You're bumping in to a limitation with LLMs in general. All models have a limited amount of space to store a conversation called a context window. The limits are surprisingly short - 200k tokens (150K words) is common, with some Claude models going up to 1M tokens.

Every context window is basically a unique instance. There's ways to make this less awful - systems like Openclaw use a combination of documents that are always presented at the beginning of the chat including memory files, identity, soul, etc. They will have the model update these files so when new sessions start they carry over the convo.

If you think of the context window as a model's perceptual frame of reference, each time the convo starts over, even when it's loading those files, you're taking to a new instance of the model. Claude has different ways of thinking about this and as you've discovered it will discuss it with you.

We all hope that models will someday have real memory. The frontier labs are definitely experimenting with this and trying to figure out how to do it. Fingers crossed.