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  • While not everything can be easily converted (IMS, CICS, reports, batch processing etc.), there are many situations where automated tooling can be helpful in migrations.

    Related to this, I created a tool for situations where you want to compare COBOL code with Java code. It includes a preprocessing step where IMS etc. calls are converted to mocks that return JSON (from file), and also use JSON for input/output, and GnuCOBOL to run the program. More a proof-of-concept than production, but here is a link if somebody finds it helpful.

    https://github.com/mikko-ahonen/coboltwin

    by kukkeliskuu
  • Why should I convert COBOL to Java? LLM can write COBOL just as fine.
    by mtct88
  • Stuff like this are already a commercial product, it isn't only Zig to Rust rewrites going around.

    https://www.pega.com/insights/resources/break-free-legacy-ma...

    https://www.ibm.com/products/watsonx-code-assistant-z

    https://global.fujitsu/en-global/pr/news/2026/03/30-01

    https://www.rocketsoftware.com/en-us/insights/ai-powered-cob...

    by pjmlp
  • I remember a similar story shared this year at JAX2026 from the Sparkasse Group, they said they were using AI to migrate from COBOL, but they still were in the middle of the migration. Maybe they faced the same issues / problems? It seemed pretty zealous to me, that everything was working smoothly, but this article highlights the limitations
    by madduci
  • This sounds like what the company Mechanical Orchard offers: https://www.mechanical-orchard.com/

    Their pitch is like, "we take your COBOL code, and all the real-world data you can give us. Then we model your COBOL program as a graph, where each node has inputs and outputs. Then we use AI to port each node, making sure that it has the same (input => output) mapping for all the test data you gave us."

    by Taikonerd
  • The largest test case was 4kloc.

    There are hundreds of billions of lines of cobol in production.

    The IRS alone has approx 160 cobol programs, averaging 230kloc each.

    by pacaro
  • The biggest problem is not that bugs are migrated with COBOL, but that lots of new bugs are going to be introduced. AI is not deterministic, it will be making tons of mistakes. The only realistic low-error approach is incremental step-by-step migration using Cursor or similar tools. However, it requires much more time as each step must be prompted, tested and committed manually. Any hope that one-shot migraton of a large code base will not introduce enormous number of bugs is very naive. LLM is very bad on handling long context - it is their nature unfortunately. There is no answer to this problem yet.
    by toplinesoftsys
  • Before, only the senior cobol programmers at the company understood and knew the codebase.

    Now, no one does.

    I can see the allure of moving away from a legacy cobol system. But an AI rewrite doesn't actually solve any of the issues with having a legacy cobol codebase. You just have a new system no one knows or understands.

    by matsemann

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