Custom Properties

Trigger

Use this skill when the user:

• Wants to attach data to objects, scenes, or other Blender datablocks that survives save and load
• Mentions bpy.props, PropertyGroup, PointerProperty, "custom properties"
• Is unsure where to store add-on settings
• Sees a deprecation warning about property assignment

Required inputs

• What you want to store: a single number, a small struct, a list of items, or a complex hierarchy
• Where it should live: Scene (per-document), Object (per-object), WindowManager (session-only), AddonPreferences (per-user)
• Whether it must persist through save/load (almost always yes)

The type annotation form (mandatory since 2.8)