Principal AI Engineer — Lead AI Platform & Learning Systems

Dex; Greater London; Hybrid; GBP 120,000 - 180,000; Full time

Job summary

Dex is partnering with a leading AI lab to hire a Staff or Principal-level IC. You will own major AI and research-engineering areas, turning ambiguous problems into clear roadmaps and driving measurable production impact while staying hands-on.

You will define direction for core platform areas, design systems for training-data creation, model fine-tuning, and evaluation, and guide peers through technical credibility from London or Paris.

Qualifications

• Deep hands-on experience training, fine-tuning, or post-training models.
• Strong understanding of AI/ML, model optimization, and RL techniques.
• Ability to translate ambiguous problems into clear roadmaps.

Responsibilities

• Define and lead technical direction for core AI platform areas.
• Design and implement systems for training-data creation, curation, and fine-tuning.
• Develop agent harnesses, sandboxed environments, and feedback loops.
• Evaluate interventions, establish baselines, and decide iteration paths.
• Influence team decisions while remaining deeply embedded in code.

Skills

AI model training

Model evaluation

Production software eng

Technical leadership

Tools

PyTorch

TensorFlow

RL frameworks

Job description

Dex is partnering with a leading AI lab to hire a Staff or Principal-level IC. You will own major AI and research-engineering areas, turning ambiguous problems into clear roadmaps and driving measurable production impact while staying hands-on.

You will define direction for core platform areas, design systems for training-data creation, model fine-tuning, and evaluation, and guide peers through technical credibility from London or Paris.