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Anthropic officially launched Claude Fable 5 on June 9, 2026, introducing it as the first generally available model in its high-capability 'Mythos' class. Designed to exceed the performance of the Claude 3 and 4 series, Fable 5 featured a 1 million token context window and was optimized for complex, multi-day agentic workflows and advanced software engineering. However, the release was followed by an immediate regulatory challenge. On June 12, 2026, Anthropic suspended access to the model in compliance with a U.S. government export control directive citing national security concerns regarding potential jailbreaks. While the model is currently unavailable to the public, its official release in June 2026 is confirmed by Anthropic's newsroom announcements and updated API documentation.