Decomposing Conditionalization: Constraint and Transport in Diachronic Coherence

Updating is not a single operation but a composite policy. This paper develops the Constraint--Transport Architecture (CTA), a modular framework that separates four roles: admissibility refinement, transport of prior states, optional posterior selection, and envelope projection to observable bid/ask prices. Rather than taking ratio conditioning as primitive, CTA isolates what coherence constrains and what requires additional normative commitments. It thus serves as a conditions-of-possibility framework, making explicit which parts of updating are forced by coherence and which are optional policy layers. We prove three core coherence-geometry results. First, soft constraint refinement is feasibility-exact under mild regularity: an evidential target is feasible exactly when it lies within prior envelope bounds. Second, posterior envelopes induced by refinement are coherent under standard bid/ask trading semantics. Third, nested refinement is diachronically safe against time books. We then prove a conditional normal-form theorem: under affine score foliation and carrier compositionality, feasible update policies factor into context shift plus constraint enforcement, with optional selection. Relaxing affine foliation yields curved evidential geometries, showing that coherence alone does not privilege classical ratio rules. Classical Bayesian and Jeffrey updating appear within CTA as specializations obtained by adding transport and selector commitments on top of refinement geometry. LP case studies serve as nonclassical stress tests, including contradiction-mass propagation and tight representability bounds in the finite two-atom setting.