fix: allow newTab() in persistent context (--extension/--profile) mode (#731)

When launched with --extension or --profile, launchPersistentContext()
is used which sets isPersistentContext=true but leaves this.browser as
null. The guard in newTab() checked !this.browser, causing a false
"Browser not launched" error even though the browser was running.

Replace !this.browser with !this.isLaunched(), which already accounts
for both launch paths (browser !== null || isPersistentContext).

Also improve the error message in newWindow() to clarify that it is
not supported in persistent context mode, since it requires a Browser
object to create a new context.

Fixes #411

src/browser.test.ts

@@ -1243,6 +1243,32 @@ describe('BrowserManager', () => {
   });
 });
 
+describe('BrowserManager (persistent context / --profile mode)', () => {
+  let profileBrowser: BrowserManager;
+  let tmpProfileDir: string;
+
+  beforeAll(async () => {
+    tmpProfileDir = path.join(os.tmpdir(), `agent-browser-test-profile-${Date.now()}`);
+    profileBrowser = new BrowserManager();
+    await profileBrowser.launch({ headless: true, profile: tmpProfileDir });
+  });
+
+  afterAll(async () => {
+    await profileBrowser.close();
+    rmSync(tmpProfileDir, { recursive: true, force: true });
+  });
+
+  it('should report as launched in persistent context mode', () => {
+    expect(profileBrowser.isLaunched()).toBe(true);
+  });
+
+  it('should create new tab in persistent context mode without throwing', async () => {
+    const result = await profileBrowser.newTab();
+    expect(result.index).toBe(1);
+    expect(result.total).toBe(2);
+  });
+});
+
 describe('getDefaultTimeout', () => {
   const originalEnv = { ...process.env };
 

src/browser.ts

@@ -1829,7 +1829,7 @@ export class BrowserManager {
    * Create a new tab in the current context
    */
   async newTab(): Promise<{ index: number; total: number }> {
-    if (!this.browser || this.contexts.length === 0) {
+    if (!this.isLaunched() || this.contexts.length === 0) {
       throw new Error('Browser not launched');
     }
 
@@ -1856,7 +1856,11 @@ export class BrowserManager {
     total: number;
   }> {
     if (!this.browser) {
-      throw new Error('Browser not launched');
+      throw new Error(
+        this.isPersistentContext
+          ? 'newWindow is not supported in extension (persistent context) mode'
+          : 'Browser not launched'
+      );
     }
 
     const context = await this.browser.newContext({