AWS Claude Fable 5.1 - Box Dev Docs

According to Anthropic, AWS Claude Fable 5.1 extends Claude Fable 5 with stronger long-running agentic coding, multistep research, and document, spreadsheet, and slide work.

Model details

Item	Value	Description
Model name	AWS Claude Fable 5.1	The name of the model.
Model category	Ultra	The category of the model: Standard, Premium, or Ultra.
API model name	`aws__claude_fable_5_1`	The name of the model that is used in the . You must provide this exact name for the API to work.
Compliance	N/A	Government compliance frameworks and authorizations applicable to this model.
Hosting layer	Amazon Web Services (AWS)	The trusted organization that securely hosts the LLM.
Model provider	Anthropic	The organization that provides this model.
Release date	September 1st, 2026	The release date for the model.
Knowledge cutoff date	June 2026	The date after which the model does not get any information updates.
Input context window	1m tokens	The number of tokens supported by the input context window.
Maximum output tokens	128k tokens	The number of tokens that can be generated by the model in a single request.
Empirical throughput	Not specified	The number of tokens the model can generate per second.
Open source	No	Specifies if the model’s code is available for public use.

Additional documentation

For additional information, see .

Last modified on September 8, 2026