Effort

Effort levels control reasoning depth vs. token spend:

max — absolute maximum capability with no constraints on token spending. Opus 4.6 only; requests using max on other models return an error. For tasks requiring the deepest possible reasoning and most thorough analysis.
high — high capability, equivalent to not setting the parameter. For complex reasoning, difficult coding problems, agentic tasks.
medium — balanced approach with moderate token savings. For agentic tasks that require a balance of speed, cost, and performance.
low — most efficient, significant token savings with some capability reduction. For simpler tasks that need the best speed and lowest costs, such as subagents.
Auto — Claude will choose the best effort level for the task.