Member of Technical Staff - Post-Training

Reflection • San Francisco, CA

10d

About The Position

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.

Requirements

• 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, high-agency 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.

Benefits

• Top-tier compensation: Salary and equity structured to recognize and retain the best talent globally.
• Health & wellness: Comprehensive medical, dental, vision, life, and disability insurance.
• Life & family: Fully paid parental leave for all new parents, including adoptive and surrogate journeys. Financial support for family planning.
• Benefits & balance: paid time off when you need it, relocation support, and more perks that optimize your time.
• Opportunities to connect with teammates: lunch and dinner are provided daily. We have regular off-sites and team celebrations.

What This Job Offers

• Job Type: Full-time
• Career Level: Mid Level
• Education Level: No Education Listed
• Number of Employees: 51-100 employees