System is simply a role name. It can take place anywhere in a list of messages.
Developer is a new message purpose that fits in with “instruction hiearchy” AI architecture, made blander for you as “chain-of-command” in newest documentation. Specifically for o1 model.
Developer messages are the new system messages: Starting with
o1-2024-12-17, o1 models supportdevelopermessages rather thansystemmessages, to align with the chain of command behavior described in the model spec. Learn more.
Basically: you have less rights and less control of AI generation, vs OpenAI’s own “platform”, and “system” message is deprecated on existing models to train you to sacrifice ultimate control.