fix: resolve flaky browser screenshot test for Monaco editor

agents-manage-ui/src/components/form/__tests__/form.browser.test.tsx

@@ -112,11 +112,16 @@ describe('Form', () => {
     agentStore.setState({ jsonSchemaMode: true });
     const { container } = render(<NestedTestForm />);
 
-    await waitFor(() => {
-      const message = container.querySelector<HTMLParagraphElement>('[data-slot="form-message"]');
-      expect(message).toBeInTheDocument();
-    });
+    await waitFor(
+      () => {
+        // Wait for Monaco editor to fully initialize (not just the skeleton loading state)
+        expect(container.querySelector('.monaco-editor')).toBeInTheDocument();
+        // Wait for form validation error message to render
+        expect(container.querySelector('[data-slot="form-message"]')).toBeInTheDocument();
+      },
+      { timeout: 20_000 }
+    );
 
     await expect(container).toMatchScreenshot();
-  }, 30_000);
+  }, 45_000);
 });

agents-manage-ui/vitest.config.ts

@@ -28,11 +28,22 @@ export default defineConfig({
     name: pkgJson.name,
     globals: true,
     onUnhandledError(error) {
+      // Extract message from Error instances or serialized browser errors.
+      // Browser-originated errors may lose their prototype chain during
+      // serialization, so we check .message directly without instanceof.
+      const message =
+        (error as { message?: string })?.message ?? (typeof error === 'string' ? error : '');
       // Suppress known Vitest worker RPC shutdown race condition.
       // Next.js triggers background dynamic imports that can outlive test execution;
       // when the worker shuts down, these pending imports cause an unhandled rejection.
       // See: https://github.com/vitest-dev/vitest/issues/9458
-      if (error instanceof Error && error.message?.includes('Closing rpc while')) {
+      if (message.includes('Closing rpc while')) {
+        return false;
+      }
+      // Suppress Monaco editor web worker initialization errors in browser tests.
+      // Monaco falls back to main-thread execution when workers fail to load,
+      // which does not affect test correctness.
+      if (message.includes('Cannot use import statement outside a module')) {
         return false;
       }
     },
@@ -60,8 +71,10 @@ export default defineConfig({
             instances: [{ browser: 'chromium' }],
             expect: {
               toMatchScreenshot: {
-                // Increase timeout because the default `5s` is insufficient on CI
-                timeout: 15_000,
+                // Increase timeout because the default `5s` is insufficient on CI.
+                // Monaco editor requires extra time to stabilize (dynamic imports,
+                // syntax highlighting, height recalculation).
+                timeout: 20_000,
                 resolveScreenshotPath,
                 resolveDiffPath: resolveScreenshotPath,
                 comparatorOptions: {