Worldwide

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

Mercor
Mercor
Verified company
RemotePosted Oct 13, 2026

$90 – $110 /hr

Compensation

Part-Time

Employment

Senior Level

Experience

Oct 13, 2026

Posted

About this opportunity

Overview: A leading AI lab is looking for Lean engineers, formal mathematicians and proof engineers to help its AI models state and prove mathematics correctly. You'll write and review Lean 4 proofs, turn informal math into precise formal statements, and help the lab's researchers judge whether a model's proof is not just accepted by the checker but actually proves the right thing. If you enjoy writing Lean, know your way around mathlib, and can explain why a formalization is faithful or subtly wrong, this role is for you. This is a part-time commitment of at least 20 hours per week, with the option to increase to up to 40 hours per week. This is a W-2 employment position with Cincinnatus LLC (or appropriate international entity), with the opportunity to be placed at a leading AI lab as part of their extended workforce.

Key responsibilities

  • Key Responsibilities:
  • Write correct, idiomatic Lean 4 statements and proofs that compile against current mathlib, across areas such as algebra, analysis, number theory, combinatorics and logic.
  • Formalize natural-language mathematics, from competition problems and textbook results to research-level lemmas, paying close attention to whether the formal statement matches the original.
  • Review AI-generated Lean statements and proofs, find where they fail or prove the wrong thing, and give clear, specific written feedback.
  • Help define guidelines and rubrics for proof quality, statement fidelity and mathlib conventions.
  • Collaborate with other Lean engineers and the lab's researchers to keep standards consistent and keep raising the quality bar.

Benefits & perks

  • Employment Details:
  • W-2 employment position with Cincinnatus LLC (or appropriate international entity), placed at a leading AI lab.
  • Part-time — at least 20 hours/week, option to increase to 40 hours/week.
  • Fully remote.
  • Offer Details:
  • Pay rate: $90 – $110/hour.
  • Referral bonus: up to $1,760 per successful referral.

Keep exploring

Similar AI roles

View all
Lean Engineer, Formal Mathematics (Lean 4, Mathlib, Theorem Proving) | AI Seeker