Senior AI-Driven Legacy Modernization Engineer

RedRock Resourcing; Reading; On-site; GBP 80,000 - 120,000; Full time

Job summary

Agentic Engineering in the UK seeks a Senior Software Engineer to modernise legacy systems using AI-driven approaches. You’ll operate at the intersection of software engineering, architecture and AI tooling to design the engineering harness and guardrails that enable safe, rapid delivery.

Bring a strong C#/.NET foundation and experience with large or legacy codebases. You’ll refactor, build AI-enabled tooling, and establish testing and evaluation frameworks to balance speed with quality.

Qualifications

• Strong software engineering foundation
• Experience with large/legacy codebases
• Exposure to AI-assisted software engineering

Responsibilities

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

Skills

C#/.NET

Software architecture

AI tooling

Code refactoring

Legacy systems

Tools

Claude Code

GitHub Copilot

Codex

MCP

Job description

Agentic Engineering in the UK seeks a Senior Software Engineer to modernise legacy systems using AI-driven approaches. You’ll operate at the intersection of software engineering, architecture and AI tooling to design the engineering harness and guardrails that enable safe, rapid delivery.

Bring a strong C#/.NET foundation and experience with large or legacy codebases. You’ll refactor, build AI-enabled tooling, and establish testing and evaluation frameworks to balance speed with quality.