Claude Fable 5 is expensive. Anthropic now recommends using it mainly as a planner, handing execution off to smaller models. The Claude developer team outlines two strategies. In the "Advisor" pattern, Sonnet 5 runs as the executor and only calls Fable 5 when it needs guidance. On SWE-bench Pro, this combo reaches about 92 percent of Fable 5's solo performance at 63 percent of the cost, according to Anthropic. Fable 5 gets called roughly once per task.
Advisor pattern: Sonnet 5 does the work and only consults Fable 5 when needed. | Image: Anthropic
In the second pattern, Fable 5 acts as a planner that delegates tasks to Sonnet 5 worker agents. On BrowseComp, this delivers 96 percent of Fable 5's performance at 46 percent of the cost. Both patterns run through Claude Managed Agents, with each sub-agent using its own cache to avoid duplicate context costs. The official documentation has more details.
Orchestrator pattern: Fable 5 plans and distributes tasks to multiple Sonnet 5 workers. | Image: Anthropic
Anthropic is likely sharing these tips because of growing price pressure. Chinese open-source models are already undercutting Western pricing, and the new GPT-5.6 Sol is much cheaper per token and reportedly more token-efficient too.
