Lean Engineer, Formal Mathematics (Lean 4, Mathlib, Theorem Proving)

About the Role

A leading AI lab needs Lean engineers, formal mathematicians and proof engineers to help its models state and prove mathematics correctly. Beyond checking that a proof compiles, the work is judging whether a formalization really captures the intended statement. The commitment is part-time, at least 20 hours per week, with room to grow to 40.

What You'll Do

• Write idiomatic Lean 4 statements and proofs that build against current mathlib, across algebra, analysis, number theory, combinatorics and logic
• Formalize natural-language mathematics, from competition problems to research-level lemmas, checking that the formal version matches the original
• Review AI-generated Lean output, find where it fails or proves the wrong thing, and give specific written feedback
• Help define guidelines and rubrics for proof quality, statement fidelity and mathlib conventions
• Work with other Lean engineers and the lab's researchers to keep standards consistent

Requirements

• Hands-on experience writing formal proofs in Lean 4 (mathlib contributions, a formalization project, a Lean tool or library, or autoformalization work)
• Comfort with mathlib and Lean 4 tactics
• Strong background in proof-based mathematics, theoretical computer science or logic, via a degree or research record
• Reliable availability of 20+ hours per week on weekdays
• Clear written communication
• Nice to have: Coq/Rocq, Isabelle, Agda or Haskell, Lean metaprogramming, or AI-for-math experience (LLM provers, miniF2F, ProofNet, PutnamBench)

Compensation & Logistics

• Pay: $90-$110 per hour
• Part-time, 20 hours per week minimum, up to 40
• Remote, no location restriction stated
• W-2 employment through Cincinnatus LLC (or an appropriate international entity), placed with the AI lab