Unexpected billing spike for Gemini API (2025-10-15 to 2025-10-18) — request logs / billing review requested

Hello, I experienced an unexpected and large billing increase for the Gemini API on [2025-10-15 to 2025-10-18].
I have already opened a case with Google Cloud Billing Support (Case #: 64081151). Billing support advised we should ask the Gemini/API team to investigate usage reports.

Summary:

  • Project ID: n8n5ch
  • Billing account ID: 018AA1-B29EB8-DBCF09
  • Date/time range of spike: 2025-10-15 → 2025-10-18
  • Observed: [Rapid increase in user fees]
  • Model(s) used (per our logs): [gemini-2.5-pro]

As we do not know how to check output Tokens per day, we checked Input Tokens per day, but it is around 126k/Day even at maximum usage, which does not explain the reason for the significant increase in the bill.

Requests:

  1. Could the Gemini/Model team please check the model-side usage logs for this project & time window and confirm whether reported usage matches our console reports (and if any anomalous spikes are visible server-side)?
  2. If this was an internal measurement/billing bug, please advise next steps for abatement/refund or a billing correction.
  3. Any quick indicators (eg. high token counts, large attachments, tool use) that we should look for?