AI01 sources

Anthropic releases Claude Sonnet 5.5 at unchanged pricing

A minimalist line-drawn desert of layered sand dunes with hatched shadows under a terracotta sun on a cream background, an animation Claude Sonnet 5.5 wrote and ran, as shown on Anthropic's announcement page.

Anthropic / Claude Sonnet 5.5 announcement pagePress kit

Anthropic released Claude Sonnet 5.5 on 28 September 2026, the mid-sized model in the Claude 5 family, one week after Claude Opus 5.5. Pricing is unchanged from Sonnet 5: $2 per million input tokens and $10 per million output tokens.

On Terminal-Bench 4.0, a benchmark of agentic work in a command-line environment, Anthropic reports a score of 70.6% for Sonnet 5.5 against 10.3% for Sonnet 5. The company says the model runs more than 30% faster than its predecessor and costs up to 30% less per task, because it needs fewer tokens to reach the same result.

Sonnet 5.5 ships with cybersecurity safeguards similar to those of Opus 5.5, with higher-risk requests routed back to Sonnet 5. It is also the first Sonnet model deployed with classifiers meant to block attempts to extract its reasoning for distillation into other models. The benchmark figures are Anthropic’s own.

The model is available through the Claude Platform, Amazon Web Services, Google Cloud and Microsoft Azure under the identifier claude-sonnet-5-5.

Sources

  1. [1]Introducing Claude Sonnet 5.5Anthropic··Newsroom