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Large Language ModelsAI Coding AssistantsGIGAZINE AIPublished: Oct 21, 2026, 13:00 JST

OpenAI's GPT-6 Astra hits 87.39% on MultiLangBench, toping GPT-5.6 Sol

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OpenAI's GPT-6 Astra hits 87.39% on MultiLangBench, toping GPT-5.6 Sol

3 Key Points

  1. What happened

    OpenAI said GPT-6 Astra passed 87.39% and GPT-6.1 Sol 87.04% of its MultiLangBench test — building a SQLite-compatible database engine in 20 programming languages — far above GPT-5.6 Sol's 26.77%; budget model GPT-6 Luna reached 40.31%.

  2. Why it matters

    The jump suggests the new models handle languages with little training data far more reliably, which could make AI more useful for maintaining and modernizing older systems, OpenAI said.

WHO IT HITSSoftware maintainers and IT teams that keep older systems running — particularly in banking and other critical infrastructure — could see AI tools handle these languages more reliably, though the figures come from OpenAI's own benchmark.

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Context & Analysis

OpenAI frames the update around a long-standing gap: languages like COBOL and Fortran are used in relatively few projects but sit inside critical systems such as banking infrastructure, and past AI models handled them with lower accuracy because training data is scarce. To measure the gap, OpenAI built MultiLangBench, which asks models to build a SQLite-compatible database engine across 20 languages.

The published pass rates show a wide separation between generations. GPT-6 Astra and GPT-6.1 Sol both cleared 87%, while the previous GPT-5.6 Sol sat at 26.77%; even the cheaper GPT-6 Luna model reached 40.31%. OpenAI also charted COBOL results against task cost, showing the GPT-6 series scoring higher than GPT-5.6 Sol, with Luna beating the older model at lower cost. Beyond writing code, OpenAI tested migrating COBOL programs to C++, Java, Kotlin, Python or Rust, reporting high success rates for the GPT-6 series.

OpenAI's stated implication is that stronger handling of COBOL and Fortran could let AI help maintain and modernize important infrastructure software. The results are OpenAI's own benchmark figures, so how they translate to real-world legacy systems remains to be seen.

FAQ
What is MultiLangBench?
It is a benchmark OpenAI designed to measure how well AI models handle rare programming languages. Models must build a SQLite-compatible database engine in 20 programming languages, including C, C#, Python, COBOL, Fortran and Visual Basic.
How did the budget GPT-6 Luna model perform?
GPT-6 Luna recorded a 40.31% pass rate on MultiLangBench, above GPT-5.6 Sol's 26.77%. OpenAI also said Luna scored higher than GPT-5.6 Sol at a lower cost on the COBOL task.
Did OpenAI test converting COBOL programs to other languages?
Yes. OpenAI ran tests migrating COBOL programs to C++, Java, Kotlin, Python or Rust. It said the GPT-6 series had high success rates, with GPT-6.1 Sol able to migrate at low cost and high accuracy.
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