Summary
Anthropic has released Claude Sonnet 5.5 at the same per-token rates as Sonnet 5. The company says the new model generates output 30%+ faster and costs up to 30% less per task in its testing.
Anthropic announced Claude Sonnet 5.5 on September 28, 2026, describing it as the second model in its Claude 5.5 family. The company positions it as a faster, lower-cost option for well-scoped everyday tasks, including bug fixes and creating documents, slides and spreadsheets. It describes Opus 5.5 as better suited to complex work requiring sustained judgment.
Performance and per-task costs
Anthropic reports that Sonnet 5.5 generates output more than 30% faster than Sonnet 5. Its listed rates remain $2 per million input tokens, $10 per million output tokens and $0.20 per million cache-read tokens. The company says the model typically uses fewer tokens to complete a task and, in its testing, costs up to 30% less per task than Sonnet 5. The lower task cost therefore comes from reported token efficiency, not a reduction in those listed rates.
On Terminal-Bench 4.0, an evaluation of multi-step tasks performed through a command-line interface, Sonnet 5.5 scored 70.6%, compared with 10.3% for Sonnet 5. Anthropic also reports a score of 1,844 on GDPval-AA, which tests work across occupations; that was two points below Opus 5.5. The company cautions that benchmark scores represent only one aspect of model capability and says Opus remains stronger at complex, open-ended work requiring sustained judgment.
These results describe performance on specific evaluations, rather than a guarantee of equivalent results across all tasks. Anthropic says that higher effort settings generally use more tokens and take longer, while lower settings are aimed at faster, routine work. Medium is the default in the Claude apps and Claude Code; the Claude Platform defaults to High.
Availability and safeguards
Anthropic says Sonnet 5.5 is available on all its platforms, including Amazon Web Services, Google Cloud and Microsoft Azure. Developers can access it through the Claude Platform using the model identifier claude-sonnet-5-5. The company also says the model is available with zero data retention.
Anthropic reports that Sonnet 5.5 improved on or matched Sonnet 5 on most measures in its automated behavioral audit, which covered roughly 1,850 scenarios. Because the company says its cybersecurity capabilities have improved substantially over Sonnet 5, higher-risk cybersecurity tasks may fall back to Sonnet 5 under its safeguards; routine software development remains supported. Sonnet 5.5 uses the same biology safeguards as Sonnet 5.