Anthropic releases Claude Sonnet 5.5, and the free tier now runs on it
Anthropic's Claude Sonnet 5.5 is out: 30%+ faster, up to 30% cheaper for most work, and now the model behind the claude.ai free tier.
Anthropic released Claude Sonnet 5.5 on September 28, 2026. It is the second model in the Claude 5.5 family. The company calls it a clear upgrade over Sonnet 5, says it runs more than 30% faster, and says it costs up to 30% less for most work.
The change that matters most for everyday users is where it runs. Simon Willison, creator of Datasette, says Sonnet 5.5 now powers the free tier on claude.ai. He points out that the free tier of OpenAI’s ChatGPT is still GPT-5.6 Luna, which he calls a lot less capable. That is his read, not a measured comparison.
On the Vals Index, the Vals AI team ranks Sonnet 5.5 second, 0.47 points behind Opus 5.5. Anthropic holds the top four spots on that index.
Free users are not all happy with it. One replied that the rate limits on the free tier are very bad. Willison also quoted a line saying Sonnet 5.5 is priced the same as Sonnet 5, but the excerpt cuts off there, so the full pricing picture is unclear. Nothing in the sources says the weights are open, so treat Sonnet 5.5 as a hosted model. Anthropic also shared early experiments, including a fall foliage simulator by @_re_pete built with Sonnet 5 and Sonnet 5.5.
The speed and cost numbers come from Anthropic alone, and none of the sources show outside measurements of them.
