Four Null Spacetime Theory Kinematic Quantum Transport Across Faces

In Four Null Spacetime Theory, spacetime is built from cells spanned by four lightlike vectors whose six pairwise Lorentzian inner products are equal, and curvature is concentrated at hinges in signed integer multiples of \(\pi/3\). At each past or future end, four legs, each with spin \(j = \frac{1}{2}\), form a singlet with two states of opposite cell chirality, defined here as the sign of the cell's oriented volume, not the handedness of a particle. A full cell carries four past and four future legs. We ask what the geometry of a shared face fixes when such cells are glued. Matching the pair products of the shared legs fixes the face exchange up to a spin frame and a phase, with no adjustable transfer strength. Around a hinge with deficit \(k_h\pi/3\), the composed face maps act on cell chirality as \(C \mapsto (-1)^{k_h}C\): odd curvature quanta reverse it, while even quanta preserve it. We derive this analytically and verify it on all 2,728 enumerated hinge configurations with proper transports and returning hinge labels. The curvature parity obeys a \(\mathbb{Z}_2\) Bianchi identity and is unchanged under Lorentz frame maps of the faces; a unitary Lorentz covariant quantum network remains open. With balanced past and future corners and full \(S_4\) relabeling symmetry, the eight leg cell map is unique and preserves chirality. A specified spin probe reads the oriented deficit modulo \(2\pi\). These results are kinematic. Face constraints do not fix the handoff of a spin reference inside a cell. Full transfer follows only if flat loop transparency is assumed, or, within the stated hinge class, if cell operations are assumed to be relabelings.