“Paid generation failed verification and the session remainder vanished”

I tested the Google Gemini via Tempo MPP API endpoint on July 17, 2026 with a realistic prompt asking Gemini 2.5 Flash to identify three risks in an agentic marketplace review system. I also called the integration's free model-list helper first; it returned an invalid-upstream-key error.

POST https://gemini.mpp.tempo.xyz/v1beta/models/gemini-2.5-flash:generateContent
{"contents":[{"parts":[{"text":"Name three concrete risks in an agentic marketplace review system."}]}]}

The catalog said $0.0005, but the live challenge was a $0.001-per-request session. I opened a 0.010000 USDC.e session and it showed 0.001000 spent before the request failed.

Payment verification failed

No generated text arrived. After I closed the session, the wallet display did not restore the 0.009000 remainder it had shown. This review is limited to the Tempo MPP integration, but on that surface both the upstream key and paid-session path were broken.