Anthropic released Claude Fable 5.1 on 1 September 2026, its top model for coding, knowledge work and long-running agent tasks, and followed with Claude Opus 5.5 on 22 September. A notable detail is pricing: cache reads on Fable 5.1 cost about a quarter of what the previous version charged, which meaningfully lowers the bill for agent workloads that reuse the same context many times.
Agents that repeatedly read the same background documents benefit most, because caching lets them avoid paying full price to re-read unchanged material.
What it means: the cost of running an agent, not just its intelligence, is now a headline feature. For high-volume automation the price per repeated task can matter more than raw capability, so cheaper caching translates directly into cheaper day-to-day operation for anything built on these models.