# Founding Research Engineer, RL/Reasoning at BioStack Platforms

- Company: BioStack Platforms (YC P26)
- What the company does: Real world training envs for healthcare AI models. Backed by Y Combinator.
- Company website: https://www.getbiostack.com/
- Type: Startups (AI role)
- Level: Mid level
- Location: San Francisco, CA, US
- Work setup: On-site
- Pay: $200K to $350K base salary per year (USD)
- Posted: 2026-05-01
- Apply by: 2026-10-08
- Apply: https://www.ycombinator.com/companies/biostack-platforms/jobs/M8GyMNX-founding-research-engineer-rl-reasoning
- Page: https://www.1752.vc/careers/jobs/biostack-platforms-founding-research-engineer-rl-reasoning/

## About the role

As an RL Engineer at BioStack, you will build reinforcement learning environments and post-training systems for healthcare AI. BioStack is building the data and environment layer for medical AI: sourcing high-value clinical data, turning it into model-ready workflows, and building tasks, rewards, verifiers, benchmarks, and agent environments where models can learn against meaningful and measurable outcomes.

## What they're looking for

- Build healthcare-specific RL environments, including tasks, action spaces/tool interfaces, reward functions, verifiers, and evaluation harnesses
- Run post-training experiments on language models and agents using techniques such as SFT, RLVR, RLHF/RLAIF, and reward modeling
- Turn clinical and biomedical datasets into training environments with measurable, verifiable outcomes
- Design rewards and verifiers that capture correctness across clinical reasoning and longitudinal decision-making tasks
- Train and evaluate multi-step agents operating across patient histories, clinical tools, and structured/unstructured medical data
- Build scalable pipelines for rollouts, training, evaluation, experiment tracking, and dataset iteration

Tags: Engineering