The default state of every AI agent is forgetting. A language model has no memory of its own: it reasons only over the tokens in its context window, and the instant that window fills or the chat ends, everything it "knew" is gone. It did not learn — it was briefly told, and then reset.
You rarely log this as a bug, because the model still sounds fluent and helpful in the moment. So the missing piece stays invisible: instead of noticing the amnesia, you quietly work around it — pasting the same context back in, re-stating the same rules, re-answering the same questions, session after session.
But the cost compounds. Every minute spent re-establishing what the agent already figured out yesterday is a minute not spent on the actual work — and the agent never gets better at your project, only repeatedly re-introduced to it. Long-term memory is the piece that turns those repeated introductions into accumulated knowledge.