Staff Software Engineer, Defensive Agent
Horizon3 AI6 hours ago
Remote, United StatesStaff+
Base Salary
$229k - $270k/yr
Responsibilities
- Own the end-to-end technical vision, roadmap, architecture, and delivery for the defensive agent workstream.
- Write production backend code, review pull requests, conduct design reviews, and raise engineering and operational standards.
- Mentor engineers and lead through architecture, code, technical direction, and accountability for outcomes rather than through direct management.
- Translate ambiguous product goals into technical roadmaps and make build-versus-buy-versus-integrate decisions.
- Design durable execution for long-running, resumable agent runs and build systems for retries, checkpointing, and partial failure.
- Design authorization, tenant isolation, workload identity, and credential-brokering systems for agents taking write actions.
- Architect connectors over heterogeneous third-party security-control APIs.
- Address prompt injection and prevent untrusted model output from authorizing privileged actions.
- Build observability that makes agent behavior explainable.
- Partner with AI research, platform engineering, Product, and PM to align research direction, platform constraints, and product sequencing.
Requirements
- Bachelor's degree in Computer Science, Computer Engineering, or a related field.
- 7+ years of professional software engineering experience using modern object-oriented or functional languages.
- Experience building applications on cloud platforms such as AWS, Azure, or GCP, using Docker and Kubernetes.
- Deep production experience with agentic or LLM-backed systems and an understanding of their failure modes and containment strategies.
- Expert proficiency in SQL.
- Demonstrated experience designing and operating distributed production systems involving asynchronous workflows, queues, retries, idempotency, and partial failure.
- Track record of shipping and operating production services, including on-call ownership.
- Preferred experience with Temporal or another durable-execution/workflow engine, or equivalent self-built checkpointing.
- Preferred experience with multi-tenant platforms requiring hard isolation, workload identity, and short-lived credential brokering.
- Preferred experience integrating many third-party APIs behind normalized abstractions.
- Preferred familiarity with security control planes and APIs, including EDR, firewalls, SIEM, and cloud IAM.
- Preferred database architecture experience with relational and graph databases and experience building GraphQL backends.
Benefits
- Remote and hybrid work models are available depending on role and location, including a Chicago office where some roles require regular in-office presence.
- Health, vision, and dental insurance are provided for employees and their families.
- Flexible vacation policy and generous parental leave.
- Full-time roles are eligible for equity in the form of stock options.
- Inclusive culture, professional growth opportunities, and a collaborative environment.
Tech Stack
Categories
About Horizon3 AI
Horizon3 AI builds NodeZero, a proactive security platform that autonomously performs penetration testing and validates attack paths across on‑prem, cloud, and hybrid environments. The company sells its software by subscription to security and IT teams at enterprises and government agencies, helping prioritize and verify fixes. Founded in 2019 and headquartered in San Francisco, it is privately held and serves customers across regulated industries and the public sector.