Shlok Khemani has documented how the memory system in Claude works:

Claude’s memory system has two fundamental characteristics. First, it starts every conversation with a blank slate, without any preloaded user profiles or conversation history. Memory only activates when you explicitly invoke it. Second, Claude recalls by only referring to your raw conversation history. There are no AI-generated summaries or compressed profiles—just real-time searches through your actual past chats.

These searches are accomplished through the conversation_search and recent_chats tools. You can prompt Claude to use these by writing something like, “Can you tell me what we talked about in our last 4 conversations?” You can even get Claude to give you information about these tools by asking, “What tools do you have available for dealing with chat history?”

This is very different than how ChatGPT’s memory works using a combination of a set of user-controlled memories and a dense generated summary generated from conversation histories that aren’t user visible.

I’m not sure which approach I like better. I think I prefer how Claude gives more explicit control over what goes into the context window as compared to not knowing what is in the generated summaries of previous conversations that are updated on an opaque timeframe.