Claude Code

Anthropic's Agentic Coding Tool for Your Terminal

What is Claude Code?

Claude Code is Anthropic's agentic coding tool that operates directly in your terminal. It understands your entire codebase, can make complex multi-file edits, run tests, fix bugs, and handle git operations—all through natural language commands.

"Claude Code is designed for software engineers who want Claude's capabilities directly in their terminal, with full context of their codebase and the ability to take real actions."

— Anthropic

Terminal Native

CLI-first design

Multi-File Edits

Complex changes

Git Integration

Commits & PRs

Test Runner

Run & fix tests

Installation

Install Claude Code

# Install via npm (recommended)
npm install -g @anthropic-ai/claude-code

# Or via Homebrew (macOS)
brew install claude-code

# Authenticate with your API key
export ANTHROPIC_API_KEY="your-api-key"

# Start Claude Code in your project
cd your-project
claude

Requirement: Claude Code requires an Anthropic API key. Get one at console.anthropic.com

Key Commands

# Start interactive mode
claude

# Run a one-shot command
claude "add error handling to the API routes"

# Resume previous conversation
claude --continue

# Start with a specific file
claude --file src/app.py "refactor this to use async/await"

# Show help
claude --help

What Can Claude Code Do?

Code Editing

Multi-file edits across codebase
Refactoring with context
Add new features from specs
Fix linting errors

Terminal Commands

Run and fix tests
Execute shell commands
Manage dependencies
Run build scripts

Git Operations

Create commits with messages
Handle merge conflicts
Search git history
Create branches

Understanding

Answer architecture questions
Explain complex code
Find patterns & bugs
Document code

Configuration (CLAUDE.md)

Create a CLAUDE.md file in your repository root to give Claude Code persistent instructions about your project.

CLAUDE.md

# Project Context for Claude Code

## Overview
This is a Python Flask web application with a React frontend.

## Tech Stack
- Backend: Python 3.11, Flask, SQLAlchemy
- Frontend: React 18, TypeScript, TailwindCSS
- Database: PostgreSQL
- Tests: pytest, React Testing Library

## Commands
- `make dev` - Start development server
- `make test` - Run all tests
- `make lint` - Run linting

## Code Style
- Use Black for Python formatting
- Use ESLint + Prettier for TypeScript
- Write docstrings for all functions

## Important Notes
- Never modify migrations/ directly
- API versioning in /api/v1/
- All new endpoints need tests

Claude Code vs OpenAI Codex

Aspect	Claude Code	OpenAI Codex
Interface	Local terminal	Web + VS Code
Execution	Local machine	Cloud sandbox
Context	Full local repo	Cloned snapshot
Model	Claude (Anthropic)	codex-1 (OpenAI)
Pricing	API usage	ChatGPT Pro subscription

Try Claude Code

Get Started

Claude Code requires an Anthropic API key. Sign up at the Anthropic Console and install the CLI to start coding with Claude in your terminal.

Learn More

Resources & References

Official Page

anthropic.com/claude-code

Documentation

Official docs