Anthropic releases Claude API version 2026-10-21
Anthropic releases Claude API version 2026-10-21, the first formal version release since 2023; version 2023-06-01 is not deprecated. This version removes temperature, top_p, and top_k from the Messages API; documents in assistant turns and citations in user turns will return 400; and some deprecated Admin and Enterprise Analytics API fields are replaced. New major versions of the Anthropic SDK and ant CLI are released the same day and use 2026-10-21 by default. You can update using the /claude-api skill in Claude Code, or handle items one by one according to the migration guide.
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The official release lists the version change log and migration entry points, so developers can handle breaking changes in advance.
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API version 2026-10-21 is now available.
The Claude API has evolved a lot, but this is our first official version release since 2023. We plan to release versions more often so you can handle breaking changes before a new model requires them.
2023-06-01 is not deprecated.