diff --git a/python/ycm/buffer.py b/python/ycm/buffer.py
new file mode 100644
index 00000000..8d931a7d
--- /dev/null
+++ b/python/ycm/buffer.py
@@ -0,0 +1,100 @@
+# Copyright (C) 2016, Davit Samvelyan
+#
+# This file is part of YouCompleteMe.
+#
+# YouCompleteMe is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# YouCompleteMe is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with YouCompleteMe.  If not, see <http://www.gnu.org/licenses/>.
+
+from __future__ import unicode_literals
+from __future__ import print_function
+from __future__ import division
+from __future__ import absolute_import
+# Not installing aliases from python-future; it's unreliable and slow.
+from builtins import *  # noqa
+
+from ycm import vimsupport
+from ycm.client.event_notification import EventNotification
+from ycm.diagnostic_interface import DiagnosticInterface
+
+
+class Buffer( object ):
+
+  def __init__( self, bufnr, user_options ):
+    self.number = bufnr
+    self._parse_tick = 0
+    self._handled_tick = 0
+    self._parse_request = None
+    self._diag_interface = DiagnosticInterface( user_options )
+
+
+  def FileParseRequestReady( self, block = False ):
+    return self._parse_tick == 0 or block or self._parse_request.Done()
+
+
+  def SendParseRequest( self, extra_data ):
+    self._parse_request = EventNotification( 'FileReadyToParse',
+                                             extra_data = extra_data )
+    self._parse_request.Start()
+    self._parse_tick = self._ChangedTick()
+
+
+  def NeedsReparse( self ):
+    return self._parse_tick != self._ChangedTick()
+
+
+  def UpdateDiagnostics( self ):
+    diagnostics = self._parse_request.Response()
+    self._diag_interface.UpdateWithNewDiagnostics( diagnostics )
+
+
+  def PopulateLocationList( self ):
+    return self._diag_interface.PopulateLocationList()
+
+
+  def GetResponse( self ):
+    return self._parse_request.Response()
+
+
+  def IsResponseHandled( self ):
+    return self._handled_tick == self._parse_tick
+
+
+  def MarkResponseHandled( self ):
+    self._handled_tick = self._parse_tick
+
+
+  def OnCursorMoved( self ):
+    self._diag_interface.OnCursorMoved()
+
+
+  def GetErrorCount( self ):
+    return self._diag_interface.GetErrorCount()
+
+
+  def GetWarningCount( self ):
+    return self._diag_interface.GetWarningCount()
+
+
+  def _ChangedTick( self ):
+    return vimsupport.GetBufferChangedTick( self.number )
+
+
+class BufferDict( dict ):
+
+  def __init__( self, user_options ):
+    self._user_options = user_options
+
+
+  def __missing__( self, key ):
+    value = self[ key ] = Buffer( key, self._user_options )
+    return value
diff --git a/python/ycm/diagnostic_interface.py b/python/ycm/diagnostic_interface.py
index 89051635..9fc9541c 100644
--- a/python/ycm/diagnostic_interface.py
+++ b/python/ycm/diagnostic_interface.py
@@ -32,6 +32,7 @@ import vim
 class DiagnosticInterface( object ):
   def __init__( self, user_options ):
     self._user_options = user_options
+    self._diagnostics = []
     self._diag_filter = DiagnosticFilter.CreateFromOptions( user_options )
     # Line and column numbers are 1-based
     self._buffer_number_to_line_to_diags = defaultdict(
@@ -60,17 +61,18 @@ class DiagnosticInterface( object ):
     return len( self._FilterDiagnostics( _DiagnosticIsWarning ) )
 
 
-  def PopulateLocationList( self, diags ):
-    vimsupport.SetLocationList(
-      vimsupport.ConvertDiagnosticsToQfList(
-          self._ApplyDiagnosticFilter( diags ) ) )
+  def PopulateLocationList( self ):
+    # Do nothing if loc list is already populated by diag_interface
+    if not self._user_options[ 'always_populate_location_list' ]:
+      self._UpdateLocationList()
+    return bool( self._diagnostics )
 
 
   def UpdateWithNewDiagnostics( self, diags ):
-    normalized_diags = [ _NormalizeDiagnostic( x ) for x in
-            self._ApplyDiagnosticFilter( diags ) ]
+    self._diagnostics = [ _NormalizeDiagnostic( x ) for x in
+                            self._ApplyDiagnosticFilter( diags ) ]
     self._buffer_number_to_line_to_diags = _ConvertDiagListToDict(
-        normalized_diags )
+        self._diagnostics )
 
     if self._user_options[ 'enable_diagnostic_signs' ]:
       self._placed_signs, self._next_sign_id = _UpdateSigns(
@@ -82,7 +84,7 @@ class DiagnosticInterface( object ):
       _UpdateSquiggles( self._buffer_number_to_line_to_diags )
 
     if self._user_options[ 'always_populate_location_list' ]:
-      self.PopulateLocationList( normalized_diags )
+      self._UpdateLocationList()
 
 
   def _ApplyDiagnosticFilter( self, diags, extra_predicate = None ):
@@ -128,6 +130,11 @@ class DiagnosticInterface( object ):
     return matched_diags
 
 
+  def _UpdateLocationList( self ):
+    vimsupport.SetLocationList(
+      vimsupport.ConvertDiagnosticsToQfList( self._diagnostics ) )
+
+
 def _UpdateSquiggles( buffer_number_to_line_to_diags ):
   vimsupport.ClearYcmSyntaxMatches()
   line_to_diags = buffer_number_to_line_to_diags[ vim.current.buffer.number ]
diff --git a/python/ycm/tests/event_notification_test.py b/python/ycm/tests/event_notification_test.py
index fa4e082a..463cd060 100644
--- a/python/ycm/tests/event_notification_test.py
+++ b/python/ycm/tests/event_notification_test.py
@@ -25,6 +25,7 @@ from __future__ import absolute_import
 from builtins import *  # noqa
 
 from ycm.tests.test_utils import ( CurrentWorkingDirectory, ExtendedMock,
+                                   EmulateCurrentBufferChange,
                                    MockVimBuffers, MockVimModule, VimBuffer )
 MockVimModule()
 
@@ -105,7 +106,10 @@ def MockEventNotification( response_method, native_filetype_completer = True ):
         'ycm.youcompleteme.YouCompleteMe.FiletypeCompleterExistsForFiletype',
         return_value = native_filetype_completer ):
 
-        yield
+        with patch( 'ycm.youcompleteme.YouCompleteMe.IsServerReady',
+                    return_value = True ):
+
+          yield
 
 
 @patch( 'ycm.vimsupport.PostVimMessage', new_callable = ExtendedMock )
@@ -138,6 +142,7 @@ def EventNotification_FileReadyToParse_NonDiagnostic_Error_test(
         call( ERROR_TEXT, truncate = True )
       ] )
 
+      EmulateCurrentBufferChange()
       # But it does if a subsequent event raises again
       ycm.OnFileReadyToParse()
       ok_( ycm.FileParseRequestReady() )
@@ -207,6 +212,7 @@ def EventNotification_FileReadyToParse_NonDiagnostic_ConfirmExtraConf_test(
           call( FILE_NAME ),
         ] )
 
+        EmulateCurrentBufferChange()
         # But it does if a subsequent event raises again
         ycm.OnFileReadyToParse()
         ok_( ycm.FileParseRequestReady() )
@@ -221,6 +227,7 @@ def EventNotification_FileReadyToParse_NonDiagnostic_ConfirmExtraConf_test(
           call( FILE_NAME ),
         ] )
 
+      EmulateCurrentBufferChange()
       # When the user rejects the extra conf, we reject it
       with patch( 'ycm.vimsupport.PresentDialog',
                   return_value = 1,
@@ -246,6 +253,7 @@ def EventNotification_FileReadyToParse_NonDiagnostic_ConfirmExtraConf_test(
           call( FILE_NAME ),
         ] )
 
+        EmulateCurrentBufferChange()
         # But it does if a subsequent event raises again
         ycm.OnFileReadyToParse()
         ok_( ycm.FileParseRequestReady() )
@@ -263,9 +271,12 @@ def EventNotification_FileReadyToParse_NonDiagnostic_ConfirmExtraConf_test(
 
 @YouCompleteMeInstance()
 def EventNotification_FileReadyToParse_Diagnostic_Error_Native_test( ycm ):
-  _Check_FileReadyToParse_Diagnostic_Error( ycm )
-  _Check_FileReadyToParse_Diagnostic_Warning( ycm )
-  _Check_FileReadyToParse_Diagnostic_Clean( ycm )
+  with MockArbitraryBuffer( 'cpp' ):
+    _Check_FileReadyToParse_Diagnostic_Error( ycm )
+    EmulateCurrentBufferChange()
+    _Check_FileReadyToParse_Diagnostic_Warning( ycm )
+    EmulateCurrentBufferChange()
+    _Check_FileReadyToParse_Diagnostic_Clean( ycm )
 
 
 @patch( 'vim.command' )
@@ -279,25 +290,24 @@ def _Check_FileReadyToParse_Diagnostic_Error( ycm, vim_command ):
     diagnostic = Diagnostic( [], start, extent, 'expected ;', 'ERROR' )
     return [ BuildDiagnosticData( diagnostic ) ]
 
-  with MockArbitraryBuffer( 'cpp' ):
-    with MockEventNotification( DiagnosticResponse ):
-      ycm.OnFileReadyToParse()
-      ok_( ycm.FileParseRequestReady() )
-      ycm.HandleFileParseRequest()
-      vim_command.assert_has_calls( [
-        PlaceSign_Call( 1, 1, 1, True )
-      ] )
-      eq_( ycm.GetErrorCount(), 1 )
-      eq_( ycm.GetWarningCount(), 0 )
+  with MockEventNotification( DiagnosticResponse ):
+    ycm.OnFileReadyToParse()
+    ok_( ycm.FileParseRequestReady() )
+    ycm.HandleFileParseRequest()
+    vim_command.assert_has_calls( [
+      PlaceSign_Call( 1, 1, 1, True )
+    ] )
+    eq_( ycm.GetErrorCount(), 1 )
+    eq_( ycm.GetWarningCount(), 0 )
 
-      # Consequent calls to HandleFileParseRequest shouldn't mess with
-      # existing diagnostics, when there is no new parse request.
-      vim_command.reset_mock()
-      ok_( not ycm.FileParseRequestReady() )
-      ycm.HandleFileParseRequest()
-      vim_command.assert_not_called()
-      eq_( ycm.GetErrorCount(), 1 )
-      eq_( ycm.GetWarningCount(), 0 )
+    # Consequent calls to HandleFileParseRequest shouldn't mess with
+    # existing diagnostics, when there is no new parse request.
+    vim_command.reset_mock()
+    ok_( ycm.FileParseRequestReady() )
+    ycm.HandleFileParseRequest()
+    vim_command.assert_not_called()
+    eq_( ycm.GetErrorCount(), 1 )
+    eq_( ycm.GetWarningCount(), 0 )
 
 
 @patch( 'vim.command' )
@@ -312,26 +322,25 @@ def _Check_FileReadyToParse_Diagnostic_Warning( ycm, vim_command ):
     diagnostic = Diagnostic( [], start, extent, 'cast', 'WARNING' )
     return [ BuildDiagnosticData( diagnostic ) ]
 
-  with MockArbitraryBuffer( 'cpp' ):
-    with MockEventNotification( DiagnosticResponse ):
-      ycm.OnFileReadyToParse()
-      ok_( ycm.FileParseRequestReady() )
-      ycm.HandleFileParseRequest()
-      vim_command.assert_has_calls( [
-        PlaceSign_Call( 2, 2, 1, False ),
-        UnplaceSign_Call( 1, 1 )
-      ] )
-      eq_( ycm.GetErrorCount(), 0 )
-      eq_( ycm.GetWarningCount(), 1 )
+  with MockEventNotification( DiagnosticResponse ):
+    ycm.OnFileReadyToParse()
+    ok_( ycm.FileParseRequestReady() )
+    ycm.HandleFileParseRequest()
+    vim_command.assert_has_calls( [
+      PlaceSign_Call( 2, 2, 1, False ),
+      UnplaceSign_Call( 1, 1 )
+    ] )
+    eq_( ycm.GetErrorCount(), 0 )
+    eq_( ycm.GetWarningCount(), 1 )
 
-      # Consequent calls to HandleFileParseRequest shouldn't mess with
-      # existing diagnostics, when there is no new parse request.
-      vim_command.reset_mock()
-      ok_( not ycm.FileParseRequestReady() )
-      ycm.HandleFileParseRequest()
-      vim_command.assert_not_called()
-      eq_( ycm.GetErrorCount(), 0 )
-      eq_( ycm.GetWarningCount(), 1 )
+    # Consequent calls to HandleFileParseRequest shouldn't mess with
+    # existing diagnostics, when there is no new parse request.
+    vim_command.reset_mock()
+    ok_( ycm.FileParseRequestReady() )
+    ycm.HandleFileParseRequest()
+    vim_command.assert_not_called()
+    eq_( ycm.GetErrorCount(), 0 )
+    eq_( ycm.GetWarningCount(), 1 )
 
 
 @patch( 'vim.command' )
@@ -339,15 +348,14 @@ def _Check_FileReadyToParse_Diagnostic_Clean( ycm, vim_command ):
   # Tests Vim sign unplacement and error/warning count python API
   # when there are no errors/warnings left.
   # Should be called after _Check_FileReadyToParse_Diagnostic_Warning
-  with MockArbitraryBuffer( 'cpp' ):
-    with MockEventNotification( MagicMock( return_value = [] ) ):
-      ycm.OnFileReadyToParse()
-      ycm.HandleFileParseRequest()
-      vim_command.assert_has_calls( [
-        UnplaceSign_Call( 2, 1 )
-      ] )
-      eq_( ycm.GetErrorCount(), 0 )
-      eq_( ycm.GetWarningCount(), 0 )
+  with MockEventNotification( MagicMock( return_value = [] ) ):
+    ycm.OnFileReadyToParse()
+    ycm.HandleFileParseRequest()
+    vim_command.assert_has_calls( [
+      UnplaceSign_Call( 2, 1 )
+    ] )
+    eq_( ycm.GetErrorCount(), 0 )
+    eq_( ycm.GetWarningCount(), 0 )
 
 
 @patch( 'ycm.youcompleteme.YouCompleteMe._AddUltiSnipsDataIfNeeded' )
@@ -364,7 +372,9 @@ def EventNotification_FileReadyToParse_TagFiles_UnicodeWorkingDirectory_test(
               'PostDataToHandlerAsync' ) as post_data_to_handler_async:
     with CurrentWorkingDirectory( unicode_dir ):
       with MockVimBuffers( [ current_buffer ], current_buffer, ( 6, 5 ) ):
-        ycm.OnFileReadyToParse()
+        with patch( 'ycm.youcompleteme.YouCompleteMe.IsServerReady',
+                    return_value = True ):
+          ycm.OnFileReadyToParse()
 
     assert_that(
       # Positional arguments passed to PostDataToHandlerAsync.
diff --git a/python/ycm/tests/test_utils.py b/python/ycm/tests/test_utils.py
index 36ce2478..30740188 100644
--- a/python/ycm/tests/test_utils.py
+++ b/python/ycm/tests/test_utils.py
@@ -40,7 +40,7 @@ BUFWINNR_REGEX = re.compile( '^bufwinnr\((?P<buffer_number>[0-9]+)\)$' )
 BWIPEOUT_REGEX = re.compile(
   '^(?:silent! )bwipeout!? (?P<buffer_number>[0-9]+)$' )
 GETBUFVAR_REGEX = re.compile(
-  '^getbufvar\((?P<buffer_number>[0-9]+), "&(?P<option>.+)"\)$' )
+  '^getbufvar\((?P<buffer_number>[0-9]+), "(?P<option>.+)"\)$' )
 MATCHADD_REGEX = re.compile(
   '^matchadd\(\'(?P<group>.+)\', \'(?P<pattern>.+)\'\)$' )
 MATCHDELETE_REGEX = re.compile( '^matchdelete\((?P<id>)\)$' )
@@ -85,10 +85,12 @@ def _MockGetBufferWindowNumber( buffer_number ):
 def _MockGetBufferVariable( buffer_number, option ):
   for vim_buffer in VIM_MOCK.buffers:
     if vim_buffer.number == buffer_number:
-      if option == 'mod':
+      if option == '&mod':
         return vim_buffer.modified
-      if option == 'ft':
+      if option == '&ft':
         return vim_buffer.filetype
+      if option == 'changedtick':
+        return vim_buffer.changedtick
       return ''
   return ''
 
@@ -230,6 +232,7 @@ class VimBuffer( object ):
     self.modified = modified
     self.window = window
     self.omnifunc = omnifunc
+    self.changedtick = 1
 
 
   def __getitem__( self, index ):
@@ -250,6 +253,10 @@ class VimBuffer( object ):
     return [ ToUnicode( x ) for x in self.contents ]
 
 
+def EmulateCurrentBufferChange():
+  VIM_MOCK.current.buffer.changedtick += 1
+
+
 class VimMatch( object ):
 
   def __init__( self, group, pattern ):
diff --git a/python/ycm/tests/youcompleteme_test.py b/python/ycm/tests/youcompleteme_test.py
index 53a95b87..6722e69d 100644
--- a/python/ycm/tests/youcompleteme_test.py
+++ b/python/ycm/tests/youcompleteme_test.py
@@ -349,6 +349,7 @@ def YouCompleteMe_ShowDiagnostics_NoDiagnosticsDetected_test(
                           'open_loclist_on_ycm_diags': 0 } )
 @patch( 'ycm.youcompleteme.YouCompleteMe.FiletypeCompleterExistsForFiletype',
         return_value = True )
+@patch( 'ycm.youcompleteme.YouCompleteMe.IsServerReady', return_value = True )
 @patch( 'ycm.vimsupport.PostVimMessage', new_callable = ExtendedMock )
 @patch( 'ycm.vimsupport.SetLocationList', new_callable = ExtendedMock )
 def YouCompleteMe_ShowDiagnostics_DiagnosticsFound_DoNotOpenLocationList_test(
@@ -388,6 +389,7 @@ def YouCompleteMe_ShowDiagnostics_DiagnosticsFound_DoNotOpenLocationList_test(
 @YouCompleteMeInstance( { 'open_loclist_on_ycm_diags': 1 } )
 @patch( 'ycm.youcompleteme.YouCompleteMe.FiletypeCompleterExistsForFiletype',
         return_value = True )
+@patch( 'ycm.youcompleteme.YouCompleteMe.IsServerReady', return_value = True )
 @patch( 'ycm.vimsupport.PostVimMessage', new_callable = ExtendedMock )
 @patch( 'ycm.vimsupport.SetLocationList', new_callable = ExtendedMock )
 @patch( 'ycm.vimsupport.OpenLocationList', new_callable = ExtendedMock )
@@ -431,6 +433,7 @@ def YouCompleteMe_ShowDiagnostics_DiagnosticsFound_OpenLocationList_test(
                           'enable_diagnostic_highlighting': 1 } )
 @patch( 'ycm.youcompleteme.YouCompleteMe.FiletypeCompleterExistsForFiletype',
         return_value = True )
+@patch( 'ycm.youcompleteme.YouCompleteMe.IsServerReady', return_value = True )
 @patch( 'ycm.vimsupport.PostVimMessage', new_callable = ExtendedMock )
 @patch( 'vim.command', new_callable = ExtendedMock )
 def YouCompleteMe_UpdateDiagnosticInterface_PrioritizeErrorsOverWarnings_test(
@@ -511,8 +514,7 @@ def YouCompleteMe_UpdateDiagnosticInterface_PrioritizeErrorsOverWarnings_test(
   with MockVimBuffers( [ current_buffer ], current_buffer, ( 3, 1 ) ):
     with patch( 'ycm.client.event_notification.EventNotification.Response',
                 return_value = diagnostics ):
-      ycm.OnFileReadyToParse()
-      ycm.HandleFileParseRequest( block = True )
+      ycm.OnFileReadyToParse( block = True )
 
     # Error match is added after warning matches.
     assert_that(
diff --git a/python/ycm/vimsupport.py b/python/ycm/vimsupport.py
index 25c0392f..f2d0f0a7 100644
--- a/python/ycm/vimsupport.py
+++ b/python/ycm/vimsupport.py
@@ -147,6 +147,14 @@ def GetBufferFilepath( buffer_object ):
   return os.path.join( GetCurrentDirectory(), str( buffer_object.number ) )
 
 
+def GetCurrentBufferNumber():
+  return vim.current.buffer.number
+
+
+def GetBufferChangedTick( bufnr ):
+  return GetIntValue( 'getbufvar({0}, "changedtick")'.format( bufnr ) )
+
+
 def UnplaceSignInBuffer( buffer_number, sign_id ):
   if buffer_number < 0:
     return
diff --git a/python/ycm/youcompleteme.py b/python/ycm/youcompleteme.py
index 254ce200..289468bb 100644
--- a/python/ycm/youcompleteme.py
+++ b/python/ycm/youcompleteme.py
@@ -33,10 +33,10 @@ import vim
 from subprocess import PIPE
 from tempfile import NamedTemporaryFile
 from ycm import base, paths, vimsupport
+from ycm.buffer import BufferDict
 from ycmd import utils
 from ycmd import server_utils
 from ycmd.request_wrap import RequestWrap
-from ycm.diagnostic_interface import DiagnosticInterface
 from ycm.omni_completer import OmniCompleter
 from ycm import syntax_parse
 from ycm.client.ycmd_keepalive import YcmdKeepalive
@@ -49,8 +49,7 @@ from ycm.client.completion_request import ( CompletionRequest,
 from ycm.client.debug_info_request import ( SendDebugInfoRequest,
                                             FormatDebugInfoResponse )
 from ycm.client.omni_completion_request import OmniCompletionRequest
-from ycm.client.event_notification import ( SendEventNotificationAsync,
-                                            EventNotification )
+from ycm.client.event_notification import SendEventNotificationAsync
 from ycm.client.shutdown_request import SendShutdownRequest
 
 
@@ -114,11 +113,9 @@ class YouCompleteMe( object ):
     self._available_completers = {}
     self._user_options = user_options
     self._user_notified_about_crash = False
-    self._diag_interface = DiagnosticInterface( user_options )
     self._omnicomp = OmniCompleter( user_options )
-    self._latest_file_parse_request = None
+    self._buffers = BufferDict( user_options )
     self._latest_completion_request = None
-    self._latest_diagnostics = []
     self._logger = logging.getLogger( 'ycm' )
     self._client_logfile = None
     self._server_stdout = None
@@ -134,6 +131,11 @@ class YouCompleteMe( object ):
       'cs': lambda self: self._OnCompleteDone_Csharp()
     }
 
+
+  def _GetCurrentBuffer( self ):
+    return self._buffers[ vimsupport.GetCurrentBufferNumber() ]
+
+
   def _SetupServer( self ):
     self._available_completers = {}
     self._user_notified_about_crash = False
@@ -353,21 +355,28 @@ class YouCompleteMe( object ):
              self.NativeFiletypeCompletionAvailable() )
 
 
-  def OnFileReadyToParse( self ):
+  def OnFileReadyToParse( self, block = False, force = False ):
     if not self.IsServerAlive():
       self._NotifyUserIfServerCrashed()
       return
 
+    if not self.IsServerReady():
+      return
+
     self._omnicomp.OnFileReadyToParse( None )
 
-    extra_data = {}
-    self._AddTagsFilesIfNeeded( extra_data )
-    self._AddSyntaxDataIfNeeded( extra_data )
-    self._AddExtraConfDataIfNeeded( extra_data )
+    self.HandleFileParseRequest()
 
-    self._latest_file_parse_request = EventNotification(
-      'FileReadyToParse', extra_data = extra_data )
-    self._latest_file_parse_request.Start()
+    current_buffer = self._GetCurrentBuffer()
+    if force_parsing or current_buffer.NeedsReparse():
+      extra_data = {}
+      self._AddTagsFilesIfNeeded( extra_data )
+      self._AddSyntaxDataIfNeeded( extra_data )
+      self._AddExtraConfDataIfNeeded( extra_data )
+
+      current_buffer.SendParseRequest( extra_data )
+      if block:
+        self.HandleFileParseRequest()
 
 
   def OnBufferUnload( self, deleted_buffer_file ):
@@ -385,7 +394,7 @@ class YouCompleteMe( object ):
 
 
   def OnCursorMoved( self ):
-    self._diag_interface.OnCursorMoved()
+    self._GetCurrentBuffer().OnCursorMoved()
 
 
   def _CleanLogfile( self ):
@@ -512,11 +521,11 @@ class YouCompleteMe( object ):
 
 
   def GetErrorCount( self ):
-    return self._diag_interface.GetErrorCount()
+    return self._GetCurrentBuffer().GetErrorCount()
 
 
   def GetWarningCount( self ):
-    return self._diag_interface.GetWarningCount()
+    return self._GetCurrentBuffer().GetWarningCount()
 
 
   def DiagnosticUiSupportedForCurrentFiletype( self ):
@@ -530,51 +539,25 @@ class YouCompleteMe( object ):
 
 
   def _PopulateLocationListWithLatestDiagnostics( self ):
-    # Do nothing if loc list is already populated by diag_interface
-    if not self._user_options[ 'always_populate_location_list' ]:
-      self._diag_interface.PopulateLocationList( self._latest_diagnostics )
-    return bool( self._latest_diagnostics )
+    return self._GetCurrentBuffer().PopulateLocationList()
 
 
-  def UpdateDiagnosticInterface( self ):
-    self._diag_interface.UpdateWithNewDiagnostics( self._latest_diagnostics )
+  def FileParseRequestReady( self ):
+    return self._GetCurrentBuffer().FileParseRequestReady()
 
 
-  def FileParseRequestReady( self, block = False ):
-    return bool( self._latest_file_parse_request and
-                 ( block or self._latest_file_parse_request.Done() ) )
+  def HandleFileParseRequest( self ):
+    current_buffer = self._GetCurrentBuffer()
+    if current_buffer.IsResponseHandled():
+      return
 
-
-  def HandleFileParseRequest( self, block = False ):
-    # Order is important here:
-    # FileParseRequestReady has a low cost, while
     # NativeFiletypeCompletionUsable is a blocking server request
-    if ( self.FileParseRequestReady( block ) and
-         self.NativeFiletypeCompletionUsable() ):
-
+    if self.NativeFiletypeCompletionUsable():
+      current_buffer.GetResponse()
       if self.ShouldDisplayDiagnostics():
-        self._latest_diagnostics = self._latest_file_parse_request.Response()
-        self.UpdateDiagnosticInterface()
-      else:
-        # YCM client has a hard-coded list of filetypes which are known
-        # to support diagnostics, self.DiagnosticUiSupportedForCurrentFiletype()
-        #
-        # For filetypes which don't support diagnostics, we just want to check
-        # the _latest_file_parse_request for any exception or UnknownExtraConf
-        # response, to allow the server to raise configuration warnings, etc.
-        # to the user. We ignore any other supplied data.
-        self._latest_file_parse_request.Response()
+        current_buffer.UpdateDiagnostics()
 
-      # We set the file parse request to None because we want to prevent
-      # repeated issuing of the same warnings/errors/prompts. Setting this to
-      # None makes FileParseRequestReady return False until the next
-      # request is created.
-      #
-      # Note: it is the server's responsibility to determine the frequency of
-      # error/warning/prompts when receiving a FileReadyToParse event, but
-      # it our responsibility to ensure that we only apply the
-      # warning/error/prompt received once (for each event).
-      self._latest_file_parse_request = None
+    current_buffer.MarkResponseHandled()
 
 
   def DebugInfo( self ):
@@ -683,8 +666,7 @@ class YouCompleteMe( object ):
     vimsupport.PostVimMessage(
         'Forcing compilation, this will block Vim until done.',
         warning = False )
-    self.OnFileReadyToParse()
-    self.HandleFileParseRequest( block = True )
+    self.OnFileReadyToParse( block = True )
     vimsupport.PostVimMessage( 'Diagnostics refreshed', warning = False )
     return True