diff --git a/elements/urth-core-behaviors/execution-complete-behavior.html b/elements/urth-core-behaviors/execution-complete-behavior.html
index a3fb028a..30270707 100644
--- a/elements/urth-core-behaviors/execution-complete-behavior.html
+++ b/elements/urth-core-behaviors/execution-complete-behavior.html
@@ -7,33 +7,35 @@
 This Behavior represents the completion of a code cell's execution.
 -->
 <script>
-  window.Urth = window.Urth || {};
+  (function() {
+    'use strict';
+    var Urth = window.Urth = window.Urth || {};
 
-  Urth.ExecutionCompleteBehavior = {
+    Urth.ExecutionCompleteBehavior = {
 
-    ready: function() {
-      // Code execution defined to be complete when an ExecuteReply is received.
-      console.debug("Registering _onExecutionComplete for Execute Reply messages.");
-      this.__replyCallback = this._onExecutionComplete.bind(this);
+      ready: function() {
+        // Code execution defined to be complete when an ExecuteReply is received.
+        console.debug("Registering _onExecutionComplete for Execute Reply messages.");
+        this.__replyCallback = this._onExecutionComplete.bind(this);
 
-      IPython.notebook.kernel.widget_manager.notebook.events.on(
-        'shell_reply.Kernel', this.__replyCallback
-      );
-    },
+        Urth.events.on(
+          'shell_reply.Kernel', this.__replyCallback
+        );
+      },
 
-    detached: function() {
-        console.debug("Unregistering _onExecutionComplete for Execute Reply messages.");
-        if (this.__replyCallback){
-            IPython.notebook.kernel.widget_manager.notebook.events.off(
-                'shell_reply.Kernel', this.__replyCallback
-            );
-        }
-    },
-
-    /**
-     * A callback fired when code execution has completed for a cell.
-     */
-    _onExecutionComplete: function() {}
-  }
+      detached: function() {
+          console.debug("Unregistering _onExecutionComplete for Execute Reply messages.");
+          if (this.__replyCallback){
+              Urth.events.off(
+                  'shell_reply.Kernel', this.__replyCallback
+              );
+          }
+      },
 
+      /**
+       * A callback fired when code execution has completed for a cell.
+       */
+      _onExecutionComplete: function() {}
+    };
+  })();
 </script>
diff --git a/elements/urth-core-behaviors/jupyter-kernel-observer.html b/elements/urth-core-behaviors/jupyter-kernel-observer.html
index 665bf2b5..7aa1ba6e 100644
--- a/elements/urth-core-behaviors/jupyter-kernel-observer.html
+++ b/elements/urth-core-behaviors/jupyter-kernel-observer.html
@@ -7,9 +7,9 @@
 This behavior is used to implement handlers to kernel events
 -->
 <script>
-    'use strict';
     (function() {
-        window.Urth = window.Urth || {};
+        'use strict';
+        var Urth = window.Urth = window.Urth || {};
 
         /**
          * Behavior that provides pre-attached callbacks to kernel events.
@@ -20,25 +20,25 @@
         Urth.JupyterKernelObserver = {
 
             created: function(){
-                if (!window.IPython) {
+                if (!Urth.events) {
                     return;
                 }
                 console.debug("Registering onKernelReady for Kernel Ready messages.")
 
                 this.__kernelReadyCallback = this.onKernelReady.bind(this);
-                IPython.notebook.events.on(
+                Urth.events.on(
                     'kernel_ready.Kernel', this.__kernelReadyCallback
                 );
 
-                if( IPython.notebook.kernel.is_connected() ){
+                if (Urth.kernel && Urth.kernel.is_connected()) {
                   this.onKernelReady();
                 }
             },
 
             detached: function(){
-                if (window.IPython && this.__kernelReadyCallback) {
+                if (this.__kernelReadyCallback) {
                     console.debug("Unregistering onKernelReady for Kernel Ready messages.")
-                    IPython.notebook.events.off(
+                    Urth.events.off(
                         'kernel_ready.Kernel', this.__kernelReadyCallback
                     );
                 }
diff --git a/elements/urth-core-behaviors/jupyter-notebook-env.html b/elements/urth-core-behaviors/jupyter-notebook-env.html
index 548539ee..232b696c 100644
--- a/elements/urth-core-behaviors/jupyter-notebook-env.html
+++ b/elements/urth-core-behaviors/jupyter-notebook-env.html
@@ -9,7 +9,7 @@
 <script>
     'use strict';
     (function() {
-        window.Urth = window.Urth || {};
+        var Urth = window.Urth = window.Urth || {};
 
         /**
          * Behavior that contains notebook related properties
@@ -22,7 +22,7 @@
             properties: {
                 _baseURL: {
                     value: function(){
-                        return window['IPython'] ? IPython.notebook.base_url : '/';
+                        return Urth._baseURL || '/';
                     }
                 },
 
diff --git a/elements/urth-core-behaviors/jupyter-save-behavior.html b/elements/urth-core-behaviors/jupyter-save-behavior.html
index 80c2b224..a77eff45 100644
--- a/elements/urth-core-behaviors/jupyter-save-behavior.html
+++ b/elements/urth-core-behaviors/jupyter-save-behavior.html
@@ -4,10 +4,10 @@
 -->
 
 <script>
-    'use strict';
     (function() {
+        'use strict';
         var SAVE_EVENT = 'before_save.Notebook';
-        window.Urth = window.Urth || {};
+        var Urth = window.Urth = window.Urth || {};
 
         /**
          * Behavior that provides registration with the save event. Elements
@@ -19,15 +19,15 @@
          */
         Urth.JupyterSaveBehavior = {
             created: function(event, callback) {
-                if (window.IPython && window.IPython.notebook && window.IPython.notebook.events) {
+                if (Urth.events) {
                     this.__saveCallback = this.onSave.bind(this);
-                    IPython.notebook.events.on(SAVE_EVENT, this.__saveCallback);
+                    Urth.events.on(SAVE_EVENT, this.__saveCallback);
                 }
             },
 
             detached: function(event, callback) {
                 if (this.__saveCallback) {
-                    IPython.notebook.events.off(SAVE_EVENT, this.__saveCallback);
+                    Urth.events.off(SAVE_EVENT, this.__saveCallback);
                 }
             },
 
diff --git a/elements/urth-core-behaviors/jupyter-widget-behavior.html b/elements/urth-core-behaviors/jupyter-widget-behavior.html
index d8b45716..3e059ba8 100644
--- a/elements/urth-core-behaviors/jupyter-widget-behavior.html
+++ b/elements/urth-core-behaviors/jupyter-widget-behavior.html
@@ -8,9 +8,9 @@
 -->
 <link rel='import' href='error-display-behavior.html'>
 <script>
-    'use strict';
     (function() {
-        window.Urth = window.Urth || {};
+        'use strict';
+        var Urth = window.Urth = window.Urth || {};
 
         /**
          * Behavior that encapsulate some of the functions needed by
@@ -45,11 +45,12 @@
 
             _doCreateModel: function(){
                 console.debug('Urth.JupyterWidgetBehavior createModel', this.kernelClass);
-                IPython.notebook.kernel.widget_manager.new_widget(
+                Urth.kernel.widget_manager.new_widget(
                     {
                         model_name: 'DeclWidgetModel',
                         widget_class: this.kernelClass
-                    }
+                    },
+                    {}
                 ).then(function(model) {
                         console.log('Model creation successful!', model);
                         this.__modelChangeCallback = this._onModelChange.bind(this);
@@ -75,7 +76,7 @@
                     this._doCreateModel();
                 }.bind(this);
 
-                IPython.notebook.events.one(
+                Urth.events.one(
                     'shell_reply.Kernel', this.__shellReplyCallback
                 );
             },
@@ -109,7 +110,7 @@
              */
             _unRegisterNotebookCallbacks: function() {
                 if (this.__shellReplyCallback){
-                    IPython.notebook.events.off(
+                    Urth.events.off(
                         'shell_reply.Kernel', this.__shellReplyCallback
                     );
                 }
@@ -181,7 +182,7 @@
             },
 
             _callbacks: function(){
-                // this.model is from IPython widgets widgets.js and
+                // this.model is from Jupyter widgets widgets.js and
                 // keeps track of a pending_msgs counter. Specifying
                 // this.model.callbacks() as the callback handler for
                 // send allows widgets.js to properly decrement the
@@ -189,7 +190,7 @@
 
                 // parentCell also has additional callbacks that will handle
                 // 'display_type' messages (among others)
-                var parentCell = this.parentCell()
+                var parentCell = this.parentCell();
 
                 var callbacks = (parentCell && parentCell.get_callbacks()) || {iopub:{}};
                 this.mixin(callbacks.iopub,this.model.callbacks().iopub);
@@ -212,7 +213,7 @@
                     if(this[funcName]){
                         this[funcName].call(this, changes[change]);
                     }
-                }.bind(this))
+                }.bind(this));
 
                 this.onModelChange.call(this, options);
             },
diff --git a/elements/urth-core-behaviors/test/jupyter-save-behavior.html b/elements/urth-core-behaviors/test/jupyter-save-behavior.html
index 69e32763..9cb1e512 100644
--- a/elements/urth-core-behaviors/test/jupyter-save-behavior.html
+++ b/elements/urth-core-behaviors/test/jupyter-save-behavior.html
@@ -62,9 +62,8 @@
         // STEP 4: Define any globals needed by the test suite.
 
         before(function () {
-            window.IPython = window.IPython || {};
-            IPython.notebook = IPython.notebook || {};
-            IPython.notebook.events = IPython.notebook.events || new function() {
+            window.Urth = window.Urth || {};
+            Urth.events = Urth.events || new function() {
                 this.__mocked = true;
                 this.__events = {};
                 this.on = function(event, cb) {
@@ -84,8 +83,8 @@
         });
 
         after(function() {
-            if (IPython.notebook.events.__mocked) {
-                delete IPython.notebook.events;
+            if (Urth.events.__mocked) {
+                delete Urth.events;
             }
         });
 
@@ -97,7 +96,7 @@
 
                 testSave.setSaveHandler(saveSpy);
 
-                IPython.notebook.events.trigger('before_save.Notebook');
+                Urth.events.trigger('before_save.Notebook');
 
                 expect(saveSpy).to.have.been.calledOnce;
             });
diff --git a/elements/urth-core-import/test/urth-core-import.html b/elements/urth-core-import/test/urth-core-import.html
index cfdddc19..b0137ce3 100644
--- a/elements/urth-core-import/test/urth-core-import.html
+++ b/elements/urth-core-import/test/urth-core-import.html
@@ -61,39 +61,53 @@
     <script>
         // STEP 4: Define any globals needed by the test suite.
         var server;
+        var serverUrthImportCalledCount = 0;
 
-        before(function() {
+        beforeEach(function() {
             server = sinon.fakeServer.create();
             server.respondImmediately = true;
         });
-        after(function() {
+        afterEach(function() {
             server.restore();
+            serverUrthImportCalledCount = 0;
         });
 
+        function setupServer() {
+            serverUrthImportCalledCount = 0;
+
+            server.respondWith('POST', '/urth_import', function(xhr, id) {
+                serverUrthImportCalledCount++;
+                xhr.respond(200, { 'Content-Type': 'application/json' }, '{ "status": 0}');
+            });
+
+            server.xhr.useFilters = true;
+            server.xhr.addFilter(function(method, uri) {
+                return !uri.startsWith('/urth_import');
+            });
+        }
+
         // STEP 5: Define suite(s) and tests.
         describe('package attribute', function() {
             it('should cause POST server request to install the package if href is not found', function(done) {
-                server.respondWith('POST', '/urth_import',
-                    [200, { 'Content-Type': 'application/json' }, '{ "status": 0}']);
-
+                setupServer();
                 var link = fixture('invalidHref');
-                var importSpy = sinon.spy(link, 'importHref');
 
                 link.addEventListener('load', function() {
-                    expect(importSpy).to.be.calledOnce;
+                    expect.fail('should have resulted in `importerror` instead of successful `load`');
                     done();
                 });
                 link.addEventListener('importerror', function() {
-                    expect(importSpy).to.be.calledOnce;
+                    expect(serverUrthImportCalledCount).to.equal(1);
                     done();
                 });
             });
 
             it('should not invoke POST server request if href exists', function(done) {
+                setupServer();
                 var link = fixture('validHref');
-                var importSpy = sinon.spy(link, 'importHref');
+
                 link.onload = function() {
-                    expect(importSpy).to.not.be.called;
+                    expect(serverUrthImportCalledCount).to.equal(0);
                     done();
                 };
                 link.onerror = function() {
@@ -114,16 +128,12 @@
             });
 
             it('should fire if the href can not be loaded', function(done) {
-                server.respondWith('POST', '/urth_import',
-                    [200, { 'Content-Type': 'application/json' }, '{ "status": 0}']);
-
+                setupServer();
                 var link = fixture('invalidHref');
-                var importSpy = sinon.spy(link, 'importHref');
 
                 link.addEventListener('importerror', function(event) {
-                    importSpy.restore();
                     expect(event.detail.msg).to.not.be.null;
-                    expect(importSpy).to.be.calledOnce;
+                    expect(serverUrthImportCalledCount).to.equal(1);
                     done();
                 });
             });
diff --git a/nb-extension/js/init/init.js b/nb-extension/js/init/init.js
index b9750092..72d55e08 100644
--- a/nb-extension/js/init/init.js
+++ b/nb-extension/js/init/init.js
@@ -8,10 +8,10 @@
  * elements.html.
  */
 define([
-    'require',
     'module',
     'jquery',
-    '../widgets/DeclWidgetModel'], function(require, module, $) {
+    '../widgets/DeclWidgetModel'
+], function(module, $, DeclWidgetModel) {
     'use strict';
 
     var COMPONENTS_DIR = 'urth_components';
@@ -115,7 +115,7 @@ define([
     function isServerExtensionAvailable(components_root, callback) {
         // Request jupyter-notebook-env.html since it is a small file with
         // no dependencies.
-        urlExist(components_root + '/urth-core-behaviors/jupyter-notebook-env.html', callback)
+        urlExist(components_root + '/urth-core-behaviors/jupyter-notebook-env.html', callback);
     }
 
     /**
@@ -138,20 +138,55 @@ define([
         });
     }
 
-    return function(baseURL, config) {
+    /**
+     * Initialize Declarative Widgets
+     * @param  {Object} config - configuration; see following entries for more information
+     * @param  {Object} config.namespace - Jupyter Notebook namespace object (or shim)
+     * @param  {Object} config.events - Notebook events object
+     * @param  {Object} config.WidgetManager - widget manager class
+     * @param  {Object} config.WidgetModel - widget model class
+     * @return {Promise} resolved when widgets have been fully initialized
+     */
+    return function(config) {
+        var Jupyter = config.namespace;
+
+        var baseURL;
+        if (typeof config === 'string') {
+            // backwards compatibility with old API, which took `baseURL` as first argument and
+            // optional `config` as second arg
+            baseURL = config;
+            config = arguments[1] || {};
+        } else {
+            baseURL = Jupyter ? Jupyter.notebook.base_url : '/';
+        }
+
+        DeclWidgetModel.register(config.WidgetManager, config.WidgetModel);
+
         // Enable shadow dom if it is there for polymer elements.
         window.Polymer = window.Polymer || {};
         window.Polymer.dom = 'shadow';
 
         // Expose the base URL being used.
-        window.Urth = window.Urth || {};
+        var Urth = window.Urth = window.Urth || {};
 
         // Global promise which is resolved when widgets are fully initialized
-        window.Urth.widgets = window.Urth.widgets || {};
-        window.Urth.widgets.whenReady = $.Deferred();
+        Urth.widgets = Urth.widgets || {};
+        Urth.widgets.whenReady = $.Deferred();
 
         // expose suppressErrors, false by default to display errors
-        window.Urth.suppressErrors = config && config.suppressErrors;
+        Urth.suppressErrors = config.suppressErrors;
+
+        Urth.events = config.events;
+
+        // specify a getter for the kernel instance, since it can be restarted and a new kernel
+        // instantiated
+        Object.defineProperty(Urth, 'kernel', {
+            get: function() {
+                // TODO What is the correct way of handling this outside of the notebook? What
+                //      should we do when using jupyter-js-services and kernel is restarted?
+                return Jupyter.notebook.kernel;
+            }
+        });
 
         isServerExtensionAvailable(baseURL + COMPONENTS_DIR, function(isAvailable){
             console.log('Server extension is ' + (isAvailable ? '' : 'NOT ') + 'available!');
@@ -160,19 +195,20 @@ define([
             // use a direct path based on this module's uri.
             var components_root = isAvailable
                 ? baseURL
-                : getModuleBasedComponentRoot(module)
+                : getModuleBasedComponentRoot(module);
 
-            window.Urth.BASE_URL = components_root;
+            Urth.BASE_URL = components_root;
+            Urth._baseURL = baseURL;
             components_root += COMPONENTS_DIR;
 
             loadPolyfill(components_root, function() {
-                var links = config && config.links;
+                var links = config.links;
                 loadComponents(components_root, links);
             }, function (e) {
                 console.error('Failed to load web components polyfill: ' + e);
             });
         });
 
-        return window.Urth.widgets.whenReady;
+        return Urth.widgets.whenReady;
     };
 });
diff --git a/nb-extension/js/main.js b/nb-extension/js/main.js
index 0bb61048..2986a434 100644
--- a/nb-extension/js/main.js
+++ b/nb-extension/js/main.js
@@ -3,8 +3,12 @@
  * Distributed under the terms of the Modified BSD License.
  */
 define([
+    'base/js/namespace',
+    'base/js/events',
+    'nbextensions/widgets/widgets/js/init',
+    'nbextensions/widgets/widgets/js/widget',
     './init/init'
-], function(init) {
+], function(Jupyter, events, widgetManager, ipywidget, init) {
     'use strict';
 
     // Some versions of IE do not have window.console defined. Some versions
@@ -16,8 +20,14 @@ define([
         window.console[method] = window.console[method] || window.console.log;
     });
     
-    init(IPython ? IPython.notebook.base_url : '/');
+    init({
+        namespace: Jupyter,
+        events: events,
+        WidgetManager: widgetManager.WidgetManager,
+        WidgetModel: ipywidget.WidgetModel
+    });
+
     return {
-      load_ipython_extension: function() { console.debug('Custom JS loaded'); }
+        load_ipython_extension: function() { console.debug('Custom JS loaded'); }
     };
 });
diff --git a/nb-extension/js/widgets/DeclWidgetModel.js b/nb-extension/js/widgets/DeclWidgetModel.js
index 4747ad16..99f5568f 100644
--- a/nb-extension/js/widgets/DeclWidgetModel.js
+++ b/nb-extension/js/widgets/DeclWidgetModel.js
@@ -1,40 +1,46 @@
 // Copyright (c) Jupyter Development Team.
 // Distributed under the terms of the Modified BSD License.
 
-define(["nbextensions/widgets/widgets/js/manager",
-    "nbextensions/widgets/widgets/js/widget",
-    "base/js/namespace"
-], function(widgetmanager, ipywidget, IPython) {
+define(function() {
     "use strict";
 
     /**
      * Collection of patches on top of ipywidgets.WidgetModel
      */
 
-    var DeclWidgetModel = function(widget_manager, model_id, comm) {
-        ipywidget.WidgetModel.apply(this, arguments);
+    function register(WidgetManager, WidgetModel) {
+        var DeclWidgetModel = WidgetModel.extend({
+            constructor: function() {
+                WidgetModel.apply(this, arguments);
+                // WidgetModel expects widgets' state to be set from kernel and won't
+                // set `_first_state` to false until that happens. But DeclWidgets
+                // are different: we do initial setup on client and then notify kernel.
+                this._first_state = false;
+            },
+    
+            /*
+             * Making request_state a noop to avoid requiring this handshake to take place to
+             * create model.
+             */
+            request_state: function(callbacks) {
+                console.trace( "Empty implementation of request_state()");
+                return Promise.resolve(this);
+            },
+    
+            /*
+             * Avoiding out of sequence messages due to new promise/async code in WidgetModel
+             */
+            send_sync_message: function(attrs, callbacks) {
+                var data = {method: 'backbone', sync_data: attrs};
+                this.comm.send(data, callbacks);
+            }
+        });
+    
+        WidgetManager.register_widget_model('DeclWidgetModel', DeclWidgetModel);
+    }
+
+    return {
+        register: register
     };
 
-    DeclWidgetModel.prototype = Object.create(ipywidget.WidgetModel.prototype);
-
-    /*
-     * Making request_state a noop to avoid requiring this handshake to take place to create model.
-     */
-    DeclWidgetModel.prototype.request_state = function(callbacks) {
-        console.trace( "Empty implementation of request_state()")
-        return Promise.resolve(this);
-    };
-
-    /*
-     * Avoiding out of sequence messages due to new promise/async code in ipywidgets.WidgetModel
-     */
-    DeclWidgetModel.prototype.send_sync_message = function(attrs, callbacks) {
-        var data = {method: 'backbone', sync_data: attrs};
-        this.comm.send(data, callbacks);
-    };
-
-    widgetmanager.WidgetManager.register_widget_model('DeclWidgetModel', DeclWidgetModel);
-
-    return DeclWidgetModel;
-
 });
\ No newline at end of file