Lean Engineer, Formal Mathematics – Lean 4, Mathlib, Theorem Proving

Mercor

. Write correct, idiomatic Lean 4 statements and proofs compiling against current mathlib .

Posted 10/11/2026part-timeRemote • United StatesMid-LevelSenior💰 $90 - $110 per hourWebsite

Core Competencies

Role fit

Core Competencies

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Demonstrates expertise in writing formal proofs in Lean 4 and a strong background in proof-based mathematics or theoretical computer science. Capable of collaborating with engineers and researchers to maintain high standards in mathematical formalization and proof quality.

Highest-signal resume keywords

Lean 4 Proof WritingMathlib FamiliarityProof-Based MathematicsClear Written CommunicationAI-For-Math Experience

ATS Keywords

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Applicant Tracking System Keywords

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Hard Skills

Formal ProofsLean 4MathlibProof CheckingTheoretical Computer ScienceLogicLean TacticsFormalizationCoqIsabelle

Soft Skills

Clear CommunicationFeedback ProvisionCollaboration

Tools & Technologies

Lean MetaprogrammingAgdaHaskell

Industry Keywords

Mathematical FormalizationProof Quality GuidelinesResearch-Level LemmasCompetition Problems

Tech Stack

Tools & technologies

Haskell

About the role

Key responsibilities & impact

Write correct, idiomatic Lean 4 statements and proofs compiling against current mathlib
Formalize natural-language mathematics, including competition problems, textbook results, and research-level lemmas
Review AI-generated Lean statements and proofs
Identify failures or proofs that establish the wrong thing and provide clear written feedback
Help define guidelines and rubrics for proof quality, statement fidelity, and mathlib conventions
Collaborate with Lean engineers and lab researchers to maintain consistent standards
Work on projects training and enhancing AI systems

Requirements

What you’ll need

Hands-on experience writing formal proofs in Lean 4
Comfort with mathlib and Lean 4 tactics, including finding and using appropriate lemmas
Strong background in proof-based mathematics, theoretical computer science, or logic, through a degree or research record
Ability to convert written statements and proofs into correct formal statements and checking proofs
Availability for at least 20 hours per week during weekdays
Clear written communication and ability to explain proof strategy and formalization choices precisely
Nice to have: experience with Coq/Rocq, Isabelle, Agda, Haskell, Lean metaprogramming, or AI-for-math work
Unable to support H1-B or STEM OPT candidates at this time

Benefits

Comp & perks

W-2 employment with Cincinnatus LLC (or appropriate international entity)
Payroll, benefits, and compliance provided by the employer of record
Fully remote work
Flexible schedule / work on your own schedule
Weekly payments via Stripe or Wise
Opportunity to collaborate with leading researchers
Referral payments of up to $1,760 for each successful referral