CPR routes token-by-token between a base model and its SFT expert, beating the SFT expert by 1.4-5.5% in domain performance while cutting the general-capability drop from 3.4-14.5% to at most 0.5%
The work proposes CPR (Critical-Point Routing), a token-level routing framework between a base model and its SFT expert derivative that trains a lightweight hierarchical router to estimate the per-token expert-call probability based on critical tokens where the base model fails but the expert succeeds, paired with an inference procedure combining momentum smoothing and threshold gating; across diverse model-domain configurations CPR achieves state-of-the-art in all settings, surpassing the SFT expert by 1.4-5.5% in domain performance while recovering its general-capability drop from 3.4-14.5% to at most 0.5%, with minimal overhead from invoking the expert on only one-third of tokens.