Anthropic Advanced Available in FlowHunt

Claude Sonnet 5.5

Claude Sonnet 5.5 is an Advanced-tier AI model developed by Anthropic and released on September 28, 2026. It is a proprietary closed-weight model, available on the Claude Platform and on Amazon Web Services, Google Cloud and Microsoft Azure. The 1M-token context window is large enough to hold entire codebases, lengthy technical documents, or extended agentic sessions without truncation.

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Sonnet 5.5 is the second model in the Claude 5.5 family and a clear upgrade over Sonnet 5. Anthropic says it runs noticeably faster than Sonnet 5 and typically needs far fewer tokens for the same work, so it costs less per task. Where Opus 5.5 is built for complex work that needs careful judgment, Sonnet 5.5 is strongest at well-scoped everyday tasks, fixing bugs, and producing polished documents, slides and spreadsheets, with a good eye for design. It is the first Sonnet model to launch with cyber safeguards and fallbacks, which target a narrow set of high-risk requests.
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Benchmarks

Each score appears once, with its rank among tracked models and who measured it.

Compared with Advanced peers on the same scale
  • Claude Sonnet 5.5this model
  • Mistral Large 4this model leads on 4 of 4
  • GPT-6 Lunathis model leads on 3 of 3
Verified independent evaluator, counted in the ranking Self-reported published by Anthropic, shown but not ranked
Overall

AA Intelligence Index

Independent composite of agent, coding, knowledge and science tests by Artificial Analysis (v4).

Source ↗

Claude Sonnet 5.5 56.0 Mistral Large 4 38.4 GPT-6 Luna 38.1
#2of 45 Verified
Coding

DeepSWE

113 long-horizon software tasks written from scratch, graded by hidden tests.

Source ↗

Claude Sonnet 5.5 71.0% Mistral Large 4 61.7% GPT-6 Luna No score
Not ranked Self-reported

SWE-bench Pro

Real issues across several languages and large codebases.

Source ↗

Claude Sonnet 5.5 81.3% Mistral Large 4 No score GPT-6 Luna No score
Not ranked Self-reported
Agents

Terminal-Bench 4.0

Multi-step professional tasks done by an agent in a command-line terminal.

Source ↗Also: Self-reported 70.6% (safeguards on; launch page https://www.anthropic.com/claude-sonnet-5-5)

Claude Sonnet 5.5 63.6% Mistral Large 4 26.8% GPT-6 Luna 12.6%
#1of 36 Verified
Reasoning

Humanity's Last Exam

Expert-written questions across 100+ subjects, no tools.

Source ↗Also: Self-reported 56.9% (no tools)

Claude Sonnet 5.5 55.0% Mistral Large 4 35.0% GPT-6 Luna 38.5%
#4of 44 Verified

What to Use Claude Sonnet 5.5 For

Everyday Coding & Bug Fixing

Anthropic describes it as strongest at well-scoped tasks and fixing bugs, and its speed suits fast iteration on less complex engineering work.

Documents, Slides & Spreadsheets

Use it to create polished documents, slides and spreadsheets. Early testers found its writing clearer than the previous generation and described it as a better partner for collaboration.

Design & Image Understanding

Anthropic points to a sharp eye for design and strong image understanding, so it works for tasks that mix visual and written material.

Large Codebase & Document Analysis

With a 1M-token context window, it can take in whole repositories or long documents in a single prompt at a lower cost per task than the Opus tier.

Strengths and limitations

Strengths

  • Faster than Sonnet 5 and lower cost per task
  • Well-scoped everyday tasks and bug fixing
  • Polished documents, slides and spreadsheets
  • Strong image understanding and design sense
  • Very long documents and large codebases (1M context)

Limitations

  • Closed-weight, so it cannot be self-hosted or fine-tuned on private data
  • Anthropic says Opus 5.5 remains clearly stronger at complex, open-ended work requiring sustained judgment
  • Cyber safeguards and fallbacks apply to a narrow set of high-risk requests

Use it in FlowHunt

Use Claude Sonnet 5.5 in any flow, next to your own tools and knowledge sources.

  1. 1Open a flow, or create one from a template
  2. 2Add an AI Agent or Generator component
  3. 3Pick Claude Sonnet 5.5 in the model selector

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About Anthropic San Francisco, CA · Founded 2021 · anthropic.com

Anthropic is an AI safety company founded in 2021 by former OpenAI researchers Dario Amodei and Daniela Amodei, along with a group of colleagues who had led OpenAI's safety and policy teams. The company's stated mission is the responsible development of AI for the long-term benefit of humanity, and its research agenda is defined by that commitment: Constitutional AI (CAI), a technique for training models to be helpful, harmless, and honest through self-critique; mechanistic interpretability, which aims to reverse-engineer what individual neurons and circuits inside large networks actually compute; and scaling science, which tries to predict how model behaviour changes with compute and data. Anthropic publishes this research openly and has become one of the most cited AI safety labs in academic literature. Claude is Anthropic's public model family, named for Claude Shannon, the founder of information theory, and runs from Claude 1 to the Claude 5.5 generation and Claude Fable 5.1. Anthropic operates a commercial API and consumer-facing Claude.ai product, and maintains deep cloud partnerships with AWS (Amazon Bedrock) and Google Cloud (Vertex AI).

anthropic.com ↗

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Frequently asked questions