Staff Software Engineer, Gustie Assist

At Gusto, we're on a mission to grow the small business economy.

You will be part of Gustie Assist, building Otto, the AI agent that Gusto's support advocates rely on to solve customers' hardest payroll, benefits, and compliance problems.

Responsibilities

• 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

Requirements

• 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

Nice to Have

• 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