diff --git a/src/rime/gear/chord_composer.cc b/src/rime/gear/chord_composer.cc
index c26007f451..dc293a82f2 100644
--- a/src/rime/gear/chord_composer.cc
+++ b/src/rime/gear/chord_composer.cc
@@ -13,8 +13,7 @@
 #include <rime/schema.h>
 #include <rime/gear/chord_composer.h>
 
-// U+FEFF works better with MacType
-static const char* kZeroWidthSpace = "\xef\xbb\xbf";  //"\xe2\x80\x8b";
+static const char* kZeroWidthSpace = "\xe2\x80\x8b";  // U+200B
 
 namespace rime {
 
@@ -118,8 +117,9 @@ ProcessResult ChordComposer::ProcessChordingKey(const KeyEvent& key_event) {
   return kAccepted;
 }
 
-inline static bool is_composing_text(Context* ctx) {
-  return ctx->IsComposing() && ctx->input() != kZeroWidthSpace;
+inline static bool is_composing(Context* ctx) {
+  return !ctx->composition().empty() &&
+      !ctx->composition().back().HasTag("phony");
 }
 
 ProcessResult ChordComposer::ProcessKeyEvent(const KeyEvent& key_event) {
@@ -133,7 +133,7 @@ ProcessResult ChordComposer::ProcessKeyEvent(const KeyEvent& key_event) {
   int ch = key_event.keycode();
   if (!is_key_up && ch >= 0x20 && ch <= 0x7e) {
     // save raw input
-    if (!is_composing_text(engine_->context()) || !raw_sequence_.empty()) {
+    if (!is_composing(engine_->context()) || !raw_sequence_.empty()) {
       raw_sequence_.push_back(ch);
       DLOG(INFO) << "update raw sequence: " << raw_sequence_;
     }
@@ -164,18 +164,17 @@ void ChordComposer::UpdateChord() {
   string code = SerializeChord();
   prompt_format_.Apply(&code);
   if (comp.empty()) {
-    // add an invisbile place holder segment
+    // add a placeholder segment
     // 1. to cheat ctx->IsComposing() == true
     // 2. to attach chord prompt to while chording
-    ctx->PushInput(kZeroWidthSpace);
-    if (comp.empty()) {
-      LOG(ERROR) << "failed to update chord.";
-      return;
-    }
-    comp.back().tags.insert("phony");
-  }
-  comp.back().tags.insert("chord_prompt");
-  comp.back().prompt = code;
+    ctx->set_input(kZeroWidthSpace);
+    Segment placeholder(0, ctx->input().length());
+    placeholder.tags.insert("phony");
+    ctx->composition().AddSegment(placeholder);
+  }
+  auto& last_segment = comp.back();
+  last_segment.tags.insert("chord_prompt");
+  last_segment.prompt = code;
 }
 
 void ChordComposer::FinishChord() {
@@ -207,20 +206,20 @@ void ChordComposer::ClearChord() {
     return;
   Context* ctx = engine_->context();
   Composition& comp = ctx->composition();
-  if (comp.empty()) {
+  if (comp.empty())
     return;
+  auto& last_segment = comp.back();
+  if (comp.size() == 1 && last_segment.HasTag("phony")) {
+    ctx->Clear();
   }
-  if (comp.input().substr(comp.back().start) == kZeroWidthSpace) {
-    ctx->PopInput(ctx->caret_pos() - comp.back().start);
-  }
-  else if (comp.back().HasTag("chord_prompt")) {
-    comp.back().prompt.clear();
-    comp.back().tags.erase("chord_prompt");
+  else if (last_segment.HasTag("chord_prompt")) {
+    last_segment.prompt.clear();
+    last_segment.tags.erase("chord_prompt");
   }
 }
 
 void ChordComposer::OnContextUpdate(Context* ctx) {
-  if (is_composing_text(ctx)) {
+  if (is_composing(ctx)) {
     composing_ = true;
   }
   else if (composing_) {