Lean Engineer - Formal Mathematics - AI Trainer

About the job

Mercor connects elite creative and technical talent with leading AI research labs. Headquartered in San Francisco, our investors include Benchmark , General Catalyst , Peter Thiel , Adam D'Angelo , Larry Summers , and Jack Dorsey .

Position: Lean Engineer, Formal Mathematics (Lean 4, Mathlib, Theorem Proving)
Type: Contract
Compensation: $90-$110/hour
Location: Remote
Commitment: 20-40 hours/week

Role Responsibilities

• Write correct, idiomatic Lean 4 statements and proofs that compile against current mathlib . Cover areas such as algebra, analysis, number theory, combinatorics, and logic.
• Formalize natural-language mathematics from competition problems and textbook results to research-level lemmas. Ensure the formal statement matches the original.
• Review AI-generated Lean statements and proofs. Identify failures or incorrect proofs and provide 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 maintain consistent standards and elevate quality.

Qualifications

Must-Have

• Hands-on experience writing formal proofs in Lean 4 . Examples include mathlib contributions, a formalization project, or a Lean library or tool.
• Comfort with mathlib and Lean 4 tactics. Ability to find and use the right lemmas.
• Strong background in proof-based mathematics, theoretical computer science, or logic through a degree or research record.
• 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.
• Clear written communication and ability to explain proof strategy and formalization choices precisely.

Preferred

• Experience with other proof assistants or dependently typed languages (Coq/Rocq , Isabelle , Agda , Haskell ).
• Experience with Lean metaprogramming or AI-for-math work such as LLM provers , Lean agent environments, or benchmarks like miniF2F , ProofNet , or PutnamBench .

Compensation & Legal

• W-2 employment with Cincinnatus LLC .
• Equal Employment Opportunity employer.

Application Process (Takes 20-30 mins to complete)

• Upload resume
• AI interview based on your resume
• Submit form

Resources & Support

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PS: Our team reviews applications daily. Please complete your AI interview and application steps to be considered for this opportunity.