Claude's official guide to picking a model and effort level in Claude Code

This is guidance on how to choose which model (such as Opus, Sonnet, or Haiku) and which effort level to use inside Claude Code. Each model trades off speed, cost, and answer quality differently, and the effort level controls how long and how deeply the model thinks before responding.

The core recommendation is to use a lighter, faster model with a lower effort level for simple, repetitive tasks like finding files, small refactors, or formatting cleanup, and to reserve a stronger model with a higher effort level for complex design decisions or tricky bug hunting where accuracy matters most. The overall message is to match the model/effort combination to the difficulty and importance of each task rather than using one fixed setting everywhere.