Yeah nah maybe fix the bugs before swapping the average COBOL dev for the average Java dev.
hyrum's law applies here
AI migrated legacy COBOL programs to Java, bugs included
21–30 of 108 posts
Re: AI migrated legacy COBOL programs to Java, bugs included
#22As I understand it, the translation isn't done by an LLM but by a deterministic AST-based migrator. Also, carrying over the bugs is the stated goal.
Re: AI migrated legacy COBOL programs to Java, bugs included
#23The 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 l…
> AI is not deterministic, it will be making tons of mistakes.
From the paper:
> The COBOL source is passed through an internal deterministic Migrator to produce a generated Java target.
Also, humans are not deterministic either. Give the same COBOL -> Java translation to multiple developers and each will come up with a different solution. Heck, even the same developer will produce a different output for the same task, depending on the day of the week.
Re: AI migrated legacy COBOL programs to Java, bugs included
#24The 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 l…
> AI is not deterministic, it will be making tons of mistakes.
Just set the sampling temperature to zero and remove any unintended non-determinism during the parallel computation of the token probability distribution. The problem is solved? Of course, not. Non-determinism has little to do with LLMs' mistakes.
Re: AI migrated legacy COBOL programs to Java, bugs included
#25The 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 l…
You don’t need the entire codebase in context in every moment to migrate it.
Also AI being non deterministic does not prevent it from one-shotting perfect solutions 100% of the time for simple enough problems.
And every model generation brings this bar higher. So that’s really not a fundamental problem.
And we can also implement llm inference deterministically if we want, it’s just that it’s not worth the loss in performance to do it.
Re: AI migrated legacy COBOL programs to Java, bugs included
#26[dead]
Re: AI migrated legacy COBOL programs to Java, bugs included
#27Stuff 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...
Re: AI migrated legacy COBOL programs to Java, bugs included
#28COBOL is not about the language, it's about the whole environment in the mainframe. LLM fanboys won't understand this. You need something like a mainframe with a 99.99% uptime no matter what happens in hardware, with live CPU swapping and such.
Erlang/Elixir/OTP has a resilient environment with hot swapping. Is that truly problematic?
Re: AI migrated legacy COBOL programs to Java, bugs included
#29The 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 l…
> The only realistic low-error approach is incremental step-by-step migration using Cursor or similar tools.
Correction: AI is not deterministic, the only realistic low-error solution is not a more complex use of non-deterministic AI, but deterministic transpilation.
The problem is that this results in COBOL-in-Java which runs correctly but it is a nightmare to maintain.
Re: AI migrated legacy COBOL programs to Java, bugs included
#30COBOL is not about the language, it's about the whole environment in the mainframe. LLM fanboys won't understand this. You need something like a mainframe with a 99.99% uptime no matter what happens in hardware, with live CPU swapping and such.
Can you explain why you need one machine never falling over ever instead of a cluster of machines never falling over at once collectively?