Extra keys are added in the Gradient Editor when undoing a background gradient edit from UI Builder Gradient

Steps to reproduce:

1. Create a new project
2. Create and open any UXML (UI Document) in the UI Builder
3. Add a VisualElement to Hierarchy and select it
4. In the Inspector, under Background, set the Image dropdown to "Gradient"
5. Click the Color field to open the Gradient Editor
6. Observe the Gradient Editor has two alpha keys (top) and two color keys (bottom)
7. Drag one of the bottom color keys to a different position
8. Drag another bottom color key to a different position
9. Press Ctrl+Z (Cmd+Z on macOS)
10. Observe the Gradient Editor

Actual results: An additional alpha key is added at the top of the Gradient Editor, and an additional color key is added at the bottom

Expected results: Undo restores the previous state without adding any keys

 

Reproducible with versions: 6000.7.0a4

Can’t test with versions: 6000.6.0b7 and lower (Background Gradients are not available)

Tested on (OS): macOS 26.5