Reasoning effort
A dial that decides how much thinking a model spends before it answers, traded directly against time and money.
The same model at a higher effort level thinks longer, produces more internal tokens, and costs more per answer. On a mechanical task that buys nothing; on a task with a trap in it, it is the difference between a right and a wrong answer.
Treat it as a per-task setting rather than a preference. Low effort for edits you could describe in a sentence, high for design decisions and debugging, and a look at the bill when a batch job runs high effort by default.