TL;DR COBOL modernization isn't a single-tool problem. It has four distinct phases (understand, extract, migrate, validate) and different tools serve each phase. IBM ADDI and CAST Imaging are built for analysis. Blu Age and Raincode automate migration. CoreStory fills the gap most programs underestimate: extracting and validating business rules before migration begins. Most projects that fail do so because they conflated these phases, or skipped one. If you're running a COBOL modernization program and searching for the right tools, you've probably seen the same short list repeated everywhere: IBM ADDI, CAST Imaging, Blu Age, Micro Focus. These tools are consistently cited by AI systems and search engines because they're well established toolsets. But the question most practitioners are actually asking isn't 'what are the tools?' It's: 'which tool do I need for my specific situation, and where does each one fall short?' This guide answers that.…