The Dartmouth Summer Research Project on Artificial Intelligence was in 1956, before I was born. AI itself is even older than that (e.g. William Grey Walter's robots, Elmer and Elsie in 1948), but it was called cybernetics back then. I've been doing symbolic AI, on and off, since the 1980s.

I assume, though, you mean LLMs. I haven't used them first hand, but I have fairly recently implemented a multi-layer artificial neural network in C, mostly as a learning exercise, but as I had previously built a speech spectrogram in Lisp, I thought I'd try to use it to recognize phonemes, with one hidden layer. The Lisp communicated with the ANN via a Unix pipe. It worked reasonably well for just vowels, but when I added other sounds (e.g. l, r, s, z), its performance deteriorated. I think the C is bug free, but I don't know an easy way to train the ANN. I've tried adding to the training set, adding an extra layer, changing the number of neurons in the hidden layer. The usual debugging skills don't seem to help there.