AnthropicLaunchAI ModelsSeptember 1, 2026

Anthropic releases Claude Fable 5.1 and Mythos 5.1

Fable 5.1 scores 55.8% on Terminal-Bench 4.0 in Claude Code, ahead of Fable 5 (42%) and Opus 5 (52.3%). Pricing matches Fable 5, but API cache reads drop 75% to $0.25/MTok; Perplexity ranked it first on its August WANDR eval at 0.601.

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