Claude Code — Environment Variables Reference

{
  "env": {
    "ANTHROPIC_MODEL": "opus",
    "ANTHROPIC_DEFAULT_HAIKU_MODEL": "claude-haiku-4-5",
    "CLAUDE_CODE_EFFORT_LEVEL": "medium",
    "DISABLE_PROMPT_CACHING": "0",
    "USE_BUILTIN_RIPGREP": "0"
  }
}

# Shell env has ANTHROPIC_MODEL=opus
# ~/.claude/settings.json has ANTHROPIC_MODEL=sonnet
# .claude/settings.json has ANTHROPIC_MODEL=haiku

# Claude Code uses: opus (shell wins)

# ~/.bash_profile or ~/.zshrc
export AWS_PROFILE=production
export AWS_REGION=us-west-2
export ANTHROPIC_USE_BEDROCK=1
export ANTHROPIC_DEFAULT_OPUS_MODEL=anthropic.claude-3-5-sonnet-20241022-v2:0:200k
export HTTP_PROXY=http://corporate-proxy.internal:8080
export NODE_EXTRA_CA_CERTS=/etc/ssl/certs/ca-bundle.crt
export CLAUDE_CODE_DISABLE_TELEMETRY=1

{
  "env": {
    "ANTHROPIC_USE_VERTEX": "1",
    "GOOGLE_CLOUD_PROJECT": "my-project-dev",
    "GOOGLE_CLOUD_REGION": "us-central1",
    "ANTHROPIC_DEFAULT_SONNET_MODEL": "claude-3-5-sonnet@20241022",
    "CLAUDECODE_EFFORT_LEVEL": "high",
    "DISABLE_PROMPT_CACHING": "0"
  }
}

export CLAUDE_CODE_MAX_TURNS=20          # Force summaries every 20 turns
export ANTHROPIC_MODEL=haiku             # Use cheaper model
export CLAUDE_CODE_EFFORT_LEVEL=low      # Reduce reasoning
export DISABLE_PROMPT_CACHING=1          # Save some token overhead

# Check which model is actually loaded
env | grep ANTHROPIC_MODEL

# Test API connectivity (before full session)
curl -X GET https://api.anthropic.com/v1/models \
  -H "x-api-key: $ANTHROPIC_API_KEY" \
  -H "anthropic-version: 2024-06"

# Enable debug output
export CLAUDE_CODE_DEBUG=1
export CLAUDE_CODE_DEBUG_MCP=1
claude

# Verify sandbox status
export CLAUDE_CODE_VERBOSE_MODE=1
# Output will show whether commands run sandboxed or unsandboxed

# All three variables often needed together
export HTTP_PROXY=http://proxy.company.com:8080
export HTTPS_PROXY=http://proxy.company.com:8080
export NO_PROXY=localhost,127.0.0.1,.company.internal

# If proxy uses client certificates
export NODE_EXTRA_CA_CERTS=/etc/ssl/certs/corporate-ca.pem

# Test connectivity
curl -x http://proxy.company.com:8080 https://api.anthropic.com

# For SOCKS5 proxies (e.g., SSH tunneling)
export SOCKS_PROXY=socks5://localhost:1080

# SSH tunnel example:
# ssh -D 1080 user@remote-host
# Then set SOCKS_PROXY=socks5://localhost:1080

export CLAUDE_CODE_MAX_TURNS=50

# Useful for:
# - Controlling costs (limits expensive operations)
# - Forcing summaries (every 50 turns, session ends)
# - Testing within quotas
# - Batch processing (restart session, use fresh token budget)

# Single custom model via gateway
export ANTHROPIC_CUSTOM_MODEL_OPTION=my-gateway/claude-opus-4-6
export ANTHROPIC_CUSTOM_MODEL_OPTION_NAME="Opus via Internal Gateway"
export ANTHROPIC_CUSTOM_MODEL_OPTION_DESCRIPTION="Routes through internal LLM gateway with monitoring"

# Result: /model picker shows "Opus via Internal Gateway" option
# Usage: claude --model custom

# Cache OFF for all models (saves no tokens, slower)
export DISABLE_PROMPT_CACHING=1

# Cache OFF for Haiku only (Haiku cache often not worth the complexity)
export DISABLE_PROMPT_CACHING_HAIKU=1

# Cache OFF for Opus only (unusual - Opus caching is most valuable)
export DISABLE_PROMPT_CACHING_OPUS=1

# Recommended: Leave all enabled (default)

# Low effort: minimal extended thinking
export CLAUDE_CODE_EFFORT_LEVEL=low
export MAX_THINKING_TOKENS=1000

# High effort: extensive reasoning
export CLAUDE_CODE_EFFORT_LEVEL=high
export MAX_THINKING_TOKENS=20000

# Max effort (Opus 4.6 only): maximum problem-solving
export CLAUDE_CODE_EFFORT_LEVEL=max
export MAX_THINKING_TOKENS=50000  # Opus 4.6 allows this

# ~/.zshrc (or ~/.bash_profile for bash)
export ANTHROPIC_API_KEY="sk-ant-v0-..."
export ANTHROPIC_MODEL="opus"

# Source this file automatically
source ~/.zshrc

# PowerShell profile: Open PowerShell, run:
# echo $profile
# Edit that file (usually: C:\Users\USERNAME\Documents\PowerShell\profile.ps1)

[System.Environment]::SetEnvironmentVariable("ANTHROPIC_API_KEY", "sk-ant-v0-...", "User")
[System.Environment]::SetEnvironmentVariable("ANTHROPIC_MODEL", "opus", "User")

# Restart PowerShell to apply

# ~/.bashrc or ~/.zshrc (whichever shell you use)
export ANTHROPIC_API_KEY="sk-ant-v0-..."
export ANTHROPIC_MODEL="opus"
export CLAUDE_CODE_EFFORT_LEVEL="medium"

# Apply without restarting:
source ~/.bashrc

# Memory constraints (limit Claude Code process)
export NODE_OPTIONS="--max-old-space-size=2048"  # 2GB limit

# Context window
export CLAUDE_CODE_DISABLE_1M_CONTEXT=0  # Keep 1M enabled if available

# Large project optimization
export USE_BUILTIN_RIPGREP=1  # Use internal ripgrep (faster)
# vs USE_BUILTIN_RIPGREP=0  # Use system ripgrep (slower but customizable)

# Session 1: Production with strict limits
export ANTHROPIC_MODEL=sonnet
export CLAUDE_CODE_MAX_TURNS=30
export CLAUDE_CODE_TASK_LIST_ID=prod-task-list
claude

# Session 2: Development with full power
export ANTHROPIC_MODEL=opus
export CLAUDE_CODE_MAX_TURNS=200
export CLAUDE_CODE_TASK_LIST_ID=dev-task-list
export CLAUDE_CODE_EFFORT_LEVEL=high
claude