Anthropic releases Claude API version 2026-10-21
Anthropic releases Claude API version 2026-10-21, the first official version release since 2023; the 2023-06-01 version is not deprecated. This version removes temperature, top_p, and top_k from the Messages API, returns 400 for documents in assistant turns and citations in user turns, and replaces several deprecated Admin and Enterprise Analytics API fields. New major versions of the Anthropic SDK and the ant CLI are released the same day and default to 2026-10-21; you can update using the /claude-api skill in Claude Code, or adjust item by item according to the migration guide.
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The official announcement lists the specific breaking changes in this API version so developers can plan their migrations in advance.
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What changes in this version: - temperature, top_p, and top_k are removed from the Messages API - documents in assistant turns and citations in user turns return a 400 - a few deprecated Admin and Enterprise Analytics API fields are replaced