                 alert_message(type:'error', message:"Failed to open history document -- #{err}")
         )
 
+    jupyter_classic: ->
+        # cached so only computed once and STABLE.
+        return @_jupyter_classic ?= !!redux.getStore('account')?.getIn(['editor_settings', 'jupyter_classic'])
+
     init_paths: =>
         #   @filename = "path/to/.file.sage-history"
         s = misc.path_split(@filename)

            @_open_file_path = @_path
        @ext = misc.filename_extension(@_path)
        if @ext == 'ipynb'
            @_path = misc.meta_file(@_path, 'jupyter2')
        if @ext == 'ipynb2'
            @_path = '.' + @_path + require('./editor_jupyter').IPYTHON_SYNCFILE_EXTENSION
        if s.head
            @_path = s.head + '/' + @_path


        opts.read_only = true
        switch @ext
            when 'ipynb'
                if @jupyter_classic()
                    @view_doc = jupyter.jupyter_notebook(@, @_open_file_path, opts).data("jupyter_notebook")
                    @element.find("a[href=\"#show-diff\"]").hide()
                else
                    @view_doc = jupyter_history_viewer_jquery_shim(@syncstring)
                    @element.find("a[href=\"#show-diff\"]").hide()
            when 'tasks'
                @view_doc = tasks.task_list(undefined, undefined, {viewer:true}).data('task_list')
                @element.find("a[href=\"#show-diff\"]").hide()
