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Monday, Sep 28, 2026

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Anthropic Releases Claude Sonnet 5.5, More Than 30% Faster and Up to 30% Cheaper Than Sonnet 5

Anthropic released Claude Sonnet 5.5 on Sept. 28, the second model in its Claude 5.5 family, available across Claude and its APIs. Anthropic calls it a clear upgrade over Sonnet 5 that runs more than 30% faster and costs up to 30% less for most work, and a lower-cost complement to the flagship Opus 5.5. Claude Haiku 5.5 will join the family in the coming weeks.

Grey tests in Claude Code ahead of the release showed pricing of $2 per million input tokens and $10 per million output tokens, with cache reads at $0.20 per million, half the rates of Opus 5.5. The model identifier claude-sonnet-5-5 appeared in a Claude Code update before the launch.

Opus 5.5, the first model in the family, was released Sept. 22 at $4/$20 per million input/output tokens and ranks No. 2 in Agent Arena and No. 1 on Xbench.

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Key sources

  1. SOURCE@claudeai“Claude Sonnet 5.5 is available everywhere today; Claude Haiku 5.5 will join the family in the coming weeks.”x.com
  2. SOURCE@anthropicai“Introducing Claude Sonnet 5.5, the second model in the Claude 5.5 family. It’s a clear upgrade over Sonnet 5, runs more than 30% faster, and costs up to 30% less for most work.”x.com
  3. SUPPORT@tradfi“*ANTHROPIC: SONNET 5.5 IS SIGNIFICANTLY FASTER THAN SONNET 5 & LOWER-COST COMPLEMENT TO OPUS 5.5”x.com
  4. SUPPORT@chetaslua“Pricing: Input: $2 Output: $10 Cache reads: $0.20/M”x.com
  5. SUPPORT@lyraxana“`claude-sonnet-5-5` shows up in the latest Claude Code update”x.com
  6. SUPPORT@kimmonismus“Makes you wonder how much more efficient sonnet 5.5 will be.”x.com
  7. DISCUSSIOND2OQZG8l5BI1S06news.ycombinator.com
  8. SOURCEhnanthropic.com
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