migration-guide changedmodels/haiku-5-5/migration-guide
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34344. If your code reads the first content block as the answer, select blocks by `type` instead. See [Configure thinking](https://platform.claude.com/docs/en/models/haiku-5-5/migration-guide#configure-thinking).
35355. Remove `temperature`, `top_p`, and `top_k` from your requests. See [Remove sampling parameters](https://platform.claude.com/docs/en/models/haiku-5-5/migration-guide#remove-sampling-parameters).
36366. If your requests end `messages` with an assistant turn for the model to continue, end them with a user turn instead. See [Replace assistant prefill](https://platform.claude.com/docs/en/models/haiku-5-5/migration-guide#replace-assistant-prefill).
377. If you use computer use, replace `computer_20250124`: on the Claude API and Google Cloud, with the `computer_toolset_20260801` toolset; on Amazon Bedrock, with `computer_20251124` and the `computer-use-2025-11-24` beta header. See [Move computer use to the toolset](https://platform.claude.com/docs/en/models/haiku-5-5/migration-guide#computer-use-toolset).
377. If you use computer use, replace `computer_20250124`: on the Claude API and Claude Models on Google Cloud (Google managed), with the `computer_toolset_20260801` toolset; on Amazon Bedrock, with `computer_20251124` and the `computer-use-2025-11-24` beta header. See [Move computer use to the toolset](https://platform.claude.com/docs/en/models/haiku-5-5/migration-guide#computer-use-toolset).
38388. If you replay stored conversations through a different account, replay each one through the account that produced it. See [Replay thinking blocks through the account that produced them](https://platform.claude.com/docs/en/models/haiku-5-5/migration-guide#replay-thinking-blocks-through-the-producing-account).
39399. If your code changes `system`, `tools`, or earlier `messages` between requests in a conversation and sends thinking blocks back, keep the conversation append-only. See [Keep earlier turns unchanged](https://platform.claude.com/docs/en/models/haiku-5-5/migration-guide#keep-earlier-turns-unchanged).
404010. Handle `stop_reason: "refusal"`. Claude Haiku 5.5 runs safety classifiers that can decline a request, and it has no server-side fallback. See [Safeguard refusals](https://platform.claude.com/docs/en/build-with-claude/prompt-engineering/prompting-claude-haiku-5-5#safeguard-refusals).
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5555Replace the Claude Haiku 4.5 model ID with the Claude Haiku 5.5 ID for your platform.
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57| Platform | Claude Haiku 4.5 | Claude Haiku 5.5 |
58| ---------------------- | ------------------------------------------------- | ---------------------------- |
59| Claude API | `claude-haiku-4-5-20251001` or `claude-haiku-4-5` | `claude-haiku-5-5` |
60| Amazon Bedrock | `anthropic.claude-haiku-4-5` | `anthropic.claude-haiku-5-5` |
61| Claude Platform on AWS | `claude-haiku-4-5` | `claude-haiku-5-5` |
62| Google Cloud | `claude-haiku-4-5@20251001` | `claude-haiku-5-5` |
63| Microsoft Foundry | `claude-haiku-4-5` | `claude-haiku-5-5` |
57| Platform | Claude Haiku 4.5 | Claude Haiku 5.5 |
58| ---------------------------------------------- | ------------------------------------------------- | ---------------------------- |
59| Claude API | `claude-haiku-4-5-20251001` or `claude-haiku-4-5` | `claude-haiku-5-5` |
60| Amazon Bedrock | `anthropic.claude-haiku-4-5` | `anthropic.claude-haiku-5-5` |
61| Claude Platform on AWS | `claude-haiku-4-5` | `claude-haiku-5-5` |
62| Claude Models on Google Cloud (Google managed) | `claude-haiku-4-5@20251001` | `claude-haiku-5-5` |
63| Microsoft Foundry | `claude-haiku-4-5` | `claude-haiku-5-5` |
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6565`claude-haiku-5-5` is a fixed model ID with no date suffix and no separate alias.
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114114
115115Claude Haiku 5.5 accepts a forced `tool_choice` (`any` or a named tool), but the response starts with the tool call and has no `thinking` block. To let the model think before it calls a tool, use `tool_choice: {"type": "auto"}` and say in the prompt when to use the tool.
116116
117Claude Haiku 5.5 reads thinking blocks from Claude Sonnet 5, Claude Opus 4.8, Claude Haiku 4.5, and earlier models, so a conversation you switch from Claude Haiku 4.5 onto Claude Haiku 5.5 keeps its reasoning. It doesn't read blocks from Claude Opus 5, Claude Opus 5.5, Claude Sonnet 5.5, or any Claude Fable or Claude Mythos model; the API drops those without an error. On the Claude API and Google Cloud, Claude Opus 5.5 and Claude Sonnet 5.5 read Claude Haiku 5.5's blocks. See [Switching models mid-conversation](https://platform.claude.com/docs/en/build-with-claude/preserved-thinking#switching-models).
117Claude Haiku 5.5 reads thinking blocks from Claude Sonnet 5, Claude Opus 4.8, Claude Haiku 4.5, and earlier models, so a conversation you switch from Claude Haiku 4.5 onto Claude Haiku 5.5 keeps its reasoning. It doesn't read blocks from Claude Opus 5, Claude Opus 5.5, Claude Sonnet 5.5, or any Claude Fable or Claude Mythos model; the API drops those without an error. On the Claude API and Claude Models on Google Cloud (Google managed), Claude Opus 5.5 and Claude Sonnet 5.5 read Claude Haiku 5.5's blocks. See [Switching models mid-conversation](https://platform.claude.com/docs/en/build-with-claude/preserved-thinking#switching-models).
118118
119119## Remove sampling parameters
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132132## Move computer use to the toolset
133133
134Claude Haiku 4.5 supports [computer use](https://platform.claude.com/docs/en/agents-and-tools/tool-use/computer-use-tool) through the `computer_20250124` tool, with the `computer-use-2025-01-24` beta header. On the Claude API and Google Cloud, Claude Haiku 5.5 supports computer use only through the `computer_toolset_20260801` toolset, and a request that declares `computer_20250124` returns a 400 error. On Amazon Bedrock, Claude Haiku 5.5 doesn't accept `computer_20250124` either; use the `computer_20251124` tool version with the `computer-use-2025-11-24` beta header.
134Claude Haiku 4.5 supports [computer use](https://platform.claude.com/docs/en/agents-and-tools/tool-use/computer-use-tool) through the `computer_20250124` tool, with the `computer-use-2025-01-24` beta header. On the Claude API and Claude Models on Google Cloud (Google managed), Claude Haiku 5.5 supports computer use only through the `computer_toolset_20260801` toolset, and a request that declares `computer_20250124` returns a 400 error. On Amazon Bedrock, Claude Haiku 5.5 doesn't accept `computer_20250124` either; use the `computer_20251124` tool version with the `computer-use-2025-11-24` beta header.
135135
136136To move an integration to the toolset, drop the `computer-use-2025-01-24` beta header and replace the `tools` entry with `{"type": "computer_toolset_20260801"}`. Then make the other request and agent-loop changes in [Migrate from `computer_20251124`](https://platform.claude.com/docs/en/agents-and-tools/tool-use/computer-use-tool#migrate-from-computer-20251124): dispatch on each member `tool_use` block's `name` and `toolset_name` rather than on `input.action`, handle every such block in a turn, and echo `toolset_name` on results. Zoom is on by default in the toolset; if your environment doesn't implement it, add `"configs": {"zoom": {"enabled": false}}`. If you send the `fine-grained-tool-streaming-2025-05-14` beta header, remove it. Alongside a toolset entry, it returns a 400 error. For other platforms, see the computer use tool's [Compatibility](https://platform.claude.com/docs/en/agents-and-tools/tool-use/computer-use-tool#compatibility) section.
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138On the Claude API and Google Cloud, Claude Haiku 5.5 also supports the [browser use tool](https://platform.claude.com/docs/en/agents-and-tools/tool-use/browser-use-tool) (`browser_toolset_20260801`) for tasks inside webpages. Claude Haiku 4.5 doesn't support it.
138On the Claude API and Claude Models on Google Cloud (Google managed), Claude Haiku 5.5 also supports the [browser use tool](https://platform.claude.com/docs/en/agents-and-tools/tool-use/browser-use-tool) (`browser_toolset_20260801`) for tasks inside webpages. Claude Haiku 4.5 doesn't support it.
139139
140140## Replay thinking blocks through the account that produced them
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147147
148148## Migrating to Claude Haiku 5.5 from Claude Haiku 3.5 and earlier Haiku models
149149
150Claude Haiku 3.5 is retired on the Claude API and Amazon Bedrock, and Claude Haiku 3 is retired on the Claude API and Google Cloud. Requests to a retired model fail. Google Cloud lists Claude Haiku 3.5 as deprecated and available only to existing customers. See [Model deprecations](https://platform.claude.com/docs/en/about-claude/model-deprecations).
150Claude Haiku 3.5 is retired on the Claude API and Amazon Bedrock, and Claude Haiku 3 is retired on the Claude API and Claude Models on Google Cloud (Google managed). Requests to a retired model fail. Claude Models on Google Cloud (Google managed) lists Claude Haiku 3.5 as deprecated and available only to existing customers. See [Model deprecations](https://platform.claude.com/docs/en/about-claude/model-deprecations).
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152152From either model, first apply every preceding section, then these changes:
153153
154* **Model ID:** Replace `claude-3-5-haiku-20241022`, its alias `claude-3-5-haiku-latest`, or `claude-3-haiku-20240307` with `claude-haiku-5-5`. On Google Cloud, replace `claude-3-5-haiku@20241022` with `claude-haiku-5-5`. On Amazon Bedrock, use the Claude Haiku 5.5 ID from [Use the Claude Haiku 5.5 model ID](https://platform.claude.com/docs/en/models/haiku-5-5/migration-guide#use-the-claude-haiku-5-5-model-id).
154* **Model ID:** Replace `claude-3-5-haiku-20241022`, its alias `claude-3-5-haiku-latest`, or `claude-3-haiku-20240307` with `claude-haiku-5-5`. On Claude Models on Google Cloud (Google managed), replace `claude-3-5-haiku@20241022` with `claude-haiku-5-5`. On Amazon Bedrock, use the Claude Haiku 5.5 ID from [Use the Claude Haiku 5.5 model ID](https://platform.claude.com/docs/en/models/haiku-5-5/migration-guide#use-the-claude-haiku-5-5-model-id).
155155* **Code execution:** Claude Haiku 5.5 accepts `code_execution_20250825` and later versions. If you use the legacy Python-only `code_execution_20250522`, move to one of them. See [Upgrade to latest tool version](https://platform.claude.com/docs/en/agents-and-tools/tool-use/code-execution-tool#upgrade-to-latest-tool-version).
156156* **Text editor:** If you use the text editor tool, move to `text_editor_20250728` (tool name `str_replace_based_edit_tool`), which has no `undo_edit` command. See [Text editor tool](https://platform.claude.com/docs/en/agents-and-tools/tool-use/text-editor-tool).
157157* **Stop reasons:** Handle `refusal` and `model_context_window_exceeded`. See [Handling stop reasons](https://platform.claude.com/docs/en/build-with-claude/handling-stop-reasons).
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