Causal Sets as Event-Selection Shadows of Modal Triplet Theory

Causal set theory describes spacetime as a discrete partially ordered set of events, while measurement theory treats events as irreversible outcomes of quantum dynamics. We show that both notions arise as the same effective four-dimensional shadow of coherence-selection events in Modal Triplet Theory (MTT). Selection events are defined as irreversible transitions between admissible coherent basins under noninvertible projection. We prove that these events generate a locally finite partial order, yielding an effective causal set whose event density, ordering, and approximate Lorentz invariance are fixed by coherent-sector bottleneck data rather than by ad hoc sprinkling assumptions. Deviations from Poisson statistics and exact Lorentz invariance are predicted near coherence-breakdown regions. We establish cross-sector closure: the same bottleneck data control event density, measurement and collapse thresholds, ultraviolet completion, and canonical geometric discreteness. All results are slab-local and admissibility-conditioned, identifying spacetime discreteness, causal order, and irreversibility as unified reduced-dynamical consequences of coherence breakdown.