# Staff Software Engineer, Gustie Assist

**Company:** [Gusto](https://hotfix.jobs/companies/gusto)
**Location:** Denver, CO, New York, NY, San Francisco, CA
**Role:** Fullstack Engineering
**Experience:** 8+ years
**Skills:** llm agents, agent runtime, tool calling, retrieval, llm evaluation, Ruby on Rails, JavaScript, React, GraphQL, federated backends, mcp, Prompt Engineering, Observability, rails
**Posted:** 2026-08-14

> Build and scale Otto, Gusto’s production AI agent for support advocates, spanning the LLM runtime, tool/action layer, backend, frontend, and evaluation systems. The role requires 8+ years of software engineering experience, production agentic-system expertise, strong full-stack ability, and mentoring skills.

## Job Description

## Responsibilities
- Design and build across the Otto platform, including the runtime and agent graph, tool/action layer, Rails/GraphQL backend, advocate-facing experience, and evaluation system.
- Expand the agent's safe capabilities through autonomous, tool-using actions with human-in-the-loop approval.
- Build secure, auditable identity and permissions models for agent actions.
- Develop evaluation and observability systems using LLM-as-judge, deterministic scorers, offline gates, and online production monitoring.
- Work with LLMs on prompting, tool/function design, retrieval, and feedback loops based on advocate interactions.
- Partner with Product, Data, Design, and Customer Experience teams to ship capabilities addressing advocate and customer pain points.
- Mentor engineers and establish responsible practices for building agentic systems at scale.

## Requirements
- Typically 8+ years of software engineering experience with end-to-end system ownership.
- Production experience building and shipping LLM-powered or agentic systems, including tool-calling, retrieval, or evaluations.
- Strong full-stack range across backend services, LLM runtimes, and customer-facing products.
- Experience owning multi-quarter projects with measurable user impact at scale.
- Sound judgment regarding safety and blast radius when software takes actions on real accounts.
- Ability to mentor engineers and raise engineering standards.

## Nice to Have
- Experience with agent frameworks, evaluations, LLM-as-judge, retrieval, or MCP-style tool architectures.
- Experience with Ruby on Rails and/or JavaScript/React, or ability to ramp quickly.
- Familiarity with GraphQL and federated backends.
- Appreciation for collaborative, test-driven, high-autonomy environments and clear communication with engineering and business stakeholders.

## Compensation and Benefits
- Competitive base pay, benefits, and equity in the form of RSUs.
- Offer amounts are determined by role, level, and location.

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