Show HN: OpenGravity – A zero-install, BYOK vanilla JS clone of Antigravity

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Summary

OpenGravity is a zero-install, vanilla JS clone of Google Antigravity that enables BYOK agentic coding using Gemini models and WebContainer API. Built to bypass rate limits, it offers a browser-based IDE with autonomous task orchestration and local file sync.

Hi. I’m a high school student studying for my GCSEs. I was using Google Antigravity heavily for my side projects, but I kept hitting the usage limits, and getting random &quot;agent terminated&quot; errors. So I decided to try build my own version of the IDE. I love the UI, so I copied it as accurately as possible, and then hooked up some logic into it, including the INCREDIBLY finicky webcontainer api.<p>I tried to keep it super lightweight, no build steps, or dependencies, and now that its open source, I&#x27;m hoping people can build things on top of it that arent possible with closed source tools, like complex custom agent workflows.<p>Some screenshots: - <a href="https:&#x2F;&#x2F;github.com&#x2F;ab-613&#x2F;OpenGravity&#x2F;blob&#x2F;main&#x2F;examples&#x2F;screenshot.png?raw=true" rel="nofollow">https:&#x2F;&#x2F;github.com&#x2F;ab-613&#x2F;OpenGravity&#x2F;blob&#x2F;main&#x2F;examples&#x2F;scr...</a> - <a href="https:&#x2F;&#x2F;github.com&#x2F;ab-613&#x2F;OpenGravity&#x2F;blob&#x2F;main&#x2F;examples&#x2F;html%20site%20example.png?raw=true" rel="nofollow">https:&#x2F;&#x2F;github.com&#x2F;ab-613&#x2F;OpenGravity&#x2F;blob&#x2F;main&#x2F;examples&#x2F;htm...</a><p>What it&#x27;s made from:<p>- Pure Vanilla JS: no react, vue, or build step. Built entirely in plain HTML&#x2F;CSS&#x2F;JS to keep it super lightweight.<p>- WebContainer API and xterm.js: Instead of faking a terminal, I (after much pain) hooked up the WebContainer API so the AI agent has a real, in browser linux environment to run shell commands, install dependencies, and edit local files.<p>- BYOK (Bring Your Own Key): API key ALWAYS stays in localStorage.<p>Whats currently happening:<p>- It works, but it&#x27;s an alpha. The AI can proactively start projects going properly and edit files, but because I built this over a few days before my exams, a lot of the UI dropdowns and buttons are currently just hardcoded placeholders.<p>- I’m open sourcing it early because I think the foundation of a Vanilla JS + WebContainer IDE is really strong, and I&#x27;d love to see where the community takes it while I&#x27;m doing my exams.<p>- Live demo: <a href="https:&#x2F;&#x2F;opengravity.pages.dev" rel="nofollow">https:&#x2F;&#x2F;opengravity.pages.dev</a> (Zoom out to 80% if not full screen. It will prompt for a gemini api key on load). Start by uploading a folder, then you can fiddle with the terminal and agent, and see how it goes!<p>Would love to hear feedback on the code, the WebContainer integration, or how to improve the agent loop!
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ab-613/opengravity

Source: https://github.com/ab-613/opengravity

OpenGravity

The zero-install agentic workspace.

OpenGravity Logo

An experimental, lightweight, BYOK (Bring Your Own Key) recreation of the Google Antigravity UI. OpenGravity provides a browser-based, reasoning-enabled IDE with a live xterm.js terminal powered by the WebContainer API. It features direct local file system sync and a proactive autonomous agent capable of orchestrating basic software engineering tasks, running shell commands, and editing files in real-time. It’s currently a work-in-progress though. It works for basic coding tasks, but consider this the “Alpha” version.

Built in pure HTML/CSS/JS for maximum speed and zero installation.

Origin

  • I was using Google Antigravity quite intensively for a load of projects I was making.
  • Very quickly, I got hit with rate limits.
  • Google Antigravity has become over the past few months quite infamous for this, and doesnt seem to be improving.
  • I was thinking of switching to a CLI, or a vscode based program instead, but I really love the Antigravity UI.
  • So I went to Google AI Studio, and put in a LOAD of screenshots, and with a load of interesting prompt engineering techniques, gemini 3.1 pro put together a beautiful clone (if I may say so myself).
  • I loved how it looked, so over a couple of days in some free time, I used it to wire together some features, like the file management and agent logic, and here we are!

📸 Examples

Autonomous Web Development

The agent can proactively initialize projects, install dependencies using pnpm, and build complete applications while you watch.

HTML Site Examples

HTML Site Examples


✨ Features

  • BYOK (Bring Your Own Key): Total privacy. Currently ONLY supports Gemini API models (e.g. gemini-3.1-pro-preview, gemini-3-flash-preview, gemini-3.1-flash-lite, [though to change you will need to modify agent.js:8]).
  • Proactive Agentic Reasoning: Uses advanced thinking models to plan, execute, and validate tasks without constant user intervention.
  • High-Performance Terminal: Integrated xterm.js with a real Linux-like environment provided by WebContainer API.
  • Interactive Tooling: The agent can execute bash commands, handle interactive terminal prompts (y/n), and manage files directly.
  • Zero Bloat: No npm install for the IDE itself. Just serve and code.
  • Secure by Design: API keys are stored only in your browser’s localStorage.

🛠️ How you can help

I’m currently heads-down in my studies, so I’m handing the baton to the community. The UI looks great and the basic logic is there, but it needs “pro” features to truly beat the original.

I want people to take this and make it usable for the average person. Specifically:

  • Better Orchestration: The current agent logic is basic; it needs better “Manager/Sub-agent” handling.
  • Provider Support: Right now it’s Gemini-only. Help me add OpenAI, Anthropic, etc…
  • Bugs: The file sync and terminal can be finicky—it needs some “battle-hardening.”
  • Polished UI: The UI is cool, but there’s a lot to be done.
  • Model Selection: The dropdown is hardcoded. It needs to switch the model in agent.js.
  • Top Menu Bars: “File,” “Edit,” and “Selection” menus are placeholders. Basic functionality like Save and Search is needed.
  • Git Support: The icon is present, but there is no logic behind it yet.
  • Settings UI: Users must click the small “a” icon in the top right to enter an API key. A proper, user-friendly settings panel is needed.

🚀 Getting Started

  1. Serve the project root using a local server (python3 server.py).
  2. Open http://localhost:8000 in your browser.
  3. Click the tiny “a” icon in the top-right corner (yeah, it’s awkward—it’s on the to-do list to fix!) and enter your Gemini API Key.
  4. Start chatting with Antigravity in the right panel.

🛠️ Status: On Hiatus

I’m balancing this with my GCSEs, so I will be reviewing and merging PRs every Sunday evening.

📜 License

Licensed under GPL-3.0. See the LICENSE file for details on commercial use and contributions.

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