Beyond Premium Performance: Strategic Model Routing Cuts AI Costs and Crashes

Fable 5's 2x premium is only justified for tasks requiring high-level judgment, not routine operations. The author discovered that routing everyday work to cheaper Claude Opus 4.8 while reserving Fable 5 for critical decisions not only reduced costs but also fixed technical crashes caused by running Fable as the primary session model. This reveals a crucial principle in AI system design: effectiveness comes from matching model capability to task requirements, not from deploying the most powerful model everywhere.