Anthropic’s Claude Opus 5 scores 61 on the Artificial Analysis Intelligence Index, edging out Fable 5 at 60 and beating GPT-5.6 Sol at 59.
This makes Opus 5 the most capable model available today, according to several benchmarks. It costs less than Fable 5 while matching or beating it across most tests.
Performance and reliability
The Artificial Analysis Intelligence Index combines nine tests covering knowledge work, coding, scientific reasoning, and factual accuracy. Artificial Analysis worked with Anthropic to test the model before its public release.
In coding, Opus 5 at “xhigh” paired with Claude Code shares first place on the Artificial Analysis Coding Index. This 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”. This matches the previous leader GPT-5.6 Sol.
For scientific reasoning, Opus 5 scored 53 percent on Humanity’s Last Exam. This is 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.
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 is uncertain. This pushes 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. This is 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. It outperforms GPT-5.6 Terra and Claude Opus 4.8. GPT-5.6 Sol leads in both categories.
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. This is 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.
At the “high” and “xhigh” tiers, however, Opus 5 beats both Opus 4.8 and Sonnet 5 while costing less.
Vals.ai tested Claude Opus 5 across all five reasoning tiers using Vibe Code Bench. This is a benchmark for programming tasks. Scores climb from 76.7 percent at “low” to 82 percent at “medium” and 89.8 percent at “high.”
Performance dips at the two highest tiers. The “xhigh” tier scores 88.3 percent and “max” scores 88.4 percent despite much higher costs.
Vals.ai found that the highest tiers tend to produce more complex solutions that contain errors more often. The “high” tier produces simpler solutions that meet the requirements more reliably.
Terminal-Bench 2.1 shows a similar pattern. The “high” tier beats “max” because the model spends more time on each attempt at the top tier. This leaves fewer attempts within the time limit.
This matches Anthropic’s guidance, with “high” set as the default tier in both the API and Claude Code.
Token pricing stays at $5 per million input tokens and $25 per million output tokens. Cache writes cost $6.25 per million tokens with a five-minute lifetime. Cache hits run just $0.50 per million tokens.
Opus 5 pulls ahead in knowledge work
Opus 5 performs especially well on the AA-Briefcase benchmark. This measures how well AI models handle typical office tasks like writing research reports, building presentations, and analyzing spreadsheets based on thousands of input files.
Performance is scored across correctness, analytical quality, and presentation quality. These scores are then rolled into an Elo rating similar to chess rankings.
At max reasoning, Opus 5 reaches an Elo of 1720. This is a full 146 points ahead of Claude Fable 5 at 1574. Its three highest tiers (max, xhigh, high) sweep the top three spots.
Combined with Fable 5, Sonnet 5, and Opus 4.8, Anthropic now holds the vast majority of top-10 positions.
Cost per task dropped 20 percent to $17.79. This is down from $22.30 for Fable 5. The “xhigh” variant costs $14.26, and “high” comes in at just $10.41. This is less than half of Fable 5.
Both still beat Fable 5 in the Elo ranking. At medium performance, Opus 5 hits an Elo of 1470. This is just behind GPT-5.6 Sol (max, 1505). At low performance, it lands at 1223 Elo, slightly below GLM-5.2 (max, 1254).
Opus 5’s biggest gains show up in analytical quality. At “max”, it reaches an Analytical Quality Elo of 2016. This is almost 300 points ahead of Fable 5.
Its Rubric Pass Rate tracks how often the model meets predefined quality standards. This sits at 58 percent (“max”), 57.2 percent (“xhigh”), and 56 percent (“high”).
Presentation quality is a different story. Opus 5 scores a Presentation Elo of 1628. This is about 40 points behind GPT-5.6 Sol at “max” (1666).
More performance takes more time. At “max”, Opus 5 needs over 36 minutes per task. This averages 103 passes. That is about 50 percent longer than Opus 4.8 at 24 minutes and 55 passes.
