Claude Code is Anthropic's agentic coding tool: a command-line assistant that lives in your terminal, reads and edits your actual codebase, runs shell commands, and drives multi-step engineering work instead of just answering questions in a chat window. It anchors a terminal-first developer workflow that shares its skills, subagents, hooks, and MCP connections with Anthropic's broader Agent SDK, so time spent configuring it compounds across every future session. The biggest mental-model shift for newcomers: Claude Code isn't a single conversational assistant, it's a configurable agent runtime — permission modes decide how much autonomy it gets, hooks enforce rules a prompt alone can't guarantee, and subagents plus git worktrees let several instances work in parallel without touching each other's files.
What This Cheat Sheet Covers
This topic spans 15 focused tables and 178 indexed concepts. Below is a complete table-by-table outline of this topic, spanning foundational concepts through advanced details.
A jump-to index of every table row in this cheat sheet.
An interactive map of every table and concept in this topic.
Table 1: Installation, Setup & Authentication
Getting Claude Code running starts with picking an install method for your platform, then authenticating with either a Claude subscription or an API key; everything else in this cheat sheet assumes one of these is already done.
| Task | Example | Description |
|---|---|---|
curl -fsSL | bash | Recommended one-line installer for macOS, Linux, and WSL; auto-updates in the background on the chosen release channel. | |
claude (then follow the browser prompt) | Requires a Pro, Max, Team, Enterprise, or Console account • the free Claude.ai plan has no Claude Code access. | |
npm install -g -ai/claude-code | Cross-platform install via Node.js 22+; downloads a native binary, so Node isn't needed at runtime. | |
brew install --cask claude-code | macOS package-manager install; requires manual updates unless the auto-update env var is set. | |
ANTHROPIC_API_KEY=sk-ant-... | Set the env var to skip the browser sign-in flow and bill per token instead of by subscription. | |
claude doctor | Prints read-only install/config diagnostics (duplicate installs, PATH issues, update status) without starting a session. | |
Install the "Claude Code" extension | Adds inline diffs, @-mentions, and plan review inside VS Code; a matching plugin covers JetBrains IDEs. |