> ## 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.

> ## Agent Instructions
> Phaseo Gateway base URL: https://api.phaseo.app/v1. Send `Authorization: Bearer $PHASEO_API_KEY` with every request.
> Model IDs look like `provider/model`, for example `openai/gpt-6-astra`. Do not guess IDs: list them with `GET /v1/models` or check https://phaseo.app/models. `phaseo/free` routes to an available free model and needs no wallet balance.
> For new text integrations prefer `POST /v1/responses`. `POST /v1/chat/completions` (OpenAI format) and `POST /v1/messages` (Anthropic format) suit existing code.
> The full API contract is https://phaseo.app/docs/openapi/v1/openapi.yaml. Official SDKs: `@phaseo/sdk` (TypeScript) and `phaseo` (Python), plus Go, C#, PHP, Ruby and Rust.
> Search these docs over MCP at https://phaseo.app/docs/mcp, and install Phaseo skills with `npx skills add https://phaseo.app/docs`. If a page is wrong or out of date, report it with the MCP `submit_feedback` tool.
> Manage Phaseo accounts with the `phaseo` CLI (`npm install -g @phaseo/cli`, then `phaseo login` or `phaseo login --device-code`), the `/v1` Management API or the MCP server at `https://mcp.phaseo.app/mcp?access=manage`. Do not send users to the dashboard for account tasks. A person is still needed for sign-up, approving a sign-in, paying the first top-up on the checkout link that `phaseo credits add` returns when no card is saved, confirming each saved-card top-up from the emailed link, and account security (password, MFA, passkeys). Create API keys with `phaseo keys create --name <name> --json`; never guess one. Credit top-ups need `phaseo login --scopes billing:write` first. Task map: https://phaseo.app/docs/v1/developers/manage-from-an-agent.md.

# Model Migrations

> Model-specific guidance for adopting new model releases safely in production.

# 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

## Model guides

Guides are ordered by the target model's release date, with the newest first.

| Model | Released | Useful for |
| - | - | - |
| [Anthropic Claude Opus 5](https://phaseo.app/docs/v1/model-migrations/anthropic-claude-opus-5.md) | July 24, 2026 | Complex reasoning and long-horizon agents |
| [OpenAI GPT-5.6](https://phaseo.app/docs/v1/model-migrations/openai-migrating-to-gpt-5-6.md) | July 9, 2026 | Tiered reasoning, coding, and professional work |
| [Anthropic Claude Opus 4.8](https://phaseo.app/docs/v1/model-migrations/anthropic-claude-opus-4-1-to-4-8.md) | May 28, 2026 | Long context and adaptive thinking |
| [Anthropic Claude Opus 4.7](https://phaseo.app/docs/v1/model-migrations/anthropic-claude-opus-4-6-to-4-7.md) | April 16, 2026 | High-effort reasoning with stricter request controls |
| [Mistral Small 4](https://phaseo.app/docs/v1/model-migrations/mistral-small-3-2-to-mistral-small-4.md) | March 16, 2026 | Efficient workloads with optional reasoning |
| [OpenAI GPT-5.4](https://phaseo.app/docs/v1/model-migrations/openai-migrating-to-gpt-5-4.md) | March 5, 2026 | Reasoning, vision, and computer use |
| [Google Nano Banana 2](https://phaseo.app/docs/v1/model-migrations/google-nano-banana-1-to-nano-banana-2.md) | February 26, 2026 | Production image generation and editing |
| [Google Gemini 3.1](https://phaseo.app/docs/v1/model-migrations/google-migrating-to-gemini-3-and-3-1.md) | February 19, 2026 | Multimodal and reasoning-heavy workloads |
| [Anthropic Claude Sonnet 4.6](https://phaseo.app/docs/v1/model-migrations/anthropic-claude-sonnet-4-5-to-4-6.md) | February 17, 2026 | Coding, computer use, and agent planning |
| [SpaceXAI Grok 4.20](https://phaseo.app/docs/v1/model-migrations/xai-grok-4-20.md) | February 17, 2026 | Reasoning and multi-agent workloads |
| [Anthropic Claude Opus 4.6](https://phaseo.app/docs/v1/model-migrations/anthropic-claude-opus-4-5-to-4-6.md) | February 5, 2026 | Long-running coding and agentic tasks |

## 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](https://phaseo.app/docs/v1/migration-guides/index.md) section instead.


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