Antigravity is Google's agent-first coding tool. This installs its VS Code extension into your Hydrogen editor and its agy command line into your container, so it sits next to Claude Code, Codex and Kimi. Nothing touches Windows or macOS itself.
1. The editor extension
Puts the Antigravity side bar in your editor (its own icon on the activity bar). Sign in with your Google account inside that panel; in a Hydrogen workspace that same sign-in covers the CLI.
From Open VSX (Google.google-antigravity). A fresh install needs one editor reload.
2. The command line
The agy CLI runs Antigravity's agent in a terminal, the way Claude and Codex have their TUIs.
Official installer into ~/.local/bin/agy. First run: agy prints a Google sign-in link when it cannot open a browser. Headless: set GEMINI_API_KEY and modelProvider: gemini in ~/.gemini/antigravity-cli/settings.json.
3. Use it
Open the Antigravity side bar in your editor (its own icon on the activity bar) and sign in with Google the first time. The AI launch bar's Antigravity icon does the same; its TUI entry runs agy.
Needs Hydrogen 1.0.224 or later, which serves forwarded ports the way this panel expects. On an older Hydrogen or on Web Hydrogen the panel is blank, and this button opens Antigravity's UI as a tab instead.
What it is
An agent that plans, writes and verifies across your files and a browser, with its own workflows and artifacts. Free tier from Google; the extension and CLI both need a Google sign-in.