AWS adds OpenLegacy to mainframe modernisation tool

AWS has integrated OpenLegacy's software into AWS Transform for Modernization, targeting companies that want to move mainframe workloads to the cloud in stages.

The integration is intended to keep modernised applications connected to mainframe systems that remain in use during migration projects. That supports a phased approach, moving one workload at a time rather than replacing an entire estate in a single cutover.

AWS Transform for Modernization is AWS's service for updating legacy systems. OpenLegacy's role is to maintain links between cloud-based applications and older systems that continue to run on the mainframe while migration work proceeds.

OpenLegacy's technology is embedded directly into the AWS Transform for Modernization workflow. During the decomposition stage of a migration, it runs within the AWS environment to generate cloud APIs and integration points without requiring teams to switch to a separate toolset.

The approach is aimed at large organisations that operate mixed technology environments for extended periods during modernisation. In sectors such as financial services, insurance and telecommunications, companies often need to keep core systems live while moving selected functions to newer platforms.

Hybrid estates

Mainframe modernisation has long been constrained by the difficulty of separating business logic from legacy code while maintaining operational continuity during the transition. A workload-by-workload process reduces the need for a wholesale migration, but it also creates a period when old and new systems must exchange data reliably.

OpenLegacy's software generates integration bridges and API facades between mainframe systems and cloud applications. The aim is to preserve communication between the environments so modernised services can continue to interact with functions that have not yet been moved.

For customers, that means migration teams can progress through projects in phases while keeping transformed applications linked to the remaining mainframe estate. The broader objective is to limit disruption to business operations during long-running technology change programmes.

The integration also expands AWS Transform for Modernization's composability framework, which is designed to bring together specialist tools for different parts of the modernisation process. Those phases include assessment, documentation, transformation, testing and deployment.

Within that framework, OpenLegacy focuses on decoupling and integration. Its role is to support coexistence between modernised applications and systems that continue to run on legacy infrastructure.

Omri Kessel, AWS General Manager, Agentic AI Modernization, described business-logic recovery as a central challenge in these projects. "Recovering the business logic in legacy code is the hard part of modernization, and doing it at machine speed is what lets customers modernize one workload at a time instead of all at once," said Kessel. "The AWS Transform for Modernization composability framework lets us bring in the right capability for each phase, and OpenLegacy is a great example: it keeps each workload we move to AWS communicating with the mainframe behind it, so customers modernize incrementally, in months, instead of betting the business on a big-bang cutover."

Phased migration

The arrangement reflects a broader shift in enterprise technology projects away from large one-off replacement programmes and towards staged migrations. For many companies, especially those with extensive legacy estates, replacing all systems at once carries high operational and financial risk.

By contrast, incremental migration lets teams modernise selected business processes while continuing to run other services on existing systems. That can make it easier to test new applications, control change and maintain service continuity, though it depends on stable connections across both environments.

Ron Rabinowitz, CEO of OpenLegacy, said coexistence between old and new systems remains central to successful modernisation. "Mainframe modernization succeeds when the old and the new can work together," said Rabinowitz. "By embedding OpenLegacy into AWS Transform for Modernization, organizations can bridge legacy systems and cloud-native environments in a coexistence model, enabling phased modernization one business process at a time."

OpenLegacy is an AWS partner with a Mainframe Modernization competency and works with enterprise customers in sectors including financial services, insurance, healthcare and government.

The integration underlines AWS's effort to build a broader modernisation toolchain around its cloud platform, with partners handling specific technical challenges that arise during complex legacy migrations.