Codex VS Code Extension: Context Limit Automatically Dropping?

I was coding just now and noticed something strange with the Codex extension in VS Code.
At first, the context usage bar showed 75%.
But after a few more interactions, it suddenly dropped to 25% — and now it’s around 35% after more chatting. 😅

I’m not sure why it reduces the context usage on its own.
Has anyone else run into this? Is this normal behavior? 🤷‍♂️

I asked GPT, and it said the drop was probably just a UI glitch, not an actual context cleanup. 🐞