COBOL

OpenAI says its models are now better at legacy languages including COBOL, Fortran and Visual Basic. On its own MultiLangBench suite, GPT-6 Astra averaged an 87.4% pass rate across 20 languages versus 26.8% for GPT-5.6 Sol, and GPT-6.1 Sol reached 97.9% accuracy on COBOL migration tasks.