Prompt trick recreates Fable 5 reasoning on cheaper Opus 4.8

A method to recreate the advanced reasoning style of Anthropic's top-tier "Claude Fable 5" on the earlier flagship "Claude Opus 4.8" using a single prompt is drawing attention across developer communities. The workflow has the model generate an "operating manual" from a pasted prompt, register it as a Project instruction within Claude Projects, and then run Opus 4.8 at High or Max effort — aiming to obtain Fable 5-grade long-horizon reasoning on a cheaper model.