EntroRouter: Learning Efficient Model Routing via Entropy Regulation

2026-06-28

AI Summary

This work addresses the “trust region collapse” problem in multi-model routing, where tight coupling between inference and routing leads to systematic suppression of high-capability experts. To resolve this, the authors propose EntroRouter, a single-round routing framework that decouples inference from routing by adopting entropy regularization as its core objective. The method introduces a high-entropy prior for exploration and a soft-anchor mechanism based on offline capability estimation, combined with soft-supervision initialization and a controlled entropy contraction strategy. These innovations effectively prevent strong experts from being underutilized. Experimental results demonstrate that EntroRouter reduces computational overhead by 48.25% while preserving 98.3% of the top expert’s accuracy.

Abstract

Model routing balances solution accuracy and computational cost by selecting among models of varying capabilities. While recent multi-round frameworks interleave reasoning and planning, we identify a structural failure mode termed Trust Region Collapse. We demonstrate that the deep coupling of reasoning and routing, exacerbated by the dominance of strong pre-training priors under sparse supervision, leads to degenerate local optima where capable experts are systematically suppressed. To decouple these processes, we propose $\textbf{EntroRouter}$, a single-round routing framework that treats entropy regulation as a core objective. We first initialize the policy via Soft Supervision, fitting a distribution of suitable models to establish a high-entropy prior for exploration. Subsequently, we stabilize Reinforcement Learning using a Soft Anchor, which utilizes offline capability estimates to orchestrate controlled entropy contraction within a safe trust region. Extensive experiments demonstrate that EntroRouter retains 98.3% of the strongest expert's accuracy while reducing computational costs by 48.25%.

Problem

• model routing
• Trust Region Collapse
• entropy regulation
• sparse supervision
• expert suppression

Innovation

• model routing
• entropy regulation
• trust region collapse
• soft supervision
• reinforcement learning