Senior Software Engineer, Agentic Systems

Horizon3.ai
United States
Workplace: RemoteFull timeUSD 169,000 - 208,000 annuallyFunction: Software EngineeringExperience: 5+ yearsSkills: ["Python","LLM","Prompt engineering","Testing","Observability","Cost control","Architecture","Engineering reliability"]

Develop and evolve autonomous agent capabilities to power a production-ready, LLM-driven web application pentester. Build the agent harness, tooling, evaluation infrastructure, and production inference, ensuring reliability, safety, and scalable performance in a security-focused autonomous system.

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FursaFursa
Horizon3.ai
Horizon3.ai
2 months ago

Senior Software Engineer, Agentic Systems

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Source: Company careers pageValidated by: Fursa AI
Last checked: 13 hours agoStatus: Live

Job Summary

Develop and evolve autonomous agent capabilities to power a production-ready, LLM-driven web application pentester. Build the agent harness, tooling, evaluation infrastructure, and production inference, ensuring reliability, safety, and scalable performance in a security-focused autonomous system.
Location: United States
Workplace: Remote
Employment Type: Full time
Job Function: Software Engineering

Key Responsibilities

  • •Build and evolve the agent harness and orchestration that turns an LLM into a reliable autonomous pentester, the loop that reasons over an application, forms attack hypotheses, acts, and verifies results.
  • •Design the tools and tool-shaped feedback the agent uses to probe and exploit, and the structured-output and validation layers that keep it reliable.
  • •Translate the team's offensive expertise into repeatable agent capabilities, encoding how attackers think into a system the agent can perform consistently.
  • •Own and grow our evaluation infrastructure: benchmark suites, failure-mode taxonomy, regression detection, and monitoring to track improvements.
  • •Manage LLM inference in production: model selection, prompt/context engineering, and cost/latency control (AWS Bedrock).

Pay and Benefits

Salary: USD 169,000 - 208,000 annually
Equity and Bonus:Equity
Perks:Health InsuranceVisionDentalEquityRemote WorkParental LeavePaid Leave

Key Requirements

  • •5+ years building production software, with strong Python.
  • •Hands-on experience building LLM-powered applications or agents, tool use / function calling, structured outputs, multi-step orchestration.
  • •A track record of making LLMs reliable in production, handling nondeterminism and modeling limitations.
  • •Real experience with evaluation: built or owned harness to measure model/agent improvement.
  • •Strong instincts for prompt and context engineering, with the ability to keep the model's job small and well-scoped.
Experience:5+ years
Skills:PythonLLMPrompt engineeringTestingObservabilityCost controlArchitectureEngineering reliability
Languages:English
Tech Stack:PythonAWS BedrockLLMAgent frameworksPrompt engineeringTestingObservability

Company Brief

Horizon3.ai
Builds NodeZero®, an autonomous penetration-testing platform that continuously finds, prioritizes, and verifies exploitable vulnerabilities across on-premises, cloud, and hybrid environments to help organizations reduce security risk.
Industry: Cybersecurity
Company Size: Large (251 to 1,000 employees)
Growth: Scaleup
Funding: Series D
Headquarters: San Francisco, United States
Founded: 2019
Glassdoor
Glassdoor: 4.9
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