Claude Code overview

$ npm install -g @anthropic-ai/claude-code

Claude Code is an agentic coding tool that lives in your terminal, understands your codebase, and helps you code faster through natural language commands. By integrating directly with your development environment, Claude Code streamlines your workflow without requiring additional servers or complex setup.

Claude Code’s key capabilities include:

• Editing files and fixing bugs across your codebase
• Answering questions about your code’s architecture and logic
• Executing and fixing tests, linting, and other commands
• Searching through git history, resolving merge conflicts, and creating commits and PRs

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Before you begin

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Check system requirements

• Operating Systems: macOS 10.15+, Ubuntu 20.04+/Debian 10+, or Windows via WSL
• Hardware: 4GB RAM minimum
• Software:
  • Node.js 18+
  • git 2.23+ (optional)
  • GitHub or GitLab CLI for PR workflows (optional)
  • ripgrep (rg) for enhanced file search (optional)
• Network: Internet connection required for authentication and AI processing
• Location: Available only in supported countries

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Install and authenticate

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Core features and workflows

Claude Code operates directly in your terminal, understanding your project context and taking real actions. No need to manually add files to context - Claude will explore your codebase as needed. Claude Code uses claude-3-7-sonnet-20250219 by default.

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Security and privacy by design

Your code’s security is paramount. Claude Code’s architecture ensures:

• Direct API connection: Your queries go straight to Anthropic’s API without intermediate servers
• Works where you work: Operates directly in your terminal
• Understands context: Maintains awareness of your entire project structure
• Takes action: Performs real operations like editing files and creating commits

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From questions to solutions in seconds

# Ask questions about your codebase
$ claude
> how does our authentication system work?

# Create a commit with one command
$ claude commit

# Fix issues across multiple files
$ claude "fix the type errors in the auth module"

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Initialize your project

For first-time users, we recommend:

1. Start Claude Code with claude
2. Try a simple command like summarize this project
3. Generate a CLAUDE.md project guide with /init
4. Ask Claude to commit the generated CLAUDE.md file to your repository

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Use Claude Code for common tasks

Claude Code operates directly in your terminal, understanding your project context and taking real actions. No need to manually add files to context - Claude will explore your codebase as needed.

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Understand unfamiliar code

> what does the payment processing system do?
> find where user permissions are checked
> explain how the caching layer works

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Automate Git operations

> commit my changes
> create a pr
> which commit added tests for markdown back in December?
> rebase on main and resolve any merge conflicts

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Edit code intelligently

> add input validation to the signup form
> refactor the logger to use the new API
> fix the race condition in the worker queue

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Test and debug your code

> run tests for the auth module and fix failures
> find and fix security vulnerabilities
> explain why this test is failing

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Encourage deeper thinking

For complex problems, explicitly ask Claude to think more deeply:

> think about how we should architect the new payment service
> think hard about the edge cases in our authentication flow

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Control Claude Code with commands

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CLI commands

CLI flags:

• --print: Print response without interactive mode
• --verbose: Enable verbose logging
• --dangerously-skip-permissions: Skip permission prompts (only in Docker containers without internet)

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Slash commands

Control Claude’s behavior within a session:

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Manage permissions and security

Claude Code uses a tiered permission system to balance power and safety:

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Tools available to Claude

Claude Code has access to a set of powerful tools that help it understand and modify your codebase:

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Protect against prompt injection

Prompt injection is a technique where an attacker attempts to override or manipulate an AI assistant’s instructions by inserting malicious text. Claude Code includes several safeguards against these attacks:

• Permission system: Sensitive operations require explicit approval
• Context-aware analysis: Detects potentially harmful instructions by analyzing the full request
• Input sanitization: Prevents command injection by processing user inputs
• Command blocklist: Blocks risky commands that fetch arbitrary content from the web like curl and wget

Best practices for working with untrusted content:

1. Review suggested commands before approval
2. Avoid piping untrusted content directly to Claude
3. Verify proposed changes to critical files
4. Report suspicious behavior with /bug

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Configure network access

Claude Code requires access to:

• api.anthropic.com
• statsig.anthropic.com
• sentry.io

Allowlist these URLs when using Claude Code in containerized environments.

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Configure Claude Code

Configure Claude Code by running claude config in your terminal, or the /config command when using the interactive REPL.

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Configuration options

Claude Code supports global and project-level configuration.

To manage your configurations, use the following commands:

• List settings: claude config list
• See a setting: claude config get <key>
• Change a setting: claude config set <key> <value>
• Push to a setting (for lists): claude config add <key> <value>
• Remove from a setting (for lists): claude config remove <key> <value>

By default config changes your project configuration. To manage your global configuration, use the --global (or -g) flag.

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Global configuration

To set a global configuration, use claude config set -g <key> <value>:

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Auto-updater permission options

When Claude Code detects that it doesn’t have sufficient permissions to write to your global npm prefix directory (required for automatic updates), you’ll see a warning that points to this documentation page.

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Recommended: Create a new user-writable npm prefix

# First, save a list of your existing global packages for later migration
npm list -g --depth=0 > ~/npm-global-packages.txt

# Create a directory for your global packages
mkdir -p ~/.npm-global

# Configure npm to use the new directory path
npm config set prefix ~/.npm-global

# Note: Replace ~/.bashrc with ~/.zshrc, ~/.profile, or other appropriate file for your shell
echo 'export PATH=~/.npm-global/bin:$PATH' >> ~/.bashrc

# Apply the new PATH setting
source ~/.bashrc

# Optional: Reinstall your previous global packages in the new location
# Look at ~/npm-global-packages.txt and install packages you want to keep
# npm install -g package1 package2 package3...

Why we recommend this option:

• Avoids modifying system directory permissions
• Creates a clean, dedicated location for your global npm packages
• Follows security best practices

Since Claude Code is actively developing, we recommend setting up auto-updates using the recommended option above.

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Project configuration

Manage project configuration with claude config set <key> <value> (without the -g flag):

For example:

# Let npm test to run without approval
$ claude config add allowedTools "Bash(npm test)"

# Let npm test and any of its sub-commands to run without approval
$ claude config add allowedTools "Bash(npm test:*)"

# Instruct Claude to ignore node_modules
$ claude config add ignorePatterns node_modules
$ claude config add ignorePatterns "node_modules/**"

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Optimize your terminal setup

Claude Code works best when your terminal is properly configured. Follow these guidelines to optimize your experience.

Supported shells:

• Bash
• Zsh (Fish shell not currently supported)

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Themes and appearance

Claude cannot control the theme of your terminal. That’s handled by your terminal application. You can match Claude Code’s theme to your terminal during onboarding or any time via the /config command

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Line breaks

You have several options for entering linebreaks into Claude Code:

• Quick escape: Type \ followed by Enter to create a newline
• Keyboard shortcut: Press Option+Enter (Meta+Enter) with proper configuration

To set up Option+Enter in your terminal:

For Mac Terminal.app:

1. Open Settings → Profiles → Keyboard
2. Check “Use Option as Meta Key”

For iTerm2 and VSCode terminal:

1. Open Settings → Profiles → Keys
2. Under General, set Left/Right Option key to “Esc+”

Tip for iTerm2 and VSCode users: Run /terminal-setup within Claude Code to automatically configure Shift+Enter as a more intuitive alternative.

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Notification setup

Never miss when Claude completes a task with proper notification configuration:

Terminal bell notifications

Enable sound alerts when tasks complete:

$ claude config set --global preferredNotifChannel terminal_bell

For macOS users: Don’t forget to enable notification permissions in System Settings → Notifications → [Your Terminal App].

iTerm 2 system notifications

For iTerm 2 alerts when tasks complete:

1. Open iTerm 2 Preferences
2. Navigate to Profiles → Terminal
3. Enable “Silence bell” and “Send notification when idle”
4. Set your preferred notification delay

Note that these notifications are specific to iTerm 2 and not available in the default macOS Terminal.

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Handling large inputs

When working with extensive code or long instructions:

• Avoid direct pasting: Claude Code may struggle with very long pasted content
• Use file-based workflows: Write content to a file and ask Claude to read it
• Be aware of VS Code limitations: The VS Code terminal is particularly prone to truncating long pastes

By configuring these settings, you’ll create a smoother, more efficient workflow with Claude Code.

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Manage costs effectively

Claude Code consumes tokens for each interaction. Typical usage costs range from $5-10 per developer per day, but can exceed $100 per hour during intensive use.

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Track your costs

• Use /cost to see current session usage
• Review cost summary displayed when exiting
• Check historical usage in Anthropic Console
• Set Spend limits

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Reduce token usage

• Compact conversations: Use /compact when context gets large
• Write specific queries: Avoid vague requests that trigger unnecessary scanning
• Break down complex tasks: Split large tasks into focused interactions
• Clear history between tasks: Use /clear to reset context

Costs can vary significantly based on:

• Size of codebase being analyzed
• Complexity of queries
• Number of files being searched or modified
• Length of conversation history
• Frequency of compacting conversations

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Use with third-party APIs

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Connect to Amazon Bedrock

CLAUDE_CODE_USE_BEDROCK=1

Optional: Override the default model (Claude 3.7 Sonnet is used by default):

ANTHROPIC_MODEL='us.anthropic.claude-3-7-sonnet-20250219-v1:0'

If you don’t have prompt caching enabled, also set:

DISABLE_PROMPT_CACHING=1

Requires standard AWS SDK credentials (e.g., ~/.aws/credentials or relevant environment variables like AWS_ACCESS_KEY_ID, AWS_SECRET_ACCESS_KEY). Contact Amazon Bedrock for prompt caching for reduced costs and higher rate limits.

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Connect to Google Vertex AI

CLAUDE_CODE_USE_VERTEX=1
CLOUD_ML_REGION=us-east5
ANTHROPIC_VERTEX_PROJECT_ID=your-project-id

Requires standard GCP credentials configured through google-auth-library. For the best experience, contact Google for heightened rate limits.

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Development container reference implementation

Claude Code provides a development container configuration for teams that need consistent, secure environments. This preconfigured devcontainer setup works seamlessly with VS Code’s Remote - Containers extension and similar tools.

The container’s enhanced security measures (isolation and firewall rules) allow you to run claude --dangerously-skip-permissions to bypass permission prompts for unattended operation. We’ve included a reference implementation that you can customize for your needs.

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Key features

• Production-ready Node.js: Built on Node.js 20 with essential development dependencies
• Security by design: Custom firewall restricting network access to only necessary services
• Developer-friendly tools: Includes git, ZSH with productivity enhancements, fzf, and more
• Seamless VS Code integration: Pre-configured extensions and optimized settings
• Session persistence: Preserves command history and configurations between container restarts
• Works everywhere: Compatible with macOS, Windows, and Linux development environments

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Getting started in 4 steps

1. Install VS Code and the Remote - Containers extension
2. Clone the Claude Code reference implementation repository
3. Open the repository in VS Code
4. When prompted, click “Reopen in Container” (or use Command Palette: Cmd+Shift+P → “Remote-Containers: Reopen in Container”)

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Configuration breakdown

The devcontainer setup consists of three primary components:

• devcontainer.json: Controls container settings, extensions, and volume mounts
• Dockerfile: Defines the container image and installed tools
• init-firewall.sh: Establishes network security rules

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Security features

The container implements a multi-layered security approach with its firewall configuration:

• Precise access control: Restricts outbound connections to whitelisted domains only (npm registry, GitHub, Anthropic API, etc.)
• Default-deny policy: Blocks all other external network access
• Startup verification: Validates firewall rules when the container initializes
• Isolation: Creates a secure development environment separated from your main system

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Customization options

The devcontainer configuration is designed to be adaptable to your needs:

• Add or remove VS Code extensions based on your workflow
• Modify resource allocations for different hardware environments
• Adjust network access permissions
• Customize shell configurations and developer tooling

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Next steps

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License and data usage

Claude Code is provided as a Beta research preview under Anthropic’s Commercial Terms of Service.

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How we use your data

We aim to be fully transparent about how we use your data. We may use feedback to improve our products and services, but we will not train generative models using your feedback from Claude Code. Given their potentially sensitive nature, we store user feedback transcripts for only 30 days.

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Feedback transcripts

If you choose to send us feedback about Claude Code, such as transcripts of your usage, Anthropic may use that feedback to debug related issues and improve Claude Code’s functionality (e.g., to reduce the risk of similar bugs occurring in the future). We will not train generative models using this feedback.

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Privacy safeguards

We have implemented several safeguards to protect your data, including limited retention periods for sensitive information, restricted access to user session data, and clear policies against using feedback for model training.

For full details, please review our Commercial Terms of Service and Privacy Policy.

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License

© Anthropic PBC. All rights reserved. Use is subject to Anthropic’s Commercial Terms of Service.