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LLMS • CURATED • UPDATED SEP 28, 2026

Claude Sonnet 5.5

Anthropic's mid-tier model that lands within a few points of Opus 5.5 at half the price

Claude Sonnet 5.5 is Anthropic's September 28, 2026 update to Sonnet 5 and the second model in the Claude 5.5 family after Opus 5.5. It keeps Sonnet 5's price of $2 per million input tokens and $10 per million output ($0.20 cache reads, $2.50 cache writes), generates output more than 30% faster, and in Anthropic's testing costs up to 30% less per task because it uses fewer tokens and tool calls. Anthropic's own benchmarks put it ahead of Opus 5.5 on Terminal-Bench 4.0 (70.6% vs 66.4%) and within two points of it on OSWorld 2.1 (80.1% vs 81.8%) and GDPval-AA v2.1 (1844 vs 1846). It is the first Sonnet to carry Opus-level cybersecurity safeguards, which route higher-risk security requests back to Sonnet 5.

QUICK FACTS

Pricing Paid
Platforms web, api, desktop
API Yes
Open Source No
Modalities LLMs, IDEs & Coding Tools
Best For Best Value Everyday Claude Model
Date Added 2026-09-28

WHY WE PICKED IT

It is the rare mid-tier release that closes almost the whole gap to the flagship on agentic work while costing half as much per token, and Anthropic's customer reports (Box, Zendesk, Lovable, Base44) all point the same way: fewer steps and fewer tokens for the same result. For most Claude users it is the new default to try before paying for Opus.

STRENGTHS

LIMITATIONS

GETTING STARTED

Select it in the Claude apps or call model id claude-sonnet-5-5 on the Claude Platform, AWS, Google Cloud or Microsoft Azure. Default effort is Medium in Claude Code and the apps and High on the Platform, so compare at the same effort level before judging it against Sonnet 5.

OFFICIAL LINKS

Website↗ API Docs↗

SIMILAR TOOLS

Google Antigravity 2.0 Claude Fable 5 GPT-6 Astra NotebookLM Claude Opus 5

PRICING

Paid

Requires a paid subscription.

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EXPLORE ALTERNATIVES

View Claude Sonnet 5.5 Alternatives (2026) →

Compare Claude Sonnet 5.5 with 5+ similar llms AI tools.

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FREQUENTLY ASKED QUESTIONS

Q

Is Claude Sonnet 5.5 free?

A

No, Claude Sonnet 5.5 requires a paid subscription.

Q

Does Claude Sonnet 5.5 have an API?

A

Yes, Claude Sonnet 5.5 offers an API for programmatic integration.

Q

What is Claude Sonnet 5.5 best for?

A

Claude Sonnet 5.5 is best for Best Value Everyday Claude Model. Claude Sonnet 5. It is the rare mid-tier release that closes almost the whole gap to the flagship on agentic work while costing half as much per token, and Anthropic's customer reports (Box, Zendesk, Lovable, Base44) all point the same way: fewer steps and fewer tokens for the same result. For most Claude users it is the new default to try before paying for Opus.

Q

What platforms does Claude Sonnet 5.5 support?

A

Claude Sonnet 5.5 supports web, api, desktop.

Q

Is Claude Sonnet 5.5 open source?

A

No, Claude Sonnet 5.5 is not open source.

Q

How do I get started with Claude Sonnet 5.5?

A

Select it in the Claude apps or call model id claude-sonnet-5-5 on the Claude Platform, AWS, Google Cloud or Microsoft Azure. Default effort is Medium in Claude Code and the apps and High on the Platform, so compare at the same effort level before judging it against Sonnet 5.

Q

How do I use Claude Sonnet 5.5?

A

Claude Sonnet 5.5 is a large language model for text generation, analysis, and conversation. Access through the web interface. Enter prompts or questions to get responses. It excels at same per-token price as sonnet 5, half of opus 5.5.

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