diff --git a/_locales/en/messages.json b/_locales/en/messages.json
index 11760a7d39..0e26d9e869 100644
--- a/_locales/en/messages.json
+++ b/_locales/en/messages.json
@@ -15,12 +15,20 @@
       "message": "Loading...",
       "description": "Message shown on the loading screen before we've loaded any messages"
     },
+    "installComplete": {
+      "message": "Install is complete",
+      "description": "Button to click when user has installed the new Signal Desktop"
+    },
     "migrationWarning": {
       "message": "The Signal Desktop Chrome app has been deprecated. Would you like to migrate to the new Signal Desktop now?",
       "description": "Warning notification that this version of the app has been deprecated and the user must migrate"
     },
+    "migrateInstallStep": {
+      "message": "The first step is to install the new Signal Desktop.",
+      "description": "The first step in the export process; installing the standalone desktop app, to ensure it is available for that platform."
+    },
     "exportInstructions": {
-      "message": "The first step is to choose a directory to store this application's exported data. It will contain your message history and sensitive cryptographic data, so be sure to save it somewhere private.",
+      "message": "Now, choose a directory to store this application's exported data. It will contain your message history and sensitive cryptographic data, so be sure to save it somewhere private.",
       "description": "Description of the export process"
     },
     "migrate": {
diff --git a/background.html b/background.html
index 5ef417c85e..5f42e88e65 100644
--- a/background.html
+++ b/background.html
@@ -17,6 +17,9 @@
         {{ #installButton }}
           <button class='install grey'>{{ installButton }}</button>
         {{ /installButton }}
+        {{ #nextButton }}
+          <button class='next grey'>{{ nextButton }}</button>
+        {{ /nextButton }}
         {{ #exportButton }}
           <button class='export grey'>{{ exportButton }}</button>
         {{ /exportButton }}
diff --git a/js/backup.js b/js/backup.js
index 38b10da06f..ab44dd37cc 100644
--- a/js/backup.js
+++ b/js/backup.js
@@ -3,6 +3,9 @@
   window.Whisper = window.Whisper || {};
 
   function stringToBlob(string) {
+    if (!string || (typeof string !== 'string' && !(string instanceof ArrayBuffer))) {
+      throw new Error('stringToBlob: provided value is something strange:', string, JSON.stringify(stringify(string)));
+    }
     var buffer = dcodeIO.ByteBuffer.wrap(string).toArrayBuffer();
     return new Blob([buffer]);
   }
@@ -61,7 +64,9 @@
   }
 
   function exportNonMessages(idb_db, parent) {
-    return createFileAndWriter(parent, 'db.json').then(function(writer) {
+    // We wouldn't want to overwrite another db file.
+    var exclusive = true;
+    return createFileAndWriter(parent, 'db.json', exclusive).then(function(writer) {
       return exportToJsonFile(idb_db, writer);
     });
   }
@@ -223,19 +228,19 @@
     });
   }
 
-  function createDirectory(parent, name) {
+  function createDirectory(parent, name, exclusive) {
     var sanitized = sanitizeFileName(name);
     console._log('-- about to create directory', sanitized);
     return new Promise(function(resolve, reject) {
-      parent.getDirectory(sanitized, {create: true, exclusive: true}, resolve, reject);
+      parent.getDirectory(sanitized, {create: true, exclusive: exclusive}, resolve, reject);
     });
   }
 
-  function createFileAndWriter(parent, name) {
+  function createFileAndWriter(parent, name, exclusive) {
     var sanitized = sanitizeFileName(name);
     console._log('-- about to create file', sanitized);
     return new Promise(function(resolve, reject) {
-      parent.getFile(sanitized, {create: true, exclusive: true}, function(file) {
+      parent.getFile(sanitized, {create: true, exclusive: exclusive}, function(file) {
         return file.createWriter(function(writer) {
           resolve(writer);
         }, reject);
@@ -322,14 +327,21 @@
 
   function writeAttachment(dir, attachment) {
     var filename = getAttachmentFileName(attachment);
-    return createFileAndWriter(dir, filename).then(function(writer) {
+    // If attachments are in messages with the same received_at and the same name,
+    //   then we'll let that overwrite happen. It should be very uncommon.
+    var exclusive = false;
+    return createFileAndWriter(dir, filename, exclusive).then(function(writer) {
       var stream = createOutputStream(writer);
       return stream.write(attachment.data);
     });
   }
 
   function writeAttachments(parentDir, name, messageId, attachments) {
-    return createDirectory(parentDir, messageId).then(function(dir) {
+    // We've had a lot of trouble with attachments, likely due to messages with the same
+    //   received_at in the same conversation. So we sacrifice one of the attachments in
+    //   this unusual case.
+    var exclusive = false;
+    return createDirectory(parentDir, messageId, exclusive).then(function(dir) {
       return Promise.all(_.map(attachments, function(attachment) {
         return writeAttachment(dir, attachment);
       }));
@@ -350,7 +362,9 @@
 
   function exportConversation(idb_db, name, conversation, dir) {
     console.log('exporting conversation', name);
-    return createFileAndWriter(dir, 'messages.json').then(function(writer) {
+    // We wouldn't want to overwrite the contents of a different conversation.
+    var exclusive = true;
+    return createFileAndWriter(dir, 'messages.json', exclusive).then(function(writer) {
       return new Promise(function(resolve, reject) {
         var transaction = idb_db.transaction('messages', "readwrite");
         transaction.onerror = function(e) {
@@ -407,6 +421,9 @@
             if (attachments && attachments.length) {
               var process = function() {
                 console._log('-- writing attachments for message', message.id);
+                if (!message.received_at) {
+                  return Promise.reject(new Error('Message', message.id, 'had no received_at'));
+                }
                 return writeAttachments(dir, name, messageId, attachments);
               };
               promiseChain = promiseChain.then(process);
@@ -496,7 +513,10 @@
           var name = getConversationLoggingName(conversation);
 
           var process = function() {
-            return createDirectory(parentDir, dir).then(function(dir) {
+            // If we have a conversation directory collision, the user will lose the
+            //   contents of the first conversation. So we throw an error.
+            var exclusive = true;
+            return createDirectory(parentDir, dir, exclusive).then(function(dir) {
               return exportConversation(idb_db, name, conversation, dir);
             });
           };
@@ -667,7 +687,9 @@
         return openDatabase().then(function(idb_db) {
           idb = idb_db;
           var name = 'Signal Export ' + getTimestamp();
-          return createDirectory(directoryEntry, name);
+          // We don't want to overwrite another signal export, so we set exclusive = true
+          var exclusive = true;
+          return createDirectory(directoryEntry, name, exclusive);
         }).then(function(directory) {
           dir = directory;
           return exportNonMessages(idb, dir);
diff --git a/js/views/migration_view.js b/js/views/migration_view.js
index e9d954849b..6219253413 100644
--- a/js/views/migration_view.js
+++ b/js/views/migration_view.js
@@ -5,7 +5,8 @@
   var State = {
     DISCONNECTING: 1,
     EXPORTING: 2,
-    COMPLETE: 3
+    COMPLETE: 3,
+    CHOOSE_DIR: 4,
   };
 
   Whisper.Migration = {
@@ -53,6 +54,7 @@
       'click .export': 'onClickExport',
       'click .debug-log': 'onClickDebugLog',
       'click .cancel': 'onClickCancel',
+      'click .next': 'onClickNext',
     },
     initialize: function() {
       if (!Whisper.Migration.inProgress()) {
@@ -77,6 +79,7 @@
       var debugLogButton = i18n('submitDebugLog');
       var installButton = i18n('installNewSignal');
       var cancelButton;
+      var nextButton;
 
       if (this.error) {
         // If we've never successfully exported, then we allow user to cancel out
@@ -98,22 +101,31 @@
           var location = Whisper.Migration.getExportLocation() || i18n('selectedLocation');
           message = i18n('exportComplete', location);
           exportButton = i18n('exportAgain');
+          installButton = null;
           debugLogButton = null;
-          cancelButton = i18n('cancelMigration');
           break;
         case State.EXPORTING:
           message = i18n('exporting');
+          installButton = null;
           break;
         case State.DISCONNECTING:
           message = i18n('migrationDisconnecting');
           installButton = null;
           break;
-        default:
+        case State.CHOOSE_DIR:
           hideProgress = true;
           message = i18n('exportInstructions');
           exportButton = i18n('export');
           debugLogButton = null;
           installButton = null;
+          break;
+        default:
+          message = i18n('migrateInstallStep');
+          hideProgress = true;
+          debugLogButton = null;
+          nextButton = i18n('installComplete');
+          cancelButton = i18n('cancel');
+          break;
       }
 
       return {
@@ -123,12 +135,17 @@
         debugLogButton: debugLogButton,
         installButton: installButton,
         cancelButton: cancelButton,
+        nextButton: nextButton,
       };
     },
     onClickInstall: function() {
       var url = 'https://support.whispersystems.org/hc/en-us/articles/214507138';
       window.open(url, '_blank');
     },
+    onClickNext: function() {
+      storage.put('migrationState', State.CHOOSE_DIR);
+      this.render();
+    },
     cancel: function() {
       console.log('Cancelling out of migration workflow after error');
       Whisper.Migration.cancel().then(function() {