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Claude Code

Claude Code is Anthropic's official CLI for Claude. It runs in your terminal, reads your codebase, executes commands, and can handle multi-step programming tasks autonomously.

Installation​

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

Requires Node.js 18+ and an Anthropic API key (or Claude Pro/Max subscription).

Basic usage​

Run it from inside your project directory:

claude

Claude Code automatically reads your project structure and can access any file in the working directory.

Key capabilities​

Agentic task execution​

Unlike chat tools, Claude Code can take actions: edit files, run tests, install packages, and iterate until a task is complete.

Fix the failing tests in src/auth/ and make sure all other tests still pass.

Full codebase context​

Claude Code indexes your repository so you don't need to paste code manually. You can reference files by name:

Refactor the UserService class to use dependency injection.

Custom commands (slash commands)​

You can define custom /commands in .claude/commands/ as Markdown files. These become reusable prompts available in any session.

Hooks​

Hooks run shell commands automatically in response to events (e.g. before a file is edited, after a tool is used). Useful for enforcing linting, running tests, or logging actions.

MCP servers​

Claude Code supports the Model Context Protocol (MCP), allowing you to connect it to external tools: databases, APIs, internal systems.

CLAUDE.md​

Create a CLAUDE.md file at the root of your project to give Claude Code persistent context: coding conventions, project structure, commands to run, things to avoid.

# Project conventions
- TypeScript strict mode, no `any`
- All API routes must have Zod validation
- Run `npm test` before committing
- Never modify migration files

Tips​

  • Be specific: tell it exactly what you want and what constraints to respect
  • Review changes: use /diff or check git diff before accepting edits
  • Scope tasks: break large tasks into smaller steps for better results
  • Use CLAUDE.md: persistent context saves you from repeating yourself every session