Stackline

A Swift application that interfaces with Yabai to display interactive stack indicators for stacked windows on macOS.

Installation

Prerequisites

• macOS 15.0 or later
• Yabai installed and running

Installing the pre-built binary

1. Download the DMG from the releases
2. Mount the DMG by double clicking
3. Drag the app from the DMG to the Applications folder
4. Run the application

The application is signed, notarized and stapled, so you should be able to just run from there!

Building from Source

Note: I recently swapped from using plain old swift to xcode to build a signed app bundle

Prerequisites

• Xcode 26+ (for the app icon)
  • It will compile with a lower version, but your mileage may vary

Steps

1. Clone the repository:

   git clone https://github.com/liam-mackie/stackline-swift.git
   cd stackline-swift

2. Build the application:

   xcodebuild -scheme Stackline -configuration Release -derivedDataPath build

3. The built app will be located at:

   build/Build/Products/Release/Stackline.app

4. Copy it to your applications folder:

   cp -r build/Build/Products/Release/Stackline.app /Applications

Configuration

Yabai Setup

There is nothing to configure: Stackline registers the Yabai signals it needs by itself and keeps them registered.

• Start order doesn't matter. If Yabai isn't running yet, Stackline waits for it (the menu bar icon is dimmed and the menu says "Waiting for yabai…") and connects as soon as it appears.
• Yabai can restart. Yabai forgets its signals when it restarts; Stackline notices the restart and registers them again.
• Signals are cleaned up. They are removed when Stackline quits — from the menu, on logout, or via SIGTERM/SIGINT. If Stackline is killed outright, each signal removes itself the next time it fires, and anything still left is swept the next time Stackline starts.

The signals are labelled stackline-<pid>-<event> (see yabai -m signal --list). Their action writes the event to a Unix socket at ~/Library/Application Support/Stackline/events.sock with nc.

Auto-start

To start Stackline automatically, run stackline, then open preferences from the menu bar icon. In the general, enable "Launch at Login"

Usage

Interacting with Stacks

You can click on a stacked application's icon, pill or dot to swap to the application.

Command Line Interface

Stackline supports several command-line options:

# Start the application
/Applications/Stackline.app/Contents/MacOS/Stackline

# Show version information
/Applications/Stackline.app/Contents/MacOS/Stackline --version

# Show help
/Applications/Stackline.app/Contents/MacOS/Stackline --help

Only one instance runs per user; a second one exits immediately.

Troubleshooting

Stackline logs to the unified log:

log stream --level debug --predicate 'subsystem == "sh.mackie.stackline"'

Development

Testing

swift test

The suite talks to an in-process fake of Yabai, so it never touches a running one.

Contributing

Contributions are welcome! Please:

1. Fork the repository
2. Create a feature branch
3. Make your changes
4. Add tests if applicable (I probably haven't)
5. Submit a pull request

Requirements

• macOS: 15.0+ (tested on macOS 26).
• Yabai: Any recent version
• Architecture: Intel x86_64 or Apple Silicon (Tested on Apple Silicon)

Acknowledgments

• Stackline by @AdamWagner - this was one of the main reasons I wanted to make this
• Yabai by @koekeishiya - Yabai is essential to my workflow, as well as many others around the world
• Apple's SwiftUI framework for making this a relatively simple step into making a UI based app