I’m Chris McCord, the creator of Elixir’s Phoenix framework. For the past several months, I’ve been working on a skunkworks project at Fly.io, and it’s time to show it off.
I wanted LLM agents to work just as well with Elixir as they do with Python and JavaScript. Last December, in order to figure out what that was going to take, I started a little weekend project to find out how difficult it would be to build a coding agent in Elixir.
A few weeks later, I had it spitting out working Phoenix applications and driving a full in-browser IDE. I knew this wasn’t going to stay a weekend project.
If you follow me on Twitter, you’ve probably seen me teasing this work as it picked up steam. We’re at a point where we’re pretty serious about this thing, and so it’s time to make a formal introduction.
World, meet Phoenix.new, a batteries-included fully-online coding agent tailored to Elixir and Phoenix. I think it’s going to be the fastest way to build collaborative, real-time applications.
Let’s see it in action:
What’s Interesting About Phoenix.new
First, even though it runs entirely in your browser, Phoenix.new gives both you and your agent a root shell, in an ephemeral virtual machine (a Fly Machine) that gives our agent loop free rein to install things and run programs — without any risk of messing up your local machine. You don’t think about any of this; you just open up the VSCode interface, push the shell button, and there you are, on the isolated machine you share with the Phoenix.new agent.
Second, it’s an agent system I built specifically for Phoenix. Phoenix is about real-time collaborative applications, and Phoenix.new knows what that means. To that end, Phoenix.new includes, in both its UI and its agent tools, a full browser. The Phoenix.new agent uses that browser “headlessly” to check its own front-end changes and interact with the app. Because it’s a full browser, instead of trying to iterate on screenshots, the agent sees real page content and JavaScript state – with or without a human present.
What Root Access Gets Us
... continue reading