Anthropic moved Claude Sonnet 4.5 into deprecated status on September 30 and fixed November 30 as its retirement date on the Claude API. It recommends Sonnet 5.5 as the replacement. Existing workloads can still use the older model during the transition, but requests will fail after retirement. Partner-operated platforms have separate schedules.
Anthropic deprecated Claude Sonnet 4.5 on September 30 and set November 30 as its retirement date on the Claude API. The recommended replacement is Sonnet 5.5. Deprecation leaves the older model functional during the transition, while removing it from the company’s recommended models.[1], [2]
Anthropic distinguishes a deprecated model from a retired one: the retired model is unavailable and requests to it fail. Its migration guidance recommends testing replacements on the application’s own tasks before the deadline. A usage export from the Claude Console breaks consumption down by API key and model, helping identify workloads that still use the older model. Anthropic also notifies customers with active deployments by email and through its documentation.[1]
The lifecycle table applies to Anthropic-operated platforms, including the Claude API, Claude Platform on AWS and Microsoft Foundry. Partner-operated Amazon Bedrock and Google Cloud have their own retirement schedules. Sonnet 4.5 previously remained active with an earliest-possible retirement date. That lower bound did not fix the last day of access. The September 30 notice now sets November 30 as the shutdown date and names Sonnet 5.5 as the replacement.[1], [2]
