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
Token Budget
A limit on how many tokens a model or agent may spend on a task, used to control cost and stop long runs from sprawling.
Agents
Agent Handoffs
A multi-agent mechanism where one agent passes control of the conversation to a more specialized agent, rather than calling it as a subroutine.
Agents
Backpressure (Agent)
A flow-control mechanism that prevents an agent pipeline from overwhelming downstream systems.
Put this concept to work
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