whats-new-haiku-5-5 changedmodels/haiku-5-5/whats-new-haiku-5-5
Nearest release: v2.1.304, published 6 hours before this site recorded the change. Shown because the two are within 24 hours of each other. Nothing here says the release caused the edit.
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First seen
8 Oct 2026
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Recorded edits4to this page, all time
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2222| [Sampling parameters can return an error](https://platform.claude.com/docs/en/models/haiku-5-5/migration-guide#remove-sampling-parameters) | Breaking | Omit `temperature`, `top_p`, and `top_k`. |
2323| [Assistant message prefill returns an error](https://platform.claude.com/docs/en/models/haiku-5-5/migration-guide#replace-assistant-prefill) | Breaking | End `messages` with a user turn. |
2424| [`computer_20250124` returns an error on the Claude API, Google Cloud, and Amazon Bedrock](https://platform.claude.com/docs/en/models/haiku-5-5/migration-guide#computer-use-toolset) | Breaking | Replace it with `computer_toolset_20260801` on the Claude API and Google Cloud, or with `computer_20251124` on Amazon Bedrock. |
25| [Structured outputs aren't available on Amazon Bedrock](https://platform.claude.com/docs/en/build-with-claude/structured-outputs) | Breaking | On Amazon Bedrock, describe the format in the prompt or use a tool without `strict`, and validate the output in your code. |
2625| [Changing earlier turns invalidates thinking blocks](https://platform.claude.com/docs/en/models/haiku-5-5/migration-guide#keep-earlier-turns-unchanged) | Breaking | Keep conversations append-only if you send thinking blocks back. |
2726| [Responses can begin with thinking blocks](https://platform.claude.com/docs/en/models/haiku-5-5/whats-new-haiku-5-5#responses-can-begin-with-thinking-blocks) | Changed | Select content blocks by `type`, not by position. |
2827| [Thinking text is omitted by default](https://platform.claude.com/docs/en/models/haiku-5-5/migration-guide#configure-thinking) | Changed | To receive summarized thinking, set `thinking.display` to `"summarized"`. |
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