Anthropic’s Claude Fable 5 costs twice as much for 5.7 percent more performance

Anthropic — claude Fable 5 tops the Artificial Analysis Intelligence Index with 64.9 points and sets records in five of ten benchmarks. But the gain over Opus 4.8 is just 5.7 percent at double the token price.

Anthropic’s new flagship model, Claude Fable 5, scores 64.9 points in the Artificial Analysis Intelligence Index, claiming first place. The gap to the best non-Anthropic model, GPT-5.5, is about five points. Anthropic now holds the top two spots on the leaderboard. That crown comes at a cost. Fable 5 runs $10 and $50 per million input and output tokens, double Opus 4.8’s $5 and $25. A full index run hits $9,940, versus $4,970 for Opus 4.8 at max reasoning. That premium buys a 5.7 percent performance gain. Opus 4.8 and 4.7 already followed the same pattern versus Opus 4.6, with steep price bumps for small gains. Anthropic itself called 4.8’s improvement over 4.7 “modest but tangible.” Companies need to weigh carefully which use cases actually justify paying double for about five percent more performance. Benchmark skeptics will note that no test suite fully captures real-world ability. The AA Index at least aggregates ten evaluations, giving it a broader base than any single benchmark. The raw benchmark numbers are nonetheless notable. Fable 5 sets records in five of the ten Intelligence Index benchmarks. On AA-Omniscience, the knowledge and hallucination benchmark, the model hits 40 points, seven more than the previous leader Gemini 3.1 Pro Preview. That lead comes mainly from higher accuracy, not a lower hallucination rate.