Research Engineer, Codex

## About the Team The Codex team is responsible for building state-of-the-art AI systems that can write code, reason about software, and act as intelligent agents for developers and non-developers alike. Our mission is to push the frontier of code generation and agentic reasoning, and deploy these capabilities in real-world products such as ChatGPT and the API, as well as in next-generation tools specifically designed for agentic coding. We operate across research, engineering, product, and infrastructure—owning the full lifecycle of experimentation, deployment, and iteration on novel coding capabilities. ## About the Role As a member of the Codex team, you will advance the capabilities, performance, and reliability of AI coding models through a combination of research, experimentation, and system optimization. You’ll collaborate with world-class researchers and engineers to develop and deploy systems that help millions of users write better code, faster—while also ensuring these systems are efficient, cost-effective, and production-ready. We’re looking for people who combine deep curiosity, strong technical fundamentals, and a bias toward impact. Whether your strengths lie in ML research, systems engineering, or performance optimization, you’ll play a pivotal role in pushing the state of the art and bringing these advances into the hands of real users. ## Responsibilities - Design and run experiments to improve code generation, reasoning, and agentic behavior in Codex models. - Develop research insights into model training, alignment, and evaluation. - Hunt down and address inefficiencies across the Codex system stack—from agent behavior to LLM inference to container orchestration—and land high-leverage performance improvements. - Build tooling to measure, profile, and optimize system performance at scale. - Work across the stack to prototype new capabilities, debug complex issues, and ship improvements to production. ## Requirements - Are excited to explore and push the boundaries of large language models, especially in the domain of software reasoning and code generation. - Have strong software engineering skills and enjoy quickly turning ideas into working prototypes. - Think holistically about performance, balancing speed, cost, and user experience. - Bring creativity and rigor to open-ended research problems and thrive in highly iterative, ambiguous environments. - Have experience operating across both ML systems and cloud infrastructure. ## Benefits - This role is based in San Francisco, CA. We use a hybrid work model of 3 days in the office per week and offer relocation assistance to new employees.