Anthropic ships Claude Sonnet 5.5 at Sonnet 5's price

Anthropic released Claude Sonnet 5.5 on September 28, saying it "runs 30%+ faster, and costs up to 30% less for most work." It is priced the same as Sonnet 5, and Simon Willison notes it appears to beat Sonnet 5 on every benchmark. In his own tests he found the highest thinking-effort setting can over-think: one prompt ran through 128,000 tokens without producing an answer, the same bug he had seen in Opus 5.5.

What it means The mid-tier model is where most production traffic runs. A faster, cheaper Sonnet at an unchanged price is a direct cost change, as long as you avoid the top effort setting.