Claude Sonnet 5.5 Ranks #2 on AI Index, Near Opus 5.5 at Lower Cost

Anthropic's Claude Sonnet 5.5 holds second place on the Artificial Analysis Intelligence Index, behind only Opus 5.5, with Artificial Analysis independently scoring it at 64% on Terminal-Bench 4.0 (max setting), a 50-point gain over Sonnet 5 (max) and slightly above Opus 5.5 and GPT-6 Astra on that benchmark. Anthropic's own published score for Terminal-Bench 4.0 is 70.6% versus Sonnet 5's 10.3%, and on GDPval-AA the model scores 1,844 against Opus 5.5's 1,846 and Sonnet 5's 1,449. The list price is unchanged from Sonnet 5 at $2/1M input and $10/1M output tokens; Anthropic claims effective per-task costs fall by up to 30 percent because the model completes tasks with fewer tokens and runs more than 30 percent faster. Third-party pipeline tests show even larger savings in some workloads: CodeRabbit found Sonnet 5.5 cost roughly 40 percent of Sonnet 5 for equivalent code reviews, a saving of about 60 percent per review. One analyst recommended sticking with Opus 5.5 for most use cases despite the price difference, and Anthropic itself states Opus 5.5 remains clearly stronger on complex open-ended work.