> ## Documentation Index
> Fetch the complete documentation index at: https://phaseo.app/docs/llms.txt
> Use this file to discover all available pages before exploring further.

# Model Migrations

> Model-specific upgrade guides for moving production traffic from an older model release to a newer one.

# Model Migrations

Use these guides when you are staying on the same platform but upgrading the model itself.

These pages focus on the changes that usually break real integrations first:

* request parameter changes
* prompt and reasoning behavior shifts
* structured output and tool-calling regressions
* rollout, fallback, and rollback strategy

## Available guides

* [Anthropic: Claude Opus 4.1 to 4.8](./anthropic-claude-opus-4-1-to-4-8)
* [Anthropic: Claude Opus 4.6 to 4.7](./anthropic-claude-opus-4-6-to-4-7)
* [Anthropic: Claude Opus 4.5 to 4.6](./anthropic-claude-opus-4-5-to-4-6)
* [Anthropic: Claude Sonnet 4.5 to 4.6](./anthropic-claude-sonnet-4-5-to-4-6)
* [OpenAI: Migrating to GPT-5.6](./openai-migrating-to-gpt-5-6)
* [OpenAI: Migrating to GPT-5.4](./openai-migrating-to-gpt-5-4)
* [Google: Migrating to Gemini 3 and 3.1](./google-migrating-to-gemini-3-and-3-1)
* [Google: Nano Banana 1 to Nano Banana 2](./google-nano-banana-1-to-nano-banana-2)
* [Mistral: Mistral Small 3.2 to Mistral Small 4](./mistral-small-3-2-to-mistral-small-4)
* [SpaceXAI: Grok 4.20](./xai-grok-4-20)

## Release timeline

| Guide                                                                                   | Model release date                                             |
| --------------------------------------------------------------------------------------- | -------------------------------------------------------------- |
| [Anthropic: Claude Opus 4.1 to 4.8](./anthropic-claude-opus-4-1-to-4-8)                 | May 28, 2026                                                   |
| [Anthropic: Claude Opus 4.6 to 4.7](./anthropic-claude-opus-4-6-to-4-7)                 | April 16, 2026                                                 |
| [Anthropic: Claude Opus 4.5 to 4.6](./anthropic-claude-opus-4-5-to-4-6)                 | February 5, 2026                                               |
| [Anthropic: Claude Sonnet 4.5 to 4.6](./anthropic-claude-sonnet-4-5-to-4-6)             | February 17, 2026                                              |
| [OpenAI: Migrating to GPT-5.6](./openai-migrating-to-gpt-5-6)                           | Current OpenAI GPT family                                      |
| [OpenAI: Migrating to GPT-5.4](./openai-migrating-to-gpt-5-4)                           | March 5, 2026                                                  |
| [Google: Migrating to Gemini 3 and 3.1](./google-migrating-to-gemini-3-and-3-1)         | Gemini 3: November 25, 2025; Gemini 3.1 Pro: February 19, 2026 |
| [Google: Nano Banana 1 to Nano Banana 2](./google-nano-banana-1-to-nano-banana-2)       | February 26, 2026                                              |
| [Mistral: Mistral Small 3.2 to Mistral Small 4](./mistral-small-3-2-to-mistral-small-4) | March 16, 2026                                                 |
| [SpaceXAI: Grok 4.20](./xai-grok-4-20)                                                  | February 17, 2026                                              |

## How to use this section

1. Start with the guide for the exact model family you are upgrading.
2. Update the request shape before testing output quality.
3. Re-run prompt and schema evaluations on production-like prompts.
4. Shift traffic gradually with explicit fallback and rollback rules.

If you are changing providers, SDKs, or gateways rather than just the model, use the [Migration Guides](../migration-guides/index) section instead.