Founding Engineer – ML Research

ABOUT THE ROLE A well-funded, Series A/B AI startup headquartered in Mountain View, CA — working with some of the world's top frontier AI labs — is looking for a Founding ML Research Engineer to help build and scale their AI research backbone from the ground up. This role sits at the intersection of applied machine learning and systems engineering. It's ideal for someone who thrives in unstructured environments, loves building fast, and obsesses over model performance and data quality. You'll work directly with the founding team to prototype, experiment, and ship research-driven features that push the boundaries of cutting-edge AI systems. The company specializes in high-quality training and post-training data, robust RL environments, and intelligent agents for frontier AI labs and enterprises — with a strong emphasis on accuracy, safety, and reliability. No visa sponsorship is available. Candidates must have current eligibility to work in the United States. WHAT YOU'LL DO - Design, tr