Staff Software Engineer, Core AI Platforms

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 500,000 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: We're looking for seasoned full-stack software engineers to join the teams behind Gusto's AI product platforms — the shared systems that our product teams build upon — to serve small business owners every day. As a Staff Software Engineer, you'll operate across the full lifecycle of foundational systems: deliver production AI agent systems — multi-agent orchestration, tool/workflow registries, agent-to-agent handoffs, human-in-the-loop escalation, and long-ru [... source excerpt omitted ...] n us! Here’s what you’ll do day-to-day: 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, among others Mentor other engineers to help solve some of the hardest technical problems out there in very complex domains and at a large scale Help scale one of the largest Ruby/Rails and Javascript/React applications in the world Coll [... source excerpt omitted ...] 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 our customers genuinely love Here’s what we're looking for: 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