Anthropic released Claude Opus 5 on 24 July. The model narrowly tops the Artificial Analysis Intelligence Index, costs half as much as the company’s own flagship Fable 5 – and, according to the independent tests, hallucinates in half the cases where it is uncertain. It is the fourth model Anthropic has shipped within two months. Claude Opus 5 has been available across all of the company’s platforms since launch day, and for developers as claude-opus-5 via the Claude API. API pricing stays exactly at the level of its predecessor Opus 4.8: 5 US dollars per million input tokens and 25 US dollars per million output tokens. Claude Fable 5, launched in June, costs 10 and 50 dollars respectively. Caching: cache writes carry a 25 percent premium, cache hits are discounted by 90 percent. Fast mode: roughly 2.5 times the default speed at twice the base price. Context window: 1 million tokens. Five effort settings (low, medium, high, xhigh, max) let users trade intelligence against token consumption. No data retention requirement for general access – unlike Fable 5, where prompts are held for 30 days. According to Artificial Analysis, output token consumption varies by a factor of roughly eight between low and max, spanning 407 Elo points on the GDPval-AA v2 benchmark. On GDPval-AA v2, Opus