Post-Training Applied Researcher
Hybrid (San Francisco)$200k - $275kFull-timePosted 7mo ago
About the role
Role focused on post-training research for fine-tuning/open-source models to outperform frontier closed models across customer domains, with hands-on LLM fine-tuning and RL experience, shipping models to production.
Responsibilities
- Design and run post-training pipelines: SFT, GRPO, DPO, RLVR, reward function engineering, and synthetic data generation.
- Build task-specific training environments and evals tailored to customer domains like healthcare, code generation, and legal, spanning multi-turn tool use, sandboxed execution, and agentic workflows.
- Work directly with customers to translate production data into training signal, designing reward loops from real usage patterns and handling distribution shift.
- Run and analyze training experiments end-to-end: diagnose reward hacking, importance sampling drift, and advantage estimation instabilities.
- Publish findings at top venues and contribute to Baseten's open-source training libraries.
Qualifications
- Hands-on experience training LLMs with reinforcement learning — demonstrated understanding of GRPO or PPO beyond recipe-level reproduction, including group advantage computation, clipped objectives, and KL penalty design
- Strong intuition for reward engineering: the ability to distinguish between a reward that trains effectively and one that will exploit at scale
- Experience building multi-turn agent environments with tool use, not limited to single-turn question-answering setups
- Comfort working across the full pipeline from dataset construction through training, evaluation, and deployment
- Experience with production ML systems. Preference for candidates who have closed a training–inference loop where production data feeds back into model improvement
Skills
Required:LLM fine-tuning with reinforcement learningReward engineeringMulti-turn agent environments with tool use
Benefits
- Competitive compensation, including meaningful equity
- (U.S. only) 100% coverage of medical, dental, and vision insurance for employee and dependents
- Flexible PTO policy including company wide Winter Break (offices closed Christmas Eve to New Year’s Day)
- Paid parental leave
- Fertility and family-building stipend through Carrot
- (U.S. only) Company-facilitated 401(k)
- Exposure to a variety of ML startups, offering unparalleled learning and networking opportunities.
Last updated Oct 21, 2026. Interested? Apply on the company site.
About Baseten
Inference is everything
Effortlessly serve optimized open source & custom models on the fastest, most reliable model delivery network.
AICloud InfrastructureDeveloper ToolsInference PlatformMachine LearningModel DeploymentModel Runtimesai-infrastructure-and-development
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