Coupling Quality

Clean couplings are the key resource for improving few-step and single-step flow generation, more important than additional training or stronger inference-time solvers. The offline correction has a favourable cost profile for deployment-constrained settings because the improvement is purchased once during data generation while inference cost is unchanged. Coupling quality is the principal bottleneck of Rectified Flow, ahead of training capacity, loss design, or inference budget. Coupling distortion propagates across reflow rounds because each Euler integrator traverses regions of nonzero divergence, producing bent trajectories that become the next round's training signal.