stream

Sends request to the Chat Completions API with stream set, and returns the model's answer as it arrives: the text piece by piece, then the whole answer. The whole answer is the one chat returns for the same request, with its tool calls and usage.

The request asks for the usage with stream_options. A server that does not know the field ignores it, and the answer then has no usage.

The flow fails with a ChatModelException when the API cannot be reached, when it returns an error, when the connection ends before the answer does, and when the model declines the request.