You could try my project Plandex (https://github.com/plandex-ai/plandex) — you can use it to explore/understand/chat with just about any codebase, including massive ones up to 20M tokens.

Here's an example, chatting with the SQLite codebase to understand how transactions are implemented: https://plandex.ai/_next/static/media/plandex-sqlite.0ee6cb2...