What is Claude Sonnet 5.5?
Claude Sonnet 5.5 is Anthropic’s faster, lower-cost Claude 5.5 model for well-scoped professional work, software development, agentic workflows, and content creation. Anthropic positions it below Claude Opus 5.5 for the most complex open-ended work, but says it can perform comparably on some benchmarks when run at higher effort settings. The model delivers a particularly large improvement in coding, including a 70.6% result on Terminal-Bench 4.0, 46.2% on FrontierCode at Max effort, and 55.5% on CursorBench 4.0. It also scores 1844 on GDPval-AA, 1811 on AA-Briefcase, 64.5% on Humanity’s Last Exam with tools, and 80.1% on OSWorld 2.1 partial. Anthropic reports that Sonnet 5.5 is better at long-horizon work, image understanding, collaboration, and codebase comprehension than Sonnet 5. The company also highlights design-oriented improvements, including the ability to produce polished documents, spreadsheets, slides, and user interfaces with less editing. Sonnet 5.5 generates output more than 30% faster than its predecessor and is Anthropic’s fastest Sonnet model to date. Although its listed token prices are unchanged from Sonnet 5, Anthropic says greater token efficiency can reduce per-task cost by up to 30%. Pricing is $2 per million input tokens, $10 per million output tokens, $2.50 per million cache-write tokens, and $0.20 per million cache-read tokens. The model includes cyber safeguards, biology safeguards, reasoning-extraction protections, and preserved-thinking controls, with some higher-risk cyber requests falling back to Sonnet 5. Claude Sonnet 5.5 is available with zero data retention across Claude products, the Claude Platform, AWS, Google Cloud, and Microsoft Azure under the model name claude-sonnet-5-5.
Pricing
Cache reads, which account for most costs in agentic and coding workloads, are priced at just $0.20 per million tokens
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Claude Sonnet 5.5 Customer Reviews
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Really fast/efficient and good reasoning abilities
Date: Sep 28 2026SummaryClaude Sonnet 5.5 is probably the model I would want as my everyday coding workhorse. It is fast, efficient, strong at practical development tasks, and capable enough that I rarely feel like I am sacrificing much by not using a heavier model.
PositiveI can give it a normal development task and it tends to get to the answer with less wandering, fewer unnecessary tool calls, and less back-and-forth than Sonnet 5. Coding is where I notice the improvement the most. It is really good for feature work, fixing bugs, refactoring, and the everyday engineering tasks where I want something fast and capable without automatically reaching for Opus. The speed is another big advantage. Sonnet 5.5 feels better suited to rapid iteration because I can make a change, test it, adjust the prompt, and keep moving without the slower pace I sometimes get from heavier reasoning models.
NegativeThe main downside is that I would still move up to Opus 5.5 for really messy architecture problems, long autonomous agent runs, or tasks where I want maximum reasoning depth.
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