Senior AI Harness Engineer, B2B SaaS

Senior AI Harness Engineer, B2B SaaS, Remote (from UK & Europe only), £100,000 to £110,000, Ref JB-174

About the Role

We are on the hunt for a Senior AI Harness Engineer to join a growing B2B SaaS scale-up. They are in the process of evolving their engineering organisation into an AI-agent-first development model, where autonomous AI systems handle the code generation. In this new paradigm, the role of engineers shifts fundamentally from writing code to designing, orchestrating, and governing systems of AI agents that build and maintain software at scale.

We are looking for a Senior Level Engineer who will act as the bridge between product vision and AI execution, ensuring that autonomous systems can deliver high-quality, reliable software outcomes.

What you will be doing:

• Partner closely with Product Managers to translate product vision into clear, executable system designs that AI agents can act on.
• Design, build, and maintain the environment in which AI agents operate, ensuring they have the structure, context, and constraints needed to perform effectively.
• Shift from traditional coding to system orchestration and AI workflow design, coordinating multiple parallel streams of AI-driven development.
• Act as an AI Orchestrator / “Puppet Master”, enabling agents to work autonomously at scale while maintaining alignment with product goals.
• Build and evolve scaffolding, guardrails, testing frameworks, and feedback loops that allow AI systems to safely and effectively generate production-grade software.
• When issues arise, focus on root-cause system thinking rather than manual code fixes, identifying gaps such as unclear documentation, ambiguous specifications, or incorrect tooling assumptions

What we are looking for:

• Strong engineering background within fast moving product focused SaaS start-up or scale-up environments 
• Proven experience in system design with a mindset of continuous improvement and curiosity, with a drive to challenge and evolve existing engineering practices.
• Actively use AI tools, copilots, or agent-based workflows as part of your day-to-day engineering practice.
• Strong product thinking, with the ability to translate ambiguity into structured technical systems.
• Backend-oriented experience, ideally with TypeScript and Node.js, though language-agnostic engineers are strongly encouraged.

This is a remote permanent role (not a B2B contract), working to UK Hours 09:00 to 18:00 with 1 hour for lunch. For more information, please get in touch with Michael Johnson at Hurren and Hope