Principal Software Engineer - AI-Driven Legacy Modernization

RedRock Resourcing; Reading; On-site; GBP 90,000 - 130,000; Full time

Job summary

RedRock Resourcing is seeking a Principal Software Engineer – Agentic Engineering to advance legacy modernisation through AI‑driven software engineering. You will shape the intersection of software engineering, AI, and developer experience, building systems, standards and guardrails for safer, faster delivery.

You will work hands‑on with complex legacy tech, designing an AI‑driven engineering harness and implementing tooling to modernise codebases while maintaining quality and safety.

Qualifications

• Requires a seriously strong software engineering foundation.
• Experience with large, complex or legacy systems is essential.
• Comfort with refactoring, architecture decisions and modernisation strategies.

Responsibilities

• Hands‑on work with complex legacy technology while applying AI tooling.
• Design the engineering harness to give AI agents proper context, rules and constraints.
• Build repository‑level instructions, agent skills, prompts and dynamic context.
• Collaborate on automated testing, evals and quality frameworks for AI‑driven development.
• Establish guardrails, sandboxes and CI/CD controls for AI‑enabled software engineering.

Skills

Strong software engineering

C#/.NET

AI tooling familiarity

Tools

Claude Code

GitHub Copilot

Codex

Cursor

MCP

Job description

RedRock Resourcing is seeking a Principal Software Engineer – Agentic Engineering to advance legacy modernisation through AI‑driven software engineering. You will shape the intersection of software engineering, AI, and developer experience, building systems, standards and guardrails for safer, faster delivery.

You will work hands‑on with complex legacy tech, designing an AI‑driven engineering harness and implementing tooling to modernise codebases while maintaining quality and safety.