Claude Fable 5.1 cuts coding costs by up to 45%
Anthropic released Claude Fable 5.1 on September 2, 2026, with a pricing cut that matters most if you run heavy agentic coding workloads.
The Pricing Change
Cache read pricing drops 75%, from its previous rate down to $0.25 per million tokens. For typical workloads, Anthropic says that translates to roughly 25% lower overall costs compared to Fable 5. For complex coding and highly agentic tasks, savings can reach approximately 45%.
Base pricing stays the same: $10 per million input tokens and $50 per million output tokens. The cache read cut is where the savings live, and Anthropic’s product lead Dianne Penn told Bloomberg that cache reads can make up the majority of tokens consumed during the most demanding workloads.
Coding Benchmark Improvements
Fable 5.1 scored 55.8% on Terminal-Bench 4.0 for agentic coding, up from 42.0% on Fable 5. On Terminal-Bench-Science 0.1, it scored 52.6% compared to Fable 5’s 24.7%.
Safety Updates
Anthropic updated its safety classifiers to cut false positives. Claude Code users can expect roughly 60% fewer cybersecurity-related interventions per session versus Fable 5. The model can now identify software vulnerabilities but not develop exploits. For biology, the classifiers fire 85% less often on benign requests related to elementary biology and medical questions compared to Fable 5’s original safeguards.
Anthropic also introduced Enterprise Frontier Safeguards, which lets business customers store data on their own cloud infrastructure while Anthropic still monitors for misuse. That feature is rolling out in phases later this fall. Until it’s available, eligible customers can use Fable 5.1 with zero data retention.
Availability and the Mythos Variant
Fable 5.1 is available on the Claude API and on Amazon Web Services, Google Cloud, and Microsoft Azure. Anthropic also released Claude Mythos 5.1 alongside it, an identical model with different safeguard levels available only to vetted partners in cybersecurity and life sciences.
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