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

Gemini API
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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?
2 Likes
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Thank you for bringing this to our attention ,we really appreciate you flagging this issue and providing such detailed information.We’ll go ahead and file an issue internally to have this reviewed.Since you’ve already opened a Billing Support case (Case #64081151), please continue working through that channel as well.
If the billed usage matches the server-side logs and if there were any anomalies detected and specifically, can you help us understand the breakdown between input and output tokens and identify any requests that resulted in unusually high token counts?