diff --git a/core/modules/contextual/js/models/Model.js b/core/modules/contextual/js/models/Model.js
new file mode 100644
index 0000000..4232051
--- /dev/null
+++ b/core/modules/contextual/js/models/Model.js
@@ -0,0 +1,33 @@
+/**
+ * @file
+ * Attaches behaviors for the Contextual module's edit toolbar tab.
+ */
+
+(function (Drupal, Backbone) {
+
+"use strict";
+
+/**
+ * Models the state of the edit mode toggle.
+ */
+Drupal.contextualToolbar.Model = Backbone.Model.extend({
+  defaults: {
+    // Indicates whether the toggle is currently in "view" or "edit" mode.
+    isViewing: true,
+    // Indicates whether the toggle should be visible or hidden. Automatically
+    // calculated, depends on contextualCount.
+    isVisible: false,
+    // Tracks how many contextual links exist on the page.
+    contextualCount: 0,
+    // A TabbingContext object as returned by Drupal.TabbingManager: the set
+    // of tabbable elements when edit mode is enabled.
+    tabbingContext: null
+  },
+  initialize: function () {
+    this.on('change:contextualCount', function (model) {
+      model.set('isVisible', model.get('contextualCount') > 0);
+    });
+  }
+});
+
+})(Drupal, Backbone);