OpenAI's new models can move old COBOL code to modern languages

OpenAI says its newer AI models are much better at writing and moving software written in older programming languages. In one test, GPT-6.1 Sol correctly moved 86.6% of COBOL programs to newer languages. The previous model, GPT-5.6 Sol, managed 5.4% at the same setting. The catch: real projects still need expert review.

What changed

OpenAI named COBOL, Fortran and Visual Basic as languages where it has seen big gains. These languages have far less code and documentation online than Python or JavaScript, so AI models have less to learn from. OpenAI says that gap has narrowed sharply.

To measure this, OpenAI built a test called MultiLangBench. It asks a model to build a database engine from scratch in 20 programming languages. GPT-6 Astra averaged an 87.4% test pass rate, up from 26.8% for GPT-5.6 Sol.

The migration results

OpenAI also tested whether models could move COBOL programs to C++, Java, Kotlin, Python or Rust without changing what the programs do. That is what migration means here: same behavior, newer language.

• GPT-6.1 Sol reached 86.6% accuracy at low reasoning effort, the setting where the model spends the least effort per task.
• GPT-5.6 Sol scored 5.4% at that same setting.
• OpenAI says the new model did this at 61% of the API cost, meaning the price companies pay to use it in their own software.
• At higher reasoning effort, accuracy reached 97.9%.

Why old languages matter

OpenAI says COBOL supports more than 40% of online banking systems, 80% of in-person credit card transactions and 95% of ATM transactions. It says Fortran is still used in areas such as weather forecasting and nuclear reactor safety analysis. These systems are old, but many people rely on them every day.

What is not known yet

These are OpenAI's own test results, and the material does not include outside checks. Test programs are also simpler than the large, tangled systems inside real banks and agencies. The material gives no dollar prices and does not say when or how businesses can get access.

OpenAI says production migrations would still require expert review and testing. That matters because a small mistake in banking or safety software can have serious costs.

What to do

If your business runs on aging software, moving off it may get cheaper and faster. Treat that as a reason to ask questions now, not a reason to skip safeguards. Budget for experienced people to review the results and test the new system before it goes live.