Environment variables

Environment variables can control Claude Code behavior such as model selection, authentication, request routing, and feature toggles. Many of the same behaviors can also be configured through a settings file field, a CLI flag, or an in-session command like /model. This page covers how to:

Set environment variables in your shell or in a settings file
Check which value applies when a behavior can be set more than one way
Look up the variables Claude Code reads
See which features stop working when a variable turns feature-flag fetching off

Reference

Glossary

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