This article develops a covariant theoretical framework in which spontaneous subatomic mass-energy interconversion is modeled as a stochastic marked point process. The central proposal is not that quantum randomness directly equals spacetime curvature, but that a large population of microscopic interconversion events may generate a stable coarse-grained stress-energy mean while leaving a smaller residual noise sector. In this construction, each event contributes a localized stress-energy packet with random spacetime position, exchanged energy, lifetime, and tensor character. The ensemble mean defines an effective macroscopic source in Einstein’s equation, while the residual fluctuations define a covariant noise kernel that sources metric perturbations through an Einstein-Langevin equation.This formulation distinguishes statistical homogeneity and isotropy in a cosmic rest frame from the stronger condition of local Lorentz invariance required for a truly vacuum-like stress tensor. Under that stronger condition, the mean interconversion sector reduces to a form proportional to the metric and therefore behaves as an emergent cosmological-constant contribution. In cosmology, the background interconversion density is expressed through the active event density: event rate per physical volume and time multiplied by mean exchanged energy and effective event lifetime. This gives a microphysical dictionary for the equation-of-state parameter and for possible late-time dark-energy-like or early-time transient behavior.The model also gives a formal route by which a transient pre-recombination component could reduce the sound horizon and thereby affect Hubble-constant inference. The manuscript emphasizes that this is a phenomenological bridge, not a completed quantum-gravity theory. Conservation, perturbation bounds, thermodynamic stability, and observational viability remain mandatory tests.