Lean 4 Proof Engineer - Formal Math, Part-Time

Mercor; San Francisco (CA); Remote; USD 28,000 - 55,000; Part time

Job summary

Cincinnatus LLC is seeking Lean engineers, formal mathematicians, and proof engineers to help an AI lab state and prove mathematics in Lean 4. You will write Lean 4 proofs, formalize informal math, and ensure proofs are faithful and correct with the checker.

This is a part-time W-2 role in the San Francisco area, requiring 20–40 hours per week with potential to increase. You will work with mathlib, contribute to formalization projects, and collaborate with researchers to raise the standard of

Qualifications

• Hands-on experience writing formal proofs in Lean 4.
• Familiarity with mathlib and Lean 4 tactics.
• Strong background in proof-based mathematics or logic.
• Ability to turn a written statement and proof into a correct formal statement and a proof that checks.
• Engage reliably for at least 20 hours/week during weekdays.

Responsibilities

• Write correct, idiomatic Lean 4 statements and proofs that compile against current mathlib.
• Formalize natural-language mathematics into precise formal statements.
• Review AI-generated Lean statements and proofs, identify failures, and provide clear feedback.
• Help define guidelines and rubrics for proof quality, statement fidelity and mathlib conventions.
• Collaborate with Lean engineers and researchers to raise the quality bar.

Skills

Lean 4

mathlib

Formal proofs

Proof assistant

Mathematics background

Education

Degree in math/CS/logic

Tools

Lean ecosystem

Lean 4 tactics

Mathlib library

Job description

Cincinnatus LLC is seeking Lean engineers, formal mathematicians, and proof engineers to help an AI lab state and prove mathematics in Lean 4. You will write Lean 4 proofs, formalize informal math, and ensure proofs are faithful and correct with the checker.

This is a part-time W-2 role in the San Francisco area, requiring 20–40 hours per week with potential to increase. You will work with mathlib, contribute to formalization projects, and collaborate with researchers to raise the standard of