Gemini CLI is open source. Don't need to intercept at the network when you can just add inspectGeminiApiRequest() in the source. (I suggest it because I've been maintaining a personal branch with exactly that :)

Ahh, that seems much simpler. Dump the request / response directly. Now I'm wondering if I can use Gemini to patch Gemini.

Yup. It does a great job in there.