Anthropic released Claude Fable 5.1 and Claude Mythos 5.1 as two safeguard-layer variants of the same underlying model. Fable 5.1 scores 52.6% on Terminal-Bench-Science 0.1. Cache reads were cut 75% to $0.25 per million tokens, and accounts created on or after 2026-08-31 face breaking API changes for agents that edit conversation history.
Anthropic released Fable 5.1 and Mythos 5.1 as updated versions of its flagship Claude models. Cache read pricing dropped 75% to $0.25 per million tokens, while Mythos 5.1 remains limited to Anthropic’s trusted access program and Fable 5.1 expands with broader Fable access via API/plan tiers. The changes also loosen cyber and biology safeguards (intervening 60% and 85% less often), add a private-preview detection API for watermarks, and roll out Enterprise Frontier Safeguards for zero data retention-style monitoring in phases starting later this fall.
Anthropic announced Claude Fable 5.1’s availability on Amazon Bedrock and Claude Platform on AWS. Claude Fable 5.1 is a Covered Model with data retention for up to 30 days and requires AWS’s aws_review mode for invocation. Customers can also opt into Enterprise Frontier Safeguards, including zero data retention until December 31, 2026, changing how prompts/outputs are stored and reviewed.
Anthropic launched its Claude Fable 5.1 and Mythos 5.1 models in response to customer complaints about price, data retention, and overly strict safeguards. Claude Fable 5.1 is claimed to be up to 45% cheaper for complex agentic tasks by reducing pricing on cached data already processed and stored. This shifts the product’s cost structure to encourage agentic use while keeping the models’ performance focus.
Claude Fable 5.1 was launched on Product Hunt as a developer-tools offering tied to Claude foundation models for coding and knowledge work. The listing claims dictation works everywhere and is 4x faster than typing. The result is a shift from typing to speaking for the supported workflow.
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