Execution of Modal Triplet Theory I: Gauge, HYM, Threshold, and Axion Status after Profile-Standard SM Closure

We present the first Tier 4 execution of Modal Triplet Theory (MTT): an explicit string compactification that realizes the geometry-free targets fixed at Tier 3. Focusing on gauge couplings, Kähler moduli, axion normalizations, and one-loop gauge threshold corrections, we construct a concrete Calabi–Yau corner in which all Tier 3 latent parameters are reproduced algebraically from standard string-theoretic data. Internal harmonic integrals are replaced by intersection numbers, Chern classes, and controlled threshold formulae. We show that a single bulk threshold direction, together with small exceptional contributions, suffices to reproduce the Tier 3 minimum-norm threshold diagnostics at multiple matching scales, while maintaining a controlled effective field theory regime. No parameters fixed in earlier tiers are retuned. This work establishes the existence of a consistent string-level realization of the gauge, geometric, and axion sectors of MTT and provides the foundation for subsequent execution of flavor and Higgs physics.