🟢 Basics & Installation

🟢 What It Is

O Claude Code is Anthropic’s coding agent that runs in your terminal. It’s not autocomplete or chat: it reads your project, plans, edits files, runs commands and tests, use git and browses the web — always asking for your approval. You speak Portuguese; it executes.

💡 Why learn

Unlike pasting code from a chat, Claude Code works inside the actual repository — understands the full context via CLAUDE.md, respects your stack and runs on any system. It's the foundation for everything in the upcoming tracks.

🔑 Where You Can Use It

🟢 What It Is

Installation via npm. Prerequisites: Node.js 18+ and, on Windows, Git Bash. Sign-in is through subscription (Pro/Max via browser) or through API key by Anthropic.

💡 Why learn

An outdated Node version causes silent failures. On Windows, Claude Code won’t run without Git Bash—it’s the #1 mistake beginners make. Following the right order avoids 90% of installation problems.

🔑 Step by Step (The Right Order)

# 1. Instale o Git (inclui o Git Bash) → git-scm.com/download/win
# 2. Instale o Node.js LTS → nodejs.org
# 3. Confira:
node -v
npm -v
# 4. Instale o Claude Code:
npm install -g @anthropic-ai/claude-code
# 5. Rode:
claude

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

sudo apt update && sudo apt install -y nodejs npm
npm install -g @anthropic-ai/claude-code
claude

# Dentro do claude, rode:
/login        # abre o navegador → conta Pro/Max (recomendado)

# OU, via API key (pague por uso):
setx ANTHROPIC_API_KEY "sk-ant-..."   # Windows
export ANTHROPIC_API_KEY="sk-ant-..." # macOS/Linux

🟢 What It Is

You run claude inside the project folder and type your request in natural language. It proposes edits like diffs that you approve or reject. @ references files and # saves something to memory.

💡 Why learn

The fear that “it’ll mess up my code” goes away when you understand the approval loop: nothing changes without you seeing the diff. Esc stops immediately if it takes the wrong direction.

🔑 Key Concepts

cd meu-projeto
claude                          # abre o modo interativo
claude "corrija o bug do login" # pedido direto
claude -p "resuma o README"     # print mode: responde e sai (scripts)

🟢 What It Is

Commands that start with / control the session (not the project). Type / and see the list. The most commonly used manage the context — the scarcest resource in a session.

💡 Why learn

/clear e /compact are what keep the session fast and inexpensive. Without them, the context fills up, Claude slows down, and "forgets" the beginning. (Track 3 explores this in more depth.)

🔑 The Essentials

🟢 What It Is

Pressing Shift+Tab you switch between session modes. In plan mode (plan mode), Claude investigates and proposes a plan — but doesn't edit anything until you approve.

💡 Why learn

For large or risky tasks, letting it “start editing” is a recipe for rework. Planning first aligns the path. The preset opusplan uses Opus (more powerful) to plan and Sonnet (cheaper/faster) to execute — quality where it matters, savings elsewhere.

🔑 The 3 Modes (Shift+Tab Cycles)

/model opusplan   # Opus planeja, Sonnet executa

🟢 What It Is

O CLAUDE.md is a file at the project root with the permanent context: how to run, conventions, rules, what not to do. The command /init generates one for you by analyzing the repo. The folder .claude/ stores settings, commands, agents, and skills.

💡 Why learn

Without CLAUDE.md, Claude starts from scratch each session and repeats the same mistakes. With it, Claude follows your stack and style from the first prompt. It’s the 5-minute investment that improves all the following sessions.

🔑 Memory Hierarchy

# Projeto X
- Stack: Next.js + TypeScript + pnpm
- Rodar: `pnpm dev` · Testar: `pnpm test`
- Convenção: componentes em PascalCase, sem default export
- NUNCA commitar direto na main

Shortcut: type # sua regra in the session to attach something to CLAUDE.md right away.

🟢 What It Is

By default, Claude asks for permission before editing files or running commands. You define lists of allow / deny e o mode permission. The command /permissions manages everything.

💡 Why learn

Permissions are your seat belt. Allow safe commands (e.g., npm test) reduces clicks; but never use bypass on machines with sensitive data or in production.

🔑 Permission Modes

/permissions          # abre o gerenciador
# em .claude/settings.json:
# "permissions": { "allow": ["Bash(npm test)"], "deny": ["Bash(rm -rf *)"] }

🟢 What It Is

You use Claude Code through subscription (Pro/Max — included usage) or through API (paid per token). /cost shows the session's spending. The choice of model has the biggest impact on cost and speed.

💡 Why learn

Using Opus for everything is expensive and unnecessary. Sonnet handles day-to-day work; Opus is for what’s difficult; opusplan combines the two. Along with /compact e /clear, you control the cost.

🔑 Models — When to Use Each

/cost                       # gasto da sessão
/model sonnet               # troca pro Sonnet
claude --model "opus[1m]"   # abre com contexto de 1M