OpenAI touts AI progress in migrating legacy COBOL code

OpenAI reported "substantial improvements" in its models' ability to migrate aging COBOL code to C++, Java, Kotlin, Python and Rust while preserving behavior. GPT-6.1 Sol hit 87% behavior-preservation accuracy at low reasoning effort and 98% at higher reasoning. Experts caution that rewriting code is not the same as replacing a system.

• GPT-6.1 Sol: 87% behavior preservation at low reasoning, 98% at high
• For comparison, GPT-6 Astra scored 86%, GPT-6 Sol 21%, GPT-5.6 Sol 5%
• COBOL underpins over 40% of online banking and 95% of ATM transactions
• Experts say OpenAI's evals miss the complexity of replacing whole systems