On September 2, 2026 Anthropic released Claude Fable 5.1 (broadly available) and Mythos 5.1 (restricted to vetted organizations), citing about 45% lower costs for agentic workloads driven largely by cheaper cache-read pricing. The release also touted enhanced cybersecurity capabilities.
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Anthropic ships Claude Fable 5.1 and Mythos 5.1, cutting agent costs ~45%
Why this matters for founders
Founders running Claude-based agents should re-benchmark on Fable 5.1 and lean on prompt caching to capture the roughly 45% cost reduction on agent workloads.
Source: Tech Startups
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