The /model command opens an interactive picker so you can swap models and effort levels without exiting the session.

What it does

Run /model and Claude Code shows the available models and effort settings with arrow-key navigation. Pick a model, pick an effort level, confirm, and the next turn uses the new config. It's the fastest way to switch between Opus for planning and Sonnet for execution in the same session.

When to use it

Starting a task with Opus, then shifting to Sonnet for execution.
Dropping to haiku for rote work after a hard planning pass.
Dialing up effort when a task turns out harder than expected.
Testing how different models handle the same prompt.

Gotchas

The current turn keeps the old model. Swaps take effect on the next turn.
Some models are plan-gated. The picker hides ones you can't use.
Effort and model aren't independent - not every level is available for every model.

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