Merge pull request #455 from XiaofuHuang/xiaofhua/pid-StdioClientTransport

fix: Expose the MCP child process PID as an accessible property in StdioClientTransport

src/client/stdio.test.ts

@@ -59,3 +59,12 @@ test("should read messages", async () => {
 
   await client.close();
 });
+
+test("should return child process pid", async () => {
+  const client = new StdioClientTransport(serverParameters);
+
+  await client.start();
+  expect(client.pid).not.toBeNull();
+  await client.close();
+  expect(client.pid).toBeNull();
+});

src/client/stdio.ts

@@ -185,6 +185,15 @@ export class StdioClientTransport implements Transport {
     return this._process?.stderr ?? null;
   }
 
+  /**
+   * The child process pid spawned by this transport.
+   *
+   * This is only available after the transport has been started.
+   */
+  get pid(): number | null {
+    return this._process?.pid ?? null;
+  }
+
   private processReadBuffer() {
     while (true) {
       try {