Claude API drops temperature in its first official version in three years, and the SDKs switch licenses

Anthropic released Claude API version 2026-10-21 and removed the temperature, top_p and top_k parameters that controlled how random responses are.

Per Anthropic's developer docs, a request that sends any of the three now returns a 400 error on every model. Putting a document block in an assistant message, or citations in a user message, also errors. The ClaudeDevs account called it "our first official version release since 2023" and said versions will ship more often. The 2023-06-01 version is not deprecated.

New SDKs default to the new version, including Python SDK 2.0.0 and TypeScript SDK 1.0.0, and they move from the MIT License to Apache 2.0. In Claude Code, the /claude-api skill can update your code.

Subscribers have a more urgent deadline. Lydia Hallie of Anthropic's Claude Code team reminded users that last month's free limit reset expires Oct 22 at 9 a.m. PT. "we already need another one" drew 106 likes. A post saying the separate Fable limit has been folded into the weekly limit also drew 558 likes.