Anthropic releases two new models in the fifth Claude generation. Claude Fable 5 claims the top spot in nearly all benchmarks, while Claude Mythos 5 (no longer in preview) is still only available to select partners.
Both models share the same base model. Fable 5 ships with conservative safety guardrails for general use. Mythos 5 drops those restrictions in areas like cybersecurity and is reserved for a small group of partners.
Anthropic says Fable 5 beats every generally available model the company has ever shipped and claims state-of-the-art results in nearly all benchmarks tested. The gap widens on long, complex tasks, the company states.
On SWE-Bench Pro, a benchmark for solving real software engineering tasks from public GitHub repos without help, Fable 5 hits 80.3 percent. Claude Opus 4.8 lands at 69.2 percent, GPT 5.5 at 58.6 percent, and Gemini 3.1 Pro at 54.2 percent.
On Cognition's FrontierCode benchmark, which tests demanding coding tasks under production standards, Fable 5 scores 29.3 percent. Claude Opus 4.8 manages 13.4 percent. GPT 5.5 gets just 5.7 percent.
