When to Correct: Update Width Shapes Terminal Refinement in Uniform Diffusion

Update width changes the relative benefit of terminal refinement even when model-call counts are fixed. We compare correction during prediction with correction after prediction, using a fixed 33-step predictor grid and eight correction calls. Increasing width moves the terminal-to-late GenPPL ratio from 0.731 to 1.043 on LM1B and from 0.693 to 0.921 on OpenWebText. Larger updates improve both schedules, with late correction gaining more relatively. The direction observed on LM1B was predicted in advance and confirmed on OpenWebText. Later tests at intermediate widths in both models and on fresh seeds at a second correction budget support the same pattern. A separate LM1B study with 3,000 outputs per configuration compares terminal refinement with calibrated nucleus sampling. Terminal achieves 4.96% lower GenPPL and 14.69% shorter measured generation time, while nucleus achieves higher held-out prefix MAUVE. A placement comparison should therefore report update width alongside predictor and correction counts and test more than one width.