APIs accepting history inputs, including Chat.from_history, currently require multi-message histories to be formatted as full chat histories (Chat instances, or dictionaries with a messages key).
These APIs should also accept iterables of messages directly, treating those iterables as if they were the messages list in a full chat history.
Both input dictionaries and input messages should be annotated as accepting the shorthand form of simple text user messages, assistant responses, and system prompts (where the content field is simply the text of the message rather than a dict with type and text keys).