Ai Engineer • Mid-Level

Who you are

You have a deep understanding of machine learning fundamentals and practical experience with large-scale LLM training — you've navigated complex ML codebases and distributed systems, demonstrating strong engineering skills. Your experience includes improving model behavior through data, reward modeling, or reinforcement learning techniques, showcasing your ability to own ambitious research or engineering agendas that led to measurable model improvements.

You thrive in a fast-paced, high-agency startup environment — your bias toward action and clarity of execution allows you to work fluidly across research and infrastructure boundaries. Strong communication capabilities are essential for you, as you enjoy collaborating with diverse teams to push the frontier of post-training initiatives.

What you'll do

In this role, you will build systems that transform powerful pre-trained models into aligned and general agents — your work will drive research and engineering initiatives that encompass everything from data curation to large-scale optimization. You will develop data generation pipelines, reward models, reinforcement learning algorithms, and inference-time scaling techniques, contributing to significant advancements in model capabilities.

Collaboration is key, as you will work closely with both pre-training and post-training teams to deliver step-function gains in model performance. Your contributions will shape the understanding of how large models learn to reason, follow instructions, and improve through reinforcement learning, making a direct impact on the company's mission to build open superintelligence.

What we offer

At Reflection, we provide a supportive environment that values your contributions and encourages professional growth. You will enjoy fully paid parental leave for all new parents, including adoptive and surrogate journeys, along with financial support for family planning. Our benefits include paid time off when you need it, relocation support, and perks that optimize your time, such as daily lunch and dinner provided. We also host regular off-sites and team celebrations to foster connections among teammates.