ResearchResearch paperLarge Language Models · Efficiency & Inference · Robotics & Embodied AI2 sources · Oct 13, 2026

LeanPRM: Lean-Grounded Process Supervision for Natural Language Proof Verification

We introduce LeanPRM, a framework that uses the Lean proof assistant to create step-level labels for natural-language proofs.

Key points

  • AI systems now write long and difficult mathematical proofs, and checking their step-by-step validity is becoming a bottleneck.
  • A model writes a natural-language proof together with a paired formal proof, without feedback from Lean.
  • A Qwen3-4B verifier trained on LeanPRM raises exact step-label accuracy on a held-out set of 200 proofs (LeanPRM-Bench) from 48.2 to 74.7, as opposed to 60.3 when the same base model is trained on PRM800K.
  • Given the labels need no human annotation, LeanPRM can grow with the supply of formal statements, offering a path to step-level feedback on AI-generated proofs that are hard for humans to check.

Sources (2)

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