Reference

Environment variables reference

Complete reference of all Claude Code environment variables: configuration, API keys, debugging, and advanced settings.

Publié le 11 mars 2026

Overview

Claude Code reads several environment variables at startup. They let you configure the tool without modifying settings.json files, which is ideal for CI/CD environments and automated deployments.

Environment variable priority

Environment variables generally have equal or lower priority compared to options explicitly set in settings.json. Check the documentation for each option to know its exact precedence.

Essential variables

`ANTHROPIC_API_KEY`

Field	Value
Description	Anthropic API key for authentication
Required	Yes (unless logged in via `claude login`)
Default	None
Format	`sk-ant-api03-...`

# In your ~/.bashrc, ~/.zshrc or ~/.profile
export ANTHROPIC_API_KEY="sk-ant-api03-xxxxxxxxxxxx"

# For a single session
ANTHROPIC_API_KEY="sk-ant-..." claude --print "hello"

# In CI/CD (GitHub Actions)
# Set in Settings > Secrets > ANTHROPIC_API_KEY
# Then in the workflow:
env:
  ANTHROPIC_API_KEY: ${{ secrets.ANTHROPIC_API_KEY }}

API key security

Never commit ANTHROPIC_API_KEY in a versioned file. Use a secret manager (AWS Secrets Manager, HashiCorp Vault, GitHub Secrets) in production. Rotate the key immediately if it gets exposed.

`CLAUDE_MODEL`

Field	Value
Description	Default Claude model to use
Required	No
Default	`claude-sonnet-4-5`
Format	Anthropic model identifier

# Use Haiku for quick sessions (3x cheaper)
export CLAUDE_MODEL="claude-haiku-4-5"

# Use Opus for complex tasks
export CLAUDE_MODEL="claude-opus-4-5"

# Override for a single command
CLAUDE_MODEL="claude-opus-4-5" claude --print "complex task"

Common model identifiers:

claude-haiku-4-5: Fast and affordable
claude-sonnet-4-5: Recommended balance
claude-opus-4-5: Deepest reasoning

`MAX_THINKING_TOKENS`

Field	Value
Description	Token budget allocated for internal reasoning (Extended Thinking)
Required	No
Default	`31999` (when Extended Thinking is enabled)
Format	Integer

# Reduce the budget to limit costs
export MAX_THINKING_TOKENS=10000

# Maximum budget for complex tasks
export MAX_THINKING_TOKENS=31999

# Disable thinking for a session (minimum value)
export MAX_THINKING_TOKENS=1000

Lowering this value reduces reasoning depth and associated costs. Only relevant when alwaysThinkingEnabled: true or when Extended Thinking is manually enabled.

Network and proxy variables

`ANTHROPIC_BASE_URL`

Field	Value
Description	Custom base URL for Anthropic API calls
Required	No
Default	`https://api.anthropic.com`
Format	Full URL

# Enterprise proxy
export ANTHROPIC_BASE_URL="https://proxy.my-company.com/anthropic"

# Local server (development/test)
export ANTHROPIC_BASE_URL="http://localhost:8080"

# Compatible with settings.json variables
# (ANTHROPIC_BASE_URL overrides customApiUrl)

`HTTP_PROXY` / `HTTPS_PROXY`

Field	Value
Description	HTTP/HTTPS proxy for all outgoing connections
Required	No
Default	None
Format	`http://[user:pass@]host:port`

# Proxy without authentication
export HTTP_PROXY="http://proxy.company.com:8080"
export HTTPS_PROXY="http://proxy.company.com:8080"

# Proxy with authentication
export HTTPS_PROXY="http://user:password@proxy.company.com:8080"

# SOCKS5 proxy
export HTTPS_PROXY="socks5://proxy.company.com:1080"

`NO_PROXY`

Field	Value
Description	Domains excluded from the proxy (comma-separated list)
Required	No
Default	None
Format	Comma-separated domain list

# Exclude local network from the proxy
export NO_PROXY="localhost,127.0.0.1,*.intranet.company.com"

# Combine with HTTPS_PROXY
export HTTPS_PROXY="http://proxy.company.com:8080"
export NO_PROXY="localhost,127.0.0.1"

Behavior variables

`DISABLE_AUTOUPDATER`

Field	Value
Description	Disable automatic update checking and installation
Required	No
Default	Not set (auto-update enabled)
Format	`1` or `true` to disable

# Disable automatic updates
export DISABLE_AUTOUPDATER=1

# Useful in CI/CD to pin the Claude Code version
# and avoid unwanted updates in production

Recommended in CI/CD for build reproducibility. Use a fixed version of Claude Code in your pipelines.

`CLAUDE_CODE_MAX_OUTPUT_TOKENS`

Field	Value
Description	Maximum number of tokens in the generated response
Required	No
Default	Model limit (varies by model)
Format	Integer

# Limit long responses
export CLAUDE_CODE_MAX_OUTPUT_TOKENS=4096

# Maximum for tasks needing long responses
export CLAUDE_CODE_MAX_OUTPUT_TOKENS=16000

`CLAUDE_CONFIG_DIR`

Field	Value
Description	Alternative directory for Claude Code configuration files
Required	No
Default	`~/.claude/`
Format	Absolute path to a directory

# Use an alternative configuration directory
export CLAUDE_CONFIG_DIR="/opt/claude-config"

# Useful for multi-user environments
# or per-project isolated configurations
export CLAUDE_CONFIG_DIR="$(pwd)/.claude-config"

# In CI/CD, for a completely isolated configuration
export CLAUDE_CONFIG_DIR="/tmp/claude-ci-config"

Summary table

Variable	Required	Default	Description
`ANTHROPIC_API_KEY`	Yes*	None	Anthropic API key
`CLAUDE_MODEL`	No	`claude-sonnet-4-5`	Default model
`MAX_THINKING_TOKENS`	No	`31999`	Extended Thinking budget
`ANTHROPIC_BASE_URL`	No	`https://api.anthropic.com`	Custom API URL
`HTTP_PROXY`	No	None	HTTP proxy
`HTTPS_PROXY`	No	None	HTTPS proxy
`NO_PROXY`	No	None	Proxy exclusions
`DISABLE_AUTOUPDATER`	No	None	Disable auto-updates
`CLAUDE_CODE_MAX_OUTPUT_TOKENS`	No	Model limit	Max output tokens
`CLAUDE_CONFIG_DIR`	No	`~/.claude/`	Alternative config directory

*Unless authenticated via claude login (Claude.ai Max account)

Configuration examples by context

Local development

# ~/.zshrc or ~/.bashrc
export ANTHROPIC_API_KEY="sk-ant-api03-..."
export CLAUDE_MODEL="claude-sonnet-4-5"

# Optional: Extended Thinking with reduced budget
export MAX_THINKING_TOKENS=10000

CI/CD (GitHub Actions)

# .github/workflows/claude.yml
jobs:
  claude-task:
    runs-on: ubuntu-latest
    env:
      ANTHROPIC_API_KEY: ${{ secrets.ANTHROPIC_API_KEY }}
      CLAUDE_MODEL: claude-haiku-4-5
      DISABLE_AUTOUPDATER: "1"
      CLAUDE_CODE_MAX_OUTPUT_TOKENS: "4096"
    steps:
      - uses: actions/checkout@v4
      - run: npm install -g @anthropic-ai/claude-code
      - run: claude --print --max-turns 5 "Check code quality"

Enterprise environment with proxy

# /etc/environment or system profile
ANTHROPIC_API_KEY="sk-ant-..."
ANTHROPIC_BASE_URL="https://ai-proxy.my-company.com"
HTTPS_PROXY="http://web-proxy.my-company.com:8080"
NO_PROXY="localhost,127.0.0.1,*.internal.my-company.com"
DISABLE_AUTOUPDATER=1
CLAUDE_CONFIG_DIR="/opt/claude-code/config"

Next steps

Cheatsheet: Quick reference: Slash commands and keyboard shortcuts
CLI: Complete reference: All flags for the claude command
settings.json: Complete guide: Advanced configuration

Settings reference

Environment variables reference

Overview

Essential variables

ANTHROPIC_API_KEY

CLAUDE_MODEL

MAX_THINKING_TOKENS