Claude Sonnet 5.5 Released by Anthropic on September 28, 2026, Sonnet 5.5 is its new mid-tier flagship model, directly succeeding Sonnet 5. Officially positioned as “a more affordable and faster daily office companion,” it emphasizes three high-frequency tasks: coding, bug fixing, and creating documents/PPTs/spreadsheets. Compared to its predecessor, its inference speed improves by ~30%, input token cost drops up to 30%, while retaining the high-spec 1M-token context window. It is now available via the Anthropic API,AWS BedrockGoogle Vertex AI, and Microsoft Azure.
core competencies
Sonnet 5.5’s most fundamental change is “always-on thinking.” Unlike the previous generation, which required manual toggling of thinking mode, this model remains perpetually in a think-ready state; developers balance depth, latency, and cost by adjusting the effort (thinking intensity) parameter—lower intensity ensures rapid responsiveness, ideal for high-frequency Agent loops; maximum intensity enables handling more complex reasoning tasks. This design delivers smoother trade-offs between cost-effectiveness and performance.
- Coding capability: Officially highlighted as especially strong at “building features and fixing bugs,” it is currently the most balanced model in the Claude family for everyday development.
- Document OutputSignificantly enhanced capability to generate polished documents, presentation outlines, and tables—delivering clearer, more structured expression than previous generations.
- 1M token contextCapable of ingesting extremely long codebases or entire reports in a single pass—ideal for enterprise-grade long-document processing.
- Security HardeningIncorporates stricter cybersecurity safeguards to prevent misuse for malicious purposes—consistent with the concurrently released Opus 5.5.
Pricing and availability
Pricing is a highlight of this upgrade. Sonnet 5.5 is priced at $2 per million input tokens / $10 per million output tokens(cached reads as low as $0.20), reducing input costs by up to 30% compared to Sonnet 5. Based on OpenRouter’s weighted average price, the effective input cost is approximately $0.62 per million tokens—a highly competitive rate for a mid-tier model featuring million-token context and always-on reasoning.
It is now live across major platforms including AWS Bedrock, Google Vertex, Azure, and OpenRouter—covering virtually all enterprise cloud channels with minimal integration overhead.
Claude Sonnet 5.5 vs. peer models—head-to-head comparison
| Model | Key specifications | Core Positioning | This Site’s Rating |
|---|---|---|---|
| Claude Sonnet 5.5 | 1M context, $2/$10, always-on reasoning | Daily office work + primary development use | 8.8 |
| Claude Opus 5.5 | Flagship-tier, strongest alignment capability | Complex reasoning, high-end tasks | 9.1 |
| GPT-6 Sol | OpenAI’s efficiency flagship | High throughput, low cost | 9.0 |
| Cohere Command A+ | 192K context, multimodal | Enterprise Agent scenarios | 8.5 |
| GLM 5.3 | Million-token context, programming Agent | Domestic cost-effective option | 8.6 |
From a coordinate-system perspective, Sonnet 5.5 occupies the “sweet spot” below flagship but above entry-level: it lacks Opus 5.5’s top-tier alignment and reasoning depth, yet delivers sufficiently strong performance for daily office work and coding at 40% lower cost. If you don’t need to run the most demanding scientific reasoning tasks, Sonnet 5.5 is the more cost-efficient choice.
User experience/limitations
advantageAlways-on thinking + effort parameter enables smooth debugging—no more hesitation over whether to enable thinking; documentation and code output quality ranks among the top tier at its price point; million-token context covers the vast majority of enterprise use cases; significant price reduction substantially lowers long-term Agent operational costs.
limitationsIt remains a “mid-tier” offering: for tasks requiring top-tier reasoning depth—such as complex mathematical proofs or deep, multi-step reasoning—you’ll still need to fall back on Opus 5.5 or higher-end models; its output cost of $10 per million tokens isn’t cheap, and heavy-generation scenarios—like producing large volumes of long-form content—will incur significantly higher costs than input-heavy ones.
Overall Score
| 维度 | Score | evaluate |
|---|---|---|
| functional completeness | 8.5 / 10 | Covers code, documentation, and long context—but reasoning depth falls short of flagship models |
| 易用性 | 9.0 / 10 | Always-on thinking + effort levels ensure smooth debugging experience |
| Cost-effectiveness | 9.2 / 10 | 30% input price reduction—standout competitiveness within the mid-tier segment |
| 中文支持 | 8.5 / 10 | Clear Chinese expression and well-structured long-form generation |
| 输出质量 | 9.0 / 10 | Documentation and code output excel relative to peers at the same price point |
Overall rating: 8.8/10
Frequently Asked Questions (FAQ)
Claude Is Sonnet 5.5 free?
No.Claude Subscribers (Pro/Max tiers) can use Sonnet 5.5 directly in-product; API calls are billed per token at $2 per million tokens for input, $10 per million tokens for output, and ~$0.20 per million tokens for cache reads.
Claude What’s the difference between Sonnet 5.5 and Opus 5.5?
Opus 5.5 is flagship-tier, with superior reasoning depth and alignment—but at a higher price; Sonnet 5.5 is a value-oriented mid-tier model, faster and more affordable, ideal for daily office work and coding. Budget-conscious users or those with high-frequency invocation needs should prioritize Sonnet 5.5.
Claude What is Sonnet 5.5’s context window size?
The context window is 1 million tokens—sufficient to ingest ultra-long codebases, full reports, or extensive document sets in a single pass, making it suitable for enterprise-grade long-text processing.
Claude Does Sonnet 5.5 support Chinese?
Yes—it delivers clear Chinese expression and well-structured outputs, ideal for Chinese writing, translation, and documentation generation.
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