diff --git a/java/src/com/android/inputmethod/latin/personalization/PersonalizationDictionaryUpdateSession.java b/java/src/com/android/inputmethod/latin/personalization/PersonalizationDictionaryUpdateSession.java
index a755f90..858aa32 100644
--- a/java/src/com/android/inputmethod/latin/personalization/PersonalizationDictionaryUpdateSession.java
+++ b/java/src/com/android/inputmethod/latin/personalization/PersonalizationDictionaryUpdateSession.java
@@ -48,6 +48,8 @@
 
     public abstract void onDictionaryReady();
 
+    public abstract void onDictionaryClosed();
+
     public void setPredictionDictionary(String locale, DynamicPredictionDictionaryBase dictionary) {
         mPredictionDictionary = new WeakReference<DynamicPredictionDictionaryBase>(dictionary);
         mLocale = locale;
@@ -68,6 +70,7 @@
 
     public void closeSession() {
         unsetPredictionDictionary();
+        onDictionaryClosed();
     }
 
     public void addBigramToPersonalizationDictionary(String word0, String word1, boolean isValid,
diff --git a/java/src/com/android/inputmethod/latin/settings/Settings.java b/java/src/com/android/inputmethod/latin/settings/Settings.java
index d432087..20b6752 100644
--- a/java/src/com/android/inputmethod/latin/settings/Settings.java
+++ b/java/src/com/android/inputmethod/latin/settings/Settings.java
@@ -27,10 +27,10 @@
 import com.android.inputmethod.latin.InputAttributes;
 import com.android.inputmethod.latin.R;
 import com.android.inputmethod.latin.utils.AdditionalSubtypeUtils;
-import com.android.inputmethod.latin.utils.DebugLogUtils;
 import com.android.inputmethod.latin.utils.LocaleUtils;
 import com.android.inputmethod.latin.utils.ResourceUtils;
 import com.android.inputmethod.latin.utils.RunInLocale;
+import com.android.inputmethod.latin.utils.StringUtils;
 
 import java.util.HashMap;
 import java.util.Locale;
@@ -90,6 +90,8 @@
     private static final String PREF_SUPPRESS_LANGUAGE_SWITCH_KEY =
             "pref_suppress_language_switch_key";
 
+    private static final String PREF_LAST_USED_PERSONALIZATION_TOKEN =
+            "pref_last_used_personalization_token";
     public static final String PREF_SEND_FEEDBACK = "send_feedback";
     public static final String PREF_ABOUT_KEYBOARD = "about_keyboard";
 
@@ -343,4 +345,14 @@
         return prefs.getBoolean(
                 DebugSettings.PREF_USE_ONLY_PERSONALIZATION_DICTIONARY_FOR_DEBUG, false);
     }
+
+    public void writeLastUsedPersonalizationToken(byte[] token) {
+        final String tokenStr = StringUtils.byteArrayToHexString(token);
+        mPrefs.edit().putString(PREF_LAST_USED_PERSONALIZATION_TOKEN, tokenStr).apply();
+    }
+
+    public byte[] readLastUsedPersonalizationToken() {
+        final String tokenStr = mPrefs.getString(PREF_LAST_USED_PERSONALIZATION_TOKEN, null);
+        return StringUtils.hexStringToByteArray(tokenStr);
+    }
 }
diff --git a/java/src/com/android/inputmethod/latin/utils/StringUtils.java b/java/src/com/android/inputmethod/latin/utils/StringUtils.java
index 0b4838c..20cc5d8 100644
--- a/java/src/com/android/inputmethod/latin/utils/StringUtils.java
+++ b/java/src/com/android/inputmethod/latin/utils/StringUtils.java
@@ -357,4 +357,30 @@
         }
         return true;
     }
+
+    @UsedForTesting
+    public static String byteArrayToHexString(byte[] bytes) {
+        if (bytes == null || bytes.length == 0) {
+            return "";
+        }
+        final StringBuilder sb = new StringBuilder();
+        for (byte b : bytes) {
+            sb.append(String.format("%02x", b & 0xff));
+        }
+        return sb.toString();
+    }
+
+    @UsedForTesting
+    public static byte[] hexStringToByteArray(String hexString) {
+        if (TextUtils.isEmpty(hexString)) {
+            return null;
+        }
+        final int N = hexString.length();
+        final byte[] bytes = new byte[N / 2];
+        for (int i = 0; i < N; i += 2) {
+            bytes[i / 2] = (byte) ((Character.digit(hexString.charAt(i), 16) << 4)
+                    + Character.digit(hexString.charAt(i + 1), 16));
+        }
+        return bytes;
+    }
 }
diff --git a/tests/src/com/android/inputmethod/latin/utils/StringUtilsTests.java b/tests/src/com/android/inputmethod/latin/utils/StringUtilsTests.java
index 175e511..c6fa943 100644
--- a/tests/src/com/android/inputmethod/latin/utils/StringUtilsTests.java
+++ b/tests/src/com/android/inputmethod/latin/utils/StringUtilsTests.java
@@ -256,4 +256,16 @@
         // code for now True is acceptable.
         assertTrue(StringUtils.lastPartLooksLikeURL(".abc/def"));
     }
+
+    public void testHexStringUtils() {
+        final byte[] bytes = new byte[] { (byte)0x01, (byte)0x11, (byte)0x22, (byte)0x33,
+                (byte)0x55, (byte)0x88, (byte)0xEE };
+        final String bytesStr = StringUtils.byteArrayToHexString(bytes);
+        final byte[] bytes2 = StringUtils.hexStringToByteArray(bytesStr);
+        for (int i = 0; i < bytes.length; ++i) {
+            assertTrue(bytes[i] == bytes2[i]);
+        }
+        final String bytesStr2 = StringUtils.byteArrayToHexString(bytes2);
+        assertTrue(bytesStr.equals(bytesStr2));
+    }
 }