OpenAI reports that GPT-6.1 Sol passed 97.9% of tests in its high-reasoning COBOL migration evaluation, compared with 5.4% for GPT-5.6 Sol at low reasoning effort. The source discusses low-resource languages including COBOL, Fortran, Visual Basic, and OCaml, as well as migrations to C++, Java, Kotlin, Python, and Rust. In a separate benchmark spanning 20 languages, GPT-6 Astra averaged 87.4%—but COBOL remained its weakest language, at 72.1%.
Source