Label-free batch-level optimal transport couplings stabilize strong CFG, FID 2.06→1.91

AlexanderTong7 · x · 2026-10-14

A paper highlighted by AlphaXIV, "Global Transport Couplings for Classifier-Free Guided Flows," tackles a core issue in flow matching: random noise-image pairings produce unstable trajectories under strong classifier-free guidance (CFG). The work instead uses optimal transport to match noise with images across the entire batch, ignoring class labels.

This shrinks the gap between conditional and unconditional predictions, enabling stronger guidance without quality loss. On ImageNet-256 it improves FID from 2.06 to 1.91 with no architecture or sampling changes. The authors also found these simple label-free mini-batch OT couplings improve conditional generation at higher guidance scales.

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