The San Francisco-based lab said the new Claude AI model was well suited for daily office and computer programming tasks.
In an interview with Reuters, Anthropic product leader Dianne Penn said the release, more efficient than May’s Opus 4.8, reflected a rapid pace of development.
“We’re building and continue to consistently deliver frontier intelligence and bring that as accessible as possible with every model generation,” said Penn.
In testing, Opus 5 was less capable of exploiting cyber vulnerabilities than Anthropic’s top-shelf AI, so its related safeguards are less restrictive than Fable 5’s. Opus 5 was also less susceptible to being tricked into misuse than Anthropic’s other current models, the startup said.
Released in June, Anthropic’s Fable 5 was temporarily unavailable following US concerns that its capabilities could be diverted to foreign military intelligence.
Users should pick Opus 5 for value and Fable 5 for “days-long, very autonomous projects,” Penn said.
Asked about the Kimi K3 “open” model from China-based Moonshot, which the US accused of freeloading off Anthropic, Penn said it “remains to be seen” how open-weight models generally perform on complicated real-world projects that users ask Claude to tackle.
Open-weight models allow users to download, run and customize the virtual brains of an AI, unlike proprietary models.
