Eventually, the context window got so bloated that they resorted to hiding function bodies in large files, which is of course a stupid idea because then the LLMs have to use other tools to read the files, wasting even more tokens, or hallucinate the content. Honestly, it is amazing that LLMs work at all in VS Code.
You can inspect the context by pressing F1 and then selecting "Developer: Show Chat Debug View" in VS Code (https://github.com/microsoft/vscode/wiki/Copilot-Issues) and marvel at all the garbage that is in there.
Make sure to regularly validate that what you think you understand is still what you actually understand. One can only safely offload so much.