Principal Software Engineer, Simulation

Principal Software EngineerOpenAI's research training infrastructure powers how our frontier models are trained and evaluated. The Agent Harness Bridge team sits at the boundary between the Codex harness, research infrastructure, and internal agent systems, ensuring the same agentic coding runtime used in product can also support large-scale training workloads.This team owns the integration layer that connects harness capabilities into the training stack. The work is highly cross-functional and high leverage: researchers depend on it to run reliably, platform teams depend on it to evolve cleanly, and failures in this surface can materially affect training velocity and correctness.We're looking for a Principal Software Engineer to lead the architecture and evolution of the Agent Harness Bridge.

You'll own a critical interface between research and engineering, building the systems, APIs, and operational patterns that let researchers use agentic coding infrastructure safely and effectively in training environments.This role is ideal for a senior backend or infrastructure engineer with strong technical judgment, product sense for highly technical users, and the ability to drive execution across multiple teams. The highest-leverage work is not novel research; it is building robust infrastructure that accelerates research without compromising engineering quality.In This Role, You WillDesign, build, and evolve the bridge between the Codex harness and research training infrastructureOwn major integration surfaces end-to-end, from architecture and API design through rollout, operations, and long-term maintenanceBuild reliable, containerized execution systems that can support demanding training workloads at scalePartner closely with research, agent, infrastructure, and platform teams to support new training use cases and harness capabilitiesDesign clean, stable interfaces and workflows for highly technical internal users who move quickly and expect strong ergonomicsPrevent one-off workarounds from becoming long-term technical debt by establishing durable abstractions and clear ownershipRaise the bar for correctness, reliability, operational rigor, and engineering judgment across a critical research-facing systemYou Might Thrive In This Role If YouHave significant experience building and scaling backend or infrastructure systems in fast-moving environmentsBring deep strength in API design, systems design, and engineering fundamentalsAre highly detail-oriented and care deeply about correctness, reliability, and operational qualityCan work directly with demanding technical users while maintaining strong engineering disciplineHave a track record of leading cross-functional technical efforts and creating clarity across organizational boundariesBring strong product sense and user empathy for internal platforms and developer toolingAre motivated by enabling researchers and accelerating their work, rather than doing research yourselfAre proficient in Python and have experience with backend platform engineering; Rust experience is a plusThis role is ideally based in San Francisco due to the close collaboration required with researchers and infrastructure partners.