Asymptotic Microcausality to Macrocausality: Complete Quantum Electrodynamics and the Regulated S-Matrix

We formulate an ultraviolet-complete, entire-function regulated QED in which operational observables form a quasi-local net \( A_F(O) \). The regulator term produces asymptotically-local operators obeying exponential spacelike commutator bounds. We show that this quantitative locality is sufficient for Haag--Ruelle scattering, yielding asymptotic in/out states, an \( S \)matrix, and an LSZ reduction formula with on-shell normalization. Perturbative unitarity and the optical theorem are maintained, while the leading infrared structure of QED is unchanged. Cross sections are expressed as detector click probabilities via quasi-local POVMs, establishing macrocausality in operational terms.