fix(popup-menu): open sibling submenu after guard-unblocked hover

packages/react/src/internal/popup-menu/components/submenu-trigger/submenu-trigger.tsx

@@ -921,6 +921,30 @@ export const PopupMenuSubmenuTrigger = React.forwardRef<
 
       // Highlight on hover (use storeId for store operations)
       parentStore.setHighlightedId(item.storeId)
+
+      // Pointer move can be the first allowed event after aim-guard unblocks
+      // this row (e.g. pointerenter was blocked earlier), so allow it to open.
+      if (!openOnHighlight || open) {
+        return
+      }
+
+      clearLeaveMonitor()
+      clearCloseTimer()
+
+      const pointerDelay = delay.pointer
+      if (pointerDelay <= 0) {
+        setOpen(true)
+        return
+      }
+
+      if (openTimerRef.current !== null) {
+        return
+      }
+
+      openTimerRef.current = setTimeout(() => {
+        openTimerRef.current = null
+        setOpen(true)
+      }, pointerDelay)
     },
     [
       onPointerMove,
@@ -931,6 +955,12 @@ export const PopupMenuSubmenuTrigger = React.forwardRef<
       guardedTriggerIdRef,
       item.id,
       item.storeId,
+      openOnHighlight,
+      open,
+      clearLeaveMonitor,
+      clearCloseTimer,
+      delay.pointer,
+      setOpen,
       logAimTrace,
       parentStore,
     ],

packages/react/src/internal/popup-menu/popup-menu.test.tsx

@@ -417,6 +417,27 @@ function NestedMenuForDataAttrs({
                     </DropdownMenu.Positioner>
                   </DropdownMenu.Portal>
                 </DropdownMenu.Submenu>
+                <DropdownMenu.Submenu>
+                  <DropdownMenu.SubmenuTrigger data-testid="submenu-trigger-sibling">
+                    Submenu sibling
+                  </DropdownMenu.SubmenuTrigger>
+                  <DropdownMenu.Portal>
+                    <DropdownMenu.Positioner>
+                      <DropdownMenu.Popup data-testid="popup-submenu-sibling">
+                        <DropdownMenu.Surface>
+                          <DropdownMenu.List>
+                            <DropdownMenu.Item
+                              data-testid="submenu-sibling-item-1"
+                              value="submenu-sibling-item-1"
+                            >
+                              Sibling submenu item
+                            </DropdownMenu.Item>
+                          </DropdownMenu.List>
+                        </DropdownMenu.Surface>
+                      </DropdownMenu.Popup>
+                    </DropdownMenu.Positioner>
+                  </DropdownMenu.Portal>
+                </DropdownMenu.Submenu>
               </DropdownMenu.List>
             </DropdownMenu.Surface>
           </DropdownMenu.Popup>
@@ -1382,6 +1403,51 @@ describe('PopupMenu', () => {
         scenario.cleanup()
       }
     })
+
+    it('opens sibling submenu on pointermove after guard timeout', async () => {
+      const scenario = await setupAimMonitoringScenario(0)
+
+      try {
+        fireEvent.pointerMove(window, { clientX: 120, clientY: 90 })
+        fireEvent.pointerMove(window, { clientX: 150, clientY: 92 })
+        fireEvent.pointerMove(window, { clientX: 180, clientY: 94 })
+
+        fireEvent.pointerLeave(scenario.submenuTrigger, {
+          clientX: 190,
+          clientY: 94,
+        })
+
+        const siblingTrigger = screen.getByTestId('submenu-trigger-sibling')
+
+        fireEvent.pointerEnter(siblingTrigger, {
+          clientX: 182,
+          clientY: 136,
+        })
+        fireEvent.pointerMove(siblingTrigger, {
+          clientX: 182,
+          clientY: 136,
+        })
+
+        expect(
+          screen.queryByTestId('popup-submenu-sibling'),
+        ).not.toBeInTheDocument()
+
+        await sleep(650)
+
+        fireEvent.pointerMove(siblingTrigger, {
+          clientX: 186,
+          clientY: 140,
+        })
+
+        await waitFor(() => {
+          expect(
+            screen.getByTestId('popup-submenu-sibling'),
+          ).toBeInTheDocument()
+        })
+      } finally {
+        scenario.cleanup()
+      }
+    })
   })
 
   describe('search and filtering', () => {