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SAGE: Shaping Anchors for Guided Exploration in RLVR of LLMs
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Proposes SAGE, which reshapes the reverse-KL anchor distribution with an intrinsic-signal guide function (entropy-based branch amplification) to expand empirical support and improve both pass@1 and pass@k in RLVR for math reasoning.
Problem
RLVR with reverse-KL regularization improves pass@1 but often fails to improve pass@k because the policy stays anchored to the reference distribution and suppresses low-density reasoning modes; removing KL or using forward-KL trades off stability and efficiency.
Approach
Treat the reverse-KL anchor as a shapeable target: replace pi_ref with q*pi_ref in the KL term, where q is a fixed per-iteration guide built from token-level entropy (branch-level: 1 + gamma*(H_t - tau)^+) or surprisal/random perturbations, so the stationary policy is pi_ref*q*exp(r/beta) and low-density reasoning branches gain mass without removing the stabilizing anchor.
Key results
- GRPO+Branch averages pass@1 0.284 and pass@256 0.729 over AIME/AMC23/MATH-500, versus GRPO 0.266 and 0.714 (5 seeds).
- GRPO w/o KL reaches avg pass@1 0.258 and pass@256 0.701, below GRPO, despite higher training reward.
- On DeepSeek-R1-Distill-Qwen-7B, GRPO+Branch gets avg pass@1 0.452 vs 0.449 for GRPO and pass@64 0.774 vs 0.771.
Surprising findings
- Removing the reverse-KL term yields higher training reward but worse test pass@1 and pass@256, indicating reward overfitting.
- On the distilled R1 model, GRPO lowers pass@64 relative to the base model (0.771 vs 0.778), and GRPO+Branch recovers only partly.
Limitations
- SAGE only redistributes mass among trajectories already supported by the reference policy; zero-probability trajectories stay unreachable.
- Guide function is instantiated with simple intrinsic signals (entropy, surprisal) rather than learned or teacher-derived guides.
- Gains are modest (e.g., avg pass@1 0.284 vs 0.266) and many differences are within reported standard deviations.
Experimental setup
Datasets: OpenMathReasoning-mini DAPO-Math-17K-Processed
Benchmarks: AIME 2024-2025 AMC23 MATH-500 (level 5) Knights and Knaves
Metrics: pass@1 pass@256 pass@64 pass@k curves
Baselines: GRPO GRPO w/o KL GRPO + Forward KL GRPO + Random GRPO + Token DAPO (no KL) BNPO (no KL)
Builds on: GRPO DAPO BNPO reverse-KL RLVR analyses pseudo-KL divergence
Closest papers by meaning
- Reinforcement Learning with Verifiable Rewards Implicitly Incentivizes Correct Reasoning in Base LLMs (ICLR 2026 · similarity 0.92)
- The Reasoning Boundary Paradox: How Reinforcement Learning Constrains Language Models (NeurIPS 2026 · similarity 0.92)
- Exploration vs Exploitation: Rethinking RLVR through Clipping, Entropy, and Spurious Reward (ICLR 2026 · similarity 0.92)
- Selective Expert Guidance for Effective and Diverse Exploration in Reinforcement Learning of LLMs (ICLR 2026 · similarity 0.91)
- Does Reinforcement Learning Really Incentivize Reasoning Capacity in LLMs Beyond the Base Model? (NeurIPS 2025 · similarity 0.91)
- On the Direction of RLVR Updates for LLM Reasoning: Identification and Exploitation (ICLR 2026 · similarity 0.91)
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