Migrating from Gemini 2.5 Pro, Flash and Flash-Lite (Vertex AI) to Gemini 3.8 Flash

What shuts down

• gemini-2.5-pro and its dated snapshots
• gemini-2.5-flash and its dated snapshots
• gemini-2.5-flash-lite and its dated snapshots

Vertex AI lists 2026-10-20 as the retirement date and says it may be extended but not moved earlier; as of 2026-10-30 the models were still available.

Source: docs.cloud.google.com. Check your provider’s deprecations page before you plan around a date.

Find every place you use it

The free scanner flags every reference in your repository and opens one issue with the deadline:

npx swapvera-scan .

Or on every push, as a GitHub Action:

- uses: pixelric-spec/swapvera-scanner@v1
  with:
    fail-on: retired

What can change when you swap the ID

Prompts tuned for one model rarely transfer perfectly to the next. Check these before you merge:

• Structured output: JSON that stays valid and keeps the same field types.
• Tool calls: the same tools called with the same arguments, and no calls where there were none.
• Instructions in your system prompt that the new model follows differently, such as length limits or policies it must quote.
• Refusals and safety behavior on your edge cases.
• Parameters the new model rejects, such as a fixed temperature on reasoning models.
• Latency and cost per call at your real input sizes.

What broke for other teams

Check the switch on your own prompts

Swapvera runs your cases on Gemini 2.5 Pro, Flash and Flash-Lite (Vertex AI) and Gemini 3.8 Flash and comments a verdict on the pull request: safe to migrate, review these cases, or do not migrate.