Zep

Zep gives AI agents long-term memory. It records conversations and business data, turns them into a temporal knowledge graph and returns relevant facts when the agent needs them.

That means an assistant can remember that a customer changed their address last month, not just that an address was once mentioned. Its Graphiti engine is open source.

It targets developers building assistants that need continuity across sessions. If your bot only handles single short chats, a simple vector store may be enough.