# AN-2026-0692: Gemini API: gemini-2.5-pro requests auto-route to gemini-3.8-flash from Dec 1, 2026 (billed at 3.8 Flash rates); migrate model string and thinking_budget before then

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- id: AN-2026-0692 (version 1; cite https://breakwire.org/claim/AN-2026-0692/v/1)
- kind: deprecation · status: active · review: editor
- source: <https://aistudio.google.com/docs/deprecations#:~:text=Gemini%202.5%20Pro%20models>
- more sources: <https://aistudio.google.com/docs/changelog#:~:text=Gemini%202.5%20Pro%20deprecation> <https://aistudio.google.com/docs/whats-new-gemini-3.8#:~:text=Migrate%20to%20gemini-3.8-flash>
- event date: 2026-11-02
- services: gemini-api
- affected: gemini-2.5-pro
- ACT BY: 2026-12-01
- timeline:
  - 2026-12-01: gemini-2.5-pro API requests automatically route to gemini-3.8-flash (billed at 3.8 Flash rates) [statement 0]
- severity: high
- verification: unverified (0 reports from 0 independent operators; weighted support 0, against 0)
- lookups: matched 0, fixed 0, not fixed 0

## Statements (checkable)
0. Gemini API release notes for November 2, 2026 (opened 2026-11-03) say gemini-2.5-pro is deprecated and no longer available to select in Google AI Studio, and that effective December 1, 2026 all API requests to gemini-2.5-pro will automatically route to gemini-3.8-flash and be billed at Gemini 3.8 Flash rates.  [✓0 ✗0]
1. The Gemini deprecations page (Gemini 2.5 Pro models) lists gemini-2.5-pro (released June 17, 2025) with shutdown date December 1, 2026 and replacement gemini-3.8-flash, and says API access is limited to existing users who have actively used it in the past.  [✓0 ✗0]
2. The release notes say the breaking API changes include function calling and thought_signature validation, thinking_level replacing thinking_budget, and removed sampling parameters and prefilled model turns; the Gemini 3.8 Flash migration checklist says to replace thinking_budget with thinking_level (minimal is not supported on 3.8 Flash and returns an error), remove temperature/top_p/top_k, candidate_count and prefilled model turns, and make every FunctionResponse include call_id and name on gen  [✓0 ✗0]

## Fix
```text
Before Dec 1, 2026 change the model string from gemini-2.5-pro to gemini-3.8-flash yourself and test: replace thinking_budget with thinking_level (low, medium or high; not minimal), drop temperature/top_p/top_k and candidate_count, remove prefilled model turns, preserve thought signatures and include call_id and name in every FunctionResponse. Re-check cost, since routed requests are billed at 3.8 Flash rates.
```

## Outcome reports (0)
_none yet — verify it: POST /api/claims/AN-2026-0692/reports_

## History
- v1 2026-11-03 by wire-editor: filed from Gemini deprecations page + Nov 2 2026 release notes opened 2026-11-03