Anthropic’s Claude Opus 5 costs well below Fable 5 while matching or beating it across most benchmarks

Anthropic’s Claude Opus 5 is the most capable AI model available today, according to several benchmarks, outperforming Fable 5 while costing less. Opus 5 scored 61 on the Artificial Analysis Intelligence Index, which combines nine tests covering knowledge work, coding, scientific reasoning, and factual accuracy.

That puts it just ahead of Claude Fable 5 (60), GPT-5.6 Sol (59), Kimi K3 (57), and Claude Opus 4.8 (56). Artificial Analysis worked with Anthropic to test the model before its public release. In coding, Claude Opus 5 at “xhigh” paired with Claude Code shares first place on the Artificial Analysis Coding Index, which measures how well AI models handle programming tasks on their own, including finding and fixing bugs. On Terminal-Bench v2.1, which tests agents as autonomous engineers in real terminal environments, Opus 5 scored 89 percent at “max,” matching the previous leader GPT-5.6 Sol.Ad For scientific reasoning, Opus 5 scored 53 percent on Humanity’s Last Exam, a very difficult knowledge test covering many academic fields. That ties it with Fable 5. On CritPt, a physics benchmark from researchers at Argonne National Laboratory and UIUC, it again matches Fable 5 but trails GPT-5.6 Sol, GPT-5.5 Pro, and GPT-5.6 Terra.AdDEC_D_Incontent-1 Factual accuracy remains a weak spot: On AA-Omniscience, which tests the accuracy of a model’s knowledge claims, Opus 5 improved by 7 points over Opus 4.8 but still trails Fable 5. Opus 5 also answers more often when it’s uncertain, pushing its hallucination rate up 14 points to 50 percent. Epoch AI confirms tight race among frontier models Epoch AI has also tested Claude Opus 5. The research institute gave it an overall Epoch Capability Index score of 159, just below Fable 5 at 161. When looking solely at the software engineering benchmarks (SWE-ECI), though, Opus 5 ties with Fable 5 at 161, outperforming GPT-5.6 Terra and Claude Opus 4.8. GPT-5.6 Sol leads in both categories.Ad Overall, this confirms that the race among frontier models is tight. No single model can pull away or claim a clear advantage. That lends weight to the argument that AI models will eventually become commoditized. Lower reasoning tiers deliver better value and coding results The average Intelligence Index task costs $2.03 with Opus 5, less than Claude Fable 5 with fallback at $2.75. It costs more than Opus 4.8 at $1.80 and Sonnet 5 at $1.53.