Type Alias ScreenCheckpointMember<Id, Kind>

ScreenCheckpointMember: Kind extends "item"
    ? unknown
    : {
        checkpoint: () => Effect.Effect<
            ScreenCheckpoint<Extract<Id, ScreenId>>,
            ScreenCheckpointFailure,
        >;
    }

The checkpoint method every screen's handle carries: items are not screens and have none. Its result names the screen, so a restore of another screen refuses it.