Claude API ships version 2026-10-21, its first bump since 2023, and drops temperature, top_p, and top_k
Released Oct 21, requests on the new anthropic-version return a 400 if they send temperature, top_p, or top_k, put document blocks in assistant messages, or attach citations to user text blocks; 2023-06-01 keeps working if you need the old behavior. New SDKs (Python 2.0.0, TypeScript 1.0.0, Go 2.0.0 and others, now Apache 2.0) send it by default (release notes).
