Principal AI-Driven Engineer: Legacy Modernisation

RedRock Resourcing; Reading; On-site; GBP 90,000 - 120,000; Full time

Job summary

RedRock Resourcing is seeking a Principal Software Engineer – Agentic Engineering to help modernise complex legacy software using AI, at the intersection of software engineering, AI, developer experience and governance.

You will design systems, standards and guardrails enabling engineers to deliver better software safely, while hands-on refactoring legacy code and integrating AI tooling and evaluation frameworks.

Qualifications

• Strong software engineering foundation.
• Experience with large, complex or legacy systems.
• Familiarity with AI-assisted software engineering tools.

Responsibilities

• Use AI coding agents to investigate, refactor and modernise legacy codebases.
• Design the engineering harness that gives AI agents the right context, rules and constraints to work effectively.
• Build repository-level instructions, agent skills, prompts and dynamic context.
• Work with technologies such as Claude Code, MCP and other agentic development tools.
• Establish automated testing and AI evaluation frameworks (evals) to ensure speed and quality.
• Build guardrails, sandboxes and CI/CD controls around AI-driven development.

Skills

C#/.NET

Legacy systems

AI tooling

Agentic development

Code refactoring

Tools

Claude Code

Cursor

GitHub Copilot

Codex

Job description

RedRock Resourcing is seeking a Principal Software Engineer – Agentic Engineering to help modernise complex legacy software using AI, at the intersection of software engineering, AI, developer experience and governance.

You will design systems, standards and guardrails enabling engineers to deliver better software safely, while hands-on refactoring legacy code and integrating AI tooling and evaluation frameworks.