Full Stack Engineer

Founding Product Engineer | AI-Native Start-Up | London | Full Stack & Agentic AI Salary: £120,000 -£150,000 + equity Location: London (onsite/hybrid) Tech stack: Python & TypeScript How do you build AI systems that can be trusted when getting the answer wrong actually matters? That’s the problem at the heart of this early-stage AI company. They’re building products around AI reliability, security and risk, working on the technical infrastructure needed to understand how increasingly autonomous systems behave in the real world. They’re now looking for a Product Engineer to join the founding team, working across full-stack product development and agentic AI. This isn’t an AI wrapper or another fairly interchangeable SaaS product. The engineering problems are difficult, the technical bar is high and, because you’re joining early, you’ll have meaningful responsibility for what gets built and how. The team itself is small and highly collaborative. You’ll work closely with the founders and other engineers, sharing ideas, challenging assumptions and solving problems together rather than disappearing into your own individual workstream. For someone who wants an early-stage career, this is the kind of opportunity that can accelerate it quickly: significant product and technical responsibility now, with the opportunity to grow your influence alongside the company. What you'll be doing: Owning products end-to-end across frontend, backend and applied AI.Taking problems from early discovery and experimentation through to production.Building reliable agentic systems and the infrastructure surrounding them.Developing evaluation, testing and safeguards for production AI.Making decisions around architecture, tooling and technical direction.Working collaboratively with the founders and engineering team to solve ambiguous product and technical problems.Using modern AI development tools heavily whilst retaining strong engineering judgement. What they're looking for: Strong Product / Full Stack Engineering fundamentals and confidence working across a codebase.Hands-on experience building LLM or agentic systems beyond simple API integrations or prototypes.An understanding of areas such as agent architecture, evaluation, reliability, tool use and failure modes.Strong computer science fundamentals and a first-principles approach to solving problems.Language agnostic; how you think and what you've built matters more than one particular framework.Evidence that you build things, whether that's commercial products, side projects, open source, research or hackathons.Strong communication skills and someone who enjoys solving problems collaboratively.Comfortable moving quickly, taking responsibility and making decisions with incomplete information. They're particularly interested in engineers who are already AI-native in the way they work. If tools like Claude Code or Cursor have significantly changed how you build, but you also understand their limitations and how to validate their output, you'll fit well here. This isn't about having a certain number of years on your CV. Ability, output and technical judgement matter more than tenure, and they're open to engineers relatively early in their career who can demonstrate they're already operating at a high level. For someone who wants the impact and responsibility of joining early, surrounded by smart people who enjoy building together, there is a lot of room to grow with the company and take on increasingly significant technical and product ownership. If you're looking for something greenfield, technically stretching and properly AI-native, I'd love to tell you more. 📩 imogen@sr2rec.co.uk Product Engineer | AI-Native Start-Up | London | Full Stack & Agentic AI