Axiom AI Formalizes Longest Math Proof in Lean in 24 Days

Axiom announced a complete Lean auto-formalization of the Classification of Finite Simple Groups, described as the longest proof in mathematics at roughly 15,000 pages spanning more than 500 papers and over 100 authors across generations. Axiom's swarm of AI agents, guided by mathematicians, produced approximately 40 million lines of Lean code in 24 days. The Classification had no single person who had read all of it. Earlier in 2026, Axiom had formalized the 246 Prime-Gaps Theorem in Lean 4 using its multi-agent system AxiomProver, which operates through a three-stage pipeline: a blueprint phase labeling every definition, lemma, and theorem with dependencies; proof generation by AxiomProver; and verification against Mathlib. Axiom attributes the capability jump from the Prime-Gaps work to the Classification formalization to simultaneous improvements across models, the agent harness, and infrastructure. Earlier this year, getting AxiomProver to write a correct 10,000-line Lean proof took weeks; the Classification task was about 4,000 times larger.