LLMilestonesA milestone timeline of AI and large language models

Act VI · The frontier and its limits

Closed modelAnthropic

Claude Opus 5

Performance close to Fable 5 at half its API price.

Why it matters

Frontier capability moved down to a cheaper tier; after launch it ranked first on the Artificial Analysis intelligence index.

Built on

Claude Fable 5

Led to

Claude Opus 5.5

Source: anthropic.com ↗

Official page not opened for verification; URL taken from citations in multiple reports.

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