I'm not sure you're talking about the same thing: OpenAI specifically has a "Assistants API" that manages long term memory and tool usage for the consumer: http

I'm not sure you're talking about the same thing: OpenAI specifically has a "Assistants API" that manages long term memory and tool usage for the consumer: https://platform.openai.com/assistants https://platform.openai.com/assistants I'd guestimate 99% of people using LLMs are using instruct-based message interfaces that have a variation of system/user/assistant. The top models mostly only come as a completion models, and even Anthropic has switched to a message based API