Anthropic: Original Claude Sonnet 4 and Opus 4 Models Retired — Migration to Sonnet 4.6 and Opus 4.8
Anthropic has retired the original Claude Sonnet 4 and Claude Opus 4 models from production. All API requests to the identifiers claude-sonnet-4-20250514 and claude-opus-4-20250514 now return an error. Development teams need to migrate to Claude Sonnet 4.6 and Claude Opus 4.8, while researchers can request access through the External Researcher Access Program.