ImProver 2: Iteratively Self-Improving LMs for Neurosymbolic Proof Optimization

ImProver 2 is a new neurosymbolic framework for automated proof optimization in Lean 4, designed to address challenges in refactoring formal mathematics proofs. It uses a data-efficient expert-iteration pipeline and a neurosymbolic scaffold, enabling a 7B-parameter model to achieve competitive performance against much larger models.