I'm very confused here. The monthly plans are meant to be used inside of Google's walled garden, but people are somehow able to capture (?) and re-use the oAuth token?

Regardless, I thought it was pretty obvious that things like OpenClaw require an API account, and not a subsidized monthly plan.

Exactly, OpenClaw (or I think possibly an addon/extension or unofficial method) is allowing Googles Antigravity authentication to connect the app. This allows for 'unlimited' calls through Antigravity models with a subscription, instead of the proper Gemini/Google AI Studio API key method (charged per million tokens)

API usage can get very high for automatic operations, especially with apps like Kilo/Roo/Cline, and now with OpenCode/OpenClaw. I often blast through $10-20 in a single day of just regular OpenCode usage through OpenRouter

If I could pay a subscription and get near unlimited use (with rate limits), of course I'd do that, but not like this. I'm pretty sure Antigravity has ToU somewhere that indicates it's only allowed for use in Antigravity and nowhere else, since I've seen other threads on this happening: https://github.com/jenslys/opencode-gemini-auth/issues/50

Sure. But a zero strike getting kicked out of your Google account is a grotesque evil.

Edit: maybe it's not the whole account? https://news.ycombinator.com/item?id=47116330

No - use OpenAI, no problem. OpenAI wins here big time.