diff --git a/plugins/kolab_files/kolab_files.js b/plugins/kolab_files/kolab_files.js
index e2495659..6e7ca0a9 100644
--- a/plugins/kolab_files/kolab_files.js
+++ b/plugins/kolab_files/kolab_files.js
@@ -6,7 +6,7 @@
  * @licstart  The following is the entire license notice for the
  * JavaScript code in this file.
  *
- * Copyright (C) 2011, Kolab Systems AG <contact@kolabsys.com>
+ * Copyright (C) 2011-2015, Kolab Systems AG <contact@kolabsys.com>
  *
  * This program is free software: you can redistribute it and/or modify
  * it under the terms of the GNU Affero General Public License as
@@ -125,6 +125,14 @@ window.rcmail && window.files_api && rcmail.addEventListener('init', function()
           display_message: function(label, type) { return rcmail.display_message('kolab_files.' + label, type); },
           gettext: function(label) { return rcmail.get_label('kolab_files.' + label); }
         });
+
+      if (rcmail.env.action == 'open') {
+        // initialize folders list (for dialogs)
+        file_api.folder_list();
+
+        // get ongoing sessions
+        file_api.request('folder_info', {folder: file_api.file_path(rcmail.env.file), sessions: 1}, 'folder_info_response');
+      }
     }
     else {
       file_api.folder_list();
@@ -395,7 +403,7 @@ function kolab_files_folder_create_dialog()
   $('form', dialog).submit(kolab_dialog_submit_handler);
 
   // build parent selector
-  kolab_files_folder_select_element(select, {empty: true});
+  file_api.folder_select_element(select, {empty: true, writable: true});
 };
 
 // folder edit dialog
@@ -440,7 +448,7 @@ function kolab_files_folder_edit_dialog()
   $('form', dialog).submit(kolab_dialog_submit_handler);
 
   // build parent selector
-  kolab_files_folder_select_element(select, {selected: path, empty: true});
+  file_api.folder_select_element(select, {selected: path, empty: true});
 };
 
 // folder mounting dialog
@@ -504,6 +512,92 @@ function kolab_files_folder_mount_dialog()
   });
 };
 
+// file edit dialog
+function kolab_files_file_edit_dialog(file, sessions, readonly)
+{
+  var content = [], items = [], height = 300;
+    dialog = $('#files-file-edit-dialog'),
+    buttons = {}, name = file_api.file_name(file),
+    title = rcmail.gettext('kolab_files.editfiledialog'),
+    mainaction = rcmail.gettext('kolab_files.select'),
+    item_fn = function(id, txt, classes) {
+        return $('<label>').attr('class', 'session' + (classes ? ' ' + classes : ''))
+          .append($('<input>').attr({name: 'opt', value: id, type: 'radio'})).append($('<span>').text(txt));
+      },
+    select_fn = function(dlg) {
+      var input = $('input:checked', dialog), id = input.val();
+
+      if (dlg)
+        kolab_dialog_close(dlg);
+
+      if (readonly && (id == 0 || !input.length))
+        return kolab_files_file_create_dialog(file);
+
+      // @todo: invitations
+      rcmail.files_edit(id ? id : true);
+    };
+
+  // Create sessions selection
+  if (sessions && sessions.length) {
+    items.push($('<div>').text(rcmail.gettext('kolab_files.editfilesessions')));
+
+    // first display owned sessions, then invited, other at the end
+    $.each(sessions, function() {
+      if (this.is_owner) {
+        var txt = rcmail.gettext('kolab_files.ownedsession');
+        items.push(item_fn(this.id, txt, 'owner'));
+      }
+    });
+
+    if (items.length == 1)
+      items.push(item_fn(0, rcmail.gettext('kolab_files.newsession' + (readonly ? 'ro' : ''))));
+
+    $.each(sessions, function() {
+      if (this.is_invited) {
+        var txt = rcmail.gettext('kolab_files.invitedsession').replace('$user', this.owner);
+        items.push(item_fn(this.id, txt, 'invited'));
+      }
+    });
+
+    $.each(sessions, function() {
+      if (!this.is_owner && !this.is_invited) {
+        var txt = rcmail.gettext('kolab_files.joinsession').replace('$user', this.owner);
+        items.push(item_fn(this.id, txt));
+      }
+    });
+
+    // check the first option
+    $('input', items[1]).attr('checked', true);
+
+    $('div', dialog).html(items);
+
+    // if there's only one session and it's owned, skip the dialog
+    if (!readonly && items.length == 2 && $('input:checked', dialog).parent().is('.owner'))
+      return select_fn();
+  }
+  // no ongoing session, folder is readonly warning
+  else {
+    title = rcmail.gettext('kolab_files.editfilerotitle');
+    height = 150;
+    $('div', dialog).text(rcmail.gettext('kolab_files.editfilero'));
+    mainaction = rcmail.gettext('kolab_files.create');
+  }
+
+  buttons[mainaction] = function() { select_fn(this); };
+  buttons[rcmail.gettext('kolab_files.cancel')] = function () {
+    kolab_dialog_close(this);
+  };
+
+  // show dialog window
+  kolab_dialog_show(dialog, {
+    title: title,
+    buttons: buttons,
+    button_classes: ['mainaction'],
+    minHeight: height - 100,
+    height: height
+  });
+};
+
 // file rename dialog
 function kolab_files_file_rename_dialog(file)
 {
@@ -511,7 +605,7 @@ function kolab_files_file_rename_dialog(file)
     buttons = {}, name = file_api.file_name(file)
     input = $('input[name="name"]', dialog).val(name);
 
-  buttons[rcmail.gettext('kolab_files.save')] = function () {
+  buttons[rcmail.gettext('kolab_files.save')] = function() {
     var folder = file_api.file_path(file), name = input.val();
 
     if (!name)
@@ -524,7 +618,7 @@ function kolab_files_file_rename_dialog(file)
 
     kolab_dialog_close(this);
   };
-  buttons[rcmail.gettext('kolab_files.cancel')] = function () {
+  buttons[rcmail.gettext('kolab_files.cancel')] = function() {
     kolab_dialog_close(this);
   };
 
@@ -541,16 +635,16 @@ function kolab_files_file_rename_dialog(file)
   });
 };
 
-// file creation dialog
-function kolab_files_file_create_dialog()
+// file creation (or cloning) dialog
+function kolab_files_file_create_dialog(file)
 {
-  var dialog = $('#files-file-create-dialog'),
-    buttons = {},
+  var buttons = {}, action = file ? 'copy' : 'create',
+    dialog = $('#files-file-create-dialog'),
     type_select = $('select[name="type"]', dialog),
     select = $('select[name="parent"]', dialog).html(''),
     input = $('input[name="name"]', dialog).val(''),
-    create_func = function (dialog, editaction) {
-      var folder = select.val(), type = type_select.val(), name = input.val();
+    create_func = function(dialog, editaction) {
+      var sel, folder = select.val(), type = type_select.val(), name = input.val();
 
       if (!name || !folder)
         return;
@@ -561,17 +655,36 @@ function kolab_files_file_create_dialog()
 
       name = folder + file_api.env.directory_separator + name;
 
-      file_api.file_create(name, type, editaction);
+      // get type of cloned file
+      if (file) {
+        if (rcmail.env.file_data)
+          type = rcmail.env.file_data.type;
+        else {
+          sel = rcmail.file_list.get_selection();
+          type = $('#rcmrow' + sel[0]).data('type');
+        }
+      }
+
+      file_api.file_create(name, type, editaction, file);
       kolab_dialog_close(dialog);
   };
 
-  buttons[rcmail.gettext('kolab_files.createandedit')] = function () {
+  buttons[rcmail.gettext('kolab_files.' + action + 'andedit')] = function() {
     create_func(this, true);
   };
-  buttons[rcmail.gettext('kolab_files.create')] = function () {
-    create_func(this);
-  };
-  buttons[rcmail.gettext('kolab_files.cancel')] = function () {
+
+  if (action == 'create') {
+    buttons[rcmail.gettext('kolab_files.create')] = function() {
+      create_func(this);
+    };
+    type_select.parent('tr').show();
+  }
+  else {
+    input.val(file_api.file_name(file));
+    type_select.parent('tr').hide();
+  }
+
+  buttons[rcmail.gettext('kolab_files.cancel')] = function() {
     kolab_dialog_close(this);
   };
 
@@ -580,37 +693,15 @@ function kolab_files_file_create_dialog()
 
   // show dialog window
   kolab_dialog_show(dialog, {
-    title: rcmail.gettext('kolab_files.createfile'),
+    title: rcmail.gettext('kolab_files.' + action + 'file'),
     buttons: buttons,
-    button_classes: ['mainaction']
+    button_classes: ['mainaction'],
+    minHeight: 150,
+    height: 250
   });
 
   // build folder selector
-  kolab_files_folder_select_element(select);
-};
-
-// builds folder selector options
-function kolab_files_folder_select_element(select, params)
-{
-  var options = [],
-    selected = params && params.selected ? params.selected : file_api.env.folder;
-
-  if (params && params.empty)
-    options.push($('<option>').val('').text('---'));
-
-  $.each(file_api.env.folders, function(i, f) {
-    var n, name = escapeHTML(f.name);
-
-    for (n=0; n<f.depth; n++)
-      name = '&nbsp;&nbsp;&nbsp;' + name;
-
-    options.push($('<option>').val(i).html(name));
-  });
-
-  select.empty().append(options);
-
-  if (selected)
-    select.val(selected);
+  file_api.folder_select_element(select, {writable: true});
 };
 
 function kolab_dialog_show(content, params, onopen)
@@ -826,11 +917,11 @@ function kolab_files_list_select(list)
     // get file mimetype
     var elem = $('tr.selected', list.list),
       type = elem.data('type'),
-      file = elem.data('file');
+      folder = file_api.file_path(elem.data('file'));
 
     rcmail.env.viewer = file_api.file_type_supported(type, rcmail.env.files_caps);
 
-    if (!file_api.is_writable(file.replace(/\/[^/]+$/, '')))
+    if (!file_api.is_writable(folder))
       rcmail.enable_command('files-delete', 'files-rename', false);
   }
   else
@@ -1152,21 +1243,40 @@ rcube_webmail.prototype.files_open = function()
 };
 
 // enable file editor
-rcube_webmail.prototype.files_edit = function()
+rcube_webmail.prototype.files_edit = function(session)
 {
-  if (this.file_editor) {
+  var files, readonly, sessions, file = this.env.file,
+    params = {action: 'edit'};
+
+  if (!file && !this.env.action) {
+    files = kolab_files_selected();
+    if (files.length == 1)
+      file = files[0];
+  }
+
+  // check if the folder is read-only or there are ongoing sessions
+  // in such cases display dialog for the user to decide what to do
+  if (!session) {
+    sessions = file_api.file_sessions(file);
+    if (sessions.length || (readonly = !file_api.is_writable(file_api.file_path(file)))) {
+      kolab_files_file_edit_dialog(file, sessions, readonly);
+      return;
+    }
+  }
+  else if (session !== true)
+    params.session = session;
+
+  if (this.file_editor && !session) {
     this.file_editor.enable();
     this.enable_command('files-save', true);
   }
   else if (this.env.file) {
     var viewer = file_api.file_type_supported(this.env.file_data.type, this.env.files_caps);
-    file_api.file_open(this.env.file, viewer, 'edit', true);
+    params.local = true;
+    file_api.file_open(file, viewer, params);
   }
-  else if (!this.env.action) {
-    var files = kolab_files_selected();
-
-    if (files.length == 1)
-      file_api.file_open(files[0], this.env.viewer, 'edit');
+  else if (file) {
+    file_api.file_open(file, this.env.viewer, params);
   }
 };
 
@@ -1270,7 +1380,6 @@ rcube_webmail.prototype.folder_mount = function()
 function kolab_files_ui()
 {
   this.requests = {};
-  this.sessions = {};
   this.uploads = [];
 
 /*
@@ -1435,7 +1544,8 @@ function kolab_files_ui()
 //    this.folder_list_tree(this.env.folders);
 
     // handle authentication errors on external sources
-    this.folder_list_auth_errors(response.result);
+    if (elem.length)
+      this.folder_list_auth_errors(response.result);
   };
 
   this.folder_select = function(folder)
@@ -2212,7 +2322,7 @@ function kolab_files_ui()
       return;
 
     if (response.result.sessions)
-      this.sessions[response.folder] = response.result.sessions;
+      this.sessions[response.result.folder] = response.result.sessions;
 
     // update files list with document session info
     $.each(file_api.env.file_list || [], function(i, file) {
@@ -2432,14 +2542,21 @@ function kolab_files_ui()
     }
   };
 
-  // file(s) create request
-  this.file_create = function(file, type, edit)
+  // file(s) create (or clone) request
+  this.file_create = function(file, type, edit, cloneof)
   {
     this.file_create_edit_file = edit ? file : null;
     this.file_create_edit_type = edit ? type : null;
+    this.file_create_folder = this.file_path(file);
 
-    this.req = this.set_busy(true, 'kolab_files.filecreating');
-    this.request('file_create', {file: file, 'content-type': type, content: ''}, 'file_create_response');
+    if (cloneof) {
+      this.req = this.set_busy(true, 'kolab_files.filecopying');
+      this.request('file_copy', {file: cloneof, 'new': file}, 'file_create_response');
+    }
+    else {
+      this.req = this.set_busy(true, 'kolab_files.filecreating');
+      this.request('file_create', {file: file, 'content-type': type, content: ''}, 'file_create_response');
+    }
   };
 
   // file(s) create response handler
@@ -2449,12 +2566,13 @@ function kolab_files_ui()
       return;
 
     // @TODO: we could update metadata instead
-    this.file_list();
+    if (this.file_create_folder == this.env.folder)
+      this.file_list();
 
     // open the file for editing if editable
     if (this.file_create_edit_file) {
       var viewer = this.file_type_supported(this.file_create_edit_type, rcmail.env.files_caps);
-      this.file_open(this.file_create_edit_file, viewer, 'edit');
+      this.file_open(this.file_create_edit_file, viewer, {action: 'edit'});
     }
   };
 
@@ -2736,14 +2854,24 @@ function kolab_files_ui()
   };
 
   // open file in new window, using file API viewer
-  this.file_open = function(file, viewer, action, local)
+  this.file_open = function(file, viewer, params)
   {
-    var href = '?' + $.param({_task: 'files', _action: action || 'open', file: file, viewer: viewer || 0});
+    var args = {
+      _task: 'files',
+      _action: params && params.action ? params.action : 'open',
+      _file: file,
+      _viewer: viewer || 0,
+    };
+
+    if (params && params.session)
+      args._session = params.session;
 
     if (rcmail.env.extwin)
-      href += '&_extwin=1';
+      args._extwin = 1;
 
-    if (local)
+    href = '?' + $.param(args);
+
+    if (params && params.local)
       location.href = href;
     else
       rcmail.open_window(href, false, true);
diff --git a/plugins/kolab_files/lib/kolab_files_engine.php b/plugins/kolab_files/lib/kolab_files_engine.php
index 427353df..5607ee63 100644
--- a/plugins/kolab_files/lib/kolab_files_engine.php
+++ b/plugins/kolab_files/lib/kolab_files_engine.php
@@ -144,6 +144,7 @@ class kolab_files_engine
                 'file-search-form'   => array($this, 'file_search_form'),
                 'file-rename-form'   => array($this, 'file_rename_form'),
                 'file-create-form'   => array($this, 'file_create_form'),
+                'file-edit-dialog'   => array($this, 'file_edit_dialog'),
                 'filelist'           => array($this, 'file_list'),
                 'filequotadisplay'   => array($this, 'quota_display'),
             ));
@@ -328,6 +329,19 @@ class kolab_files_engine
         );
     }
 
+    /**
+     * Template object for file edit dialog/warnings
+     */
+    public function file_edit_dialog($attrib)
+    {
+        $this->plugin->add_label('select', 'create', 'cancel', 'editfiledialog', 'editfilesessions',
+            'newsession', 'ownedsession', 'invitedsession', 'joinsession', 'editfilero', 'editfilerotitle',
+            'newsessionro'
+        );
+
+        return '<div></div>';
+    }
+
     /**
      * Template object for file_rename form
      */
@@ -398,7 +412,8 @@ class kolab_files_engine
             $out = $this->rc->output->form_tag($attrib, $out);
         }
 
-        $this->plugin->add_label('create', 'cancel', 'filecreating', 'createfile', 'createandedit');
+        $this->plugin->add_label('create', 'cancel', 'filecreating', 'createfile', 'createandedit',
+            'copyfile', 'copyandedit');
         $this->rc->output->add_gui_object('file-create-form', $attrib['id']);
         $this->rc->output->set_env('file_extensions', $types);
 
@@ -893,7 +908,9 @@ class kolab_files_engine
     protected function action_open()
     {
         $this->rc->output->set_env('files_caps', $_SESSION['kolab_files_caps']);
-        $this->file_opener(intval($_GET['viewer']) & ~4);
+        $this->rc->output->set_env('file_mimetypes', $this->get_mimetypes());
+
+        $this->file_opener(intval($_GET['_viewer']) & ~4);
     }
 
     /**
@@ -901,7 +918,7 @@ class kolab_files_engine
      */
     protected function action_edit()
     {
-        $this->file_opener(intval($_GET['viewer']));
+        $this->file_opener(intval($_GET['_viewer']));
     }
 
     /**
@@ -1191,14 +1208,16 @@ class kolab_files_engine
      */
     protected function file_opener($viewer)
     {
-        $file = rcube_utils::get_input_value('file', rcube_utils::INPUT_GET);
+        $file    = rcube_utils::get_input_value('_file', rcube_utils::INPUT_GET);
+        $session = rcube_utils::get_input_value('_session', rcube_utils::INPUT_GET);
 
         // get file info
         $token   = $this->get_api_token();
         $request = $this->get_request(array(
-            'method' => 'file_info',
-            'file'   => $file,
-            'viewer' => $viewer,
+            'method'  => 'file_info',
+            'file'    => $file,
+            'viewer'  => $viewer,
+            'session' => $session,
             ), $token);
 
         // send request to the API
diff --git a/plugins/kolab_files/localization/en_US.inc b/plugins/kolab_files/localization/en_US.inc
index e9eeeee7..b8eb0ac7 100644
--- a/plugins/kolab_files/localization/en_US.inc
+++ b/plugins/kolab_files/localization/en_US.inc
@@ -46,6 +46,8 @@ $labels['printfile'] = 'Print file';
 $labels['renamefile'] = 'Rename a file';
 $labels['createfile'] = 'Create a file';
 $labels['createandedit'] = 'Create and Edit';
+$labels['copyfile'] = 'Copy a file';
+$labels['copyandedit'] = 'Copy and Edit';
 $labels['documenttitle'] = 'Title:';
 
 $labels['collection_audio'] = 'Audio';
@@ -89,6 +91,17 @@ $labels['fileoverwrite'] = 'Overwrite';
 $labels['fileoverwriteall'] = 'Overwrite all';
 $labels['filemoveconfirm'] = 'This action is going to overwrite the destination file: <b>$file</b>.';
 
+$labels['editfiledialog'] = 'Confirm editing action';
+$labels['editfilesessions'] = 'There are ongoing sessions on the selected file. Please, select the action you want to take.';
+$labels['newsession'] = 'Create a new session';
+$labels['newsessionro'] = 'Create a new session (copy the file into read-write location)';
+$labels['ownedsession'] = 'Continue your existing session';
+$labels['invitedsession'] = 'Join the session of $user';
+$labels['joinsession'] = 'Request an invitation from $user';
+$labels['editfilero'] = 'This file is read-only. Do you want to create and edit a copy of the file?';
+$labels['editfilerotitle'] = 'Read-only file';
+$labels['select'] = 'Select';
+
 $labels['storepasswords'] = 'remember password';
 $labels['storepasswordsdesc'] = 'Stored passwords will be encrypted. Enable this if you do not want to be asked for the password on every login or you want this storage to be available via WebDAV.';
 
@@ -109,6 +122,7 @@ $labels['arialabelattachmentoptions'] = 'Attachment save options';
 $labels['arialabelfilesavedialog'] = 'File(s) saving dialog';
 $labels['arialabelfileprops'] = 'File properties';
 $labels['arialabelfilecontent'] = 'File content';
+$labels['arialabelfileeditdialog'] = 'File editing dialog';
 
 $labels['type.plain'] = 'Plain Text Document';
 $labels['type.vndoasisopendocumenttext'] = 'Text Document (ODF)';
diff --git a/plugins/kolab_files/skins/larry/style.css b/plugins/kolab_files/skins/larry/style.css
index 7963e7bb..dd61b9f5 100644
--- a/plugins/kolab_files/skins/larry/style.css
+++ b/plugins/kolab_files/skins/larry/style.css
@@ -396,6 +396,7 @@
 #files-compose-dialog,
 #files-file-rename-dialog,
 #files-file-create-dialog,
+#files-file-edit-dialog,
 #files-folder-mount-dialog,
 #files-folder-auth-dialog,
 #files-folder-create-dialog,
@@ -463,6 +464,11 @@
   cursor: pointer;
 }
 
+#files-file-edit-dialog label {
+  display: block;
+  height: 20px;
+}
+
 a.filesaveall {
   display: inline-block;
   margin-top: .5em;
diff --git a/plugins/kolab_files/skins/larry/templates/filepreview.html b/plugins/kolab_files/skins/larry/templates/filepreview.html
index a0b51393..f669e32f 100644
--- a/plugins/kolab_files/skins/larry/templates/filepreview.html
+++ b/plugins/kolab_files/skins/larry/templates/filepreview.html
@@ -35,7 +35,17 @@
 
 </div>
 
+<div id="files-file-create-dialog" role="dialog" aria-labelledby="aria-label-filecreateform" aria-hidden="true">
+    <h3 id="aria-label-filecreateform" class="voice"><roundcube:label name="kolab_files.arialabelfilecreateform" /></h3>
+    <roundcube:object name="file-create-form" />
+</div>
+<div id="files-file-edit-dialog" role="dialog" aria-labelledby="aria-label-fileeditdialog" aria-hidden="true">
+    <h3 id="aria-label-fileeditdialog" class="voice"><roundcube:label name="kolab_files.arialabelfileeditdialog" /></h3>
+    <roundcube:object name="file-edit-dialog">
+</div>
+
 <roundcube:include file="/includes/footer.html" />
+
 <script type="text/javascript">
 kolab_files_ui_init();
 </script>
diff --git a/plugins/kolab_files/skins/larry/templates/files.html b/plugins/kolab_files/skins/larry/templates/files.html
index 0d1a6da2..6b8b8178 100644
--- a/plugins/kolab_files/skins/larry/templates/files.html
+++ b/plugins/kolab_files/skins/larry/templates/files.html
@@ -105,6 +105,10 @@
     <h3 id="aria-label-folderauthform" class="voice"><roundcube:label name="kolab_files.arialabelfolderauthform" /></h3>
     <roundcube:object name="folder-auth-options">
 </div>
+<div id="files-file-edit-dialog" role="dialog" aria-labelledby="aria-label-fileeditdialog" aria-hidden="true">
+    <h3 id="aria-label-fileeditdialog" class="voice"><roundcube:label name="kolab_files.arialabelfileeditdialog" /></h3>
+    <roundcube:object name="file-edit-dialog">
+</div>
 
 <div id="listoptions" class="propform popupdialog" data-editable="true" role="dialog" aria-labelledby="aria-label-listoptions" aria-hidden="true">
     <h3 id="aria-label-listoptions" class="voice"><roundcube:label name="kolab_files.arialabellistoptions" /></h3>