We introduce Coherence–Regulated Gravity (CRG), a covariant field theory in which spacetime curvature and inertia emerge from a regulated coherence field rather than a fixed gravitational constant. Gravity is mediated by a scalar coherence density , non-minimally coupled to curvature and dynamically stabilized by a Frost potential at high density. Mach’s principle is realized through a causal memory functional embedded directly in the action, encoding the historical stress–energy content of the universe. The resulting equations recover general relativity in the weak-field limit, eliminate curvature singularities, and predict measurable deviations in cosmological expansion and gravitational-wave propagation. Inertia is thus rendered relational, bounded, and observationally testable.