diff --git a/web/src/services/topicService.test.ts b/web/src/services/topicService.test.ts
new file mode 100644
index 00000000..e07f2454
--- /dev/null
+++ b/web/src/services/topicService.test.ts
@@ -0,0 +1,59 @@
+/*
+ * 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';
+import { getTopicConsumers, getTopicRoutes, listTopics } from './topicService';
+
+vi.mock('../config', () => ({
+  API_BASE_URL: '/api',
+  USE_MOCK: true,
+}));
+
+describe('topic service mock data', () => {
+  it('returns copied topic rows', async () => {
+    const first = await listTopics({ search: 'order-create' });
+    expect(first[0].name).toBe('order-create');
+
+    first[0].name = 'mutated-topic';
+
+    const second = await listTopics({ search: 'order-create' });
+    expect(second[0].name).toBe('order-create');
+    expect(second[0]).not.toBe(first[0]);
+  });
+
+  it('returns copied topic route rows', async () => {
+    const first = await getTopicRoutes('order-create');
+    expect(first[0].brokerName).toBe('broker-a-0');
+
+    first[0].brokerName = 'mutated-broker';
+
+    const second = await getTopicRoutes('order-create');
+    expect(second[0].brokerName).toBe('broker-a-0');
+    expect(second[0]).not.toBe(first[0]);
+  });
+
+  it('returns copied topic consumer rows', async () => {
+    const first = await getTopicConsumers('order-create');
+    expect(first[0].group).toBe('GID_order_service');
+
+    first[0].group = 'mutated-group';
+
+    const second = await getTopicConsumers('order-create');
+    expect(second[0].group).toBe('GID_order_service');
+    expect(second[0]).not.toBe(first[0]);
+  });
+});
diff --git a/web/src/services/topicService.ts b/web/src/services/topicService.ts
index 39d25cc1..78cc8c46 100644
--- a/web/src/services/topicService.ts
+++ b/web/src/services/topicService.ts
@@ -10,6 +10,11 @@ import type {
 } from '../api/metadata';
 import { topics as mockTopics, topicRoutes, topicConsumers } from '../mock/topics';
 
+const cloneTopic = (topic: Topic): Topic => ({ ...topic });
+const cloneRoutes = (routes: BrokerRoute[]): BrokerRoute[] => routes.map((route) => ({ ...route }));
+const cloneConsumers = (consumers: ConsumerGroupInfo[]): ConsumerGroupInfo[] =>
+  consumers.map((consumer) => ({ ...consumer }));
+
 export async function listTopics(params?: TopicQuery): Promise<Topic[]> {
   if (USE_MOCK) {
     let result = [...mockTopics];
@@ -19,7 +24,7 @@ export async function listTopics(params?: TopicQuery): Promise<Topic[]> {
     }
     if (params?.type) result = result.filter((t) => t.type === params.type);
     if (params?.clusterId) result = result.filter((t) => t.clusterId === params.clusterId);
-    return result as unknown as Topic[];
+    return (result as unknown as Topic[]).map(cloneTopic);
   }
   return metadataApi.listTopics(params);
 }
@@ -35,7 +40,7 @@ export async function createTopic(data: Partial<Topic>): Promise<Topic> {
       consumerGroupCount: 0,
     } as unknown as Topic;
     mockTopics.unshift(topic as never);
-    return topic;
+    return cloneTopic(topic);
   }
   return metadataApi.createTopic(data);
 }
@@ -45,7 +50,7 @@ export async function updateTopic(data: Partial<Topic>): Promise<Topic> {
     const idx = mockTopics.findIndex((t) => t.name === data.name);
     if (idx < 0) throw new Error(`Topic not found: ${data.name}`);
     Object.assign(mockTopics[idx], data, { updatedAt: new Date().toISOString() });
-    return mockTopics[idx] as unknown as Topic;
+    return cloneTopic(mockTopics[idx] as unknown as Topic);
   }
   return metadataApi.updateTopic(data);
 }
@@ -67,12 +72,12 @@ export async function batchDeleteTopics(names: string[]): Promise<void> {
 }
 
 export async function getTopicRoutes(name: string): Promise<BrokerRoute[]> {
-  if (USE_MOCK) return (topicRoutes[name] as unknown as BrokerRoute[]) ?? [];
+  if (USE_MOCK) return cloneRoutes((topicRoutes[name] as unknown as BrokerRoute[]) ?? []);
   return metadataApi.getTopicRoutes(name);
 }
 
 export async function getTopicConsumers(name: string): Promise<ConsumerGroupInfo[]> {
-  if (USE_MOCK) return (topicConsumers[name] as unknown as ConsumerGroupInfo[]) ?? [];
+  if (USE_MOCK) return cloneConsumers((topicConsumers[name] as unknown as ConsumerGroupInfo[]) ?? []);
   return metadataApi.getTopicConsumers(name);
 }