# Claude Fable 5.1 leads refreshed Artificial Analysis index

_Published Saturday, September 5, 2026 at 4:17 PM EDT · AI · Latest · Tier 2 — Notable_

![Claude Fable 5.1 Retakes the Top AI Benchmark Spot From GPT-6 Astra — Primary](https://startupfortune.com/wp-content/uploads/2026/09/sf-20215-1788625625390.jpg)

Artificial Analysis published version 4.2 of its Intelligence Index on September 4, placing Anthropic's Claude Fable 5.1 first with a score of 57 and OpenAI's GPT-6 Astra second at 55, according to the report.

The update raised the weighting of private, held-out test sets to 40% from 20% in version 4.1 and removed GPQA Diamond after Artificial Analysis said it had become saturated. The interim index combines 10 evaluations, including tests of linked knowledge-work tasks and reasoning across 100 PDFs.

## Sources

- [startupfortune.com](https://startupfortune.com/claude-fable-51-retakes-the-top-ai-benchmark-spot-from-gpt-6-astra/)

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Canonical: https://techandbusiness.org/newswire/tsMEbFTExSttjOLXpLBGnM
Published: 2026-09-05T20:17:35.939Z
Story chronology: 2026-09-04T00:00:00.000Z
Retrieved: 2026-10-21T02:04:44.217Z
Publisher: Tech & Business (techandbusiness.org)