This paper establishes the universal reduction layer of the canonical QMS–spectral program. It proves that any relativistic quantum theory satisfying a minimal and widely accepted set of physical requirements necessarily reduces to the canonical operator-theoretic framework developed in the preceding papers of the series. The minimal structural requirements assumed are: Positive-definite Hilbert space and unitary time evolution Microcausality (local net structure) Existence of stable, jointly consultable macroscopic records A local finite-derivative low-energy effective field theory limit Local fermionic degrees of freedom No geometric assumptions, field equations, or spectral triples are postulated. The paper proves a universal implication chain: Stable macroscopic records plus coarse-graining force a contractive completely positive semigroup on the record sector. Reflection positivity enforces Hilbert (p = 2) geometry. Local consultability and microcausality force commutativity of record observables. A local finite-derivative EFT limit excludes nonlocal generators and anomalous heat-kernel behavior. Strong locality implies classical diffusion and Seeley–DeWitt asymptotics. Local fermions force spin structure and a Dirac-type generator. From these steps, it follows that any theory satisfying the above physical requirements must induce the canonical QMS–spectral structure developed in Papers I–III. As a consequence: A smooth four-dimensional geometric carrier emerges. The low-energy bosonic action is forced to contain the cosmological term and the Einstein–Hilbert term at leading order. Lovelock uniqueness in four dimensions fixes the second-order field equations uniquely to the Einstein equations with cosmological constant. Higher-curvature corrections are present but fixed by the same spectral data and introduce no independent tunings at leading order. The result is conditional but universal within the standard “physicists’ quantum gravity” problem class: Einstein gravity is not assumed but structurally forced once the minimal QFT requirements are imposed. This paper serves as the bridge between the structural closure layer (algebraic collapse, modular rigidity, primitive completeness) and the final universality theorem that completes the program.