Yet Another LLM Rant

Summary

2025-08-09 large-lying-model, rant Note: This was a thread on Mastodon, but for archival and reading-pleasure purposes, I’m collecting it here, too. A contact just told me that my old “LLMs generate nonsense code” blog post from 2 years ago is now very outdated with GPT5 because it’s so awesome and so helpful. So I asked him to give it a test for me, and asked it my favorite test question based on a use-case I had myself recently: Without adding third-party dependencies, how can I compress a Data stream with zstd in Swift on an iPhone? and here is the answer from ChatGPT 5. Very confident, very bold, even claims “Works on iOS 16+”. Problem with that: Just like any other LLM I’ve tested that provided similar responses, it is - excuse my language but I need to use it - absolute horseshit. No version of any Apple SDK ever supported or supports ZSTD (see the official docs from Apple for a real piece of knowledge). It was never there. Not even in private code. Not even as a mention of “things we might do in the future” on some developer event. It fundamentally does not exist. It’s completely made up nonsense. This concludes all the testing for GPT5 I have to do. If a tool is able to actively mislead me this easy, which potentially results in me wasting significant amounts of time in trying to make something work that is guaranteed to never work, it’s a useless tool. I don’t like collaborating with chronic liars who aren’t able to openly point out knowledge gaps, so I’m also not interested in burning resources for a LLM that does the same. Because it already happened: if you read my post and you feel an urge to respond with something along the lines of “it’s just a hallucination”, “it’s just a bug”, “it will be better in ChatGPT 6”, or anything even close into that direction, please stop. Read this post and the next post, think about them, and if you have a factual argument to respond to me, only then reply. Focus on my factual claims, not on some inaccuracies in my analo...