Senior AI Engineer, AI Platform (up to £150k)

This role is with one of Dex's trusted partner companies. We work closely with their teams to truly understand their culture, goals, and what they're looking for, so we can match you with the right opportunity and give you context about the role before you commit to a process. *If you're interested sign up to Dex to apply.* Dex is an AI recruiter agent that helps you run your job search. Tell Dex your stack, seniority, and what you want to build. We will manage your applications and surface other opportunities that are a fit. The role This lab builds the digital environments where AI agents learn by doing. Not just simulating, but actively navigating software, failing, and improving through trial and error. They're generating the experiential data that trains the next generation of AI, backed by significant funding and working directly with frontier AI labs. You'll own difficult AI and research-engineering problems end-to-end. This isn't about short-term experiments or isolated features; it's substantial technical work, hands-on for months, turning ambiguous questions into production impact. You'll design approaches for high-quality training data, fine-tune models, build evaluation loops, and connect models to interactive software tasks. This is a seat for someone who wants to prototype quickly, then build robust, observable systems, not just theorize. The work * Design and implement methods for generating and curating high-quality experiential data for AI agent training. * Fine-tune and post-train large models using supervised fine-tuning, reinforcement learning, and automated optimisation techniques. * Build robust evaluation and feedback loops to measure and improve model and agent performance in interactive environments. * Develop agent harnesses and sandboxed environments that connect AI models to complex software tasks. * Take ambiguous research questions from initial concept through to production-grade, observable AI systems. What You Bring * You have directly fine-tuned or post-trained models, and can articulate the methods, your ownership, and evaluation. * A strong command of modern AI/ML fundamentals, including practical experience with SFT, RL, RLHF, or similar post-training methods. * You write production-grade Python, capable of building clean, testable code and solving complex engineering challenges. * Proven ability to tackle highly ambiguous problems from first principles, without a predefined playbook. * You have owned significant technical outcomes, navigating trade-offs across research, data, and engineering. Why apply through Dex This is a rare role at a lab pushing the boundaries of AI agent training. Dex helps you cut through the noise: sign up once, get matched to this and other high-calibre roles, and receive a full brief before you even apply. Skip the cold outreach and get properly prepared for a process that matters. If you're interested, sign up to Dex to apply - https://jobs.meetdex.ai/jobs/93b274e1-e50a-4087-aa78-42db7ba029aa *As part of the recruitment process at Dex, we process your personal data in accordance with our Privacy Notice for Job Applicants. This notice explains how and why your data is collected and used, and how you can contact us if you have any concerns.*