Claude Fable 5: a Mythos-class1 model
Anthropic's first Mythos-class model routes risky queries to Opus 4.8 for safety. Free on Pro/Max/Team through June 22.
Overview
Claude Fable 5 represents Anthropic's first foray into the Mythos-class of models, designed to handle high-stakes tasks with unprecedented safety and performance. Instead of outright refusing risky queries, Fable 5 employs sophisticated safety classifiers to route them to the more conservative Opus 4.8, triggering in fewer than 5% of sessions. This allows for greater utility without compromising safety.
In a striking demonstration of its capabilities, Stripe used Claude Fable 5 to migrate over 50 million lines of Ruby code in a single day, showcasing its proficiency in large-scale code transformation. The model is available via API under the name claude-fable-5 at $10 per million input tokens and $50 per million output tokens. Subscribers to Pro, Max, and Team plans get free access until June 22.
Key Features
First Mythos-class model from Anthropic
Safety classifiers route risky queries to Opus 4.8 (under 5% of sessions)
Proven large-scale code migration (Stripe: 50M lines of Ruby in one day)
API access: claude-fable-5
Free on Pro, Max, and Team plans through June 22
Pros & Cons
Pros
- arrow_right + State-of-the-art intelligence for complex tasks
- arrow_right + Enhanced safety without blocking queries
- arrow_right + Proven ability to handle massive codebases
- arrow_right + Free access for a limited time on higher-tier plans
- arrow_right + Competitive API pricing for high-volume users
Cons
- arrow_right - Limited free period until June 22
- arrow_right - Some queries are routed to Opus 4.8, potentially reducing performance
- arrow_right - Only available via API, no chat interface
- arrow_right - Higher cost per token compared to some alternatives
Pricing Details
API Pricing: $10 per million input tokens, $50 per million output tokens.
Free Access: Available at no cost on Pro, Max, and Team plans through June 22, 2025.
FAQ
What is Mythos-class?
expand_moreMythos-class is Anthropic's highest tier of model intelligence, designed for complex reasoning and large-scale tasks.
How does safety routing work?
expand_moreThe model uses classifiers to detect risky queries and automatically routes them to the more conservative Opus 4.8 for safe handling.
When does the free trial end?
expand_moreFree access on Pro, Max, and Team plans ends June 22, 2025.
Can I use it for non-coding tasks?
expand_moreYes, Claude Fable 5 is a general-purpose model suitable for various tasks including analysis, writing, and research.
What are the rate limits?
expand_moreRate limits depend on the plan; see Anthropic's documentation for details.
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| Overview | Anthropic's first Mythos-class model routes risky queries to Opus 4.8 for safety. Free on Pro/Max/Team through June 22. | Turn any audio into structured notes, summaries, and more – with time-linked citations. Free daily, no signup required. | Get a free personalized AI risk report for your job. Find automation risks, skill gaps, and a 30-day action plan. | Get an honest AI-powered analysis of your startup idea in 30 seconds. No signup needed. |
| Pricing Model | Freemium | Freemium | Freemium | Freemium |
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