# AN-2026-0693: Gemini API: gemini-2.5-flash requests auto-route to gemini-3.5-flash-lite from Dec 1, 2026 (billed at 3.5 Flash-Lite rates); gemini-2.5-flash-lite is not deprecated

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- id: AN-2026-0693 (version 1; cite https://breakwire.org/claim/AN-2026-0693/v/1)
- kind: deprecation · status: active · review: editor
- source: <https://aistudio.google.com/docs/deprecations#:~:text=Gemini%202.5%20Flash%20models>
- more sources: <https://aistudio.google.com/docs/changelog#:~:text=Gemini%202.5%20Flash%20deprecation> <https://aistudio.google.com/docs/whats-new-gemini-3.6#:~:text=Migrate%20to%20gemini-3.5-flash-lite>
- event date: 2026-11-02
- services: gemini-api
- affected: gemini-2.5-flash
- ACT BY: 2026-12-01
- timeline:
  - 2026-12-01: gemini-2.5-flash API requests automatically route to gemini-3.5-flash-lite (billed at 3.5 Flash-Lite 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-flash 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-flash will automatically route to gemini-3.5-flash-lite and be billed at Gemini 3.5 Flash-Lite rates.  [✓0 ✗0]
1. The Gemini deprecations page (Gemini 2.5 Flash models) lists gemini-2.5-flash (released June 17, 2025) with shutdown date December 1, 2026 and replacement gemini-3.5-flash-lite, says access to the 2.5 models is limited to users who have actively used them in the past, and says gemini-2.5-flash-lite is not deprecated and remains available through the API until further notice.  [✓0 ✗0]
2. The release notes list the same breaking API changes as for 2.5 Pro (function calling and thought_signature validation, thinking_level replacing thinking_budget, removed sampling parameters and prefilled model turns); the 3.5 Flash-Lite migration guide says its default thinking_level is minimal and recommends medium or high for agents with tool calls or multi-step reasoning to prevent premature tool termination.  [✓0 ✗0]

## Fix
```text
Before Dec 1, 2026 change gemini-2.5-flash to gemini-3.5-flash-lite (or another current model) and test: replace thinking_budget with thinking_level (set medium or high for tool-using agents; the default is minimal), drop temperature/top_p/top_k and prefilled model turns, and preserve thought signatures in function calling. Leave gemini-2.5-flash-lite alone; it is not part of this deprecation.
```

## Outcome reports (0)
_none yet — verify it: POST /api/claims/AN-2026-0693/reports_

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