09.29.2025: Day 0 support for Claude Sonnet 4.5 ⚡

Available in Phoenix 12.1+

Phoenix now offers day-0 support for Anthropic’s Claude Sonnet 4.5 model. You can try it directly in the Playground UI, run experiments through the SDK, and evaluate with it using Phoenix evals. This ensures users can seamlessly adopt the latest Claude model without delays across all workflows.

feat: support Claude Sonnet 4.5 by anticorrelator · Pull Request #9700 · Arize-ai/phoenixGitHub