Epsilon Health
Research Engineer / Research Scientist, Post-Training & Reinforcement Learning
San Francisco, CA · On-site · Full-time · Posted Aug 31, 2026
About the job
Develops post-training and reinforcement learning methods for multimodal medical AI to produce accurate, reliable radiology reports from medical images.
What you'll do
- Develop post-training methods, reward models, and multimodal reasoning capabilities, and explore agentic tool use and inference-time optimization.
- Own research from experimental design through distributed training and evaluation, with deployment handoff.
- Create rigorous clinical evaluations and contribute original research and technical insights.
What they ask for
- Expertise in reinforcement learning, language model post-training, or multimodal machine learning.
- Demonstrated ability to develop, train, or improve state-of-the-art machine learning models.
- Strong understanding of post-training techniques, including reinforcement learning, reward modeling, and preference optimization.
- Experience with large-scale distributed training using PyTorch or JAX.
Nice to have
- Publications at leading ML conferences such as NeurIPS, ICML, ICLR, CVPR, or ACL.
- Experience with RL algorithms, reward models or RLHF, large-scale RL infrastructure, multimodal reasoning, inference-time optimization, medical imaging, or reliability evaluation.
Tools
PyTorch, JAX, GRPO, DAPO, vLLM, SGLang, verl, TRL
AI focus
Post-training and reinforcement learning for multimodal medical AI, including reward modeling, clinical reasoning, agentic tool use, and inference-time optimization.
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