AI coding models now handle legacy languages far better
OpenAI’s latest models make it more practical to build and migrate software in COBOL, Fortran, and Visual Basic, languages that underpin critical services but have less training data and documentation. GPT-6 Astra’s SQLite-compatible engine pass rate reached 87.4% across 20 languages, versus 26.8% for GPT-5.6 Sol, while GPT-6.1 Sol scored 86.6% on COBOL migration at low reasoning effort and 97.9% at higher effort. The evaluations check both writing new systems and preserving existing behavior during migration.