CLAUDE LABJP
MODEL — Claude Fable 5.1 and Claude Mythos 5.1 arrived on September 1. They are the same model; only the level of safeguards differs between themPRICING — Cache reads dropped 75%, from $1.00 to $0.25 per million tokens. Anthropic measures that as roughly 25% lower cost on typical workloads and up to 45% on agentic onesCAVEAT — Only cache reads got cheaper. Base input stays at $10 and output at $50, so the savings land on setups that re-read the same long context, not on one-off promptsAPI — The model ID is claude-fable-5-1, generally available through the Claude API as well as AWS, Google Cloud, and Microsoft AzureEFFORT — At low and medium effort it matches or beats Fable 5; at higher effort it pulls further ahead. The choice is the same result for less, or more reach for the same spendCLI — Claude Code v2.1.263 shipped on September 6 with a single CLI change: fewer crashes and steadier commands. No new features in this oneMODEL — Claude Fable 5.1 and Claude Mythos 5.1 arrived on September 1. They are the same model; only the level of safeguards differs between themPRICING — Cache reads dropped 75%, from $1.00 to $0.25 per million tokens. Anthropic measures that as roughly 25% lower cost on typical workloads and up to 45% on agentic onesCAVEAT — Only cache reads got cheaper. Base input stays at $10 and output at $50, so the savings land on setups that re-read the same long context, not on one-off promptsAPI — The model ID is claude-fable-5-1, generally available through the Claude API as well as AWS, Google Cloud, and Microsoft AzureEFFORT — At low and medium effort it matches or beats Fable 5; at higher effort it pulls further ahead. The choice is the same result for less, or more reach for the same spendCLI — Claude Code v2.1.263 shipped on September 6 with a single CLI change: fewer crashes and steadier commands. No new features in this one
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API & SDK/2026-09-07Intermediate

A 75% cheaper cache read moved one bill by 29% and another by 2.8%

Fable 5.1 and Mythos 5.1 changed the cache read multiplier from 0.1 to 0.025. Here is how to estimate your own saving from your token mix, and how to fix code that hard-codes the multiplier.