diff --git a/WeaselIPC/WeaselClientImpl.cpp b/WeaselIPC/WeaselClientImpl.cpp
index 26122ad50a..56511885b2 100644
--- a/WeaselIPC/WeaselClientImpl.cpp
+++ b/WeaselIPC/WeaselClientImpl.cpp
@@ -126,15 +126,24 @@ void ClientImpl::UpdateInputPosition(RECT const& rc) {
   int height = max(0, min(127, (rc.bottom - rc.top) >> hi_res));
   DWORD compressed_rect = ((hi_res & 0x01) << 31) | ((height & 0x7f) << 24) |
                           ((top & 0xfff) << 12) | (left & 0xfff);
+  if (has_last_input_position && last_input_position_session == session_id &&
+      last_input_position_rect == compressed_rect) {
+    return;
+  }
+  has_last_input_position = true;
+  last_input_position_session = session_id;
+  last_input_position_rect = compressed_rect;
   _SendMessage(WEASEL_IPC_UPDATE_INPUT_POS, compressed_rect, session_id);
 }
 
 void ClientImpl::FocusIn() {
+  has_last_input_position = false;
   DWORD client_caps = 0; /* TODO */
   _SendMessage(WEASEL_IPC_FOCUS_IN, client_caps, session_id);
 }
 
 void ClientImpl::FocusOut() {
+  has_last_input_position = false;
   _SendMessage(WEASEL_IPC_FOCUS_OUT, 0, session_id);
 }
 
@@ -149,21 +158,25 @@ void ClientImpl::StartSession() {
   _WriteClientInfo();
   UINT ret = _SendMessage(WEASEL_IPC_START_SESSION, 0, 0);
   session_id = ret;
+  has_last_input_position = false;
 }
 
 void ClientImpl::EndSession() {
   _SendMessage(WEASEL_IPC_END_SESSION, 0, session_id);
   session_id = 0;
+  has_last_input_position = false;
 }
 
 void ClientImpl::StartMaintenance() {
   _SendMessage(WEASEL_IPC_START_MAINTENANCE, 0, 0);
   session_id = 0;
+  has_last_input_position = false;
 }
 
 void ClientImpl::EndMaintenance() {
   _SendMessage(WEASEL_IPC_END_MAINTENANCE, 0, 0);
   session_id = 0;
+  has_last_input_position = false;
 }
 
 bool ClientImpl::Echo() {
diff --git a/WeaselIPC/WeaselClientImpl.h b/WeaselIPC/WeaselClientImpl.h
index 7602792869..b9ecfb9806 100644
--- a/WeaselIPC/WeaselClientImpl.h
+++ b/WeaselIPC/WeaselClientImpl.h
@@ -42,8 +42,11 @@ class ClientImpl {
   UINT session_id;
   std::wstring app_name;
   bool is_ime;
+  bool has_last_input_position = false;
+  UINT last_input_position_session = 0;
+  DWORD last_input_position_rect = 0;
 
   PipeChannel<PipeMessage> channel;
 };
 
-}  // namespace weasel
\ No newline at end of file
+}  // namespace weasel
diff --git a/WeaselTSF/Composition.cpp b/WeaselTSF/Composition.cpp
index 62852bc7f8..e27aea3e12 100644
--- a/WeaselTSF/Composition.cpp
+++ b/WeaselTSF/Composition.cpp
@@ -72,6 +72,7 @@ STDAPI CStartCompositionEditSession::DoEditSession(TfEditCookie ec) {
 
 void WeaselTSF::_StartComposition(com_ptr<ITfContext> pContext,
                                   BOOL fCUASWorkaroundEnabled) {
+  _hasLastCompositionPosition = FALSE;
   com_ptr<CStartCompositionEditSession> pStartCompositionEditSession;
   pStartCompositionEditSession.Attach(new CStartCompositionEditSession(
       this, pContext, fCUASWorkaroundEnabled, _cand->style().inline_preedit));
@@ -239,6 +240,17 @@ void WeaselTSF::_SetCompositionPosition(const RECT& rc) {
       return;
     }
   }
+  BOOL same_position = _hasLastCompositionPosition &&
+                       _lastCompositionPosition.left == rc.left &&
+                       _lastCompositionPosition.top == rc.top &&
+                       _lastCompositionPosition.right == rc.right &&
+                       _lastCompositionPosition.bottom == rc.bottom;
+  if (same_position) {
+    return;
+  }
+  _lastCompositionPosition = rc;
+  _hasLastCompositionPosition = TRUE;
+
   RECT _rc;
   _rc.left = _rc.right = rc.left;
   _rc.top = _rc.bottom = rc.bottom;
@@ -404,6 +416,7 @@ STDAPI WeaselTSF::OnCompositionTerminated(TfEditCookie ecWrite,
 }
 
 void WeaselTSF::_AbortComposition(bool clear) {
+  _hasLastCompositionPosition = FALSE;
   m_client.ClearComposition();
   if (_IsComposing()) {
     _EndComposition(_pEditSessionContext, clear);
diff --git a/WeaselTSF/KeyEventSink.cpp b/WeaselTSF/KeyEventSink.cpp
index c885dddf94..16ab8af4ac 100644
--- a/WeaselTSF/KeyEventSink.cpp
+++ b/WeaselTSF/KeyEventSink.cpp
@@ -63,6 +63,7 @@ void WeaselTSF::_ProcessKeyEvent(WPARAM wParam, LPARAM lParam, BOOL* pfEaten) {
 }
 
 STDAPI WeaselTSF::OnSetFocus(BOOL fForeground) {
+  _hasLastCompositionPosition = false;
   if (fForeground)
     m_client.FocusIn();
   else {
diff --git a/WeaselTSF/WeaselTSF.h b/WeaselTSF/WeaselTSF.h
index 696d3cce4b..7e6bc96c79 100644
--- a/WeaselTSF/WeaselTSF.h
+++ b/WeaselTSF/WeaselTSF.h
@@ -233,4 +233,6 @@ class WeaselTSF : public ITfTextInputProcessorEx,
   BOOL _async_edit = false;
   BOOL _committed = false;
   BOOL _isToOpenClose = false;
+  BOOL _hasLastCompositionPosition = false;
+  RECT _lastCompositionPosition = {0, 0, 0, 0};
 };