AI migrated legacy COBOL programs to Java, bugs included

Researchers have developed an AI-powered validation method called 'Locksmith Loop' that uses agentic testing to identify bugs when migrating legacy COBOL programs to Java, achieving 91.90% branch coverage on production-like code and demonstrating deterministic parity verification between source and target implementations. This addresses a critical risk in legacy modernization initiatives where AI-assisted code generation must be rigorously validated to ensure functional equivalence before production deployment. For IT organizations undertaking digital transformation, this research signals both the promise and peril of AI-driven migration tools—they can accelerate modernization efforts but require sophisticated validation frameworks to prevent introducing defects during system transformation.