Applied AI Engineer, Codex Core Agent

OpenAI; Greater London; On-site; GBP 90,000 - 130,000; Full time

Job summary

OpenAI is seeking applied AI engineers to advance Codex agents from demos to dependable tools in London. You will focus on improving agent performance on real software tasks, making improvements practical, measurable, and valuable for users.

The role involves collaborating with research, infra, and product to ensure agents are powerful, steerable, and reliable in practice. Join a team shaping the future of agent technology, with emphasis on robustness, evaluation, and real-world impact across

Qualifications

• Experience shipping ML/LLM-powered products.
• Strong Python and ML tooling skills.
• Experience with evaluation, fine-tuning, or prompt design.
• Think in terms of systems and user outcomes.

Responsibilities

• Design and iterate agent behaviors on real-world coding tasks and long-horizon workflows.
• Collaborate with research to run evals measuring performance and edge cases.
• Improve performance through prompting, tool-use strategies, and context construction.
• Analyze production failures and improve robustness and reliability.
• Build data systems that feed real-task data into evaluation and research.
• Collaborate with product teams to shape user-facing agent experiences.

Skills

Python

ML tooling

Model evaluation

Prompt design

Systems thinking

Debugging

Job description

About the Team

The Codex Core Agent team builds the kernel of Codex. We own making the agent better, accelerating research, and making those improvements real in production for our users.

That means working across the systems that make Codex actually function as an agent in the real world: the production performance envelope around tokens, latency, reliability, cost, and capacity; the core execution loop and interfaces that turn models into useful behavior; the shared infrastructure that enables other teams to build on Codex; and the feedback loops that turn real‑world usage into better models and better agent behavior over time.

About the Role

We’re looking for applied AI engineers to help bring Codex agents from impressive demos to dependable tools. This role is about improving agent performance on real software engineering tasks and closing the gap between research capability and real‑world usefulness.

You’ll work closely with research, infrastructure, and product to ensure agents are not just powerful, but useful, steerable, and reliable in practice. The job is not only to improve model behavior in isolation, but to turn those improvements into measurable gains in solve rate, usefulness, and economic value for users.

What You’ll Do

• Design and iterate on agent behaviors across real‑world coding tasks and long‑horizon workflows.
• Work closely with research to develop and run evals to measure agent performance, regressions, failure modes, and edge cases.
• Improve performance through prompting, tool‑use strategies, context construction, and model‑facing experimentation.
• Analyze failures in production and systematically improve robustness and reliability.
• Build feedback loops and data systems that get better real‑task data into evaluation and research.
• Work with product teams to shape user‑facing agent experiences and the interfaces the agent depends on.
• Help define what “good” looks like for agents completing complex tasks end‑to‑end.

You Might Be a Good Fit If You

• Have experience building or shipping machine learning or LLM‑powered products.
• Are strong in Python and comfortable with modern ML tooling.
• Have worked on model evaluation, fine‑tuning, or prompt design.
• Think in terms of systems and user outcomes, not just model metrics.
• Enjoy debugging messy, real‑world failures and turning them into improvements.
• Want to work in the layer that turns research and model potential into systems that actually work for users.

Bonus Points

• Experience with agent frameworks or tool‑using LLM systems.
• Research experience with code generation models or developer tooling.
• Experience working with large, messy datasets or production logs.

About OpenAI

OpenAI is an AI research and deployment company dedicated to ensuring that general‑purpose artificial intelligence benefits all of humanity. We push the boundaries of the capabilities of AI systems and seek to safely deploy them to the world through our products. AI is an extremely powerful tool that must be created with safety and human needs at its core, and to achieve our mission, we must encompass and value the many different perspectives, voices, and experiences that form the full spectrum of humanity.

Equal Opportunity Employer

We are an equal opportunity employer, and we do not discriminate on the basis of race, religion, color, national origin, sex, sexual orientation, age, veteran status, disability, genetic information, or other applicable legally protected characteristic.

Background checks for applicants will be administered in accordance with applicable law, and qualified applicants with arrest or conviction records will be considered for employment consistent with those laws, including the San Francisco Fair Chance Ordinance, the Los Angeles County Fair Chance Ordinance for Employers, and the California Fair Chance Act, for US‑based candidates. For unincorporated Los Angeles County workers: we reasonably believe that criminal history may have a direct, adverse and negative relationship with the following job duties, potentially resulting in the withdrawal of a conditional offer of employment: protect computer hardware entrusted to you from theft, loss or damage; return all computer hardware in your possession (including the data contained therein) upon termination of employment or end of assignment; and maintain the confidentiality of proprietary, confidential, and non‑public information. In addition, job duties require access to secure and protected information technology systems and related data security obligations.

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