What are the types of AI agent memory?

The 4 Types of AI Memory — Chain of Thought

An AI agent needs four kinds of memory, mapped to how the human brain works: working memory for what it is holding right now, semantic memory for the facts it knows, episodic memory for things that happened, and procedural memory for how to do a task. Most AI today runs on only the first one.

1. Working memory: what it is holding right now

The active context window. The scratch pad. Small, temporary, whatever is on the desk this moment. It is what almost every chatbot today relies on, and it is why your AI forgets you the second the chat ends.

2. Semantic memory: the facts it knows

Reference knowledge it can reuse: your policies, your docs, the decontextualized facts that do not change much. The textbook on the shelf. This is the institutional knowledge an agent pulls from again and again.

3. Episodic memory: what happened

Time-stamped interactions. Past conversations, tied to when they occurred. The diary. This is what lets an agent say “last week you decided X” instead of starting every session from zero.

4. Procedural memory: how to do the task

Skills and routines. The standard operating procedures it runs without re-reasoning every time. Muscle memory. The how-to layer that turns a one-off into a repeatable workflow.

Don’t delete — forget

When a memory gets old, you do not erase it. Richmond Alake’s rule is to let it fade by how recent, relevant, and important it is, the same way human memory decays. Hard-deleting loses the audit trail, which is a problem in any regulated industry. So the system forgets gracefully instead of deleting outright.

Why it matters

The teams winning with agents are not using a smarter model. They are giving it all four kinds of memory, kept in separate lanes. You cannot train a frontier model on your own, but a single developer can build a memory system that remembers better than ChatGPT. Memory is the one layer where individual effort still beats the big labs.