Full Stack Engineer - AI/ML

Mercor; San Francisco (CA); On-site; USD 140,000 - 210,000; Full time

Job summary

Mercor seeks experienced Full-Stack Software Engineers to build, integrate, and stress-test production software atop frontier AI models. You’ll work with Python, Java, Rust, C#, C++, and TypeScript across the stack, shipping end-to-end solutions with a focus on reliability and observability.

This is a 40-hour/week W-2 role through Cincinnatus LLC, with placement at a leading AI lab. Candidates should onboard quickly and contribute working code early.

Qualifications

• 3+ years of dedicated professional experience building and shipping production software at a recognized, top-tier organization.
• Proficient in multiple languages (Python, Java, Rust, C#, C++, TypeScript) and able to contribute across the full stack.
• Experience with backend services, APIs, front-end frameworks (React or similar), databases, and cloud deployment.

Responsibilities

• Build and ship full-stack applications, services, and internal tools that exercise frontier model capabilities end to end.
• Integrate pre-release model APIs into working software and related scaffolding including interfaces, evaluation harnesses, and telemetry.
• Diagnose and document model and integration failure modes and provide clear feedback to research teams.
• Prototype quickly against shifting requirements and deliver working increments with limited upfront specification.
• Collaborate with the engineering manager and other engineers to maintain code quality, architecture, and documentation.

Job description

Join 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 Full-Stack Software Engineers with hands-on production experience across modern application stacks — Python, Java, Rust, C#, C++, and TypeScript — to build, integrate, and stress-test real software on top of frontier models before they ship. Engineers work directly with the AI lab's engineering manager on fast-moving projects and are expected to onboard quickly and contribute working code early. This is a full-time commitment of 40 hours per week.

This is a W-2 employment position with Cincinnatus LLC, with the opportunity to be placed at a leading AI Lab as part of their extended workforce.

2. Key Responsibilities

• Build and ship full-stack applications, services, and internal tools — in Python, Java, Rust, C#, C++, or TypeScript — that exercise frontier model capabilities end to end.
• Integrate pre-release model APIs into working software, including the surrounding scaffolding: tool interfaces, evaluation harnesses, and telemetry.
• Diagnose and document model and integration failure modes surfaced while building, translating engineering observations into clear written feedback for the research team.
• Prototype quickly against shifting requirements, delivering working increments with limited up-front specification.
• Collaborate with the engineering manager and other engineers to maintain consistency in code quality, architecture, and technical documentation.

3. Core Qualifications

• 3+ years of dedicated professional experience building and shipping production software at a recognized, top-tier organization.
• Production experience in at least one of Python, Java, Rust, C#, or C++, plus working proficiency in a second language — this cohort is intentionally staffed across multiple language ecosystems.
• Hands-on experience across the stack: backend services and APIs, a modern front-end framework (React or equivalent), relational or document databases, and cloud deployment.
• Demonstrated ability to onboard onto an unfamiliar codebase and deliver working code quickly with minimal ramp-up.
• Demonstrable career progression.
• Ability to engage reliably for at least 40 hours/week during weekdays.
• 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 W-2 employment, payroll, benefits, and compliance, while placing employees 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.