diff --git a/packages/react-web-cli/src/AblyCliTerminal.test.tsx b/packages/react-web-cli/src/AblyCliTerminal.test.tsx
index 90141195..48bd116c 100644
--- a/packages/react-web-cli/src/AblyCliTerminal.test.tsx
+++ b/packages/react-web-cli/src/AblyCliTerminal.test.tsx
@@ -2467,3 +2467,48 @@ describe("AblyCliTerminal - Initial Command Execution", () => {
     expect(hasTestCmd).toBe(true);
   }, 15_000);
 });
+
+describe("AblyCliTerminal - Unmount cleanup", () => {
+  test("sends close code 4001 (user-closed-panel) on unmount", async () => {
+    mockClose.mockClear();
+
+    const { unmount } = render(
+      <AblyCliTerminal
+        websocketUrl="wss://test.ably.com"
+        ablyApiKey="test-key"
+      />,
+    );
+
+    await act(async () => {
+      await new Promise((resolve) => setTimeout(resolve, 50));
+    });
+
+    expect(mockSocketInstance).toBeTruthy();
+    expect(mockSocketInstance.readyState).toBe(WebSocket.OPEN);
+
+    unmount();
+
+    expect(mockClose).toHaveBeenCalledWith(4001, "user-closed-panel");
+  });
+
+  test("does not call close if socket already closing", async () => {
+    mockClose.mockClear();
+
+    const { unmount } = render(
+      <AblyCliTerminal
+        websocketUrl="wss://test.ably.com"
+        ablyApiKey="test-key"
+      />,
+    );
+
+    await act(async () => {
+      await new Promise((resolve) => setTimeout(resolve, 50));
+    });
+
+    mockSocketInstance.readyState = WebSocket.CLOSING;
+
+    unmount();
+
+    expect(mockClose).not.toHaveBeenCalled();
+  });
+});
diff --git a/packages/react-web-cli/src/AblyCliTerminal.tsx b/packages/react-web-cli/src/AblyCliTerminal.tsx
index bf6c00cf..1ce5781c 100644
--- a/packages/react-web-cli/src/AblyCliTerminal.tsx
+++ b/packages/react-web-cli/src/AblyCliTerminal.tsx
@@ -2419,9 +2419,10 @@ const AblyCliTerminalInner = (
         socketReference.current &&
         socketReference.current.readyState < WebSocket.CLOSING
       ) {
-        // close websocket
+        // close websocket with code 4001 to signal intentional close
+        // This tells the server to cleanup immediately (no grace period)
         debugLog("[AblyCLITerminal] Closing WebSocket on unmount.");
-        socketReference.current.close();
+        socketReference.current.close(4001, "user-closed-panel");
       }
       grResetState(); // Ensure global state is clean
       clearConnectionTimeout(); // Clear any pending connection timeout
@@ -3559,7 +3560,7 @@ const AblyCliTerminalInner = (
         debugLog(
           "[AblyCLITerminal] Closing secondary WebSocket on terminal cleanup.",
         );
-        secondarySocketReference.current.close();
+        secondarySocketReference.current.close(4001, "user-closed-panel");
         secondarySocketReference.current = null;
       }