Senior Software Engineer, Full Stack (Python, Java, Rust, C#, C++)

About this role

**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 Senior Full-Stack Software Engineers with deep, hands-on production expertise 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 - 6+ years of dedicated professional experience building and shipping production software at a recognized, top-tier organization, including ownership of systems end to end. - Deep production experience in at leas