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HomeDocsClaude Developer Platform 28 Oct 2026
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migration-guide changedmodels/opus-5-5/migration-guide

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279279* Remove `thinking: {"type": "disabled"}` and `thinking: {"type": "enabled", ...}`; choose an effort level instead.
280280* Set `effort` explicitly: the default is `medium`, where Claude Opus 5’s is `high`.
281281* Replace `tool_choice` types `any` and `tool` with `auto` plus strict tool use or structured outputs.
282* If you use computer use on the Claude API or Claude Models on Google Cloud (Google managed), declare `computer_toolset_20260801` (no beta header) instead of `computer_20251124` and update your agent loop for the toolset. On Amazon Bedrock, keep `computer_20251124`; check the computer use tool’s [Compatibility](https://platform.claude.com/docs/en/agents-and-tools/tool-use/computer-use-tool#compatibility) section for other platforms.
282* If you use computer use on the Claude API or Claude Models on Google Cloud (Google managed), declare `computer_toolset_20260801` (no beta header) instead of `computer_20251124` and update your agent loop for the toolset. On Amazon Bedrock, keep `computer_20251124`; check the computer use tool’s [API support](https://platform.claude.com/docs/en/agents-and-tools/tool-use/computer-use-tool#availability-feature-support) section for other platforms.
283283* If a router or fallback can move a conversation from Claude Opus 5.5 to another model, expect that model to run without Claude Opus 5.5’s thinking blocks (Claude Fable 5.1 and Claude Mythos 5.1 on the Claude API are the exception and keep them). Claude Opus 5.5 itself reads thinking from Claude Opus 5, from earlier Opus, Sonnet, and Haiku models, and, on the Claude API and Claude Models on Google Cloud (Google managed), from Claude Sonnet 5.5 and Claude Haiku 5.5, but not from Claude Fable or Claude Mythos models.
284284* Read content blocks by `type`, and pass `thinking` blocks back unmodified in tool-use loops.
285285* If your interface renders text between tool calls, set `display: "updates"` (beta) or `"summarized"` and render the non-empty `thinking` blocks.
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881881#### The `computer_20251124` computer use tool is not supported on the Claude API and Claude Models on Google Cloud (Google managed)
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883On the Claude API and Claude Models on Google Cloud (Google managed), a `tools` entry of type `computer_20251124` returns a 400 error (`'claude-opus-5-5' does not support tool types: computer_20251124.`, followed by the tool types the model accepts). Declare the `computer_toolset_20260801` toolset instead: drop the beta header and send the entry with no `name` or display dimensions. In your agent loop, handle member `tool_use` blocks (the action is the block’s `name`, not `input.action`), several of them per turn, and echo `toolset_name` on every result. The request change is shown below; the agent-loop changes are listed in [Migrate from `computer_20251124`](https://platform.claude.com/docs/en/agents-and-tools/tool-use/computer-use-tool#migrate-from-computer-20251124). On Amazon Bedrock, the earlier `computer_20251124` tool continues to work on Claude Opus 5.5 as it does on Claude Opus 5, so no change is needed there; 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. See [The `computer_20251124` computer use tool is not supported on the Claude API and Claude Models on Google Cloud (Google managed)](https://platform.claude.com/docs/en/models/opus-5-5/whats-new-opus-5-5#computer-20251124-is-not-supported).
883On the Claude API and Claude Models on Google Cloud (Google managed), a `tools` entry of type `computer_20251124` returns a 400 error (`'claude-opus-5-5' does not support tool types: computer_20251124.`, followed by the tool types the model accepts). Declare the `computer_toolset_20260801` toolset instead: drop the beta header and send the entry with no `name` or display dimensions. In your agent loop, handle member `tool_use` blocks (the action is the block’s `name`, not `input.action`), several of them per turn, and echo `toolset_name` on every result. The request change is shown below; the agent-loop changes are listed in [Migrate from `computer_20251124`](https://platform.claude.com/docs/en/agents-and-tools/tool-use/computer-use-tool#migrate-from-computer-20251124). On Amazon Bedrock, the earlier `computer_20251124` tool continues to work on Claude Opus 5.5 as it does on Claude Opus 5, so no change is needed there; for other platforms, see the computer use tool’s [API support](https://platform.claude.com/docs/en/agents-and-tools/tool-use/computer-use-tool#availability-feature-support) section. See [The `computer_20251124` computer use tool is not supported on the Claude API and Claude Models on Google Cloud (Google managed)](https://platform.claude.com/docs/en/models/opus-5-5/whats-new-opus-5-5#computer-20251124-is-not-supported).
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885885Before. Claude Opus 5 accepts this request, and on the Claude API and Claude Models on Google Cloud (Google managed), Claude Opus 5.5 rejects it with a 400 error:
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