Agents
Fable 5
Anthropic's most capable widely released model, launched June 9, 2026 as the first Mythos-class model available for general use, with a 1M-token context window and up to 128K output tokens at $10 per million input and $50 per million output tokens.
In depth
Anthropic's most capable widely released model, launched June 9, 2026 as the first Mythos-class model available for general use, with a 1M-token context window and up to 128K output tokens at $10 per million input and $50 per million output tokens. Its lead grows the longer and more complex the task, making it a strong driver for long-horizon agent runs. Its model ID is claude-fable-5, thinking is always on, and the effort parameter replaces the old sampling and budget_tokens dials.
Example
In practice, developers reach for Fable 5 when they need the capability described above as part of an AI feature or workflow.
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FAQ
Common questions
What is Fable 5?
Anthropic's most capable widely released model, launched June 9, 2026 as the first Mythos-class model available for general use, with a 1M-token context window and up to 128K output tokens at $10 per million input and $50 per million output tokens.
Why does Fable 5 matter for AI developers?
Fable 5 sits in the Agents part of the AI stack. Understanding it helps you make better decisions when building, debugging, and shipping AI features.
Where can I learn more about Fable 5?
Developers Digest publishes tutorials and videos that cover Agents topics including Fable 5. Check the blog and YouTube channel for hands-on walkthroughs.
Related
Related terms
Agents
Backpressure (Agent)
A flow-control mechanism that prevents an agent pipeline from overwhelming downstream systems.
Agents
Refusal Fallback
A safety architecture where a model routes blocked queries to a more constrained model instead of refusing outright.
Agents
Task Decomposition
The process of breaking a complex goal into smaller, manageable sub-tasks that an agent can execute individually.
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