Staff Software Engineer

Who you are

• Typically 8+ years of software engineering experience, owning systems end-to-end
• You've built and shipped LLM-powered or agentic systems in production, including tool-calling/agents, retrieval, or evals, and you know where they break and how to make them reliable
• Strong full-stack range. Must be comfortable moving between backend services, an LLM runtime, and customer-facing product, and picking up whatever the problem needs
• Experience owning multi-quarter projects that make measurable user impact at scale
• Sound judgment about safety and blast radius when software takes real actions on real accounts
• Ability to mentor engineers and raise the bar around you
• Experience with agent frameworks, evals/LLM-as-judge, retrieval, or MCP-style tool architectures
• Experience with Ruby on Rails and/or JavaScript/React (our stack), or the ability to ramp quickly
• Familiarity with GraphQL and federated backends
• Appreciation for a collaborative, test-driven, high-autonomy environment, and clear communication with engineering and business stakeholders

What the job involves

• 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
• Gustie Assist builds Otto, the AI agent that Gusto's support advocates rely on to solve customers' hardest payroll, benefits, and compliance problems
• When a small business hits a wall and reaches out, the advocate turns to Otto: it reasons over the customer's full context, answers in the moment, and increasingly takes real actions across Gusto's systems on the advocate's behalf to make the customer whole
• We're a small platform team building an agent that reasons, acts, and has to get it right when the stakes are someone's payroll
• This is unusually broad, hands-on applied-AI work: you'll own an LLM agent runtime and the full stack around it, including the tool layer that lets it act over Gusto's systems, the Rails/GraphQL backend, the advocate-facing frontend, and the eval system that keeps it trustworthy while it touches live customer accounts
• We keep the path from idea to production short, and measure ourselves on customer outcomes, not model novelty
• Design and build across the Otto platform, including the runtime and agent graph, the tool/action layer, the Rails/GraphQL backend, and the advocate-facing experience, owning a meaningful slice end-to-end
• Expand what the agent can safely do: autonomous, tool-using actions with human-in-the-loop approval, built on a secure, auditable identity and permissions model
• Build the eval and observability systems (LLM-as-judge + deterministic scorers, offline gates and online production monitoring) that let us change the agent in production weekly without regressing correctness or escalation behavior
• Work directly with LLMs, including prompting, tool/function design, retrieval, and the feedback loops that turn real advocate interactions into a better Otto
• Partner closely with Product, Data, Design, and our CX teams to turn advocate and customer pain into shipped capabilities
• Mentor engineers and set the bar for how we build agentic systems responsibly and at scale

Benefits

• Medical, dental, and vision insurance for employees and dependents
• Family care and support, including family planning and fertility benefits
• Gender-affirming care and support
• A variety of mental health resources
• Paid vacation, sick time, bereavement, and holidays, paid leaves, sabbatical, and more
• Free meals and refreshments at the office (conversation and community is an added bonus!)