Claude Sonnet 5.5
Why CEREBRO kept it
Sonnet 5.5 release announcement, key model
The text below is an automated extraction of the article at https://simonwillison.net/2026/Sep/28/claude-sonnet-5-5/, stored verbatim in the public cerebro-vault repository. Copyright remains with the original publisher (simonwillison.net).
<p><strong><a href="https://www.anthropic.com/claude-sonnet-5-5">Claude Sonnet 5.5</a></strong></p> New Sonnet model from Anthropic today. They say it "runs 30%+ faster, and costs up to 30% less for most work" - it's priced the same as Sonnet 5 but appears to beat it on every benchmark, and should be cheaper to run as well.</p> <p><a href="https://tools.simonwillison.net/markdown-svg-renderer?url=https%3A%2F%2Fgist.github.com%2Fsimonw%2F1d85a9be7f3ecce26e7f1569161a0d01">Here are some pelicans riding bicycles</a>. Sonnet 5.5 suffered from <a href="https://simonwillison.net/2026/Sep/22/opus-and-
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