# Claude API 2026-10-21 becomes the default in new major SDK releases



Anthropic



Anthropic announced Claude API version 2026-10-21 on October 22, 2026 \(Beijing time\), its first official API version since 2023. The new Messages API rejects temperature, top_p and top_k. It also returns HTTP 400 for document blocks placed directly in assistant messages and non-empty citations arrays on text blocks in user messages; supported uses such as documents nested in tool results and citations in assistant text remain valid. Some deprecated Admin and Enterprise Analytics fields have been replaced. New major releases of the Anthropic SDKs and ant CLI use the new version by default. Version 2023-06-01 is not deprecated. Update and test integrations before upgrading; on Bedrock, the new version supports only Claude 4.7 and later models.

- Review updated: Oct 22, 2026 10:49 Thu · Beijing Time (UTC+8)

## Sources

- Source excerpt: https://x.com/ClaudeDevs/status/2113013247209021918
- Source excerpt: https://x.com/ClaudeDevs/status/2113013248714744208
- Source excerpt: https://x.com/ClaudeDevs/status/2113013250136662488
- Source excerpt: https://platform.claude.com/docs/en/api/migration-2026-10-21

Canonical entry: https://www.ailyre.com/source/?id=anthropic-claude-api-version-2026-10-21&lang=en