Senior AI Engineer - Legacy Modernisation & Agentic Dev

RedRock Resourcing; Reading; On-site; GBP 85,000 - 125,000; Full time

Job summary

RedRock Resourcing is seeking three experienced Principal Software Engineers to join a brand-new team focussed on agentic engineering. You will work at the intersection of software engineering, architecture and AI to modernise complex legacy software, creating systems, standards and guardrails for safe, high-quality delivery.

This role is not a traditional ticket-driven position. You will be hands-on with complex legacy tech, using AI tooling to tackle debt and deliver value.

Qualifications

• Requires a seriously strong software engineering foundation.
• Deep experience with C#/.NET and large, complex or legacy systems.
• Comfort with AI-assisted development and modern tooling.

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.
• 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 to balance speed and quality.
• Build guardrails, sandboxes and CI/CD controls around AI-driven development.

Skills

C#/.NET

Software architecture

Legacy systems experience

Tools

Claude Code

Cursor

GitHub Copilot

Codex

Job description

RedRock Resourcing is seeking three experienced Principal Software Engineers to join a brand-new team focussed on agentic engineering. You will work at the intersection of software engineering, architecture and AI to modernise complex legacy software, creating systems, standards and guardrails for safe, high-quality delivery.

This role is not a traditional ticket-driven position. You will be hands-on with complex legacy tech, using AI tooling to tackle debt and deliver value.