Ethan Mollick Watches Fable 5 Run 9.5 Hours Unattended to Build a Survey-Analysis Tool From a 19-Page Design Doc

One Useful Thing (Ethan Mollick)·medium signal

With early access to the Mythos-class Claude 5 Fable, Mollick reported handing it a 19-page design document and having it execute for roughly nine and a half hours to produce a full survey-answer analysis tool — turning open-ended text into defensible quantitative analysis with calibration, corrected statistics, and evidence inspection. It's a vivid data point on how far a single autonomous run now stretches when you give an agent a specification rather than a prompt. The builder lesson: the bottleneck is shifting from 'can it code' to 'can you write the spec' — mission over prompt.