Well, calling it a browser is a bit of a stretch I suppose. It's really just chromium + playwright with a terminal screen bolted on.
But damn does this thing actually work. I've tried every other kind of browser use agent and they all try to get the model to use websites by taking screenshots and moving the mouse around. Which is slow and inefficient and expensive too. By contrast I've used this browser to do things like scrape thousands of pictures or automatically configure fly.io billing for 100 orgs, while playing slay the spire in the foreground.
It's very rough around the edges, but hopefully other people find it useful!