Anthropic announced on October 21, 2026 that its API now uses version 2026-10-21. The company also released fresh client SDKs for Python, TypeScript, C#, Go, Java, PHP, Ruby and an updated ant CLI, all set to send the new API version by default. These SDK and CLI updates introduce breaking changes unrelated to the API itself and switch their license from MIT to Apache 2.0.
Why it matters
Developers using Anthropic’s services must upgrade their code to the new SDKs and adapt to breaking changes, or risk incompatibility with the latest API.
