Geometric Origin of the Fine-Structure Constant from Event Exclusion

We present a geometric derivation of the fine-structure constant based on a discrete event-exclusion framework on S³. The theory replaces renormalization-based explanations with a finite, combinatorial structure governed by quaternionic phase space, a minimal 16-cell angular grammar, and observational equivalence. The fine-structure constant emerges as a visibility density determined by global event exclusion rather than local field distortions. The resulting prediction,α⁻¹ = 136.9148936…,differs from the CODATA 2022 value by 0.088% without introducing any adjustable parameters. We prove that this deviation cannot be accounted for by local measurement effects and must arise from global exclusion structure. Key results include:• a rigorous separation between local deficit and event exclusion,• a proof of minimality and uniqueness of the 16-cell grammar,• a quaternionic power-counting origin of the integers 512, 390, and 360,• explicit falsifiability under grammar modification. This work is intended as a preprint and a basis for further investigation connecting geometric observability to early-universe structure and cosmic background signatures.