Senior Software Engineer, Agentic Systems

Horizon3.ai, Inc.

Job Overview

Location

US, Remote

Job Type

Full-time

Full Job Description

📋 Description

• Senior Software Engineer, Agentic Systems at Horizon3.ai, Inc. is a critical role focused on building an autonomous, black-box web application penetration tester that mimics skilled human pentesters to find real vulnerabilities in production environments without false positives.
• The person will design and evolve the agent harness and orchestration layer, create tools for probing and exploiting web applications, translate offensive security expertise into repeatable agent capabilities, own evaluation infrastructure to measure agent improvements, manage LLM inference in production on AWS Bedrock, and ensure every agent finding is production-safe and reproducible.
• Horizon3.ai is a fast-growing, remote cybersecurity company founded by former U.S. Special Operations cyber operators, startup engineers, and frustrated security practitioners, dedicated to solving systemic security issues like alert fatigue, blind spots, and the cybersecurity skills shortage through its NodeZero™ platform, which delivers autonomous pentests at scale across cloud, hybrid, and on-prem environments.
• The person will gain deep expertise in LLM-powered autonomous agents, production-grade agent reliability, offensive security engineering, evaluation system design, and scalable AI safety practices while contributing to a mission-driven team that values ownership, collaboration, and results in a high-impact cybersecurity domain.

🎯 Requirements

• 5+ years building production software with strong Python proficiency
• Hands-on experience building LLM-powered applications or agents, including tool use, function calling, structured outputs, and multi-step orchestration
• Proven track record of making LLMs reliable in production by addressing nondeterminism, model limitations, and shipping dependable systems
• Experience building or owning evaluation harnesses to measure model or agent improvements objectively
• Strong instincts for prompt and context engineering with judgment to keep model tasks small and well-scoped
• Solid software fundamentals including testing, observability, and disciplined debugging practices for complex systems
• Ownership mentality and comfort owning a critical, fast-moving subsystem end to end

🏖️ Benefits

• Inclusive Team: Diversity-valued culture where everyone can thrive
• Growth Opportunities: Dynamic team with numerous career development paths
• Innovative Culture: Collaborative environment encouraging creativity and out-of-the-box thinking
• Hybrid & Remote Work: Flexible work models including remote options and Chicago office access
• Competitive Compensation: Salary range $169,000 - $208,000 annually, equity package, health/vision/dental insurance, flexible vacation, generous parental leave

Skills & Technologies

Python

Neo4j

AWS

Senior

Remote

$169k-208k

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Horizon3.ai, Inc.

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About Horizon3.ai, Inc.

Horizon3.ai provides autonomous security testing and attack surface management software. Its NodeZero platform continuously assesses enterprise networks, clouds, and applications to find exploitable weaknesses, validate fixes, and prioritize risks. The company serves Fortune 500, government, and mid-market organizations seeking proactive defense without manual red teams.

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