Here's a standalone product which is a chatbot with a memory. But look at LangChain for several ways to implement the same thing.

The basic idea is: periodically feed your conversation history to the embeddings API and save the embeddings to a local vectorstore, which is the "long-term memory". Then, any time you send a message or question to the bot, first send that message to embeddings API (super cheap and fast), run a local comparison, and prepend any relevant contextual info ("memories") to your prompt as it gets sent to the bot.