[menu] Always highlight the first item on open

packages/react/src/menu/root/MenuRoot.test.tsx

@@ -692,7 +692,6 @@ describe('<Menu.Root />', () => {
         await user.keyboard('[ArrowDown]');
         await user.keyboard('[ArrowDown]');
         await user.keyboard('[ArrowDown]');
-        await user.keyboard('[ArrowDown]');
 
         const submenuTrigger1 = await screen.findByTestId('submenu-trigger');
         await waitFor(() => {
@@ -999,6 +998,31 @@ describe('<Menu.Root />', () => {
         });
       });
 
+      it('focuses the first item when the menu is opened programmatically', async () => {
+        function App() {
+          const [open, setOpen] = React.useState(false);
+          return (
+            <div>
+              <button type="button" onClick={() => setOpen(true)}>
+                external
+              </button>
+              <TestMenu rootProps={{ open, onOpenChange: setOpen }} />
+            </div>
+          );
+        }
+
+        const { user } = await render(<App />);
+
+        await user.click(screen.getByRole('button', { name: 'external' }));
+
+        const [firstItem, ...otherItems] = await screen.findAllByRole('menuitem');
+        await waitFor(() => expect(firstItem).toHaveFocus());
+        expect(firstItem.tabIndex).toBe(0);
+        otherItems.forEach((item) => {
+          expect(item.tabIndex).toBe(-1);
+        });
+      });
+
       it('focuses the trigger after the menu is closed', async () => {
         const { user } = await render(
           <div>

packages/react/src/menu/root/MenuRoot.tsx

@@ -423,6 +423,8 @@ export const MenuRoot = fastComponent(function MenuRoot<Payload>(props: MenuRoot
     openOnArrowKeyDown: parent.type !== 'context-menu',
     externalTree: nested ? floatingTreeRoot : undefined,
     focusItemOnHover: highlightItemOnHover,
+    // Ensure an item is highlighted on open even when opened programmatically (no trigger keydown).
+    focusItemOnOpen: true,
   });
 
   const onTyping = React.useCallback(

packages/react/src/menubar/Menubar.test.tsx

@@ -587,13 +587,11 @@ describe('<Menubar />', () => {
         const fileTrigger = screen.getByTestId('file-trigger');
         await user.click(fileTrigger);
 
-        // Menu should be open
+        // Menu should be open with the first item focused
         await waitFor(() => {
           expect(screen.queryByTestId('file-menu')).not.toBe(null);
         });
 
-        // Navigate with keyboard
-        await user.keyboard('{ArrowDown}');
         const firstItem = screen.getByTestId('file-item-1');
         await waitFor(() => {
           expect(firstItem).toHaveFocus();