diff --git a/web/src/services/connectionsService.test.ts b/web/src/services/connectionsService.test.ts
new file mode 100644
index 00000000..5461a0a0
--- /dev/null
+++ b/web/src/services/connectionsService.test.ts
@@ -0,0 +1,44 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import { describe, expect, it, vi } from 'vitest';
+
+vi.mock('../config', () => ({
+  USE_MOCK: true,
+  API_BASE_URL: '/api',
+}));
+
+import { listConnections } from './connectionsService';
+
+describe('connectionsService mock connections', () => {
+  it('returns defensive copies after applying filters', async () => {
+    const connections = await listConnections({ clusterId: 'ns-prod', type: 'Consumer' });
+    const originalClientId = connections[0].clientId;
+    const originalAddress = connections[0].address;
+
+    connections[0].clientId = 'mutated-client';
+    connections[0].address = '127.0.0.1:8081';
+
+    const fresh = await listConnections({ clusterId: 'ns-prod', type: 'Consumer' });
+
+    expect(fresh[0].clientId).toBe(originalClientId);
+    expect(fresh[0].address).toBe(originalAddress);
+    expect(fresh[0]).not.toBe(connections[0]);
+    expect(fresh.every((connection) => connection.clusterName === 'ns-prod')).toBe(true);
+    expect(fresh.every((connection) => connection.type === 'Consumer')).toBe(true);
+  });
+});
diff --git a/web/src/services/connectionsService.ts b/web/src/services/connectionsService.ts
index b773cea9..d29b58a0 100644
--- a/web/src/services/connectionsService.ts
+++ b/web/src/services/connectionsService.ts
@@ -3,13 +3,17 @@ import * as connApi from '../api/connections';
 import type { ClientConnection, ClientConnectionQuery } from '../api/connections';
 import { mockClients } from '../mock/clients';
 
+function copyConnection(connection: ClientConnection): ClientConnection {
+  return { ...connection };
+}
+
 export async function listConnections(params?: ClientConnectionQuery): Promise<ClientConnection[]> {
   if (USE_MOCK) {
     let result = [...mockClients];
     if (params?.clusterId)
       result = result.filter((connection) => connection.clusterName === params.clusterId);
     if (params?.type) result = result.filter((c) => c.type === params.type);
-    return result as unknown as ClientConnection[];
+    return (result as unknown as ClientConnection[]).map(copyConnection);
   }
   return connApi.listConnections(params);
 }