Senior Harness Engineer
The Opportunity
The model is only one part of an agent. The harness around it — its tools, context, memory, execution loop, safety boundaries, and feedback mechanisms — often determines whether it succeeds outside a demo.
We're looking for a senior Python engineer to own and grow Pydantic AI Harness, our open source library of reusable capabilities for building production-grade agents with Pydantic AI. These capabilities bundle tools, lifecycle hooks, instructions, and model settings so developers can add sophisticated agent behavior without rebuilding their agent or changing the framework.
This is a hands-on product and open source engineering role. You'll build the components that let agents work effectively over long-running, complex tasks; use Logfire traces and rigorous evaluations to understand where they fail; and turn those findings into measurable improvements. You'll also help shape Pydantic AI's core extension mechanisms when the work calls for it.
Harness engineering is still a young discipline. We want someone who has already learned the hard lessons of shipping agents in production and is excited to define what good looks like in public.
