Reproduction steps:
1. Create a new project and make sure that “Use new Hierarchy window” option is enabled (Edit > Preferences… > General > New Hierarchy)
2. Select one of the GameObjects in the Hierarchy
3. Right-click on the selected GameObjects and select “Invert Selection” option
4. Right-click again and select “Select Children” option
5. Move highlighted GameObjects around
6. Observe the Console

Actual result: “ArgumentNullException: Value cannot be null.” errors are thrown
Expected result: No warnings or errors are thrown

Reproducible with: 6000.3.12f1, 6000.4.1f1, 6000.5.0b1, 6000.6.0a1

Couldn’t reproduce with: 6000.0.72f1 (No New Hierarchy)

Reproduced on: Windows 11, macOS Tahoe 26.3 (M4)

Note:

• Issue is not reproducible with old Hierarchy
• Full error:

{code:java}
ArgumentNullException: Value cannot be null.
Parameter name: node
Unity.Hierarchy.HierarchyViewModel.GetNodeType (Unity.Hierarchy.HierarchyNode& node) (at <d27f519091aa46ec8712df9066467ea9>:0)
Unity.Hierarchy.Editor.HierarchyGameObjectHandler.DoHandleDrop (Unity.Hierarchy.HierarchyViewDragAndDropHandlingData& data, System.Boolean perform) (at /Users/bokken/build/output/unity/unity/Modules/HierarchyEditor/ScriptBindings/HierarchyGameObjectHandler.bindings.cs:701)
Unity.Hierarchy.Editor.HierarchyGameObjectHandler.Unity.Hierarchy.IHierarchyEditorNodeTypeHandler.CanDrop (Unity.Hierarchy.HierarchyViewDragAndDropHandlingData& data) (at /Users/bokken/build/output/unity/unity/Modules/HierarchyEditor/ScriptBindings/HierarchyGameObjectHandler.bindings.cs:327)
Unity.Hierarchy.HierarchyViewDragHandler.HandleNodeHandlersDrop (Unity.Hierarchy.HierarchyViewDragHandler+HierarchyViewDragAndDropTargets dragAndDropTargets, UnityEngine.UIElements.DragAndDropData dragAndDropData, Unity.Hierarchy.HierarchyNode& parentNode, System.Boolean perform) (at /Users/bokken/build/output/unity/unity/Modules/Hierarchy/Managed/HierarchyViewDragHandler.cs:290)
Unity.Hierarchy.HierarchyViewDragHandler.GetVisualMode (UnityEngine.UIElements.HandleDragAndDropArgs& args) (at /Users/bokken/build/output/unity/unity/Modules/Hierarchy/Managed/HierarchyViewDragHandler.cs:228)
Unity.Hierarchy.HierarchyViewDragHandler.DragAndDropUpdate (UnityEngine.UIElements.HandleDragAndDropArgs args) (at /Users/bokken/build/output/unity/unity/Modules/Hierarchy/Managed/HierarchyViewDragHandler.cs:206)
UnityEngine.UIElements.HierarchyV2.CollectionView.RaiseHandleDragAndDrop (UnityEngine.Vector2 pointerPosition, UnityEngine.UIElements.DragAndDropArgs dragAndDropArgs) (at /Users/bokken/build/output/unity/unity/Modules/UIElements/Core/Controls/CollectionView/CollectionView.cs:1434)
UnityEngine.UIElements.HierarchyV2.CollectionViewDragger.GetVisualMode (UnityEngine.Vector3 pointerPosition, UnityEngine.EventModifiers modifiers, UnityEngine.UIElements.HierarchyV2.CollectionViewDragger+DragPosition& dragPosition) (at /Users/bokken/build/output/unity/unity/Modules/UIElements/Core/Controls/CollectionView/CollectionViewDragger.cs:215)
UnityEngine.UIElements.HierarchyV2.CollectionViewDragger.UpdateDrag (UnityEngine.Vector3 pointerPosition, UnityEngine.EventModifiers modifiers) (at /Users/bokken/build/output/unity/unity/Modules/UIElements/Core/Controls/CollectionView/CollectionViewDragger.cs:105)
UnityEngine.UIElements.DragEventsProcessor.OnDragUpdate (UnityEngine.UIElements.DragUpdatedEvent evt) (at /Users/bokken/build/output/unity/unity/Modules/UIElements/Core/DragAndDrop/DragEventsProcessor.cs:249)
UnityEngine.UIElements.EventCallbackFunctor`1[TEventType].Invoke (UnityEngine.UIElements.EventBase evt) (at /Users/bokken/build/output/unity/unity/Modules/UIElements/Core/Events/EventCallback.cs:64)
UnityEngine.UIElements.EventCallbackRegistry+DynamicCallbackList.Invoke (UnityEngine.UIElements.EventBase evt, UnityEngine.UIElements.BaseVisualElementPanel panel, UnityEngine.UIElements.VisualElement target) (at /Users/bokken/build/output/unity/unity/Modules/UIElements/Core/Events/EventCallbackRegistry.cs:245)
UnityEngine.UIElements.EventDispatchUtilities.HandleEventAcrossPropagationPath (UnityEngine.UIElements.EventBase evt, UnityEngine.UIElements.BaseVisualElementPanel panel, UnityEngine.UIElements.VisualElement target, System.Boolean isCapturingTarget) (at /Users/bokken/build/output/unity/unity/Modules/UIElements/Core/Events/EventDispatchUtilities.cs:212)
UnityEngine.UIElements.EventDispatchUtilities.DispatchToCapturingElementOrElementUnderPointer (UnityEngine.UIElements.EventBase evt, UnityEngine.UIElements.BaseVisualElementPanel panel, System.Int32 pointerId, UnityEngine.Vector2 position) (at /Users/bokken/build/output/unity/unity/Modules/UIElements/Core/Events/EventDispatchUtilities.cs:566)
UnityEngine.UIElements.MouseEventBase`1[T].Dispatch (UnityEngine.UIElements.BaseVisualElementPanel panel) (at /Users/bokken/build/output/unity/unity/Modules/UIElements/Core/Events/MouseEvents.cs:336)
UnityEngine.UIElements.EventDispatcher.ProcessEvent (UnityEngine.UIElements.EventBase evt, UnityEngine.UIElements.BaseVisualElementPanel panel) (at /Users/bokken/build/output/unity/unity/Modules/UIElements/Core/EventDispatcher.cs:420)
UnityEngine.UIElements.EventDispatcher.Dispatch (UnityEngine.UIElements.EventBase evt, UnityEngine.UIElements.BaseVisualElementPanel panel, UnityEngine.UIElements.DispatchMode dispatchMode) (at /Users/bokken/build/output/unity/unity/Modules/UIElements/Core/EventDispatcher.cs:216)
UnityEngine.UIElements.BaseVisualElementPanel.SendEvent (UnityEngine.UIElements.EventBase e, UnityEngine.UIElements.DispatchMode dispatchMode) (at /Users/bokken/build/output/unity/unity/Modules/UIElements/Core/Panel.cs:723)
UnityEditor.UIElements.EditorEventDispatchUtility.DoDispatch (UnityEngine.UIElements.BaseVisualElementPanel panel, UnityEngine.Event eventInstance) (at /Users/bokken/build/output/unity/unity/Modules/UIElementsEditor/EditorEventDispatchUtility.cs:89)
UnityEditor.UIElements.DefaultWindowBackend.ProcessEvent (UnityEngine.Event e) (at /Users/bokken/build/output/unity/unity/Modules/UIElementsEditor/WindowBackends/DefaultWindowBackend.cs:114)
UnityEditor.GUIView.ProcessEvent (UnityEngine.EntityId entityId, System.IntPtr nativeEventPtr, System.Boolean& result) (at /Users/bokken/build/output/unity/unity/Editor/Mono/GUIView.cs:70) {code}