Senior Software Engineer, Full Stack (Python, Java, Rust, C#, C++) Full-time position United States $90-$110 per hour Job

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

Full-time position United States $90-$110 per hour

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 least one of Python, Java, Rust, C#, or C++, plus demonstrated delivery in a second language across a different ecosystem — this cohort is intentionally staffed across multiple language ecosystems.

Hands-on ownership across the stack: backend service and API design, a modern front-end framework (React or equivalent), data modelling, and cloud deployment

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.

Apply Directly PAste
ttps://t.mercor.com/6Gtus

Your work will shape how models learn, reason, and perform through high-quality, real-world input. No prior experience in AI is required — your domain knowledge is what matters.