Breaking

Anthropic Releases Claude Fable 5.1 to Cut Agent Costs and Expand Business AI Work

September 22, 2026 at 15:25 EDT

Foundation Models
AI Agents
Sales & Business

Anthropic has released Claude Fable 5.1 and Claude Mythos 5.1, positioning the new Fable model as a cheaper way to run high-end coding, knowledge-work and long-running agent tasks. Fable 5.1 is generally available, while Mythos 5.1 uses the same underlying model with more permissive safeguards for vetted cybersecurity and life-sciences users.

Sep 2026 · Anthropic

Fable 5.1 lowers the agent cost curve

The release targets long-running coding, knowledge-work and business agents, with cheaper cache reads and enterprise controls for sensitive workloads.

75%

cache-read price cut

25%

typical workload savings

45%

highly agentic savings

$0.25

per million cache-read tokens

Cache reads shrink to one quarter

A 75% cut means the relative cache-read cost moves from 100% to 25%.

Fable 5

100%

Fable 5.1

25%

Business workflow score rises

AutomationBench measures end-to-end business workflows. Columns are proportional.

Fable 5

17.1%

Fable 5.1

31.4%

What improves

Lower cached-context costs make long code reviews, browser agents and document-heavy finance work easier to run repeatedly.

What remains gated

Mythos 5.1 is limited to vetted users, and some dual-use cybersecurity and life-sciences tasks stay routed away from Fable.

Continue reading

The rest of this article is for AI News Blitz readers. Choose an option below to keep reading.