Claude Fable 5.2 and Mythos 5.2 now available on Amazon Bedrock

Two models, two access paths

AWS has made Anthropic's Claude Fable 5.2 and Claude Mythos 5.2 available on Amazon Bedrock and Claude Platform on AWS. Fable 5.2 is Anthropic's most capable generally available model for technical work. Mythos 5.2 is reserved for high-risk domains and is reachable only through Anthropic's verification programs.

What Fable 5.2 promises

The model focuses on the hardest problems in coding, math and science. It takes on ambiguous, multi-step work, verifies its own output and can run unattended for hours to days. In Anthropic's alignment testing, Mythos 5.2 hallucinates less, completes tasks more reliably and self-reports issues more honestly than Opus 5.5, Sonnet 5.5 and Mythos 5.1. Anthropic expects Fable 5.2 to behave similarly.

Use cases

Fable 5.2 is pitched for agentic coding across large, multi-repository codebases, long-running agents coordinating subagents on multi-day work, scientific research and formal proofs, financial analysis, and design for 3D, hardware and motion. Mythos 5.2 covers security engineering, red teaming and penetration testing, plus biomolecular design and research synthesis.

Data retention and safeguards

Anthropic designates Fable 5.2 a Covered Model: by default it requires retention for up to 30 days and human safety review. On Amazon Bedrock, Amazon personnel perform that review within the AWS boundary, and customers must set the aws_review data retention mode before invoking the model. Enterprise Frontier Safeguards (EFS), built with AWS, pairs zero data retention with misuse detection. A version keeping data in a customer-controlled bucket has not launched yet; until then, eligible customers can use Fable 5.2 with zero data retention through June 30, 2027.

Getting started

To try the model, open the Amazon Bedrock console, go to Test > Playground and select Fable 5.2. Programmatically, the Anthropic Messages API is callable against bedrock-runtime via the Anthropic SDK, and the Invoke and Converse APIs work through the AWS CLI and AWS SDK. Prerequisites include an active AWS account with Bedrock access, a configured AWS CLI, Python 3.9 or later and Boto3.