Lean 4 Proof Engineer — Formal Mathematics & AI Proofing

Obsidian; San Francisco (CA); On-site; USD 60,000 - 90,000; Part time

Job summary

Cincinnatus LLC is placing highly skilled professionals in engagements with leading technology companies. The Lean engineer will craft correct Lean 4 statements and proofs, formalize complex mathematics, and evaluate AI-generated Lean outputs with clear feedback.

The role requires hands-on Lean 4 experience, mathlib familiarity, and the ability to work 20 hours per week minimum, with potential to scale up. This is a W-2 employment arrangement managed by Cincinnatus.

Qualifications

• Hands-on experience writing formal proofs in Lean 4.
• Comfort with mathlib and Lean 4 tactics.
• Strong background in proof-based mathematics, theoretical CS or logic.
• Ability to turn written statements and proofs into correct formal statements and proofs.
• Able to commit at least 20 hours/week on weekdays.

Responsibilities

• Write correct Lean 4 statements and proofs that compile with mathlib.
• Formalize natural-language mathematics into precise formal statements.
• Review AI-generated Lean statements and proofs and provide clear feedback.
• Help define guidelines and rubrics for proof quality and mathlib conventions.
• Collaborate with Lean engineers and researchers to maintain high standards.

Skills

Lean 4

Mathlib familiarity

Formal proofs

Proof engineering

Clear communication

Education

Degree in math/CS/logic

Job description

Cincinnatus LLC is placing highly skilled professionals in engagements with leading technology companies. The Lean engineer will craft correct Lean 4 statements and proofs, formalize complex mathematics, and evaluate AI-generated Lean outputs with clear feedback.

The role requires hands-on Lean 4 experience, mathlib familiarity, and the ability to work 20 hours per week minimum, with potential to scale up. This is a W-2 employment arrangement managed by Cincinnatus.