Why doesn't lowering effort guarantee that Claude Sonnet 5 skips thinking?

Effort and the disabled/adaptive thinking setting are two separate, independently-configurable controls: effort influences how much the model reasons when it does reason, while whether it reasons at all is governed by whether thinking is left on (adaptive) or explicitly disabled.

Because adaptive thinking is genuinely adaptive, the model can still recognize that a specific problem warrants some reasoning even at low effort, meaning a low-effort request on a hard problem may still incur some thinking tokens rather than none at all.

For workloads where the actual requirement is guaranteed zero thinking, regardless of how hard a given request turns out to be, the correct control is explicitly setting thinking: {"type": "disabled"} rather than relying on a low effort setting to produce that same guarantee indirectly.

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