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Day 1 Overview ​

Gemini CLI puts a terminal AI agent on your machine. You type a prompt, it reads files, runs commands, and edits code. No browser, no IDE, no context-switching. By the end of Day 1 you'll have it installed, authenticated, and completing real coding tasks from a terminal.

The five lessons move from zero to productive: install and authenticate, learn the REPL, master slash commands, configure persistent project context with GEMINI.md, and run sandboxed code with Docker.

Important note for every lesson: Gemini CLI is transitioning to Antigravity CLI on June 18, 2026. If you're reading this after that date and are on the free tier or Google One, your Gemini CLI install will have migrated to Antigravity CLI. Enterprise users remain on Gemini CLI. The commands and workflows in Day 1 are the same on both platforms. Where they differ, we call it out.

What you'll build ​

By the end of these five lessons you will:

  • Have Gemini CLI installed and authenticated with your Google account
  • Navigate the REPL and complete file-editing tasks
  • Use slash commands to manage sessions and switch models
  • Write a GEMINI.md file that gives every session persistent context about your project
  • Run Gemini CLI inside a Docker sandbox for safe execution of untrusted code

Lessons ​

  1. Installation & Authentication -- Install via npm, brew, or npx and authenticate with OAuth. System requirements, common install failures, and how to verify it worked.

  2. The REPL & Your First Task -- Interactive mode, one-shot -p flag, --yolo for auto-approval, and completing a real coding task: fix a buggy script.

  3. Slash Commands -- /help, /clear, /compact, /memory, /init, /model, /config, /status, /exit. When to use each and what they actually do.

  4. GEMINI.md -- Project Context -- Write a GEMINI.md file that Gemini CLI loads at session start. What to put in it, what to leave out, and how it differs from CLAUDE.md and COPILOT.md.

  5. Sandbox & Docker Execution -- The --sandbox flag, pre-built sandbox images, Docker/Podman setup, and when you should use sandbox mode versus trusting the host.

Next: Day 2 -- Gemini CLI: Advanced Features