Open Source Maintainer / Core Contributor – Software Engineer

About the Role

Mercor is staffing a full-time project for a leading AI lab's GenAI team. The lab needs open-source maintainers and core contributors who know a mature, widely used codebase well, to bring real engineering and code review judgment to the training of large language models. It is a W-2 position with Cincinnatus LLC, placed with the AI lab as part of its extended workforce.

What You'll Do

• Help research and engineering teams close knowledge gaps in software engineering, code review and open-source maintenance
• Design realistic engineering tasks (features, refactors, bug fixes) based on the open-source project you know best, with accurate reference solutions
• Evaluate AI-written code, tests and grading rubrics against the repository's architecture, conventions and quality bar, giving clear written feedback
• Build, run and test the project locally, including with Docker
• Write precise rationales explaining what a strong solution looks like and where AI changes fall short
• Work with other subject matter experts for consistent, accurate training data

Requirements

• Maintainer (listed in MAINTAINERS/CODEOWNERS or 10+ PR reviews in 12 months) or core contributor (3+ substantive merged PRs in 12 months) of a widely used open-source project
• Repository is 2+ years old, has real users, an active review culture and is mainly human-written
• Years of verifiable public contributions on your own GitHub account
• Senior-level code review judgment, including critique of AI-written code and tests
• Ability to build and run the project and its tests locally, including with Docker
• Authorized to work in the United States on a W-2 basis
• Able to pass background checks, sign confidentiality agreements and use a company-provided device
• Writes all rationales personally; strong written communication

Compensation & Logistics

• $150/hr, full-time 40 hours per week on weekdays
• Exclusive engagement: no other full-time job and no other AI training or evaluation projects, including other Mercor projects
• Remote, United States only (US work authorization required)
• Employer of record: Cincinnatus LLC (W-2, payroll, benefits)