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AI Systems Engineer, Codex Agents

OpenAI· Applied AI
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San FranciscoFull-timePosted 5mo ago

About the role

Engineer to build the AI systems that make Codex agents dependable in production, spanning low-level systems, ML workflows, and production-grade harnesses for Codex Core Agents.

Responsibilities

  • Design and build the core agent harness and execution loop that lets Codex agents interpret model outputs, use tools, execute code, and complete long-horizon tasks safely.
  • Build sandboxing, isolation, orchestration, state, and workflow infrastructure for agents operating in real development environments.
  • Develop evaluation, experimentation, and debugging systems that distinguish harness issues, model behavior, inference/runtime issues, and product failures.
  • Run ablations across prompts, model-facing interfaces, context construction, tool-use strategies, and harness behavior to improve solve rate, reliability, latency, and cost.
  • Improve observability, profiling, and diagnostics across the agent stack, from backend systems to inference, GPUs, and fleet capacity.
  • Work closely with research to make the harness trainable, measurable, and useful for improving frontier agentic models.
  • Build shared primitives that make Codex faster, safer, more reliable, and easier for other teams and open-source users to build on.

Qualifications

  • Have built or operated production systems in distributed systems, infrastructure, developer tooling, sandboxing, virtualization, cloud platforms, or ML systems.
  • Enjoy working across layers: Rust systems code, Python configuration layers, APIs, agent orchestration, evals, logs/traces, inference behavior, runtime constraints, and user outcomes.
  • Have hands-on experience with LLM applications, coding agents, evals, model deployment, inference, compiler/runtime performance, or developer platforms.
  • Care deeply about reliability, safety, performance, debuggability, and clean abstractions.
  • Can debug from evidence and move quickly from ambiguous production failures to practical, durable fixes.
  • Want to work close to research while still shipping changes to production
  • Still write meaningful code, show strong ownership, and can lead scoped or multi-team AI systems work.

Skills

Required:Distributed systems experiencePython configuration and toolingLLM workflows / agent systems
Nice to have:Rust

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
Last updated Sep 3, 2026. Interested? Apply on the company site.

About OpenAI

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