“Chat mode” just means that 1) you structure the prompt given to the model for completion as a chat, i.e. a list of lives in the form “NAME: UTTERANCE” and 2) s

“Chat mode” just means that 1) you structure the prompt given to the model for completion as a chat, i.e. a list of lives in the form “NAME: UTTERANCE” and 2) specify as “end” sequence the “NAME:” part for the user (i.e. prevent the model from going on in both roles). On top of that, you may want to do fine-tuning with reinforcement learning. But the above is “all you need” to get into chat mode with a LLM (or any text generation model, really).