diff --git a/package-lock.json b/package-lock.json
index 1165b751..04a801e9 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -1,12 +1,12 @@
 {
   "name": "@modelcontextprotocol/sdk",
-  "version": "1.9.0",
+  "version": "1.11.1",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "@modelcontextprotocol/sdk",
-      "version": "1.9.0",
+      "version": "1.11.1",
       "license": "MIT",
       "dependencies": {
         "content-type": "^1.0.5",
diff --git a/src/shared/protocol.test.ts b/src/shared/protocol.test.ts
index fb5ecd13..0bd0a03c 100644
--- a/src/shared/protocol.test.ts
+++ b/src/shared/protocol.test.ts
@@ -63,6 +63,22 @@ describe("protocol tests", () => {
     expect(oncloseMock).toHaveBeenCalled();
   });
 
+  it("should not overwrite existing hooks when connecting transports", async () => {
+    const oncloseMock = jest.fn();
+    const onerrorMock = jest.fn();
+    const onmessageMock = jest.fn();
+    transport.onclose = oncloseMock;
+    transport.onerror = onerrorMock;
+    transport.onmessage = onmessageMock;
+    await protocol.connect(transport);
+    transport.onclose();
+    transport.onerror(new Error());
+    transport.onmessage("");
+    expect(oncloseMock).toHaveBeenCalled();
+    expect(onerrorMock).toHaveBeenCalled();
+    expect(onmessageMock).toHaveBeenCalled();
+  });
+
   describe("progress notification timeout behavior", () => {
     beforeEach(() => {
       jest.useFakeTimers();
diff --git a/src/shared/protocol.ts b/src/shared/protocol.ts
index 4694929d..79659492 100644
--- a/src/shared/protocol.ts
+++ b/src/shared/protocol.ts
@@ -279,15 +279,21 @@ export abstract class Protocol<
    */
   async connect(transport: Transport): Promise<void> {
     this._transport = transport;
+    const _onclose = this.transport?.onclose;
     this._transport.onclose = () => {
+      _onclose?.();
       this._onclose();
     };
 
+    const _onerror = this.transport?.onerror;
     this._transport.onerror = (error: Error) => {
+      _onerror?.(error);
       this._onerror(error);
     };
 
+    const _onmessage = this._transport?.onmessage;
     this._transport.onmessage = (message, extra) => {
+      _onmessage?.(message, extra);
       if (isJSONRPCResponse(message) || isJSONRPCError(message)) {
         this._onresponse(message);
       } else if (isJSONRPCRequest(message)) {
@@ -295,7 +301,9 @@ export abstract class Protocol<
       } else if (isJSONRPCNotification(message)) {
         this._onnotification(message);
       } else {
-        this._onerror(new Error(`Unknown message type: ${JSON.stringify(message)}`));
+        this._onerror(
+          new Error(`Unknown message type: ${JSON.stringify(message)}`),
+        );
       }
     };