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Pyyan / Compare / Claude Mythos 5.1 vs Claude Fable 5

Claude Mythos 5.1 vs Claude Fable 5

2 of 5

Language Models · verified 2 Sept 2026

Claude Mythos 5.1Anthropiccurrent
Claude Fable 5Anthropiccurrent
3 slots left
SpecificationClaude Mythos 5.1Claude Fable 5
SummaryFable 5.1 with the safety classifiers removed. You cannot simply buy it.Most capable widely released model, for the hardest reasoning and long-horizon agentic work.
Context1M1M
Input ($/Mtok)$10$10
Output ($/Mtok)$50$50
LicenceProprietary, gatedProprietary
Max output128K128K
ParametersNot published—
Released1 Sep 2026—
Model IDclaude-mythos-5-1claude-fable-5
CategoryLanguage ModelsLanguage Models
Official—Anthropic ↗

Highlighted rows are where these differ.

Claude Mythos 5.1

  • The same underlying model as Fable 5.1, at a different safeguard level
  • US organisations and individuals in Anthropic's trusted access programmes only
  • Safety classifiers and high-risk fallbacks removed for Project Glasswing participants

Best for vetted frontier research.

Full spec sheet →

Claude Fable 5

  • Thinking is always on — the `thinking` param is rejected
  • Raw chain of thought is never returned
  • Requires 30-day data retention; unavailable under ZDR

Best for the hardest problems.

Full spec sheet →