Anthropic: 2 Ways to Use Fable 5 with Sonnet 5 to Cut Costs
Anthropic revealed several of its use cases: which are often used with Fable 5
1. Use Fable 5 as an “advisor” (Advisor)
In this scenario, Sonnet 5 acts as the executor and turns to Fable 5 for recommendations.
Most tokens are billed at the executor’s lower rate.
On the SWE-bench Pro benchmark, the Sonnet 5 + Fable 5 (as Advisor) setup achieves about 92% of Fable 5’s quality, while the cost is roughly 63% of the cost of using Fable 5 alone.
With this approach, Fable 5 is called infrequently (about once per task) to define the strategy, and Sonnet 5 does most of the work.
More details in the documentation.
2. The second approach is to use Fable 5 as an orchestrator
In this case, Fable 5 plans the task execution and distributes it among executors (Sonnet 5).
Most tokens are billed at the executors’ lower rate.
In BrowseComp tests, Claude Managed Agents were used with Fable 5 as the orchestrator and Sonnet 5 sub-agents as executors. This configuration delivers 96% of Fable 5’s performance at 46% of its cost.
Resource-intensive research tasks are handed off to Sonnet 5.
P.S. Claude Managed Agents supports both approaches
With sub-agents you can:
- pass complex tasks up to the Fable 5 level in the Advisor role;
- delegate task execution to Sonnet 5 executors.
Each sub-agent uses its own cache, so on repeated calls you don’t have to pay again for processing the same context in full.