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Research Engineer, Codex

OpenAI· Research
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San Francisco$380k - $500kFull-timePosted 11mo ago

About the role

OpenAI is seeking a Research Engineer for the Codex Research team to improve the capabilities, reliability, and product fit of agentic models. The role is broad and involves research, engineering, data, evals, and product work to advance world-facing AI agents.

Responsibilities

  • Design and run experiments that improve agentic model behavior across coding, tool use, function calling, computer use, multi-agent collaboration, long-horizon tasks, factuality, instruction following, and calibrated reasoning.
  • Own end-to-end improvements to the post-training stack, including RL, data pipelines, graders, reward signals, evals, diagnostics, and model-behavior analysis.
  • Build evals and environments that expose the next set of model failures, then turn those failures into training data, product fixes, or new research directions.
  • Partner with Codex, API/platform, ChatGPT, and general-agent product teams to understand what users need and translate product signal into model improvements.
  • Work on early-training and alignment interventions, including data mixtures, objectives, synthetic data, and eval loops that shape downstream agent behavior.
  • Help decide which integrations, capabilities, and fixes are ready for inclusion in major model runs.
  • Improve the machinery for large-scale training and launch: experiment velocity, reliability, observability, reproducibility, cost, latency, and production readiness.
  • Take on cross-functional projects that touch model training, product infrastructure, and the production agent harness, such as multi-agent systems or training directly against production-like environments.
  • Debug hard failures in shipped or near-shipped models and turn messy qualitative behavior into concrete hypotheses, experiments, and fixes.

Qualifications

  • Have strong technical fundamentals in machine learning, software engineering, systems, statistics, or a related field, and can learn quickly across the parts you have not worked in before.
  • Have hands-on experience with LLMs, RL, RLHF/RLAIF, post-training, evals, graders, synthetic data, model training, coding agents, tool-using agents, or production ML systems.
  • Are excited by open-ended problems where the path is unclear, the signal is noisy, and the right answer requires both research taste and engineering execution.
  • Care about product impact and model behavior, not just benchmark movement. You have opinions about what makes an agent useful, reliable, honest, tasteful, and easy to work with.
  • Can move from a vague behavioral problem to a concrete experiment: define the hypothesis, build the pipeline, run the model, analyze the result, and decide what to do next.
  • Are comfortable working across research, product, infrastructure, data, evals, and safety boundaries, and can communicate clearly with each group.
  • Like building load-bearing systems and processes when that is what the team needs, even if the work is not glamorous.
  • Want to train and ship the models that make agents genuinely useful for developers, enterprises, researchers, and everyday users.

Skills

Required:Machine learning fundamentalsLLMs / RL / RLHF / RLAIFPost-training and evals
Nice to have:Research-to-product translation

Benefits

  • Medical, dental, and vision insurance for you and your family, with employer contributions to Health Savings Accounts
  • Pre-tax accounts for Health FSA, Dependent Care FSA, and commuter expenses (parking and transit)
  • 401(k) retirement plan with employer match
  • Paid parental leave (up to 24 weeks for birth parents and 20 weeks for non-birthing parents), plus paid medical and caregiver leave (up to 8 weeks)
  • Paid time off: flexible PTO for exempt employees and up to 15 days annually for non-exempt employees
  • 13+ paid company holidays, and multiple paid coordinated company office closures throughout the year for focus and recharge, plus paid sick or safe time
  • Mental health and wellness support
  • Employer-paid basic life and disability coverage
  • Annual learning and development stipend
  • Daily meals in offices, and meal delivery credits as eligible
  • Relocation support for eligible employees
  • Additional taxable fringe benefits, such as charitable donation matching and wellness stipends may also be provided.
Last updated Sep 3, 2026. Interested? Apply on the company site.

About OpenAI

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