Sr Staff Frontend Engineer, Builder Enablement

San Francisco, CA About Gusto At Gusto, we're on a mission to grow the small business economy. We handle the hard stuff — payroll, health insurance, 401(k)s, and HR — so owners can focus on their craft and their customers. With teams in Denver, San Francisco, and New York, we support more than 400,000 small businesses nationwide and are building a workplace that reflects the people we serve. All full-time employees receive competitive base pay, benefits, and equity (RSUs) — because everyone who helps build Gusto should share in its success. Offer amounts are determined by role, level, and location. Learn more about our Total Rewards philosophy. AI is a fundamental part of how work gets done at Gusto. We expect all team members to actively engage with AI tools relevant to their role and grow their fluency as the technology evolves. AI experience requirements vary by role and will be assessed during the interview process. About the Role: As a Sr Staff Engineer on the Builder Enablement team, you will be instrumental in defining how every builder (engineer, designer, and beyond) at Gusto ships high-quality products with AI assistance. You'll help lead the development of AI tooling that teaches people and LLMs to use our design system correctly and drive experiments that improve AI-assisted builder workflows. If you're passionate about building tools that multiply the impact of an entire organization, this is your chance to lead and innovate. About the Team: The Builder Enablement team's mission is to make high-quality, AI-assisted shipping the default for every builder at Gusto. We own the design system, but also own how it gets expressed to AI tools and builders. Most of our focus is on AI tooling and enablement, such as: building MCP servers, agent skills, prompt engineering, eval systems, and experiments that make LLMs produce compliant, high-quality output. This is a great time to join to help define the direction for the team as we tackle the new challenges and opportunities that AI presents for the frontend at Gusto! Here’s what you’ll do day-to-day:

• Build and maintain AI tooling (MCP servers, agent skills, prompts) that enables builders to ship with the design system
• Develop tools to ensure that the quality, performance, and accessibility of Gusto’s reusable components continuously improve
• Develop tools to expand the pool of contributors and quality of contributions to Gusto’s frontend
• Run experiments to test hypotheses about what makes AI-assisted building better
• Shadow builders to understand real workflows and proactively fix blockers
• Partner with designers to build and maintain a system of reusable components, tokens, patterns, and documentation that empowers all of Gusto
• Develop eval systems to measure AI output quality against design system standards
• Communicate visibly and educate widely to technical and non-technical audiences

Here’s what we're looking for:

• 10+ years of technical experience in a frontend engineering role
• Highly proficient in HTML, CSS, JavaScript, React, TypeScript
• Experience building developer tooling plugins or AI-powered tools
• Familiarity with LLM ecosystems (prompt engineering MCP agent skills or similar)
• Experiment-driven mindset: comfortable framing hypotheses scoping small tests measuring outcomes
• Strong history of cross-functional collaboration with Design and/or other non-technical teams
• Experience in building UI components that are modular composable flexible maintainable well-documented
• Experience with a JavaScript testing library for unit integration end-to-end validation
• Appreciation for a collaborative test-driven environment
• Experience turning wireframes mockups into responsive accessible tested code
• Passionate about creating inclusive accessible experiences for everyone
• Familiar with emerging trends in frontend development including various approaches to styling (CSS Modules CSS-in-JS Sass) component libraries (Material UI Carbon Polaris Lightning) accessibility tooling (axe) observability (RUM Synthetic Testing) AI (MCPs prompting evals agents)
• Comfortable being visible communicative

Our cash compensation amount for this role is targeted at $225000/yr to $275000/yr for San Francisco CA Stock equity is additional Final offer amounts are determined by multiple factors including candidate experience expertise. Gusto has physical office spaces in Denver San Francisco New York City Employees based there expected 2–3 days per week onsite or more depending on role Same applies for Symmetry roles in Scottsdale office. Note SF office expectations include SF & San Jose metro areas. When approved remote work from other locations requires secure reliable internet connection. Our customers come from all walks of life so do we We hire great people from wide variety backgrounds not just because right thing but makes company stronger If you share values enthusiasm for small businesses you will find home at Gusto. Gusto is proud equal opportunity employer no discrimination based on race color religion national origin etc. Gusto considers qualified applicants with criminal histories consistent with law. Committed reasonable accommodations for qualified individuals with disabilities & disabled veterans throughout application process. Gusto takes security & protection of personal info seriously see Fraudulent Activity Disclaimer & Applicant Privacy Notice.