Anthropic releases Claude Sonnet 5.5, a faster and cheaper Opus 5.5 companion

Anthropic released Claude Sonnet 5.5 on Monday, a week after it launched Claude Opus 5.5, the company said. The model completes the second entry in the Claude 5.5 family, built as a faster, lower-cost complement to Opus 5.5 rather than a replacement for the flagship.

Anthropic said Sonnet 5.5 is strongest on well-scoped everyday tasks: fixing bugs and producing documents, slides and spreadsheets. Pricing stays the same as Claude Sonnet 5, at $2 per million input tokens, $10 per million output tokens and 20 cents per million cache reads, according to Anthropic. The company did not change the rate card for the new model.

The company said Sonnet 5.5 produces outputs more than 30% faster than Sonnet 5, making it the fastest Sonnet model it has released to date. Anthropic added that typical tasks now cost up to 30% less overall, a saving it attributed to the model needing fewer tokens and fewer tool calls to complete a job, rather than to a lower rate card.

On Anthropic's internal benchmarks, Sonnet 5.5 scored 1844 on GDPval-AA v2.1, close to Opus 5.5's 1846 and well ahead of Sonnet 5's 1449. It reached 80.1% on OSWorld 2.1, a test of computer-use tasks, and 64.5% with tools on Humanity's Last Exam, a difficult general-knowledge benchmark.

The model is available across Anthropic's platforms, including Amazon Web Services, Google Cloud and Microsoft Azure, under the model ID claude-sonnet-5-5, and is live in Claude Code, Anthropic's coding tool. That puts it in front of developers and enterprise customers already using those services from day one.

Anthropic said Sonnet 5.5 is the first Sonnet model launched with the cyber safeguards it applies to its most capable systems, describing its cyber capability as comparable to that of Opus 5. Its output carries an invisible text watermark, which SiliconANGLE reported was added to meet rules including the EU AI Act. Its biology safeguards are unchanged from Sonnet 5, the publication added.

A Haiku 5.5 model has not yet shipped. Anthropic's Opus 5.5 announcement, made a week earlier, said both Sonnet 5.5 and Haiku 5.5 would follow it within weeks, meaning the smallest model in the family remains outstanding for now.

Sonnet sits between the flagship Opus line and the smaller, cheaper Haiku line in Anthropic's range. Releasing Sonnet 5.5 six days after Opus 5.5 brings the newer generation's gains in speed and efficiency to the middle tier, which Anthropic aims at everyday work rather than the hardest reasoning jobs.

Anthropic did not give a release date for Haiku 5.5, only that it would arrive in the coming weeks. Until then, Opus 5.5 and Sonnet 5.5 are the two members of the Claude 5.5 family the company has actually shipped, released six days apart.