Principal Harness Engineer

About FICO and the Role

FICO, a global leader in analytics software serving more than 100 countries, is seeking a Principal Harness Engineer to join their engineering team in England. This role plays a crucial part in the emerging field of Harness Engineering, which focuses on creating environments that guide AI coding agents to produce reliable, maintainable, and well-structured code without requiring tedious human review of every change.

Key Responsibilities

• Design, develop, deploy, and maintain core harness components such as guides, guardrails, feedback loops, and shared context to transform raw AI model capabilities into production-ready engineering outputs. Emphasis is on systems development over manual coding.
• Manage and standardize feedforward elements including agent instruction files, reusable skills, architectural rules, documentation, and codemods to enhance first-time accuracy of AI agents.
• Create feedback mechanisms like custom linters, static analysis tools, architectural fitness tests, verification processes, and AI-based reviewers that automatically identify issues prior to human review.
• Define and uphold quality gates and release criteria governing how much agent-produced work can be merged automatically versus what requires human escalation.
• Develop infrastructure and methodologies for testing and evaluating large language model (LLM) outputs to ensure safety and quality, including consumer and contract testing approaches such as Pact for integration reliability.
• Implement continuous improvement by engineering controls to prevent repeated agent mistakes and managing repository knowledge to avoid drift through ongoing cleanup practices.
• Strategically place controls in the production pipeline for efficiency—fast checks pre-commit, thorough post-integration tests, and ongoing monitoring to maintain quality cost-effectively.
• Enhance observability of agent performance and track key metrics like cost per merged pull request (PR), time to merge, review throughput, defect escape rates, and survival rates of agent-assisted PRs to prioritize improvements.
• Collaborate with product and platform teams to translate specifications and acceptance criteria into enforceable systemic controls.
• Provide technical leadership and mentorship across teams on harness engineering methodologies and responsible AI tool usage.

Candidate Profile

• Degree in Computer Science or related field, or equivalent practical expertise in software architecture, design, development, and testing.
• Experienced software engineer with a strong background in managing extensive codebases, architecture design, and a rigorous focus on testing and maintainability.
• Practical knowledge of AI coding agents such as Claude Code, Codex, or similar, with insight into their strengths and limitations.
• Skilled in building engineering tooling within contemporary technology stacks including linters, static analysis, CI/CD pipelines, containerized testing/build environments, and observability tools. Familiarity with conventions like AGENTS.md.
• Experience in spec-driven development, context engineering, agent orchestration, fitness function design, and developer platform integration.
• A systems-oriented mindset prioritizing environmental fixes over isolated output corrections, with the ability to translate quality standards into repeatable mechanical rules.
• Good judgment balancing deterministic controls (e.g., type checkers, linters) and inferential methods (e.g., AI-based reviews), understanding their relative cost, speed, and reliability.
• Proven track record managing quality gates and release policies to consistently meet engineering standards.
• Awareness of security concerns related to autonomous agents including prompt injection, scoped permissions, sandbox execution, and auditing; experience designing least-privilege guardrails.
• Familiarity with consumer and contract testing techniques like Pact to ensure system reliability in distributed environments.
• Excellent communication skills enabling clear articulation of designs and collaboration with architects and stakeholders.

Why Join FICO?

• Work in a company embodying inclusive values such as ownership, customer delight, and respect.
• Opportunities for professional growth by leveraging unique strengths and engaging in impactful projects.
• Competitive salary and benefits designed to reward your contribution and promote work-life balance.
• An employee-centric culture featuring diverse resource groups and social activities that foster camaraderie.

Additional Information

FICO is committed to diversity and equal opportunity, encouraging applications from candidates who may not meet every qualification but demonstrate relevant strengths. Applicant data is handled according to FICO's privacy policies.