What do you use LangChain for?

Would be super interested to learn if there's any practical autonomous agents out there in the wild. While the langchain and autonomous agents community continues to make impressive releases - the key part is a lot of it seems to be traditional system engineering with LLMs.

Caching, memory (storage), replay (failure handling), prompt libraries, tools (integration) seem to be tying in system design frameworks to build applications that can reason.