Introducing Claude Opus 5
Willison flags Opus 5 as a cheaper near-frontier Claude model already topping Artificial Analysis.
He had not tested it yet, but notes positive buzz around Anthropic’s release. Anthropic describes it as close to Claude Fable 5 at half the price, with pricing unchanged from Opus 4.8 and a higher-cost fast mode. Willison points to its proactive behavior in a FreeCAD reconstruction example, and to Anthropic’s claim that it improved at finding vulnerabilities without being trained to exploit them. Simon Willison's note
He had not tested it yet, but notes positive buzz around Anthropic’s release. Anthropic describes it as close to Claude Fable 5 at half the price, with pricing unchanged from Opus 4.8 and a higher-cost fast mode. Willison points to its proactive behavior in a FreeCAD reconstruction example, and to Anthropic’s claim that it improved at finding vulnerabilities without being trained to exploit them. Simon Willison's note
score 8