I'm not sure of the exact event name, but event type `817` in `CGSEventType` (or when used with `CGSRegisterNotifyProc`) corresponds to a window changing its space, likely only for managed spaces. The data size is 8 bytes: the first 4 bytes represent the new `spaceId` as a `UInt32`, and the last 4 bytes seem to be unused. I thought it would be helpful to mention this, as it might assist someone else. Also, thank you for your work—it has been incredibly helpful to me.