Fable 5.1 medium effort matches Fable 5 high, no longer breaks prompt cache

lydiahallie · x · 2026-09-05

Lydiahallie shares hands-on observations of Fable 5.1: at medium effort it performs roughly on par with Fable 5 at high, making it the first model where medium is her default in Claude Code. She also notes an engineering fix — switching /effort levels no longer breaks the prompt cache — and recommends builders try /effort medium this weekend.

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