Classical physics models fields and forces as independent constructs acting on matter. In the MID/QC framework, these behaviors emerge instead from tension geometry within the quantized substrate. This paper develops the substrate‑first architecture in which gradients, curvature, torsion, and coherence channels form a unified geometric system that governs motion, interaction, and stability. Tension geometry provides a single substrate‑native mechanism underlying gravitational behavior, electromagnetic interaction, inertial response, and force transmission. This work establishes the foundational geometric layer that links the Applied Substrate Series to the broader MID/QC field architecture