AI Engineer - Stealth

Staff AI Engineer | Stealth Mode AI Start-up | London | Up to £200k

Oliver Bernard have partnered with a stealth-mode start-up in the AI & Research space
, who are looking for a Staff AI Engineer to join the team and work on some genuinely challenging problems across LLMs, reinforcement learning and agentic systems.

This is a hands‑on research + engineering role, where you’ll be involved in:

LLM training & fine‑tuning – including reinforcement learning and post‑training

Evaluation & feedback loops – building systems to continuously assess and optimise models

Agent development – designing and building sophisticated AI agents

AI research – exploring LLM training, RL, evaluation and optimisation techniques

Software engineering – applying strong engineering fundamentals to complex AI problems

• Strong experience working with LLMs and/or foundation models
• Deep experience with training, fine‑tuning, RL or post‑training
• Strong background in model evaluation and optimisation
• Experience building AI agents / agentic systems
• Excellent software engineering fundamentals
• A strong track record in AI research and solving technically complex problems

If you’re a Staff‑level AI Engineer who wants to work at the intersection of cutting‑edge research and production engineering.