Claude Sonnet 5.5: capabilities, pricing, pros and cons

Strengths

Anthropic reports 70.6% on Terminal-Bench 4.0, higher than Opus 5.5 (66.4%).
Anthropic reports 1844 on the GDPval-AA v2.1 office work rating, almost the same as Opus 5.5 (1846), at half the price: $2 / $10 per million tokens.
Artificial Analysis measures it as faster than Opus 5.5: about 138 output tokens per second versus 98.
Anthropic says it is more than 30% faster and up to 30% cheaper per task than Sonnet 5.

Weaknesses

It is the wordiest model in the Artificial Analysis tests, so its cost per task ($10.02) ends up almost the same as Opus 5.5.
Quality depends heavily on the effort setting: it scores 54 on the Artificial Analysis index at max, 41 at high and 30 at medium. Medium is the default in the Claude apps and Claude Code.
Anthropic itself says Opus 5.5 is clearly stronger at complex, open-ended work that needs sustained judgment.
Higher-risk security requests fall back to Sonnet 5, and biology filters may wrongly flag harmless microbiology and virology questions.
Thinking cannot be fully turned off, and setting parameters such as temperature through the API returns an error.

Best for

Everyday work assistant
AI-assisted coding at a lower cost
Terminal automation and server administration
Reading images and charts
Business apps that need both speed and quality

Not ideal for

The hardest open-ended reasoning tasks
Cheap high-volume classification, Haiku 5.5 is far cheaper for that

How to use it in Europe

In Europe you can use it in the Claude app with a Pro, Max, Team or Enterprise plan and in Claude Code. The free plan offers a Sonnet model, but Anthropic does not say which version. Developers call it through the Anthropic API or through cloud partners. Slovakia and Czechia are supported countries. The direct API processes data globally or in the US and stores it in the US, with no EU region to choose.

Price compared with similar models

Output price in USD per 1M tokens (log scale). Lighter bars are open-weight models.

Benchmark results

Benchmark	Score	Source
Artificial Analysis Intelligence Index v5.0 (max effort)	54 (#8 of 52)	artificialanalysis.ai ↗, October 2026
Terminal-Bench 4.0	70.6%	anthropic.com ↗ (vendor-reported), September 2026
GDPval-AA v2.1 Elo	1844	anthropic.com ↗ (vendor-reported), September 2026
Humanity's Last Exam, with tools	64.5%	anthropic.com ↗ (vendor-reported), September 2026
OSWorld 2.1 partial	80.1%	anthropic.com ↗ (vendor-reported), September 2026

Benchmarks cover only a narrow slice of ability and vendors often report them at their best settings. Treat them as a rough guide.

More models from this vendor

Claude Opus 5.5: Anthropic's main model for demanding work, coding and long documents, and the one Anthropic recommends starting with.
Claude Fable 5.1: Claude's most expensive model, meant for the hardest tasks and long autonomous work when even Opus 5.5 falls short.
Claude Haiku 5.5: Claude's cheapest and fastest model, built for classification, data extraction and large volumes of simple tasks.

Similar models from other vendors

Command A+ (Cohere): An open business model from Canada's Cohere that officially supports Slovak and Czech and runs on your own server.
Gemini 3.8 Flash (Google): Google's fast, lower-cost model for everyday work, coding and document analysis. You can try it in the API for free.
Muse Spark 1.3 (Meta): Meta's balanced model with a 1-million-token window and a fair price. The Muse Spark line also powers the Meta AI assistant.
Muse Spark Open (Meta): Meta's large open model that a company can run on its own servers, so data never leaves its infrastructure.
Llama 4 Maverick (Meta): The larger model in the newest Llama generation, from April 2025. Cheap through providers, but its license excludes people and companies in the EU.
Mistral Medium 3.5 (Mistral AI): Mistral's mid-size open-weight model and the default in the Vibe app. Good for everyday work and coding with data kept in the EU.

Sources

Prices and models change often. The data comes from official vendor pricing pages and documentation, and every page shows when it was last checked. Before a larger purchase, confirm the price with the vendor.