Anthropic launches Claude Sonnet 5.5 at unchanged API token prices

Anthropic launched Claude Sonnet 5.5 on September 28, making the model immediately available across its platforms and through Amazon Web Services, Google Cloud and Microsoft Azure. Developers using the Claude Platform can select it with the model identifier claude-sonnet-5-5.

The listed API rates are unchanged from Sonnet 5: $2 per million input tokens and $10 per million output tokens. Cache reads remain $0.20 per million tokens, while cache writes cost $2.50 per million tokens.

Anthropic says Sonnet 5.5 generates output more than 30% faster than Sonnet 5. In company testing, Anthropic says, the model can also cost up to 30% less per completed task because it typically uses fewer tokens to do the same work. Those figures have not been independently benchmarked. The savings claim concerns total task execution; Anthropic did not cut its per-token API prices.

Sonnet 5.5 arrives after Anthropic released Claude Fable 5.1 and restricted Mythos 5.1 access earlier in September.

Anthropic also said Sonnet 5.5 is the first Sonnet release to ship with cyber safeguards and fallback measures similar to those used for its more capable models. The model retains the biology safeguards introduced with Sonnet 5.