OpenAI claims GPT-6 significantly improves legacy programming language support

OpenAI reports that its latest GPT-6 models substantially improve performance on legacy programming languages with limited training data, such as COBOL and Fortran. On the MultiLangBench evaluation, GPT-6 Astra achieved an average 87.4 percent test pass rate across 20 languages, up from about 38 percent for previous models. On a specific COBOL-to-code translation benchmark, GPT-6.1 Sol reached 86.6 percent accuracy at low reasoning effort and 97.9 percent with maximum reasoning effort, compared to single-digit success rates for GPT-5.6.