Introducing Claude Fable 5.1 and Claude Mythos 5.1
Claude @claudeai · x · 2026-09-01 · ★★★★ · archived
Launch post for Anthropic's September 2026 frontier models, billed as the world's most advanced for coding and knowledge work.
Summary
The official Claude account announced Fable 5.1 and Mythos 5.1 as 'the world's most advanced models for coding and knowledge work'. Fable 5.1 is generally available in Claude, Claude Code, the API and Cursor, while Mythos 5.1 stays in trusted-access programs. Per coverage, Fable 5.1 more than doubled Fable 5 on Terminal-Bench-Science and scored 55.8% vs 42.0% on Terminal-Bench 4.0. The launch also introduced Enterprise Frontier Safeguards. Verified via syndication: 2026-09-01T18:03:14Z.
Archived text
We’re introducing Claude Fable 5.1 and Claude Mythos 5.1.
They're the world’s most advanced models for coding and knowledge work. https://t.co/8P9PSrWPi3
Media: https://pbs.twimg.com/media/HRJlwmVWcAEyYzf.jpg
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Archived 2026-09-29 via syndication.
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