Large Language Models

Training Reasoning Models on Saturated Problems via Failure-Prefix Conditioning

MMinwu KimSSafal ShresthaKKeith Ross
Published
January 28, 2026
Authors
3
Word Count
7,784
Code
Includes code

Enhances learning by conditioning on failure prefixes.

Abstract

Reinforcement Learning with Verifiable Rewards (RLVR) has substantially improved the reasoning abilities of large language models (LLMs), yet training often stalls as problems become saturated. We identify the core challenge as the poor accessibility of informative failures: learning signals exist but are rarely encountered during standard rollouts. To address this, we propose failure-prefix conditioning, a simple and effective method for learning from saturated problems. Rather than starting from the original question, our approach reallocates exploration by conditioning training on prefixes derived from rare incorrect reasoning trajectories, thereby exposing the model to failure-prone states. We observe that failure-prefix conditioning yields performance gains matching those of training on medium-difficulty problems, while preserving token efficiency. Furthermore, we analyze the model's robustness, finding that our method reduces performance degradation under misleading failure prefixes, albeit with a mild trade-off in adherence to correct early reasoning. Finally, we demonstrate that an iterative approach, which refreshes failure prefixes during training, unlocks additional gains after performance plateaus. Overall, our results suggest that failure-prefix conditioning offers an effective pathway to extend RLVR training on saturated problems.

Key Takeaways

  • 1

    Improves model performance by focusing on failure-prone states.

  • 2

    Maintains token efficiency while enhancing learning.

  • 3

    Robust across different target accuracy hyperparameters.

Limitations

  • Mild reduction in adherence to correct early reasoning.

  • Assumes prefixes are not excessively off-policy.

Keywords

reinforcement learninglarge language modelsreasoning abilitiestraining stagnationinformative failuresfailure-prefix conditioningexplorationtoken efficiencyrobustnessiterative approachsaturated problems

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