diff --git a/packages/core/src/agents/browser/browserManager.test.ts b/packages/core/src/agents/browser/browserManager.test.ts
index ed6c336420..28092bc06e 100644
--- a/packages/core/src/agents/browser/browserManager.test.ts
+++ b/packages/core/src/agents/browser/browserManager.test.ts
@@ -152,7 +152,7 @@ describe('BrowserManager', () => {
       });
 
       expect(result.isError).toBe(true);
-      expect(result.content[0]?.text).toContain('not permitted');
+      expect((result.content || [])[0]?.text).toContain('not permitted');
       expect(Client).not.toHaveBeenCalled();
     });
 
@@ -170,7 +170,7 @@ describe('BrowserManager', () => {
       });
 
       expect(result.isError).toBe(false);
-      expect(result.content[0]?.text).toBe('Tool result');
+      expect((result.content || [])[0]?.text).toBe('Tool result');
     });
 
     it('should allow navigate_page to subdomain when wildcard is used', async () => {
@@ -187,7 +187,7 @@ describe('BrowserManager', () => {
       });
 
       expect(result.isError).toBe(false);
-      expect(result.content[0]?.text).toBe('Tool result');
+      expect((result.content || [])[0]?.text).toBe('Tool result');
     });
 
     it('should block new_page to disallowed domain', async () => {
@@ -204,7 +204,7 @@ describe('BrowserManager', () => {
       });
 
       expect(result.isError).toBe(true);
-      expect(result.content[0]?.text).toContain('not permitted');
+      expect((result.content || [])[0]?.text).toContain('not permitted');
     });
   });
 
@@ -235,6 +235,25 @@ describe('BrowserManager', () => {
       expect(args[userDataDirIndex + 1]).toMatch(/cli-browser-profile$/);
     });
 
+    it('should pass --host-rules when allowedDomains is configured', async () => {
+      const restrictedConfig = makeFakeConfig({
+        agents: {
+          browser: {
+            allowedDomains: ['google.com', '*.openai.com'],
+          },
+        },
+      });
+
+      const manager = new BrowserManager(restrictedConfig);
+      await manager.ensureConnection();
+
+      const args = vi.mocked(StdioClientTransport).mock.calls[0]?.[0]
+        ?.args as string[];
+      expect(args).toContain(
+        '--chromeArg="--host-rules=MAP * 127.0.0.1, EXCLUDE google.com, EXCLUDE *.openai.com, EXCLUDE 127.0.0.1"',
+      );
+    });
+
     it('should pass headless flag when configured', async () => {
       const headlessConfig = makeFakeConfig({
         agents: {
diff --git a/packages/core/src/agents/browser/browserManager.ts b/packages/core/src/agents/browser/browserManager.ts
index b9d0e6c5db..0cb3a829d7 100644
--- a/packages/core/src/agents/browser/browserManager.ts
+++ b/packages/core/src/agents/browser/browserManager.ts
@@ -118,7 +118,7 @@ export class BrowserManager {
         content: [
           {
             type: 'text',
-            text: `Tool '${toolName}' is not permitted for the requested URL/domain based on your current browser settings. DO NOT attempt to call with same URL/domain`,
+            text: `Tool '${toolName}' is not permitted for the requested URL/domain based on your current browser settings.`,
           },
         ],
         isError: true,
@@ -287,6 +287,18 @@ export class BrowserManager {
       mcpArgs.push('--userDataDir', defaultProfilePath);
     }
 
+    if (
+      browserConfig.customConfig.allowedDomains &&
+      browserConfig.customConfig.allowedDomains.length > 0
+    ) {
+      const exclusionRules = browserConfig.customConfig.allowedDomains
+        .map((domain) => `EXCLUDE ${domain}`)
+        .join(', ');
+      mcpArgs.push(
+        `--chromeArg="--host-rules=MAP * 127.0.0.1, ${exclusionRules}, EXCLUDE 127.0.0.1"`,
+      );
+    }
+
     debugLogger.log(
       `Launching chrome-devtools-mcp (${sessionMode} mode) with args: ${mcpArgs.join(' ')}`,
     );