Part-Time Lean 4 Proof Engineer (Formal Math)

Mercor; Greater London; Hybrid; GBP 40,000 - 80,000; Part time

Job summary

Cincinnatus LLC is seeking Lean engineers and formal mathematicians to help an AI lab state and prove mathematics in Lean 4. You will write proofs, translate informal math to formal statements, and evaluate model proofs for fidelity.

The role is part-time (≥20 hours/week, up to 40 hours) and employed via W-2 with Cincinnatus LLC, with placement at a leading AI lab within the extended workforce.

Qualifications

• Hands-on experience writing formal proofs in Lean 4 or related tools.
• Ability to translate informal math to formal Lean statements and proofs.
• Proven ability to review AI-generated Lean content and provide precise feedback.

Responsibilities

• Write correct Lean 4 statements and proofs compatible with mathlib.
• Formalize natural-language mathematics and compare with original statements.
• Review AI-generated Lean content and provide clear feedback.
• Help define proof-quality guidelines and rubrics.
• Collaborate to raise the overall proof quality standards.

Skills

Lean 4

Formal proofs

Mathlib familiarity

Proof engineering

Written communication

20+ hrs/week commitment

Education

Bachelor's or higher in Mathematics/CS/Logic

Tools

Lean tactics

Coq/Rocq/Isabelle (nice to have)

Lean metaprogramming (nice to have)

Job description

Cincinnatus LLC is seeking Lean engineers and formal mathematicians to help an AI lab state and prove mathematics in Lean 4. You will write proofs, translate informal math to formal statements, and evaluate model proofs for fidelity.

The role is part-time (≥20 hours/week, up to 40 hours) and employed via W-2 with Cincinnatus LLC, with placement at a leading AI lab within the extended workforce.