feat(mcp): add network offline state tools

packages/playwright-core/src/cli/daemon/commands.ts

@@ -667,6 +667,17 @@ const unroute = declareCommand({
   toolParams: ({ pattern }) => ({ pattern }),
 });
 
+const networkStateSet = declareCommand({
+  name: 'network-state-set',
+  description: 'Set the browser network state to online or offline',
+  category: 'network',
+  args: z.object({
+    state: z.enum(['online', 'offline']).describe('Set to "offline" to simulate offline mode, "online" to restore network connectivity'),
+  }),
+  toolName: 'browser_network_state_set',
+  toolParams: ({ state }) => ({ state }),
+});
+
 // Export
 
 const screenshot = declareCommand({
@@ -950,6 +961,7 @@ const commandsArray: AnyCommandSchema[] = [
   routeMock,
   routeList,
   unroute,
+  networkStateSet,
 
   // config category
   configPrint,

packages/playwright-core/src/mcp/browser/tools/network.ts

@@ -15,7 +15,7 @@
  */
 
 import { z } from '../../../mcpBundle';
-import { defineTabTool } from './tool';
+import { defineTool, defineTabTool } from './tool';
 
 import type * as playwright from '../../../..';
 
@@ -83,7 +83,30 @@ export async function renderRequest(request: playwright.Request): Promise<string
   return result.join(' ');
 }
 
+const networkStateSet = defineTool({
+  capability: 'network',
+
+  schema: {
+    name: 'browser_network_state_set',
+    title: 'Set network state',
+    description: 'Sets the browser network state to online or offline. When offline, all network requests will fail.',
+    inputSchema: z.object({
+      state: z.enum(['online', 'offline']).describe('Set to "offline" to simulate offline mode, "online" to restore network connectivity'),
+    }),
+    type: 'action',
+  },
+
+  handle: async (context, params, response) => {
+    const browserContext = await context.ensureBrowserContext();
+    const offline = params.state === 'offline';
+    await browserContext.setOffline(offline);
+    response.addTextResult(`Network is now ${params.state}`);
+    response.addCode(`await page.context().setOffline(${offline});`);
+  },
+});
+
 export default [
   requests,
   networkClear,
+  networkStateSet,
 ];

tests/mcp/cli-network-offline.spec.ts

@@ -0,0 +1,29 @@
+/**
+ * Copyright (c) Microsoft Corporation.
+ *
+ * Licensed 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 { test, expect } from './cli-fixtures';
+
+test('network-state-set toggles offline state', async ({ cli, server }) => {
+  await cli('open', server.EMPTY_PAGE);
+
+  // Set offline
+  const { output: offlineOutput } = await cli('network-state-set', 'offline');
+  expect(offlineOutput).toContain('offline');
+
+  // Restore online
+  const { output: onlineOutput } = await cli('network-state-set', 'online');
+  expect(onlineOutput).toContain('online');
+});

tests/mcp/network-offline.spec.ts

@@ -0,0 +1,99 @@
+/**
+ * Copyright (c) Microsoft Corporation.
+ *
+ * Licensed 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 { test, expect, parseResponse } from './fixtures';
+
+// Enable the 'network' capability for context-level tools
+test.use({
+  mcpCaps: ['network'],
+});
+
+test('browser_network_state_set sets network to offline', async ({ client }) => {
+  // Set offline
+  const setResponse = parseResponse(await client.callTool({
+    name: 'browser_network_state_set',
+    arguments: { state: 'offline' },
+  }));
+  expect(setResponse.result).toContain('Network is now offline');
+});
+
+test('browser_network_state_set restores network to online', async ({ client }) => {
+  // Set offline first
+  await client.callTool({
+    name: 'browser_network_state_set',
+    arguments: { state: 'offline' },
+  });
+
+  // Restore online
+  const setResponse = parseResponse(await client.callTool({
+    name: 'browser_network_state_set',
+    arguments: { state: 'online' },
+  }));
+  expect(setResponse.result).toContain('Network is now online');
+});
+
+test('network requests fail when offline', async ({ client, server }) => {
+  // Navigate to a page first
+  await client.callTool({
+    name: 'browser_navigate',
+    arguments: { url: server.EMPTY_PAGE },
+  });
+
+  // Set offline
+  await client.callTool({
+    name: 'browser_network_state_set',
+    arguments: { state: 'offline' },
+  });
+
+  // Try to navigate - should fail
+  // Error messages vary by browser:
+  // - Chrome: net::ERR_INTERNET_DISCONNECTED
+  // - Firefox: NS_ERROR_OFFLINE
+  // - WebKit: WebKit encountered an internal error
+  expect(await client.callTool({
+    name: 'browser_navigate',
+    arguments: { url: server.PREFIX + '/one-style.html' },
+  })).toHaveResponse({
+    isError: true,
+    error: expect.stringMatching(/net::ERR_INTERNET_DISCONNECTED|NS_ERROR_OFFLINE|WebKit encountered an internal error/),
+  });
+});
+
+test('network requests succeed after restoring online', async ({ client, server }) => {
+  // Navigate to initial page
+  await client.callTool({
+    name: 'browser_navigate',
+    arguments: { url: server.EMPTY_PAGE },
+  });
+
+  // Set offline then back online
+  await client.callTool({
+    name: 'browser_network_state_set',
+    arguments: { state: 'offline' },
+  });
+  await client.callTool({
+    name: 'browser_network_state_set',
+    arguments: { state: 'online' },
+  });
+
+  // Navigate should succeed
+  expect(await client.callTool({
+    name: 'browser_navigate',
+    arguments: { url: server.PREFIX + '/one-style.html' },
+  })).toHaveResponse({
+    isError: undefined,
+  });
+});