Advanced Claude — Book 3 · Thinking, Effort and Depth

A control that sits beside the words entirely: how much work Claude does before it replies. Adaptive thinking, and which models use it. The five effort levels, what each is for, and why setting it to high is identical to not setting it. What effort actually changes — not just thinking, but every token including tool calls, which is why lowering it is the first fix for an agent that calls too many tools. Defaults and availability by model. Prompting against overthinking, including the instructions written for older models that are now actively harmful. The trap where effort is not a length dial. And the caching consequence that catches everyone once.