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News · Anthropic · September 28, 2026

Claude Sonnet 5.5 is out: what changed, and what it costs you

What Anthropic announced with Claude Sonnet 5.5, each point linked to Anthropic's own pages, then what it means for you in llmwise: which plans have it, and what one Sonnet 5.5 message costs.

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Published .

Facts checked against Anthropic: Introducing Claude Sonnet 5.5, Claude Platform Docs: Models overview, Claude Platform Docs: What's new in Claude Sonnet 5.5. Updated .

Short answer

Anthropic released Claude Sonnet 5.5 on September 28, 2026, at $2 per million input tokens and $10 per million output tokens, the same price as Sonnet 5. Claude Sonnet 5.5 has been in llmwise since September 28, 2026: up to 125 Claude Sonnet 5.5 messages a month on Pro ($20), about $0.16 a message if all of Pro's month goes to it, and it's in the 5-message free trial.

What Anthropic announced

Each point is from Anthropic's own announcement unless its source says otherwise; the numbers link to the sources below.

  1. Anthropic calls Sonnet 5.5 the second model in the Claude 5.5 family, and a faster, lower-cost complement to Claude Opus 5.5.[1]

  2. Anthropic says Sonnet 5.5 writes its output more than 30% faster than Sonnet 5, and costs up to 30% less per task because it needs far fewer tokens for the same work.[1]

  3. Cache reads cost $0.20 per million tokens and cache writes $2.50 per million, half of Opus 5.5's cache-write price.[1]

  4. Its context window is 1 million tokens, it can write up to 128,000 tokens in one reply, and its training data runs to June 2026.[2]

  5. On Terminal-Bench 4.0, an agentic coding test, Anthropic reports 70.6% for Sonnet 5.5, against 10.3% for Sonnet 5 and 66.4% for Opus 5.5.[1]

  6. Anthropic says Opus 5.5 remains clearly stronger at complex, open-ended work that needs sustained judgment.[1]

  7. It's the first Sonnet with safety classifiers that can decline a request; Anthropic retries its cyber and AI-development declines on Claude Sonnet 5.[3]

  8. It's on the Claude Platform as claude-sonnet-5-5, and through Amazon Web Services, Google Cloud and Microsoft Azure.[1]

  9. Anthropic says Claude Haiku 5.5 will join the Claude 5.5 family in the coming weeks.[1]

What it means for you in llmwise

What Claude Sonnet 5.5 costs you in llmwise, from the plans themselves.

Claude Sonnet 5.5

Claude Sonnet 5.5 has been in llmwise since September 28, 2026. llmwise's catalog prices it at $2.00 per million tokens in and $10.00 out (Anthropic's list price), but a Claude Sonnet 5.5 message isn't billed by the token: the table below has its count on every plan.

Claude Sonnet 5.5 on every llmwise plan
PlanClaude Sonnet 5.5
Free ($0)In the 5-message trial
Pro ($20)Up to 125 a month, about $0.16 each
Max ($50)Up to 400 a month, about $0.13 each
Ultra ($100)Up to 900 a month, about $0.11 each
Studio ($200)Up to 2,000 a month, about $0.10 each

A paid plan's month is one allowance the models share, so each monthly count is the most you get if the month goes to that model, and “each” is the plan's price divided by it. Every message's price is shown before you send it. Every plan.

Every limit is published. Paid plans also have a monthly fair-use limit on AI cost: Pro $7.50, Max $20, Ultra $42, Studio $85. Using every message on your plan at typical sizes stays under it; very large messages and heavy research use it faster. Every limit, explained.

Sources

  1. [1] Anthropic: Introducing Claude Sonnet 5.5, published .
  2. [2] Claude Platform Docs: Models overview, checked .
  3. [3] Claude Platform Docs: What's new in Claude Sonnet 5.5, checked .

Questions

Can I use Claude Sonnet 5.5 in llmwise?

Yes, since September 28, 2026. Claude Sonnet 5.5's messages a month: up to 125 on Pro ($20), 400 on Max ($50), 900 on Ultra ($100), 2,000 on Studio ($200). It's also in the 5-message free trial.

Claude, GPT, Gemini, DeepSeek, Grok, Kimi, and GLM, in one chat.

See what a message costs before you send it. Free is 5 messages to try; sign in with an email link, no password or card.

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