Claude Fable 5 (by Anthropic)

Overview

Anthropic's model for the most demanding reasoning and long-horizon agentic work. Claude Fable 5.1 is the current successor, priced the same, with always-on adaptive thinking.

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Quick facts

• Modes: Text → Text · Image → Text · Video → Text

• Default output / size: Text responses (token-limited)

• Thinking: Adaptive (always on for 5.1)

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What it's great for

• Long-running agent loops.

• Highest-stakes analysis and planning.

• Tasks that need extended thinking time.

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Parameters

Control	Type	Default	Notes
Prompt	Text	—	Natural-language instruction (required)
Input Texts	List	—	Optional supporting documents

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Modes

Mode	Estimated time	Required inputs	Typical use
Text → Text	~25s	Prompt	Deep reasoning & agentic work
Image → Text	~25s	Images, Prompt	Complex visual analysis
Video → Text	~25s	Videos, Prompt	Long-form video understanding

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