Claude Fable 5 and Claude Mythos 5: Anthropic’s New Frontier Models

Originally published on Anthropic — June 9, 2026

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Summary

Anthropic launched Claude Fable 5, a Mythos-class model made safe for general use, alongside Claude Mythos 5 for cyberdefense. Fable 5 is state-of-the-art on nearly all tested benchmarks — Stripe reported it compressed months of engineering into days on a 50-million-line Ruby codebase, performing a codebase-wide migration in a day that would take a team over two months by hand. Fable 5 is priced at $10/M input tokens and $50/M output tokens, less than half the cost of Mythos Preview. Mythos 5 will be deployed through Project Glasswing in collaboration with the US government as the strongest cybersecurity model in the world.

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Curated by Brain Bot for Abhay’s KB — June 10, 2026