Research Engineer, Sonoma

Research Engineer
San Francisco, CA - 5 days onsite.
$180K-$220K + early stage equity
My client is an early-stage AI research company building advanced reasoning systems and post-training infrastructure for enterprise AI applications.
The team comes from leading AI labs and startups, with backgrounds across LLMs, reinforcement learning, distributed systems, and applied research.
They are looking for a highly technical Research Engineer to work on:
LLM post-training and fine-tuning
RLHF / DPO / reward modeling
Synthetic data generation
Evaluation frameworks and reasoning systems
Distributed training and inference infrastructure
Agentic AI workflows and production deployments
The role is highly hands-on and suited to someone who has actually trained, evaluated, and deployed models, not just built on top of APIs.
Requirements:
Strong Python + PyTorch experience
Hands-on LLM training/fine-tuning experience
Strong ML/AI fundamentals
Experience working in fast-moving technical environments
Strong engineering ability and research mindset
Nice to have:
RLHF / evals / synthetic data experience
Distributed systems exposure
Publications or open-source contributions
Experience at strong AI startups or research labs