Antigravity without Negative Mass: A Closure–Residual Framework for Sign-Rigidity and Device-Level Repulsion Analogues

Why does gravity appear to have only one “charge sign”—attraction—while electromagnetism admits both attraction and repulsion? This paper addresses that question in a way that is faithful to established gravitational theory and directly usable at the device level. At the source level, it reviews why classical general relativity sourced by stress–energy satisfying standard positivity assumptions does not admit fundamental gravitational repulsion between isolated bodies. This is framed as sign-rigidity: the obstruction lies in the admissible macroscopic sources, not in the metric formalism itself. At the protocol level, the paper introduces a closure–residual framework showing how many laboratory and engineering phenomena described as “antigravity” arise from closed control cycles whose boundary conditions return but leave measurable residuals due to order-dependent (commutator) structure. Residual observables, reversal and commutator probes, scaling and persistence filters, and echo diagnostics are defined. The result is an operational demarcation: claims of antigravity become falsifiable checklists rather than slogans. The framework unifies geometric phases, nonholonomic control, baseline subtraction, and energy-condition constraints into a single audit procedure applicable across gravity-adjacent experiments and cyclic devices.