Sr. Machine Learning Engineer I

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 model selection and performance benchmarking

• Work closely with product engineers and PMs to translate customer quality problems into ML hypotheses and solutions

• Own models end-to-end: from research and experimentation to production deployment

What We're Looking For

• 5+ years of experience in a dedicated ML Engineer role (not ML-adjacent software engineering)

• Strong Python skills; experience with PyTorch, VLLM, DSPy or similar LLM optimization frameworks

• Hands-on experience working with large language models in production: prompt engineering, fine-tuning, evaluation, inference optimization

• Ability to move from ambiguous problem ("this agent isn't performing well") to experimental design to shipped improvement

• Comfort working with limited supervision in an early-stage product environment

Why This Role

• Autonomy with impact: Small team, large surface area. Your work directly affects the quality of agents that hundreds of customers build.

• Strategic positioning: Breeze Studio is how HubSpot competes in the AI-native CRM market. Agent quality is the bottleneck while you'll help own.

• Interesting ML problems: Evaluating open-ended agent behavior, optimizing for latency and quality simultaneously, working at the frontier of LLM capabilities.

Pay & Benefits

The cash compensation below includes base salary, on-target commission for employees in eligible roles, and annual bonus targets under HubSpot’s bonus plan for eligible roles. In addition to cash compensation, some roles are eligible to participate in HubSpot’s equity plan to receive restricted stock units (RSUs). Some roles may also be eligible for overtime pay. Individual compensation packages are tailored to your skills, experience, qualifications, and other job-related reasons.

This resource will help guide how we recommend thinking about the range you see. Learn more about HubSpot’s compensation philosophy.

Benefits are also an important piece of your total compensation package. Explore the benefits and perks HubSpot offers to help employees grow better.

At HubSpot, fair compensation practices aren’t just about checking off the box for legal compliance. It’s about living out our value of transparency with our employees, candidates, and community.

Annual Cash Compensation Range:
$165,500—$248,300 USD

We know the confidence gap and impostor syndrome can get in the way of meeting spectacular candidates, so please don’t hesitate to apply — we’d love to hear from you.

If you need accommodations or assistance due to a disability, please reach out to us using this form.

At HubSpot, we value both flexibility and connection. Whether you’re a Remote employee or work from the Office, we want you to start your journey here by building strong connections with your team and peers. If you are joining our Engineering team, you will be required to attend a regional HubSpot office for in-person onboarding. If you join our broader Product team, you’ll also attend other in-person events, such as your Product Group Summit and other gatherings, to continue building on those connections.

If you require an accommodation due to travel limitations or other reasons, please inform your recruiter during the hiring process. We are committed to supporting candidates who may need alternative arrangements

Massachusetts Applicants: It is unlawful in Massachusetts to require or administer a lie detector test as a condition of employment or continued employment. An employer who violates this law shall be subject to criminal penalties and civil liability.

Germany Applicants: (m/f/d) - link to HubSpot's Career Diversity page here.

India Applicants: link to HubSpot India's equal opportunity policy here.

About HubSpot

HubSpot (NYSE: HUBS) is an AI-powered customer platform with all the software, integrations, and resources customers need to connect marketing, sales, and service. HubSpot's connected platform enables businesses to grow faster by focusing on what matters most: customers.

At HubSpot, bold is our baseline. Our employees around the globe move fast, stay customer-obsessed, and win together. Our culture is grounded in four commitments: Solve for the Customer, Be Bold, Learn Fast, Align, Adapt & Go!, and Deliver with HEART. These commitments shape how we work, lead, and grow.

We’re building a company where people can do their best work. We focus on brilliant work, not badge swipes. By combining clarity, ownership, and trust, we create space for big thinking and meaningful progress. And we know that when our employees grow, our customers do too.

Recognized globally for our award-winning culture by Comparably, Glassdoor, Fortune, and more, HubSpot is headquartered in Cambridge, MA, with employees and offices around the world.

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• HubSpot Careers

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