Upgrading the Anthropic SDK Now Changes Your API Version, Your Auth Header, and Whether temperature Works

Sat, 24 Oct 2026 08:30:00 +0530

If your Anthropic integration goes through an official SDK, you have never had to think about the anthropic-version header. The SDK sent it for you. That convenience is now the risk: the migration guide for API version 2026-10-21 says an SDK uses the API version that was current when its major version was released, and the new majors (Python 2.0.0, TypeScript 1.0.0, Go 2.0.0, Java 3.0.0, Ruby 2.0.0, PHP 1.0.0, C# 13.0.0, ant CLI 2.0.0) all send 2026-10-21. A dependency bump is therefore also a server-side contract change, and the two failures that matter most look very different: one is a loud 400, the other is a header that your own infrastructure silently stops seeing.

Sdk on Kuldeep Pisda

Upgrading the Anthropic SDK Now Changes Your API Version, Your Auth Header, and Whether temperature Works