OpusPlan is a hybrid model setting that uses Opus for planning and Sonnet for execution. You get Opus-quality architecture with Sonnet's speed and cost for the actual work.

What it does

When you pick OpusPlan, Claude Code runs plan-mode turns and reasoning-heavy steps on Opus, then hands off the concrete tool calls to Sonnet. The split happens automatically - you don't manually swap models. Results tend to be better than pure Sonnet on hard tasks and cheaper than pure Opus.

When to use it

Complex refactors where the plan is the hard part but execution is mechanical.
Cost-conscious workflows that still need strong reasoning.
Long sessions where flat Opus pricing would be painful.
Default model for day-to-day work on non-trivial projects.

Gotchas

Handoffs between models add a small amount of latency per turn.
Execution still benefits from extended thinking - don't assume Sonnet can coast.
Some benchmarks measure pure models only. OpusPlan numbers may not match reported Opus or Sonnet scores.

Official docs: https://code.claude.com/docs/en/model-config.md#opusplan-model-setting