When Google launched a major upgrade to AI Studio on March 18, 2026, it wasn't just another chat interface refresh. The company embedded an autonomous coding agent called Antigravity directly into the browser-based build environment, then wired it to Firebase so that data storage, authentication, and hosting get provisioned the moment a prompt signals the need for them. The result is a full-stack app builder that works entirely in a browser tab, free with a Google account. No local environment, no config files — describe what you want, click "Enable Firebase" when the agent asks, and get a shareable URL. This guide covers what Antigravity actually does, how the Firebase integration works under the hood, where the tool fits against Cursor and Lovable, and what the real limitations look like before you commit to it for a project. What Is the Antigravity Agent Antigravity is not a code completion overlay.…