Founding Harness Engineer

About the role

An early-stage AI team is looking for a Founding Harness Engineer to build the agent runtime and evaluation systems that help an AI coworker act reliably in real team workflows. The engineer shapes when agents take initiative, request approval or stay quiet. The position is remote, from Serbia, Poland or another Eastern European country.

Key responsibilities

• Design and build the agent runtime for providing context, selecting tools, requesting approvals and completing work.
• Write and refine system prompts so agent behavior is proactive without being noisy or unsafe.
• Build evaluation and regression tests for real tasks, tool use and failure cases.
• Improve reliability across long-running tasks, interruptions and retries.
• Implement safeguards such as approval gates and multi-tenant data separation.
• Work with the founding team and early users to move broad problems from prototype to production.

Required profile

• Production experience shipping tool-using LLM agents, beyond demos or thin prompt wrappers.
• Hands-on system prompt design, improved through testing and iteration.
• Experience building evaluation and regression test harnesses for LLM or agent behavior.
• Understanding of safe tool execution, approval workflows and multi-user data risks.
• Strong ownership of broad technical problems and the ability to explain tradeoffs.

Required skills

• LLM agents, tool use and evaluations
• Prompt engineering
• Test harnesses for agent behavior

What we offer

• Founding equity, with percentage and vesting terms to be confirmed.
• Remote work from Serbia, Poland or another Eastern European country.
• Local employment or contractor structure and working-hour overlap to be confirmed.