diff --git a/application.go b/application.go
index fc4da83..6391b72 100644
--- a/application.go
+++ b/application.go
@@ -15,8 +15,9 @@ type Application interface {
 	// Describe returns a description of the application.
 	Describe () ApplicationDescription
 
-	// Init performs the initial setup of the application.
-	Init () error
+	// Init performs the initial setup of the application. This behavior
+	// should return a window if it creates one.
+	Init () (tomo.Window, error)
 }
 
 // ApplicationURLOpener is an application that can open a URL.
@@ -29,12 +30,15 @@ type ApplicationURLOpener interface {
 	//
 	// Applications should support the file:// scheme at the very least, and
 	// should also support others like http:// and https:// if possible.
-	OpenURL (*url.URL) error
+	//
+	// This behavior should return a window if it creates one.
+	OpenURL (*url.URL) (tomo.Window, error)
 
 	// OpenNone is called when the application is launched without any URLs
 	// to open. The application may create some sort of default starting
-	// window, or call tomo.Stop().
-	OpenNone ()
+	// window, or do nothing. This behavior should return a window if it
+	// creates one.
+	OpenNone () (tomo.Window, error)
 }
 
 // ApplicationFlagAdder is an application that supports reading command line
@@ -148,14 +152,18 @@ func RunApplication (application Application) {
 	if err != nil { log.Fatalln("nasin: could not set icon set:", err) }
 	err = reg.SetFaceSet()
 	if err != nil { log.Fatalln("nasin: could not set face set:", err) }
-	err = application.Init()
+	window, err := application.Init()
 	if err != nil { log.Fatalln("nasin: could not run application:", err) }
+	manageWindow(window)
 
 	// open URLs
 	args := flag.Args()
 	applicationOpenUrls(application, args...)
-	err = backend.Run()
-	if err != nil { log.Fatalln("nasin: could not run application:", err) }
+
+	if windows > 0 {
+		err = backend.Run()
+		if err != nil { log.Fatalln("nasin: could not run application:", err) }
+	}
 }
 
 // NewApplicationWindow creates a window for an application. It will
@@ -173,44 +181,80 @@ func NewApplicationWindow (application Application, bounds image.Rectangle) (tom
 	return window, nil
 }
 
-func applicationOpenUrls (application Application, args ...string) {
-	if application, ok := application.(ApplicationURLOpener); ok {
-		if len(args) <= 0 {
-			application.OpenNone()
-		}
+var windows int
 
-		openedAny := false
-		for _, arg := range flag.Args() {
-			ur, err := url.Parse(arg)
-			if err != nil {
-				log.Fatalf (
-					"nasin: invalid URL %v: %v",
-					arg, err)
-			}
-			if ur.Scheme == "" {
-				ur.Scheme = "file"
-			}
-			err = application.OpenURL(ur)
-			if err != nil {
-				dialog, err := objects.NewDialogOk (
-					objects.DialogError, nil,
-					"Could Not Open URL",
-					fmt.Sprintf (
-						"Could not open %v: %v",
-						arg, err),
-					func () {
-						if !openedAny {
-							application.OpenNone()
-						}
-					})
-				if err != nil { log.Fatal(err) }
-				dialog.SetVisible(true)
-			}
+func manageWindow (window tomo.Window) {
+	if window == nil { return }
+	windows ++
+	window.OnClose(func () {
+		windows --
+		if windows < 1 {
+			tomo.Stop()
 		}
-	} else {
+	})
+}
+
+func errorPopupf (title, format string, v ...any) func (func ()) {
+	return func (callback func ()) {
+		dialog, err := objects.NewDialogOk (
+			objects.DialogError, nil,
+			title,
+			fmt.Sprintf(format, v...),
+			callback)
+		if err != nil { log.Fatal(err) }
+		dialog.SetVisible(true)
+		manageWindow(dialog)
+	}
+}
+
+func applicationOpenUrls (app Application, args ...string) {
+	application, ok := app.(ApplicationURLOpener)
+	if !ok {
 		if len(args) > 0 {
 			log.Fatal("nasin: this application cannot open URLs")
 		}
+		return
+	}
+	
+	openNone := func () bool {
+		window, err := application.OpenNone()
+		if err != nil {
+			log.Fatalf("nasin: could not open main window: %v", err)
+			return false
+		}
+		manageWindow(window)
+		return true
+	}
+	
+	if len(args) <= 0 {
+		openNone()
+		return
+	}
+
+	openedAny := false
+	for _, arg := range flag.Args() {
+		ur, err := url.Parse(arg)
+		if err != nil {
+			log.Fatalf (
+				"nasin: invalid URL %v: %v",
+				arg, err)
+		}
+		if ur.Scheme == "" {
+			ur.Scheme = "file"
+		}
+		window, err := application.OpenURL(ur)
+		if err != nil {
+			errorPopupf(
+				"Could Not Open URL",
+				"Could not open %v: %v",
+				arg, err,
+			)(func () {
+				if !openedAny {
+					openNone()
+				}
+			})
+		}
+		manageWindow(window)
 	}
 }