Foundational Mechanisms of Tension, Oscillation, and Emergence Across Physical Domains The primary entry point and foundational paper of the MID/QC series. This work introduces the MID substrate, a generative physical primitive that unifies quantum and gravitational behavior through a single geometric architecture. The framework defines the substrate’s tension‑based dynamics, coherence wells, oscillatory modes, and emergent field behavior, establishing a mechanism‑first foundation for quantum, sub‑quantum, and gravitational phenomena. The paper presents the core definitions, primitives, and conceptual structure upon which all downstream derivations, applications, and engineering pathways depend. This publication serves as the upstream anchor for the broader MID/QG research arc, providing the foundational architecture for subsequent papers on electromagnetism, charge polarity, torsion, relativistic deformation, fusion barriers, cosmic structure, and substrate‑level field emergence. A full rights reservation and stewardship statement is included to ensure clarity, prevent misuse, and support responsible development of the framework.