diff --git a/app/index.js b/app/index.js
index b817e9fb8..7c2b97a89 100644
--- a/app/index.js
+++ b/app/index.js
@@ -68,6 +68,7 @@ async function main() {
   const App = require('@jupyterlab-classic/application').App;
   const app = new App();
 
+  const disabled = [];
   // TODO: formalize the way the set of initial extensions and plugins are specified
   let mods = [
     // @jupyterlab-classic plugins
@@ -150,6 +151,32 @@ async function main() {
     ]);
   }
 
+  /**
+   * Iterate over active plugins in an extension.
+   *
+   * #### Notes
+   * This also populates the disabled
+   */
+  function* activePlugins(extension) {
+    // Handle commonjs or es2015 modules
+    let exports;
+    if (Object.prototype.hasOwnProperty.call(extension, '__esModule')) {
+      exports = extension.default;
+    } else {
+      // CommonJS exports.
+      exports = extension;
+    }
+
+    let plugins = Array.isArray(exports) ? exports : [exports];
+    for (let plugin of plugins) {
+      if (PageConfig.Extension.isDisabled(plugin.id)) {
+        disabled.push(plugin.id);
+        continue;
+      }
+      yield plugin;
+    }
+  }
+
   const extension_data = JSON.parse(
     PageConfig.getOption('federated_extensions')
   );
@@ -200,7 +227,9 @@ async function main() {
   );
   federatedExtensions.forEach(p => {
     if (p.status === 'fulfilled') {
-      mods.push(p.value);
+      for (let plugin of activePlugins(p.value)) {
+        mods.push(plugin);
+      }
     } else {
       console.error(p.reason);
     }
diff --git a/packages/application-extension/style/base.css b/packages/application-extension/style/base.css
index 1c814d5cd..20233875b 100644
--- a/packages/application-extension/style/base.css
+++ b/packages/application-extension/style/base.css
@@ -9,11 +9,6 @@
   flex-shrink: 1;
 }
 
-/* TODO: move to edit-extension */
-.jp-Document {
-  height: 100%;
-}
-
 .jp-MainAreaWidget {
   height: 100%;
 }
diff --git a/packages/docmanager-extension/style/base.css b/packages/docmanager-extension/style/base.css
index e69de29bb..2c9c509f0 100644
--- a/packages/docmanager-extension/style/base.css
+++ b/packages/docmanager-extension/style/base.css
@@ -0,0 +1,3 @@
+.jp-Document {
+  height: 100%;
+}
diff --git a/packages/notebook-extension/package.json b/packages/notebook-extension/package.json
index f54347860..1407bd2db 100644
--- a/packages/notebook-extension/package.json
+++ b/packages/notebook-extension/package.json
@@ -44,6 +44,7 @@
     "@jupyterlab/apputils": "^3.0.0",
     "@jupyterlab/docmanager": "^3.0.0",
     "@jupyterlab/notebook": "^3.0.0",
+    "@lumino/polling": "^1.3.3",
     "@lumino/widgets": "^1.14.0"
   },
   "devDependencies": {
diff --git a/packages/notebook-extension/src/index.ts b/packages/notebook-extension/src/index.ts
index c50fcb873..72adc3c11 100644
--- a/packages/notebook-extension/src/index.ts
+++ b/packages/notebook-extension/src/index.ts
@@ -20,6 +20,8 @@ import {
   IClassicShell
 } from '@jupyterlab-classic/application';
 
+import { Poll } from '@lumino/polling';
+
 import { Widget } from '@lumino/widgets';
 
 /**
@@ -84,9 +86,16 @@ const checkpoints: JupyterFrontEndPlugin<void> = {
     if (classicShell) {
       classicShell.currentChanged.connect(onChange);
     }
-    // TODO: replace by a Poll
-    onChange();
-    setInterval(onChange, 2000);
+
+    new Poll({
+      auto: true,
+      factory: () => onChange(),
+      frequency: {
+        interval: 2000,
+        backoff: false
+      },
+      standby: 'when-hidden'
+    });
   }
 };
 
diff --git a/packages/notebook-extension/style/base.css b/packages/notebook-extension/style/base.css
index 1fd02e8c2..c6296bfc6 100644
--- a/packages/notebook-extension/style/base.css
+++ b/packages/notebook-extension/style/base.css
@@ -19,8 +19,7 @@
 }
 
 .jp-ClassicKernelStatus {
-  /* TODO: replace with lab variable  */
-  font-size: 12px;
+  font-size: var(--jp-ui-font-size1);
   margin: 0;
   font-weight: normal;
   color: var(--jp-ui-font-color0);