All skills
Skillintermediate
Environment variables
> ## Documentation Index > Fetch the complete documentation index at: https://code.claude.com/docs/llms.txt > Use this file to discover all available pages before exploring further.
Claude Code Knowledge Pack7/10/2026
Overview
Documentation Index
Fetch the complete documentation index at: https://code.claude.com/docs/llms.txt Use this file to discover all available pages before exploring further.
Environment variables
Complete reference for environment variables that control Claude Code behavior.
Claude Code supports the following environment variables to control its behavior. Set them in your shell before launching claude, or configure them in settings.json under the env key to apply them to every session or roll them out across your team.
| Variable | Purpose |
|---|---|
ANTHROPIC_API_KEY | API key sent as X-Api-Key header. When set, this key is used instead of your Claude Pro, Max, Team, or Enterprise subscription even if you are logged in. In non-interactive mode (-p), the key is always used when present. In interactive mode, you are prompted to approve the key once before it overrides your subscription. To use your subscription instead, run unset ANTHROPIC_API_KEY |
ANTHROPIC_AUTH_TOKEN | Custom value for the Authorization header (the value you set here will be prefixed with Bearer ) |
ANTHROPIC_BASE_URL | Override the API endpoint to route requests through a proxy or gateway. When set to a non-first-party host, MCP tool search is disabled by default. Set ENABLE_TOOL_SEARCH=true if your proxy forwards tool_reference blocks |
ANTHROPIC_BEDROCK_BASE_URL | Override the Bedrock endpoint URL. Use for custom Bedrock endpoints or when routing through an LLM gateway. See Amazon Bedrock |
ANTHROPIC_BEDROCK_MANTLE_BASE_URL | Override the Bedrock Mantle endpoint URL. See Mantle endpoint |
ANTHROPIC_BETAS | Comma-separated list of additional anthropic-beta header values to include in API requests. Claude Code already sends the beta headers it needs; use this to opt into an Anthropic API beta before Claude Code adds native support. Unlike the --betas flag, which requires API key authentication, this variable works with all auth methods including Claude.ai subscription |
ANTHROPIC_CUSTOM_HEADERS | Custom headers to add to requests (Name: Value format, newline-separated for multiple headers) |
ANTHROPIC_CUSTOM_MODEL_OPTION | Model ID to add as a custom entry in the /model picker. Use this to make a non-standard or gateway-specific model selectable without replacing built-in aliases. See Model configuration |
ANTHROPIC_CUSTOM_MODEL_OPTION_DESCRIPTION | Display description for the custom model entry in the /model picker. Defaults to Custom model (<model-id>) when not set |
ANTHROPIC_CUSTOM_MODEL_OPTION_NAME | Display name for the custom model entry in the /model picker. Defaults to the model ID when not set |
ANTHROPIC_CUSTOM_MODEL_OPTION_SUPPORTED_CAPABILITIES | See Model configuration |
ANTHROPIC_DEFAULT_HAIKU_MODEL | See Model configuration |
ANTHROPIC_DEFAULT_HAIKU_MODEL_DESCRIPTION | See Model configuration |
ANTHROPIC_DEFAULT_HAIKU_MODEL_NAME | See Model configuration |
ANTHROPIC_DEFAULT_HAIKU_MODEL_SUPPORTED_CAPABILITIES | See Model configuration |
ANTHROPIC_DEFAULT_OPUS_MODEL | See Model configuration |
ANTHROPIC_DEFAULT_OPUS_MODEL_DESCRIPTION | See Model configuration |
ANTHROPIC_DEFAULT_OPUS_MODEL_NAME | See Model configuration |
ANTHROPIC_DEFAULT_OPUS_MODEL_SUPPORTED_CAPABILITIES | See Model configuration |