IBM watsonx Code Assistant for Z Adds AI Code Generation and Assembler Support

Modernizing mainframe applications is no longer a question of if, but how fast and effectively it can be done. With 89% of organizations modernizing their mainframe environments, the strategic importance of these systems in achieving business goals is clearer than ever. At the forefront of this transformation is IBM watsonx Code Assistant for Z: a purpose-built AI and automation solution designed to accelerate mainframe modernization with lower risk, reduced cost and full lifecycle support.

Today, we’re excited to announce key enhancements coming to watsonx Code Assistant for Z—available to clients starting 27 June 2025—as part of version 2.6. These enhancements streamline development, bridge knowledge gaps and boost productivity.

With the new Code Generation capability in watsonx Code Assistant for Z, you can now create new or update existing COBOL code with precision and speed. Developers can interact with AI using simple, natural language prompts through a chat interface within their VS Code IDE, quickly generating code aligned with their specifications and project context.

Watsonx Code Assistant for Z also provides real-time, in-line code suggestions as you work—helping you code faster and more efficiently. These suggestions are context-aware, leveraging surrounding code in the program, and coding standards to make recommendations that are more accurate and relevant.

Backed by a fine-tuned large language model trained on COBOL as well as IBM Z middleware , the generated code is optimized for the quality and performance required in mainframe applications.

The Code Generation capability helps clients shorten development cycles, reduce manual effort, and deliver consistent, high-quality COBOL code—helping both junior developers come up to speed more quickly as well as seasoned developers be more efficient.

IBM watsonx Code Assistant for Z Code Explanation helps clients faster understand mainframe applications by explaining the code in natural language. It currently supports COBOL, JCL, PL/I and REXX, and is available in multiple languages including English, Japanese, Portuguese, German, French and Spanish. In Q1 2025, we launched AI chat and agentic AI features for code explanation, empowering clients to interact with their code and effortlessly gain holistic understanding through context-rich, application-relevant insights.

With version 2.6, we’re expanding support even further:

• Assembler support: Clients can get a first preview on how to faster understand Assembler logic through natural language explanations.
• Additional local languages: We’re adding support for Explanations being provided in Dutch and Korean, making code explanations even more accessible to global teams.

The Code Explanation capability can be deployed on-premises and as-a-service.

Consider this scenario: Angie, a newly onboarded application architect, is asked to add functionality to her insurance application by adding a new piece of logic for a customer promotion and implement a 15% discount for Electric Vehicle customers of a Motor insurance policy. She’s unfamiliar with the existing business rules and needs to quickly identify the logic behind discount calculations.

With watsonx Code Assistant for Z, Angie takes a smarter path. Using business rule discovery and generative AI, she selects the relevant application, enters a few keywords or prompts into the AI chat, and instantly filters hundreds of programs and variables into a focused, relevant scope. She can visualize how variables and application artifacts are connected, review business rules and identify the logic she needs in minutes.

With Business Rule Discovery, clients can:

• Understand policies, calculations, and decision logic embedded in COBOL applications
• Improve documentation and rule transparency
• Provide a reliable reference for development and decision-making

The simplified UI, combined with AI chat and search, makes application analysis more intuitive—delivering instant, context-aware insights and leverages  specialized mainframe analysis AI agents.

We expect the enhanced application understanding capabilities to be available in watsonx Code Assistant for Z in late 2025.

To learn more about how watsonx Code Assistant for Z can help accelerate your application modernization journey, schedule a demo with our team.