A Conditional Structural Derivation of the Fine-Structure Constant from Neutral Codimension-Two Holonomy Capacity

The fine-structure constant is an empirical boundary datum of quantum electrodynamics (QED), not a value derived by the Standard Model. We give a conditional structural derivation in which its inverse is matched to the response capacity of a neutral codimension-two holonomy defect. The Indefinite Reconstruction Stability Principle and the topology of a punctured transverse space select codimension two and an integer winding group Z. Phase and spin read-outs are represented by native norm-one groups U(1) and SU(2). Preserving their algebraic identities and multiplicative norms fixes the measures 2π and 2π2. Their three nonempty exposures have total capacity Ω=4π3+π2+π. Four first-interface roles and one protected identity select Z/5Z; its 24 nonzero outgoing–returning state pairs form one symmetry orbit, fixing the first correction. At later resolutions, a separately declared asymmetric complete-source/exposed-target transfer rule—not the Chinese remainder theorem used only for common refinement—fixes the coefficients by unit counting without assuming composite-level transitivity. With a declared paired-interface grading rule, they yield an absolutely convergent odd-power tower with an exact logarithmic sum. A separate low-energy QED matching postulate identifies the structural response with the renormalized zero-momentum Maxwell coefficient, giving α(0)−1=137.035999176142, 0.041 standard deviations below the 2022 CODATA value. No numerical coefficient is adjusted once the declared read-out, counting, transfer, grading, and matching assumptions are fixed. The construction does not derive QED dynamics or the running coupling.