Claude Sonnet 4.5 will retire from the API on November 30
Anthropic announced the deprecation of Claude Sonnet 4.5 on September 30, 2026. Retirement on the Claude API is scheduled for November 30, 2026, and Anthropic recommends migrating to Claude Sonnet 5.5.
SessionWatcher editorial · Published · Updated · Source announcement: 2026-09-30
Related guide: How to check your Claude Code usage
Claude API retirement date
Anthropic's September 30, 2026 release notes announce the deprecation of Claude Sonnet 4.5, identified as claude-sonnet-4-5-20250929. Retirement on the Claude API is scheduled for November 30, 2026. The announcement distinguishes the deprecation announcement from the later scheduled retirement date.
Sources: Anthropic release notes: 2026-09-30
Recommended replacement
Anthropic recommends migrating to Claude Sonnet 5.5 and points readers to its Model deprecations documentation. For developers using the named Sonnet 4.5 API model, the notice supplies both a scheduled retirement date and the vendor's recommended replacement for that specific Claude API model.
Sources: Anthropic release notes: 2026-09-30
AI assisted reporting, checked against the linked official sources. Source pages checked 2026-10-03. Editorial process and corrections.