Summary
BetterSnapTool is causing a crash in Xcode’s SwiftUI PreviewShell process when dragging in a SwiftUI preview on an iOS 26 or higher simulator.
Affected input device (e.g. MacBook Trackpad, Magic Mouse/Trackpad, Touch Bar, etc.):
Trackpad on MacBook Pro and external Magic Trackpad.
Screenshots
Here’s a zip file containing screenshots of all the tabs in BetterSnapTool settings, plus the crash log and a copy of ~/Library/Preferences/com.hegenberg.BetterSnapTool.plist.
Archive.zip (3.6 MB)
Device information
- Type of Mac: MacBook Pro M4 Max (Mac16,5), and also confirmed on Mac Studio M1 Ultra (Mac13,2)
- macOS version: Tahoe 26.4 (25E246)
- BetterTouchTool version: BetterSnapTool 1.9.12
Additional information (e.g. crash logs, related issues, etc.):
See crash log attached in Archive.zip (3.6 MB).
Repro Steps
- Quick BetterSnapTool and BetterTouchTool, if they are running.
- Open Xcode 26.4.
- Make a new iOS SwiftUI project.
- In
ContentView, add a simple button, likeButton("Yo") {} - Open a SwiftUI preview running iOS 26.4.
- Click and drag on the button in the SwiftUI preview. Or, in a more complex app, try dragging on a scroll view or Liquid Glass UI element.
- Notice that everything works fine.
- Lauch BetterSnapTool. Seem above attachments for my particular configuration. I use BetterSnapTool as a successor to MondoMouse, to enable dragging and resizing windows by holding down a key combination while moving the mouse so I don't have to be clicking while dragging.
- Repeat the previous step about dragging on the button or other UI element.
- The SwiftUI PreviewShell process crashes, resulting in the crash report seen above.
- Confirm that merely clicking the button does not crash; only dragging does.
- Switch your SwiftUI preview simulator to iOS 18.6 and observe that there is no crash.
- Run the app in the actual iOS 26.4 simulator, not just the SwiftUI preview, and notice that it does not crash, even when BetterSnapTool is running.