Anthropic added features like this into 4.5 release:

https://claude.com/blog/context-management

> Context editing automatically clears stale tool calls and results from within the context window when approaching token limits.

> The memory tool enables Claude to store and consult information outside the context window through a file-based system.

But it looks like nobody has it as a part of an inference loop yet: I guess it's hard to train (i.e. you need a training set which is a good match for what people use context in practice) and make inference more complicated. I guess more high-level context management is just easier to implement - and it's one of things which "GPT wrapper" companies can do, so why bother?