After upgrading to macOS 26, I noticed that showing a Quicklook preview in my app is very slow. Showing small text files is fine, but some other files I've tried, such as a Numbers document, take about 30 seconds (during which the indeterminate loading indicator appears) before the preview is shown. When showing the preview of an app, such as Xcode, the panel opens immediately with a placeholder image for the Xcode icon, and the actual Xcode icon is shown only after about 25 seconds. During this time many logs appear:
FPItemsFromURLsWithTimeout timed out (5.000000s) for: file:///.file/id=6571367.2/ (/)
FPItemsFromURLsWithTimeout timed out (5.000000s) for: file:///.file/id=6571367.23684/ (/Users)
FPItemsFromURLsWithTimeout timed out (5.000000s) for: file:///.file/id=6571367.248032/ (/Users/n{9}k)
FPItemsFromURLsWithTimeout timed out (5.000000s) for: file:///.file/id=6571367.248084/ (/Users/n{9}k/Downloads)
Failed to add registration dmf.policy.monitor.app with error: Error Domain=NSCocoaErrorDomain Code=4099 "The connection to service named com.apple.dmd.policy was invalidated: failed at lookup with error 159 - Sandbox restriction." UserInfo={NSDebugDescription=The connection to service named com.apple.dmd.policy was invalidated: failed at lookup with error 159 - Sandbox restriction.}
Failed to register application policy monitor with identifier 69DDBDB4-0736-42FA-BA7A-C8D7EA049E29 for types {(
applicationcategories,
websites,
categories,
applications
)} with error: Error Domain=NSCocoaErrorDomain Code=4099 "The connection to service named com.apple.dmd.policy was invalidated: failed at lookup with error 159 - Sandbox restriction." UserInfo={NSDebugDescription=The connection to service named com.apple.dmd.policy was invalidated: failed at lookup with error 159 - Sandbox restriction.}
FPItemsFromURLsWithTimeout timed out (5.000000s) for: file:///.file/id=6571367.155797561/ (~/Downloads/X{3}e.app)
It seems that Quicklook tries to access each parent directory of the previewed file, and each one fails after 5 seconds.
Why is Quicklook all of a sudden so slow? It used to be almost instant in macOS 15.
I created FB20268201.
import Cocoa
import Quartz
@main
class AppDelegate: NSObject, NSApplicationDelegate, QLPreviewPanelDataSource, QLPreviewPanelDelegate {
var url: URL?
func applicationDidFinishLaunching(_ notification: Notification) {
let openPanel = NSOpenPanel()
openPanel.runModal()
url = openPanel.urls[0]
QLPreviewPanel.shared()!.makeKeyAndOrderFront(nil)
}
override func acceptsPreviewPanelControl(_ panel: QLPreviewPanel!) -> Bool {
return true
}
override func beginPreviewPanelControl(_ panel: QLPreviewPanel!) {
panel.dataSource = self
panel.delegate = self
}
override func endPreviewPanelControl(_ panel: QLPreviewPanel!) {
panel.dataSource = nil
panel.delegate = nil
}
func numberOfPreviewItems(in panel: QLPreviewPanel!) -> Int {
return 1
}
func previewPanel(_ panel: QLPreviewPanel!, previewItemAt index: Int) -> QLPreviewItem! {
return url as? QLPreviewItem
}
}
