AI Engineer

Principal AI Engineer | Up to £220k + Equity | London, HybridWe’re working with a well-funded frontier AI company building the systems used to train, evaluate and improve advanced AI agents.They’re hiring a Principal AI Engineer to take ownership across model training, post-training, RL, evaluation and agent infrastructure. This is a hands-on IC role with real influence over technical direction.ResponsibilitiesLead major AI and research-engineering initiatives end to endBuild and improve training, fine-tuning and post-training pipelinesDevelop evaluation systems, agent harnesses and feedback loopsOwn technically ambiguous problems from experimentation through to productionSet technical direction while remaining close to code and modelsRequirementsStrong experience with LLM training, post-training, RL or evaluationExcellent software engineering fundamentals, ideally PythonTrack record of solving difficult AI problems in productionExperience within a top-tier AI lab, technology company or high-bar startupStrong academic background in Computer Science, ML, Mathematics or a related STEM fieldEvidence of operating at Principal or equivalent senior IC levelLocationLondon, typically 2 days per week onsite.PackageUp to £220,000 base + meaningful equity.