Anthropic is recommending a pattern that uses its more expensive Claude Fable 5 model as a planner while delegating execution to Sonnet 5. The approach is designed to preserve much of the quality while lowering task cost.
This kind of model routing is becoming a core production strategy as frontier models get more capable but expensive. Systems can reserve premium models for planning, review, or hard decisions while cheaper models handle routine work.
The pattern also reinforces the move from single-model chatbots toward orchestrated AI systems with explicit roles and cost controls.