whats-new-sonnet-5 changedmodels/sonnet-5/whats-new-sonnet-5
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1891892. **Extended thinking:** if you still set `budget_tokens`, migrate to [adaptive thinking](https://platform.claude.com/docs/en/build-with-claude/thinking). Manual extended thinking (`thinking: {type: "enabled"}`) is not supported and returns a 400 error.
1901903. **Sampling parameters:** requests that set sampling parameters (`temperature`, `top_p`, `top_k`) to a non-default value return a 400 error; remove them when migrating. Tool definitions and response shapes are unchanged, and assistant message prefilling was already unsupported on Claude Sonnet 4.6.
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192See the [Claude Sonnet 5 section of the migration guide](https://platform.claude.com/docs/en/about-claude/models/migration-guide#migrating-from-claude-sonnet-4-6-to-claude-sonnet-5) for details.
192See [Migrating to Claude Sonnet 5 from Claude Sonnet 4.6](https://platform.claude.com/docs/en/models/sonnet-5/migration-guide#migrating-from-claude-sonnet-4-6-to-claude-sonnet-5) for details.
193193
194194## Next steps
195195
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