Trying to one-shot large codebases is a exercise in futility. You need to let Claude figure out and document the architecture first, then setup agents for each major part of the project. Doing this keeps the context clean for the main agent, since it doesn't have to go read the code each time. So one agent can fill it's entire context understanding part of the code and then the main agent asks it how to do something and gets a shorter response.

It takes more work than one-shot, but not a lot, and it pays dividends.

Is there a guide for doing that successfully somewhere? I would love to play with this on a large codebase. I would also love to not reinvent the wheel on getting Claude working effectively on a large code base. I don’t even know where to start with, e.g., setting up agents for each part.