Sr. Model Engineer

SpaceXSI is building Super Intelligence to help humanity understand the universe. We train frontier coding agents and scale RL on real user data to make them increasingly effective. We're looking for Research Scientists who can drive effective RL or mid-training research in a small-team setting. You'll own ambiguous, hard research problems end-to-end: forming hypotheses, designing experiments, building the training/eval/data needed to test them, and pushing results into the next model.

• Design and run rigorous experiments that turn research ideas into measurable gains in model capability
• Improve data recipes through data quality, deduplication, and mixture experiments
• Define what makes RL data and rewards good, including grader design and preventing reward hacking
• Advance training science, from architecture and scaling experiments to post-training recipes for coding and computer-use agents
• Build evals and targeted tasks that expose model weaknesses and guide where the team invests next