15. Undo, autosave and recovery

Ctrl+Z / Ctrl+Shift+Z use Material Paint's stroke history first, then Blender's undo (chapter 9). Stack edits use Blender's undo, and OP rebuilds the needed cache.

Autosave writes the active canvas after 30 seconds idle, and every canvas when you save the .blend (UDIM tiles too). Keep the project folders beside the .blend when moving stuff.

Removing a Paint or Image sublayer also keeps a temporary image backup for undo/redo during that session. This is not a backup history, save your project regularly.