Open Source Maintainer / Core Contributor – Software Engineer

Mercor; United States; Remote; USD 170,000 - 243,000; Full time

Job summary

Mercor is seeking an Open Source Maintainer / Core Contributor – Software Engineer to join a GenAI team. You’ll own maintenance of a mature open-source codebase, review AI-generated code, and guide tasks from conception to validated solutions, leveraging Docker for local testing.

This remote, hourly contract role emphasizes independent work with periodic lab meetings. Applicants should have a strong open-source track record, demonstrated code review judgment, and the ability to build and run

Qualifications

• Maintainer (named in MAINTAINERS or CODEOWNERS, or 10+ PR reviews in the last 12 months) or core contributor (3+ substantive merged PRs in the last 12 months).
• Repository is 2+ years old, with real users and active code review culture.
• Years of sustained open-source contributions with verifiable public history.
• Senior-level code review judgment, including assessing AI-written code and edge cases.
• Hands-on ability to build and run the project and tests locally, including with Docker.

Responsibilities

• Guide research and engineering teams to close knowledge gaps and improve AI model performance in software engineering, code review, and open-source maintenance topics.
• Design engineering tasks based on the codebase, and write accurate reference solutions.
• Evaluate AI-written code, tests and rubrics against architecture and quality standards, with clear feedback.
• Build, run and test the project locally, including with Docker, to verify task behavior.
• Write precise rationales explaining strongest solutions and limitations of AI-generated changes.
• Collaborate with experts to ensure training data consistency and accuracy.

Skills

Maintainer

Core contributor

Open-source

Code review

Docker

Written communication

Git

Tools

Docker

Job description

Open Source Maintainer / Core Contributor – Software Engineer

Company: MercorCompensation: $150 per hourCommitment: Hourly contractLocation: US, Canada and EuropeReferral Reward: Earn up to $2,000 per successful referral.Referral Link: https://work.mercor.com/explore?listingId=list_AAABoZ5Af5H0GMoyXaBBDKW2

Location requirementsUnited StatesJoin a leading AI lab's cutting-edge GenAI team to be at the core of the AI revolution, where your expertise fuels the development of the most advanced Large Language Models.

1. Overview

Join a leading AI lab's cutting-edge GenAI team and help build foundational AI models from the ground up. We're seeking talented open-source maintainers and core contributors with deep, hands‑on ownership of a mature, widely used open‑source codebase to bring real-world engineering and code review judgment and elevate the quality of our AI training data. The role requires 30–40 hours per week, with flexible scheduling. Most work is asynchronous and can be done in the evenings or on weekends, with occasional meetings with the lab's researchers as needed. You'll be engaged through Cincinnatus LLC, with the opportunity to be placed at a leading AI lab as part of their extended workforce.

2. Key Responsibilities

• Guide research and engineering teams to close knowledge gaps and improve AI model performance in software engineering, code review, and open‑source maintenance topics.
• Design challenging, realistic engineering tasks grounded in the open‑source codebase the expert knows best, such as the features, refactors and bug fixes a maintainer would assign, and write accurate, well‑structured reference solutions.
• Evaluate AI‑written code, tests and grading rubrics against the repository's architecture, conventions and quality bar, and provide clear, written technical feedback.
• Build, run and test the project locally, including with Docker, to confirm that tasks, solutions and tests behave as intended.
• Write precise rationales that explain what a strong solution looks like and where AI‑generated changes fall short.
• Collaborate with other subject matter experts to ensure consistency and accuracy in training data.

3. Core Qualifications

• Maintainer (named in MAINTAINERS or CODEOWNERS, or 10+ PR reviews in the last 12 months) or core contributor (3+ substantive merged PRs in the last 12 months) of a widely used open‑source project.
• The repository is 2+ years old, has real users and an active code review culture, and is primarily human‑written.
• Years of sustained open‑source contributions, with a public history that can be verified against the candidate's own GitHub account.
• Senior‑level code review judgment, including the ability to critically assess AI‑written code, tests and edge cases.
• Hands‑on ability to build and run the project and its test suite locally, including with Docker.
• Ability to commit 30–40 hours/week as your primary work focus, with availability for occasional meetings with the lab's researchers. Given that time commitment, this role isn't a fit alongside a full‑time job.
• Exclusivity: no work with another AI lab or AI training company, including other Mercor projects, during the engagement.
• Authorized to work in the country you live in.
• Able to complete any necessary background checks and confidentiality agreements before starting, and to work on a company‑provided device to protect the security of information.
• Writes all rationales and feedback personally, in their own words.
• Strong written communication skills and the ability to explain complex technical decisions clearly.

About Cincinnatus LLC:

Cincinnatus LLC is an enterprise staffing company that partners with leading technology companies to source and employ highly skilled professionals for contingent and contract‑based opportunities. Cincinnatus serves as the employer of record for these engagements, providing employment, payroll, benefits, and compliance, while placing professionals directly within client teams to work on high‑impact initiatives.

Equal Employment Opportunity:

Cincinnatus is proud to be an Equal Employment Opportunity employer. We do not discriminate based upon race, religion, color, national origin, sex (including pregnancy, childbirth, reproductive health decisions, or related medical conditions), sexual orientation, gender identity, gender expression, age, status as a protected veteran, status as an individual with a disability, genetic information, political views or activity, or any other legally protected characteristic. We consider all qualified applicants without regard to legally protected characteristics and provide reasonable accommodations upon request.

Contract and Payment Terms

You will be engaged as an independent contractor. This is a fully remote role that can be completed on your own schedule. Projects can be extended, shortened, or concluded early depending on needs and performance. Your work at Mercor will not involve access to confidential or proprietary information from any employer, client, or institution. Payments are weekly on Stripe or Wise based on services rendered. Please note: We are unable to support H1-B or STEM OPT candidates at this time.

About Mercor

Mercor partners with leading AI labs and enterprises to train frontier models using human expertise. You will work on projects that focus on training and enhancing AI systems. You will be paid competitively, collaborate with leading researchers, and help shape the next generation of AI systems in your area of expertise.