Measuring what breaks when every user action can be undone forever means looking at systems that depend on irreversible consequences. The first thing to go is accountability, because actions without lasting impact weaken responsibility and decision making. Undoability also erodes trust in logs, records, and shared reality since nothing feels final or reliable. Interfaces start to simplify aggressively because feedback loops lose weight and users stop learning from errors. Even design systems shift toward cautionless behavior, which paradoxically makes outcomes harder to predict or optimize.