete store entries).

ts
createMCPServer({
  name: "my-server",
  version: "1.0.0",
  onSessionDestroy: async (sessionId, data) => {
    const user = data.get("user");
    if (user) {
      await store.delete(`user:${user}:preferences`);
    }
  },
});

What's Next ​