Staff ML Engineer — Open Foundation Models

Reflection; Greater London; On-site; GBP 120,000 - 180,000; Full time

Benefits offered by this job

Top-tier pay

Stock options

Health & wellness

Meals provided

Parental leave

Vacation days

Visa sponsorship

Team events

Job summary

Reflection, a research lab developing open models, seeks engineers to transform powerful pre-trained models into aligned, general agents. You will drive post-training work from data curation to large-scale optimization and collaborate across teams to deliver measurable gains in model capability.

You will build data generation pipelines, reward models, RL algorithms and inference-time scaling techniques while shaping our understanding of how large models learn to reason and follow instructions in

Qualifications

• Deep understanding of machine learning fundamentals and practical experience with large-scale LLM training.
• Strong engineering skills, comfortable diving into complex ML codebases and distributed systems.
• Experience improving model behavior through data, reward modeling, or RL techniques.
• Evidence of owning ambitious research or engineering agendas that led to measurable model improvements.
• Thrive in a fast-paced startup environment; bias toward action and clarity of execution.
• Able to work fluidly across research and infra boundaries
• Strong communication capabilities and comfort working collaboratively
• Passionate about advancing the frontier of intelligence.

Responsibilities

• Build systems that transform powerful pre-trained models into aligned and general agents.
• Drive research and engineering initiatives that push the frontier of post-training, from data curation to large-scale optimization.
• Develop data generation pipelines, reward models, reinforcement learning algorithms, and inference-time scaling techniques.
• Collaborate across pre-training and post-training teams to deliver step-function gains in model capability.
• Contribute to shaping our understanding of how large models learn to reason, follow instructions, and improve through reinforcement learning.

Job description

Reflection, a research lab developing open models, seeks engineers to transform powerful pre-trained models into aligned, general agents. You will drive post-training work from data curation to large-scale optimization and collaborate across teams to deliver measurable gains in model capability.

You will build data generation pipelines, reward models, RL algorithms and inference-time scaling techniques while shaping our understanding of how large models learn to reason and follow instructions in