Principal AI Engineer: Technical Lead, AI Platform

Dex; Greater London; Hybrid; GBP 150,000 - 190,000; Full time

Job summary

Dex seeks a Staff/Principal-level AI research engineer to own major AI and research-engineering areas, from problem definition and technical direction to measurable production impact.

This role is not a management track; it targets engineers with genuine technical authority who will work hands-on on defining research questions, roadmaps, and success metrics, influencing other engineers through credibility.

Qualifications

• Deep hands-on experience training, fine-tuning, or post-training models.
• Strong understanding of modern AI/ML, model optimization, evaluation, and RL techniques.
• Proven ability to translate ambiguous technical or research problems into clear plans.

Responsibilities

• Define and lead technical direction for core AI platform areas from ambiguous problems to measurable outcomes.
• Design and implement systems for training-data creation, curation, and model fine-tuning.
• Develop and improve agent harnesses, sandboxed execution environments, and feedback loops for continuous learning.
• Rigorously evaluate model interventions and agent improvements with baselines and iteration decisions.
• Influence technical decisions across the team while coding and experimenting.

Skills

AI model training

RL techniques

production-grade software

technical leadership

ambiguous problems translation

Tools

PyTorch

TensorFlow

Job description

Dex seeks a Staff/Principal-level AI research engineer to own major AI and research-engineering areas, from problem definition and technical direction to measurable production impact.

This role is not a management track; it targets engineers with genuine technical authority who will work hands-on on defining research questions, roadmaps, and success metrics, influencing other engineers through credibility.