Senior Full-Stack Software Engineer

Build and ship full-stack software that exercises frontier generative AI model capabilities end to end. You will work on fast-moving projects that integrate pre-release models into production-quality services, tools, and evaluation harnesses, contributing working code early while collaborating closely with an engineering manager at a leading AI research lab.

• Design, implement, and deploy full-stack applications, internal tools, and services using Python, Java, Rust, C#, C++, or TypeScript that exercise frontier model capabilities.
• Integrate pre-release model APIs into working software, including tool interfaces, evaluation harnesses, telemetry, and operational scaffolding.
• Diagnose, document, and communicate model and integration failure modes discovered during development, translating engineering observations into clear written feedback for research teams.
• Rapidly prototype and deliver working increments against shifting requirements with limited up-front specification.
• Collaborate with the engineering manager and other engineers to maintain consistent code quality, architecture, and technical documentation.

• 6+ years of professional experience building and shipping production software at a recognized, top-tier organization, with end-to-end ownership of systems.
• Deep production experience in at least one of Python, Java, Rust, C#, or C++, plus demonstrated delivery in a second language from a different ecosystem. This cohort is intentionally staffed across multiple language ecosystems.
• Hands-on ownership across the stack, including backend service and API design, a modern front-end framework such as React or equivalent, data modeling, and cloud deployment and operations.
• Proven ability to onboard onto unfamiliar codebases and deliver working code quickly with minimal ramp-up.
• Demonstrable career progression and strong written communication skills to explain complex technical decisions.
• Ability to engage reliably for at least 40 hours per week during weekdays.

This is a full-time, hourly position requiring a 40 hours per week commitment, weekday availability. Employment is W-2 through Cincinnatus LLC, which serves as the employer of record and places employees within client teams. Placed engineers work directly with the AI lab engineering manager on high-impact, fast-paced projects and are expected to onboard quickly and contribute working code early. Cincinnatus LLC provides payroll, benefits, and compliance for its W-2 employees.

Hourly pay range: $90 to $110 per hour.

• Role is based in the United States; candidates should expect to work within U.S. time zones and be authorized to work in the United States as required for W-2 employment.
• Cincinnatus LLC is an Equal Employment Opportunity employer. Employment decisions are made without regard to legally protected characteristics.

Candidates who advance will be placed on a client team at a leading AI lab as W-2 employees of Cincinnatus LLC and will begin a rapid onboarding process with the lab''s engineering manager. New hires should be prepared to start contributing working code early in the engagement.