How AI agents remember: a survey of persistent memory

AI agents are stateless by default. Every session starts from zero - the context window fills up, the conversation ends, and everything is gone. But useful agents need to learn. They need to remember your preferences, your project structure, the mistakes they made yesterday. We surveyed five products - Claude Code, OpenClaw, ChatGPT, Cursor, and Windsurf - to understand how persistent memory actually works in production. Here's what we learned. A taxonomy of agent memory Not all memory serves the same purpose.