Pier: a desktop GUI for pi
A macOS app for the pi coding agent. Every session is a real pi process, so everything you've set up in the terminal still works.
pi is a coding agent that runs in the terminal, and I use it for most of my day. The problem is when I have four sessions going in four different projects. A terminal only shows one at a time, and the one I'm looking at is almost never the one that just finished or is waiting for me to say yes.
Pier is a macOS app I built for that. The sidebar lists every project pi has ever been run in, with its sessions underneath. If a session gets new output while I'm looking at something else, it gets an unread marker. If it's waiting on me, it gets a different marker. Either way, the Dock icon shows a badge. That's the feature I really wanted, and the rest of the app grew from there.
It's still just pi
Pier doesn't reimplement any part of pi. Every open session is a real pi process running in RPC mode, and Pier just displays what it sends back. Your models, settings, extensions, and slash commands all work, because it's literally the same program. You can quit Pier, run pi -c in the terminal, and pick up right where you left off.
The only things Pier stores are its own preferences, in ~/.pi/gui/settings.json, and an error log next to it. Everything else stays in pi's config.
What you see
The transcript streams in as pi writes it: markdown, thinking (collapsed by default), tool calls with their output showing up live, and edit diffs inline. The input box supports pi's slash commands, @ file mentions, pasted images, and up-arrow history.
You can keep typing while a turn is running. Follow-up prompts go into a queue, and you can promote any of them to a steering message that interrupts the current turn. The header shows the git branch, and the model, thinking level, and a context meter sit under the input box.
Next to the transcript there's a read-only diff of the working tree against HEAD that updates as files change, plus a login shell in the project directory. Extension dialogs show up as sheets, and notifications show up as toasts.
Installing it
Download the DMG from the latest release and drag Pier to Applications. It's signed and notarized, so it opens like any other app, and it checks for updates on its own and installs them when you say so. You'll need a Mac with Apple silicon on macOS 13 or newer, and pi 0.85 or newer on your PATH.