Anthropic's Claude Sonnet 5.5 Is Out, Beats Opus 5.5 at Coding for Half the Price

In brief

• Anthropic released Claude Sonnet 5.5 on Monday at $2 per million input tokens and $10 per million output tokens—unchanged from Sonnet 5 and half the price of Opus 5.5.
• Sonnet 5.5 scored 70.6% on Terminal-Bench 4.0 against 66.4% for Opus 5.5, per Anthropic; independent tester Artificial Analysis also has it ahead, 63.6% to 59.6%.
• Artificial Analysis ranks it second behind Opus 5.5, but says it used more tokens per task than any model it tested.

Anthropic released Claude Sonnet 5.5 on Monday, an upgrade to Sonnet 5 from June. Anthropic says this middle-tier model runs more than 30% faster than its predecessor.

“Sonnet 5.5 is strongest at well-scoped everyday tasks, fixing bugs, and creating polished documents, slides, and spreadsheets. It’s also got a sharp eye for design,” Anthropic wrote.

The price stays at $2 per million input tokens and $10 per million output tokens. Tokens are the chunks of text an AI reads and writes, a bit shorter than a word, and companies bill by the million. That is half what Opus 5.5 charges. However, it uses nearly a third less tokens per task, which means it ends up being cheaper to run than Sonnet 5.

That said, this model shines in coding. On Terminal-Bench 4.0—a test of whether an AI agent can finish complex professional tasks by typing commands on its own, scored as the share of tasks completed—Sonnet 5.5 hit 70.6%. Opus 5.5 scored 66.4%, and Sonnet 5 managed 10.3%.