UI pattern in which the interface changes state immediately upon user action — e.g. flipping the submit button into success mode on click — under the assumption that most requests succeed (98% of AJAX requests exceed, per Dimitry Salahutdinov). Avoids spinners, disabled buttons, and waiting, which all hurt psychological perception of time and can cause users to lose focus (Google RAIL model: >100ms delay leads to focus loss). Requires strategies for handling the cases where the server rejects, network errors occur, or concurrent edits conflict.