Anthropic's Claude Haiku 5.5 debuts as fastest model tested; Sonnet 5.5 tops coding index
Anthropic released Claude Haiku 5.5 on October 7, replacing the year-old Haiku 4.5; Artificial Analysis scored it 43 on its Intelligence Index (13th among available models, ahead of all "fast" models) and measured 237 tokens per second, the fastest it has tested, though average time to first token is 337 seconds. API pricing is $0.10/$0.01/$0.50 per million input/cached/output tokens, with all prices 5x above 100k tokens. Claude Sonnet 5.5, launched September 28 at Sonnet 5's per-token prices ($2/$0.10/$10 per million), ranked first on Artificial Analysis' Coding Agent Index (68), second on its Intelligence Index (56) and second on Vals AI's Vals Index (67.04%), but Artificial Analysis says another model matches or beats it at every effort level at lower cost per task, and at max effort Sonnet generates about 193,000 output tokens per task. Anthropic says Sonnet 5.5 is the first Sonnet to block reasoning extraction without falling back to another model, part of an effort to make distillation harder.
Per-token prices don't capture real cost: Sonnet 5.5's cost per task on the Intelligence Index varies more than eighteenfold across reasoning levels, so developers should measure cost, accuracy and completion time at each effort level on their own tasks.