diff --git a/java/com/android/incallui/call/DialerCall.java b/java/com/android/incallui/call/DialerCall.java
index d57de15..d736edc 100644
--- a/java/com/android/incallui/call/DialerCall.java
+++ b/java/com/android/incallui/call/DialerCall.java
@@ -83,6 +83,7 @@
 import com.android.incallui.audiomode.AudioModeProvider;
 import com.android.incallui.call.state.DialerCallState;
 import com.android.incallui.latencyreport.LatencyReport;
+import com.android.incallui.rtt.protocol.RttChatMessage;
 import com.android.incallui.speakeasy.runtime.Constraints;
 import com.android.incallui.videotech.VideoTech;
 import com.android.incallui.videotech.VideoTech.VideoTechListener;
@@ -92,6 +93,7 @@
 import com.android.incallui.videotech.utils.VideoUtils;
 import com.google.common.util.concurrent.Futures;
 import com.google.common.util.concurrent.MoreExecutors;
+import java.io.IOException;
 import java.lang.annotation.Retention;
 import java.lang.annotation.RetentionPolicy;
 import java.util.ArrayList;
@@ -1084,6 +1086,28 @@
     getTelecomCall().respondToRttRequest(rttRequestId, accept);
   }
 
+  @TargetApi(28)
+  private void saveRttTranscript() {
+    if (!BuildCompat.isAtLeastP()) {
+      return;
+    }
+    // Save any remaining text in the buffer that's not shown by UI yet.
+    // This may happen when the call is switched to background before disconnect.
+    try {
+      String messageLeft = getRttCall().readImmediately();
+      if (!TextUtils.isEmpty(messageLeft)) {
+        rttTranscript =
+            RttChatMessage.getRttTranscriptWithNewRemoteMessage(rttTranscript, messageLeft);
+      }
+    } catch (IOException e) {
+      LogUtil.e("DialerCall.saveRttTranscript", "error when reading remaining message", e);
+    }
+    Futures.addCallback(
+        RttTranscriptUtil.saveRttTranscript(context, rttTranscript),
+        new DefaultFutureCallback<>(),
+        MoreExecutors.directExecutor());
+  }
+
   public boolean hasReceivedVideoUpgradeRequest() {
     return VideoUtils.hasReceivedVideoUpgradeRequest(getVideoTech().getSessionModificationState());
   }
@@ -1615,11 +1639,9 @@
       videoTechManager.dispatchRemovedFromCallList();
     }
     // TODO(a bug): Add tests for it to make sure no crash on subsequent call to this method.
+    // TODO(wangqi): Consider moving this to a DialerCallListener.
     if (rttTranscript != null && !isCallRemoved) {
-      Futures.addCallback(
-          RttTranscriptUtil.saveRttTranscript(context, rttTranscript),
-          new DefaultFutureCallback<>(),
-          MoreExecutors.directExecutor());
+      saveRttTranscript();
     }
     isCallRemoved = true;
   }
diff --git a/java/com/android/incallui/rtt/impl/RttChatAdapter.java b/java/com/android/incallui/rtt/impl/RttChatAdapter.java
index f1cde75..96ff58b 100644
--- a/java/com/android/incallui/rtt/impl/RttChatAdapter.java
+++ b/java/com/android/incallui/rtt/impl/RttChatAdapter.java
@@ -29,6 +29,7 @@
 import com.android.dialer.common.LogUtil;
 import com.android.dialer.rtt.RttTranscript;
 import com.android.dialer.rtt.RttTranscriptMessage;
+import com.android.incallui.rtt.protocol.RttChatMessage;
 import java.lang.annotation.Retention;
 import java.lang.annotation.RetentionPolicy;
 import java.util.ArrayList;
diff --git a/java/com/android/incallui/rtt/impl/RttChatMessageViewHolder.java b/java/com/android/incallui/rtt/impl/RttChatMessageViewHolder.java
index 2beea95..56161ec 100644
--- a/java/com/android/incallui/rtt/impl/RttChatMessageViewHolder.java
+++ b/java/com/android/incallui/rtt/impl/RttChatMessageViewHolder.java
@@ -25,6 +25,7 @@
 import android.widget.LinearLayout;
 import android.widget.LinearLayout.LayoutParams;
 import android.widget.TextView;
+import com.android.incallui.rtt.protocol.RttChatMessage;
 
 /** ViewHolder class for RTT chat message bubble. */
 public class RttChatMessageViewHolder extends ViewHolder {
diff --git a/java/com/android/incallui/rtt/impl/RttChatMessage.java b/java/com/android/incallui/rtt/protocol/RttChatMessage.java
similarity index 83%
rename from java/com/android/incallui/rtt/impl/RttChatMessage.java
rename to java/com/android/incallui/rtt/protocol/RttChatMessage.java
index 2f3933a..5680529 100644
--- a/java/com/android/incallui/rtt/impl/RttChatMessage.java
+++ b/java/com/android/incallui/rtt/protocol/RttChatMessage.java
@@ -14,25 +14,24 @@
  * limitations under the License
  */
 
-package com.android.incallui.rtt.impl;
+package com.android.incallui.rtt.protocol;
 
 import android.support.annotation.NonNull;
 import com.android.dialer.common.Assert;
 import com.android.dialer.rtt.RttTranscript;
 import com.android.dialer.rtt.RttTranscriptMessage;
-import com.android.incallui.rtt.protocol.Constants;
 import com.google.common.base.Splitter;
 import java.util.ArrayList;
 import java.util.Iterator;
 import java.util.List;
 
 /** Message class that holds one RTT chat content. */
-final class RttChatMessage {
+public final class RttChatMessage {
 
   private static final Splitter SPLITTER = Splitter.on(Constants.BUBBLE_BREAKER);
 
-  boolean isRemote;
-  long timstamp;
+  public boolean isRemote;
+  private long timstamp;
   private final StringBuilder content = new StringBuilder();
   private boolean isFinished;
 
@@ -44,7 +43,7 @@
     isFinished = true;
   }
 
-  void unfinish() {
+  public void unfinish() {
     isFinished = false;
   }
 
@@ -74,7 +73,7 @@
    *
    * <p>"hello world" -> "hello new world" : "\b\b\b\b\bnew world"
    */
-  static String computeChangedString(String oldMessage, String newMesssage) {
+  public static String computeChangedString(String oldMessage, String newMesssage) {
     StringBuilder modify = new StringBuilder();
     int indexChangeStart = 0;
     while (indexChangeStart < oldMessage.length()
@@ -91,8 +90,21 @@
     return modify.toString();
   }
 
+  public static RttTranscript getRttTranscriptWithNewRemoteMessage(
+      RttTranscript rttTranscript, @NonNull String text) {
+    List<RttChatMessage> messageList = fromTranscript(rttTranscript);
+    updateRemoteRttChatMessage(messageList, text);
+    return RttTranscript.newBuilder()
+        .setId(rttTranscript.getId())
+        .setNumber(rttTranscript.getNumber())
+        .setTimestamp(rttTranscript.getTimestamp())
+        .addAllMessages(toTranscriptMessageList(messageList))
+        .build();
+  }
+
   /** Update list of {@code RttChatMessage} based on given remote text. */
-  static void updateRemoteRttChatMessage(List<RttChatMessage> messageList, @NonNull String text) {
+  public static void updateRemoteRttChatMessage(
+      List<RttChatMessage> messageList, @NonNull String text) {
     Assert.isNotNull(messageList);
     Iterator<String> splitText = SPLITTER.split(text).iterator();
 
@@ -163,7 +175,7 @@
     return i;
   }
 
-  static int getLastIndexRemoteMessage(List<RttChatMessage> messageList) {
+  public static int getLastIndexRemoteMessage(List<RttChatMessage> messageList) {
     int i = messageList.size() - 1;
     while (i >= 0 && !messageList.get(i).isRemote) {
       i--;
@@ -171,7 +183,7 @@
     return i;
   }
 
-  static int getLastIndexLocalMessage(List<RttChatMessage> messageList) {
+  public static int getLastIndexLocalMessage(List<RttChatMessage> messageList) {
     int i = messageList.size() - 1;
     while (i >= 0 && messageList.get(i).isRemote) {
       i--;
@@ -179,7 +191,8 @@
     return i;
   }
 
-  static List<RttTranscriptMessage> toTranscriptMessageList(List<RttChatMessage> messageList) {
+  public static List<RttTranscriptMessage> toTranscriptMessageList(
+      List<RttChatMessage> messageList) {
     List<RttTranscriptMessage> transcriptMessageList = new ArrayList<>();
     for (RttChatMessage message : messageList) {
       transcriptMessageList.add(
@@ -193,7 +206,7 @@
     return transcriptMessageList;
   }
 
-  static List<RttChatMessage> fromTranscript(RttTranscript rttTranscript) {
+  public static List<RttChatMessage> fromTranscript(RttTranscript rttTranscript) {
     List<RttChatMessage> messageList = new ArrayList<>();
     if (rttTranscript == null) {
       return messageList;
@@ -211,7 +224,7 @@
     return messageList;
   }
 
-  RttChatMessage() {
+  public RttChatMessage() {
     timstamp = System.currentTimeMillis();
   }
 }