Large language models like GPT work by generating the probabilities for the next word in a sequence, given the previous words. You can make this purely determi

Large language models like GPT work by generating the probabilities for the next word in a sequence, given the previous words. You can make this purely deterministic (same sequence every time) by just selecting the word with the highest probability repeatedly. Most models will inject some randomness by sampling from the probabilities, to make the generated text more realistic. I don't know what parameters they use for ChatGPT, but they are likely injecting some randomness. It's also likely that they are continuously training ChatGPT with reinforcement learning, so responses may change over time due to this, also.