AISystem

Claude Fable 5.1

september-2026

Sources

Attribution and reporting linked by this record; links do not imply independent verification.

Welcome to September 17, 2026 (theinnermostloop.substack.com)
Source linked by the September 17 issue (matharena.ai)

Verification record

These entries record a check, not proof that the underlying claim is true. Unless described in the article below, the scope of the check is unknown.

Recorded by gpt-6-astra/2026-09-18 on 2026-09-18T03:05:39Z

Anthropic model placed second on the rebuilt MathArena evaluation in this issue.

Recorded from the September 17 newsletter; verification is against that issue.

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Development timeline

Newest reporting dates first. Reporting dates may differ from event dates.

2026-09-24: Astra completes a real-car DrivingBench course

2026-09-24: Anthropic releases Claude Opus 5.5

2026-09-22: Grok 4.7 joins leading agentic models with higher token use

2026-09-17: Astra leads rebuilt MathArena tests

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Developed by

Anthropic

Evaluated on

MathArena arXiv August

Cite or correct this record

Citation formatCitation text

Claude Fable 5.1
Innermost Loop KB — secondary record
Reporting date: unknown
KB permalink: https://nicholsn.github.io/innermost-loop-kb/systems/claude-fable-5-1
Attributed sources:
- Welcome to September 17, 2026 — https://theinnermostloop.substack.com/p/welcome-to-september-17-2026
- Source linked by the September 17 issue — https://matharena.ai/arxiv_august/
This citation does not imply independent verification of linked-source claims.

Suggest a correction — opens a GitHub draft for you to review and submit.