added test for session id using in memory transport

Author: jwvictor

src/inMemory.ts

@@ -11,6 +11,7 @@ export class InMemoryTransport implements Transport {
  onclose?: () => void;
  onerror?: (error: Error) => void;
  onmessage?: (message: JSONRPCMessage) => void;
+ sessionId?: string;
 
  /**
  * Creates a pair of linked in-memory transports that can communicate with each other. One should be passed to a Client and one to a Server.

src/server/mcp.test.ts

@@ -323,6 +323,59 @@ describe("tool()", () => {
  mcpServer.tool("tool2", () => ({ content: [] }));
  });
 
+ test("should pass sessionId to tool callback via RequestHandlerExtra", async () => {
+ const mcpServer = new McpServer({
+ name: "test server",
+ version: "1.0",
+ });
+
+ const client = new Client(
+ {
+ name: "test client",
+ version: "1.0",
+ },
+ {
+ capabilities: {
+ tools: {},
+ },
+ },
+ );
+
+ let receivedSessionId: string | undefined;
+ mcpServer.tool("test-tool", async (extra) => {
+ receivedSessionId = extra.sessionId;
+ return {
+ content: [
+ {
+ type: "text",
+ text: "Test response",
+ },
+ ],
+ };
+ });
+
+ const [clientTransport, serverTransport] = InMemoryTransport.createLinkedPair();
+ // Set a test sessionId on the server transport
+ serverTransport.sessionId = "test-session-123";
+
+ await Promise.all([
+ client.connect(clientTransport),
+ mcpServer.server.connect(serverTransport),
+ ]);
+
+ await client.request(
+ {
+ method: "tools/call",
+ params: {
+ name: "test-tool",
+ },
+ },
+ CallToolResultSchema,
+ );
+
+ expect(receivedSessionId).toBe("test-session-123");
+ });
+
  test("should allow client to call server tools", async () => {
  const mcpServer = new McpServer({
  name: "test server",