Heirloom® recognized as the multi-platform Global Leader for Mainframe Application Modernization Software
ISG Mainframe Report—Introduction
Information Services Group (ISG), a well-known technology research and advisory firm renowned for its industry and technology expertise, has named Heirloom Computing a Leader in its Mainframe Services & Solutions U.S. 2026 Quadrant Report.
Heirloom Computing offers progressive modernization. Its incremental approach is designed to deliver value at each step, enabling clients to move at their own pace and de-risk the modernization program.
Companies that receive the Leader award in the ISG mainframe report have a comprehensive product and service offering, a strong market presence, and an established competitive position. The product portfolios and competitive strategies of Leaders are strongly positioned to win business in the markets covered by the study. The Leaders also represent innovative strength and competitive stability.
Enterprises are no longer treating mainframe modernization as a one-time migration decision. The 2026 report finds that modernization has become a long-term operating reality, driven by workforce constraints, regulatory requirements, and demand for faster application change cycles rather than cost reduction alone. Heirloom combines deterministic compilation with agentic AI to produce cloud-native Java that runs on any platform, including the mainframe.
Highlights from the report:
Heirloom Computing transforms mainframe workloads into maintainable, cloud-native Java while preserving functional behavior. Its approach combines replatforming and refactoring, advancing to idiomatic Java through Heirloom/X, including a specialized AI agent that uses local LLMs trained on the company’s IP.
Industry Analysis
From U.S. to Global
The 2025 study evaluated 54 providers across the U.S. market. This year, ISG expanded to a global scope covering the U.S., U.S. public sector, and Europe. The 2026 study evaluated 61 companies, with 24 qualifying for the Mainframe Application Modernization Software quadrant and 10 earning Leader status.
Governance Over Speed
The report finds that enterprises are assessing modernization software based on governance depth and transparency rather than solely on speed of code transformation. Buyers expect auditable workflows, approval checkpoints, and test equivalence before production cutover. Tools that enforce a single transformation outcome are increasingly viewed as misaligned with enterprise reality.
Deterministic Tools, Not LLM-Generated Code
ISG draws a sharp distinction between deterministic modernization tools and generative approaches. Qualifying solutions assure consistency and repeatability with predictable outputs from identical inputs. The study explicitly excludes generic LLM and coding assistants. Vendors that balance AI automation with deterministic toolchains for compliance and governance are better positioned to support large-scale programs.
Competitive Landscape
ISG assessed providers across strategy and vision, technology innovation, brand awareness, partner landscape, portfolio depth, and customer experience. Heirloom Computing earned Leader status as the highest-ranked independent modernization software vendor in the global study, recognized for its deterministic toolchain, Heirloom/X refactoring with agentic AI, automated testing through Probe, and deployment flexibility across every major cloud and on-premises environment.