AI Agent Systems Engineer — Build Reliable Harnesses

OpenAI; California (MO); On-site; USD 180,000 - 240,000; Full time

Job summary

OpenAI is seeking an AI Systems Engineer for Codex Core Agents to design and build the core agent harness and execution loop. You will enable Codex agents to interpret model outputs, use tools, execute code, and complete long-horizon tasks safely in real environments.

You will work across Rust systems code and Python configuration layers, focusing on reliability, safety, and performance. This role involves collaboration with research, infrastructure, and product to push frontier agent

Qualifications

• Have built or operated production systems in distributed systems, infrastructure, developer tooling, sandboxing, virtualization, cloud platforms, or ML systems.

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.

Skills

Distributed systems

Infrastructure

Developer tooling

Sandboxing

Virtualization

Cloud platforms

ML systems

Tools

Rust

Python

Job description

OpenAI is seeking an AI Systems Engineer for Codex Core Agents to design and build the core agent harness and execution loop. You will enable Codex agents to interpret model outputs, use tools, execute code, and complete long-horizon tasks safely in real environments.

You will work across Rust systems code and Python configuration layers, focusing on reliability, safety, and performance. This role involves collaboration with research, infrastructure, and product to push frontier agent