diff --git a/client/commonFramework/end.js b/client/commonFramework/end.js
index 811e154192..8356b6a591 100644
--- a/client/commonFramework/end.js
+++ b/client/commonFramework/end.js
@@ -1,7 +1,12 @@
 $(document).ready(function() {
   const common = window.common;
   const { Observable } = window.Rx;
-  const { challengeName, challengeType, challengeTypes } = common;
+  const {
+    addLoopProtect,
+    challengeName,
+    challengeType,
+    challengeTypes
+  } = common;
 
   common.init.forEach(function(init) {
     init($);
@@ -29,7 +34,13 @@ $(document).ready(function() {
       .filter(() => common.challengeType === challengeTypes.HTML)
       .flatMap(code => {
         return common.detectUnsafeCode$(code)
+          .map(() => {
+            const combinedCode = common.head + code + common.tail;
+
+            return addLoopProtect(combinedCode);
+          })
           .flatMap(code => common.updatePreview$(code))
+          .flatMap(() => common.checkPreview$({ code }))
           .catch(err => Observable.just({ err }));
       })
       .subscribe(
diff --git a/client/commonFramework/update-preview.js b/client/commonFramework/update-preview.js
index ea30f4abf2..e1a68e076d 100644
--- a/client/commonFramework/update-preview.js
+++ b/client/commonFramework/update-preview.js
@@ -12,6 +12,11 @@ window.common = (function(global) {
   window.$ = parent.$.proxy(parent.$.fn.find, parent.$(document));
   window.loopProtect = parent.loopProtect;
   window.__err = null;
+  window.loopProtect.hit = function(line) {
+    window.__err = new Error(
+      'Potential infinite loop at line ' + line
+    );
+  };
 </script>
 <link
   rel='stylesheet'
@@ -39,9 +44,13 @@ window.common = (function(global) {
   // and prime it with false
   common.previewReady$ = new BehaviorSubject(false);
 
-  // runPreviewTests$ should be set up in the preview window
+  // These should be set up in the preview window
+  // if this error is seen it is because the function tried to run
+  // before the iframe has completely loaded
   common.runPreviewTests$ =
-    () => Observable.throw(new Error('run preview not enabled'));
+    common.checkPreview$ =
+    () => Observable.throw(new Error('Preview not fully loaded'));
+
 
   common.updatePreview$ = function updatePreview$(code = '') {
     const preview = common.getIframe('preview');
diff --git a/client/iFrameScripts.js b/client/iFrameScripts.js
index b2d21bf77c..2fc6ac8b69 100644
--- a/client/iFrameScripts.js
+++ b/client/iFrameScripts.js
@@ -10,12 +10,6 @@ window.$(document).ready(function() {
   var tests = parent.tests;
   var common = parent.common;
 
-  window.loopProtect.hit = function(line) {
-    window.__err = new Error(
-      'Potential infinite loop at line ' + line
-    );
-  };
-
   common.getJsOutput = function evalJs(code = '') {
     let output;
     try {
@@ -40,11 +34,13 @@ window.$(document).ready(function() {
         return Rx.Observable.throw(window.__err);
       }
 
+      // Iterate throught the test one at a time
+      // on new stacks
       return Rx.Observable.from(tests, null, null, Rx.Scheduler.default)
+        // add delay here for firefox to catch up
         .delay(100)
         .map(test => {
           const userTest = {};
-          common.appendToOutputDisplay('');
           try {
             /* eslint-disable no-eval */
             eval(test);
@@ -65,10 +61,19 @@ window.$(document).ready(function() {
           }
           return userTest;
         })
+        // gather tests back into an array
         .toArray()
         .map(tests => ({ ...rest, tests, originalCode }));
     };
 
+  // used when updating preview without running tests
+  common.checkPreview$ = function checkPreview$(args) {
+    if (window.__err) {
+      return Rx.Observable.throw(window.__err);
+    }
+    return Rx.Observable.just(args);
+  };
+
   // now that the runPreviewTest$ is defined
   // we set the subject to true
   // this will let the updatePreview