Sr. Machine Learning Engineer I

Job description

POS-23565 About the Role: HubSpot's Agent Platform team is building Breeze Studio, our custom agent creation product that lets customers define, deploy, and improve AI agents that work on their behalf inside HubSpot. As a Machine Learning Engineer on the Agent Orchestration ML team, you'll own the models and systems that determine whether those agents are any good. This is core ML work: prompt optimization, LLM evaluation, model fine-tuning, and inference infrastructure. You'll work directly with LLM vendors like OpenAI, run model performance experiments, and ship improvements that customers notice. The team is small (currently 2 MLEs), the surface area is large, and the scope is yours to define. Custom agents are central to HubSpot's strategic direction as an AI-first CRM. This is not a supporting role. What You'll Do: - Design and run experiments to improve agent quality: better tool use, better reasoning, better outputs, using frameworks like DSPy and VLLM - Build and maintain evaluation infrastructure to measure what's working and catch regressions before customers do - Optimize LLM inference: latency, cost, model routing, and quality tradeoffs - Partner with product teams on m...