Claude Fable 5
Suspended Model: A Mythos-class reasoning model built for long-horizon agentic planning, suspended on June 12, 2026.
Overview
Claude Fable 5 was an experimental 'Mythos-class' model released by Anthropic on June 9, 2026. Designed for complex planning and autonomous software engineering, it introduced a 2 million token context window. Following a U.S. government export directive on June 12, 2026, access to the model was suspended pending compliance review. This record is preserved for historical tracking.
Unique Factor
Anthropic's first Mythos-class reasoning agent, designed for long-horizon planning and recursive self-debugging.
Key Capabilities
Benchmarks
Top Use Cases
Autonomous System Migration
Migrating a legacy monolithic application to a microservices architecture completely autonomously.
Detailed Features
Mythos Reasoning Core: Optimized for multi-hour autonomous tasks without human intervention.
2,000,000 Token Context Window: Large context coherence for massive repository parsing.
Recursive Self-Correction: Able to run unit tests locally, audit logs, and self-patch logic loops.
✓ Strengths & Pros
- • Unmatched agentic planning and code execution capabilities
- • Massive 2M context window with high recall rates
✕ Limitations & Cons
- • Currently suspended and unavailable via API
- • High compute requirements
Ideal Usage & Target Audience
Best For
Historical analysts and compliance researchers tracking frontier AI regulation.
Not Recommended For
Active software development teams requiring reliable, accessible APIs.
Frequently Asked Questions
Why is Claude Fable 5 suspended?
Anthropic suspended access to Fable 5 and Mythos 5 on June 12, 2026 in compliance with a U.S. government export control directive.
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Quick Links
Technical Specs
API Pricing
Access suspended due to export controls
Developer
Industry leader in AI safety and reasoning — the creators of Claude, the world's most nuanced and steerable LLM family.
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