Context window + project size + Aider?

Forgive the naivety of this post, I'm a noob, bear with me! If a project, understood as a set of files, is larger than the context window of a model, how do you fit it in? After doing some naive research, various major LLMs like Deepseek, Kimi, and company say the solution is Aider, which creates a sort of "map" of the project and tells the agent which portion should be used at that moment. But this sort of "map" isn't a permanent memory but something temporary. Is this really the case, or are these just collective hallucinations of major LLMs? Searching here on Reddit, very few people talk about Aider, and those few speak badly of it. I'm trying Aider and I'm finding it very inconvenient, but I'm just starting out. What are the alternatives, if any? Or is this problem currently unsolvable? That is, in reality, an agent can't act on a project if it's larger than its context window? Thank you all for your attention.