Why it matters

Memory is how an agent gets better at your project specifically without anyone retraining the model. It is the difference between an agent that re-learns your test command every session and one that just knows it. It is also where reliability comes from: an anti-hallucination constraint written into shared rules ("never invent API names; grep the codebase first") applies to every session forever. And because it is all plain files in the repo, it is portable, reviewable, and version-controlled, which is exactly what you want for something that shapes how an agent behaves on your code.