Founding Harness Engineer

Join an early-stage AI company building an AI coworker for teams. You will develop the runtime and safeguards that help AI agents take useful initiative, work reliably, and handle real tasks safely.

• Design and build the agent runtime for context gathering, deciding when to act, tool selection, approval, and task completion.

• Write and refine system prompts to encourage useful initiative without noisy or risky behavior.

• Build evaluation and regression tests for real tasks, tool use, and failure cases, and catch regressions as prompts change.

• Improve reliability across long-running work, interruptions, and retries.

• Implement safety boundaries, including approval gates and multi-tenant data separation.

• Work directly with the founding team and early users to shape the product.

• Production experience shipping tool-using LLM agents, beyond demos or thin prompt wrappers.

• Hands-on system prompt design, with iterative testing and improvement.

• 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 across prototyping and production, with the ability to explain technical tradeoffs.

• Experience with LLM agents, tool use, evaluation, and prompt engineering.

Salary range: $0 to $200,000 USD annually. Founding equity is available; percentage and vesting details are to be determined.

On-site in San Francisco, United States. Candidates should be based in the Bay Area or willing to relocate.