Title: Stabilizing Knowledge, Promoting Reasoning: Dual-Token Constraints for RLVR
Primary area: reinforcement learning
Keywords: Large Language Model, Reinforcement Learning, Token Entropy

Abstract: Reinforcement Learning with Verifiable Rewards (RLVR) has become an effective post-training method for improving the reasoning abilities of Large Language Models (LLMs), mainly by shaping higher-order behaviors such as reflection and planning. However, previous RLVR algorithms often apply uniform training signals to all tokens, without considering the different roles of low-entropy \textbf{knowledge-related tokens} and high-entropy \textbf{reasoning-related tokens}. Some recent methods try to separate these token types by gradient masking or asynchronous updates, but these approaches may break semantic dependencies in the model output and hinder effective learning. In this work, we propose \textbf{Archer}, an entropy-aware RLVR approach with \textbf{dual-token constraints} and synchronous updates. Specifically, our method applies weaker KL regularization and higher clipping thresholds to reasoning tokens to encourage exploration, while using stronger constraints on knowledge tokens to maintain factual knowledge. Experimental results on several mathematical reasoning and code generation benchmarks show that our approach significantly  outperforms previous RLVR methods, reaching or exceeding state-of-the-art performance among models of comparable size.