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Legacy Modernisation

Accelerated by AI

Delivered in bounded, provable steps.

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AI changes the business case for legacy modernisation

Legacy software is what everyone wants tackled but nobody dares to take on. They're hugely expensive, hold tremendous risk and provide no added value. Yet they hold back every innovation.

AI changes the business case fundamentally. Our proven approach eliminates the risk. Small incremental steps, each proving business value.

The cost of standing still is greater than the cost of change

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Deliver new features at the pace your business expects

A modern, enterprise-ready stack your teams can confidently build on.

Understand your systems without relying on a handful of experts

Critical knowledge is often buried in legacy code or held by a few people. Recover and validate the business rules before you modernise.

Build the foundation for your AI and data ambitions

Legacy systems can hold back AI, data and new digital services. Create a modern foundation that can evolve with your business.

Trust your technology landscape again

Create a governed, well-documented landscape you can understand, maintain and evolve with confidence.

How can we help you

Modernise business-critical systems with AI-assisted engineering, human validation and architecture-first delivery. Reducing risk while building knowledge and control into every step.

Modernise the core without disrupting the business

Modernise complex legacy estates where continuity, architecture and business knowledge are critical. We uncover and validate what matters first, then redesign and modernise progressively without disrupting what needs to keep running. 

Rebuilding a legacy ERP for continuous change

Customer case

For a leading property management company, we're modernising a business-critical legacy ERP system using AI-generated specifications, tests and code. Through a structured, iterative approach, we're building a future-ready platform that supports continuous business change without disrupting daily operations.

→  A future-ready platform that evolves with the business.

Modernise a contained application or domain.

Upgrade, refactor or re-platform ageing applications with AI-assisted engineering. Start with a focused scope, prove the approach in working software and expand where it creates value. 

 

WebDev → .NET: From legacy code to team ownership

Customer case

A legacy WebDev application that had become difficult to maintain was fully documented, modernised and re-implemented in .NET. The result: a supported codebase the internal team can confidently maintain and evolve again.

From legacy code to team ownership
Modernised, documented and firmly back in the hands of the team.

Keep control while building internal capability

Embed architecture, quality, security and knowledge transfer throughout the journey, so your teams can govern and evolve the modernised landscape themselves. 

Iteration cycle

One iteration. Four steps. Continuous improvement.

Each iteration focuses on one module, with a clearly defined scope and price, following the same four steps. Every cycle builds knowledge and capabilities that stay with your organisation.

Plan

Agree on what to tackle in this iteration.

One clearly defined module with measurable success criteria agreed upfront.

Do

Understand first, then build with a safety net.

We document how the existing system actually works, use those specifications to build modern code and establish a golden master to compare old and new behaviour.

Check

Your people test. The golden master proves.

User acceptance testing and automated regression tests demonstrate that the modernised system behaves as expected with measurable evidence.

Act

Turn every lesson into a better next iteration.

We refine the approach, evaluate the results and agree on the next module — or stop, with everything delivered so far remaining yours.

Customer cases

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Rebuilding a legacy ERP for continuous change

Spec-driven modernisation with AI-generated tests, code and a migration roadmap.

Features flowing again on a supported, enterprise-aligned platform.

Health insurance fund logo

Documenting decades of COBOL in days, not years

AI-assisted documentation and migration across 630+ COBOL programs.

Business rules recovered in days; first migration in 3 days.

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From black-box legacy to .NET in days

AI-generated documentation and migration planning, enriched with domain expertise.

10×

faster migration, 3 days instead of 3 weeks

A leading Belgian Insurance Company

Mapping first. Testing smarter.

AI mapped the brownfield application before automating its tests.

Higher quality

Fewer bugs, with test automation live in production.

A leading Belgian provider of pharmacy management software

A trusted foundation for modernisation

Turning undocumented legacy assets into a clear, validated foundation for redesign.

From legacy uncertainty to a documented, validated basis for confident modernisation.

One way to start

Start focused. Prove the approach.

For a contained application or domain, a first iteration turns the approach into working, validated software before you decide how to continue.

Rather than starting with a lengthy assessment, we select a contained domain and modernise it end-to-end. That gives you working software, validated knowledge and a proven approach before you commit to the wider transformation. What you get:

A modernised, production-ready scope 

Verified business logic

Living documentation your team owns

 A reusable approach for the next iterations 

A clear go/no-go decision before scaling 

Automated regression testing

We do not start from scratch

Proven methods, reusable AI building blocks and production-ready foundations help us deliver faster, with less risk.

Every engagement builds on assets we have already developed and tested in practice. That means less time spent reinventing the basics and more time focused on your specific business challenge.

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Proven playbooks

Know what to do next

Methods for process redesign, change management, and AI governance.



Governance & operating model: a proven framework for how AI and data initiatives get decided, owned and scaled responsibly.

Adoption & change playbook: a structured way to bring people along, so new tools and ways of working actually stick.

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Reusable AI patterns

Reuse what already works

Proven approaches for agents, RAG, evaluation, and guardrails



Agentic Delivery Pipeline: an AI-native delivery pipeline that plans, builds, tests and documents faster on every engagement.

Adoption & change playbook: a structured way to bring people along, so new tools and ways of working actually stick.

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Production-ready foundations

Build a solid foundation

Production-ready foundations (Software Development Kit & Platforms) that help teams build and scale AI solutions faster.



Data & AI foundation: A governed data platform that gives every AI initiative a solid foundation to run on.

AI Reliability Engineering: Our principles translated into an SDK, ready to be used in your AI applications with built-in monitoring of performance, quality and business value.

The right technology for the job

Our modernisation method is tool-agnostic. Models, agents and frameworks are selected to fit your stack and governance.

Contact us

Enough about us, let’s talk about you

Do you have questions or need support? At AE, we are committed to helping you achieve success in the digital landscape.