Why did it also try Google Gemini and fail

If your model config includes Google Gemini as a fallback (or you switched to a Gemini shorthand), OpenClaw will try it during model fallback. If you haven’t configured Google credentials, you’ll see No API key found for provider "google".
Fix: either provide Google auth, or remove/avoid Google models in agents.defaults.model.fallbacks / aliases so fallback doesn’t route there.
LLM request rejected message thinking signature required google antigravity
Cause: the session history contains thinking blocks without signatures (often from an aborted/partial stream). Google Antigravity requires signatures for thinking blocks.
Fix: OpenClaw now strips unsigned thinking blocks for Google Antigravity Claude. If it still appears, start a new session or set /thinking off for that agent.