Staff Software Engineer, Core AI Platforms

Gusto is on a mission to grow the small business economy, handling payroll, health insurance, 401(k)s, and HR for over 500,000 small businesses nationwide. With teams in Denver, San Francisco, and New York, Gusto is building a workplace that reflects the people it serves. All full-time employees receive competitive base pay, benefits, and equity (RSUs).

As a Staff Software Engineer on the Core AI Platforms team, you will operate across the full lifecycle of foundational systems, delivering production AI agent systems including multi-agent orchestration, tool/workflow registries, agent-to-agent handoffs, human-in-the-loop escalation, and long-running conversation state. You will shape architecture early in the design process, build self-service internal features and APIs, and own their performance long after launch.

• Design and maintain evaluation frameworks across offline and online environments, including golden datasets, LLM-as-judge pipelines, and production replay, while establishing regression gates and end-to-end observability and tracing for agent runs.
• Design, build, and test Gusto core platform services – communications, reporting, dashboards, access, workflows, risk, payments, and compliance capabilities.
• Mentor other engineers to solve some of the hardest technical problems in very complex domains and at a large scale.
• Help scale one of the largest Ruby/Rails and Javascript/React applications in the world.
• Collaborate with Product Engineering, Product Management, Data, and Design teams to understand customer pain points, come up with solutions, and then prototype, iterate, and launch daily.
• Build platforms that engineering teams rely on and trust to deliver products that customers love.

• Successful applicants typically have 8+ years of software development experience.
• Hands-on experience taking AI/LLM capabilities to production – agent orchestration, tool integration, retrieval, and evaluation/feedback loops that keep AI improving safely.
• AI fluency: fluent, daily use of AI coding assistants (e.g., Claude Code, or equivalent AI harness) across the development lifecycle – writing, reviewing, debugging, and documenting code – with strong judgment on when to apply them, how to evaluate output quality, and how to stay current as the tooling evolves.
• Passion for creating scalable, efficient platforms for users.
• Curiosity and experimentation with emerging AI frameworks, applying and sharing best practices to evaluate and scale AI use safely across teams.
• Experience in, or interest working in, Ruby on Rails.
• Appreciation for a collaborative, test-driven environment.
• Ability to build well-structured, maintainable, well-documented code.
• Ability to effectively communicate across engineering teams and with business stakeholders.

Cash compensation for this role is targeted at $163,000–$204,000 in Denver & most remote locations, and $197,000–$247,000 for San Francisco & New York. Stock equity is additional. Final offer amounts are determined by multiple factors including candidate experience and expertise and may vary from the amounts listed above.

Please note that a two day travel to a Gusto office for onboarding is required for this position. If you have any questions regarding this requirement, please share with your recruiter.