diff --git a/dictionaries/fr_wordlist.combined.gz b/dictionaries/fr_wordlist.combined.gz
index 0763b62..1d988d6 100644
--- a/dictionaries/fr_wordlist.combined.gz
+++ b/dictionaries/fr_wordlist.combined.gz
Binary files differ
diff --git a/dictionaries/iw_wordlist.combined.gz b/dictionaries/iw_wordlist.combined.gz
new file mode 100644
index 0000000..36b0478
--- /dev/null
+++ b/dictionaries/iw_wordlist.combined.gz
Binary files differ
diff --git a/dictionaries/pt_BR_wordlist.combined.gz b/dictionaries/pt_BR_wordlist.combined.gz
index 0dd8472..221ea75 100644
--- a/dictionaries/pt_BR_wordlist.combined.gz
+++ b/dictionaries/pt_BR_wordlist.combined.gz
Binary files differ
diff --git a/dictionaries/pt_PT_wordlist.combined.gz b/dictionaries/pt_PT_wordlist.combined.gz
index 00d50d0..6a041d9 100644
--- a/dictionaries/pt_PT_wordlist.combined.gz
+++ b/dictionaries/pt_PT_wordlist.combined.gz
Binary files differ
diff --git a/dictionaries/ru_wordlist.combined.gz b/dictionaries/ru_wordlist.combined.gz
index 1c85d66..572314d 100644
--- a/dictionaries/ru_wordlist.combined.gz
+++ b/dictionaries/ru_wordlist.combined.gz
Binary files differ
diff --git a/java/res/raw/main_fr.dict b/java/res/raw/main_fr.dict
index 31fb2af..10adad0 100644
--- a/java/res/raw/main_fr.dict
+++ b/java/res/raw/main_fr.dict
Binary files differ
diff --git a/java/res/raw/main_pt_br.dict b/java/res/raw/main_pt_br.dict
index 557d46e..f9ae9b5 100644
--- a/java/res/raw/main_pt_br.dict
+++ b/java/res/raw/main_pt_br.dict
Binary files differ
diff --git a/java/res/raw/main_ru.dict b/java/res/raw/main_ru.dict
index 86c368e..7dec624 100644
--- a/java/res/raw/main_ru.dict
+++ b/java/res/raw/main_ru.dict
Binary files differ
diff --git a/java/src/com/android/inputmethod/latin/AbstractDictionaryWriter.java b/java/src/com/android/inputmethod/latin/AbstractDictionaryWriter.java
index ebbcedc..269b3a2 100644
--- a/java/src/com/android/inputmethod/latin/AbstractDictionaryWriter.java
+++ b/java/src/com/android/inputmethod/latin/AbstractDictionaryWriter.java
@@ -42,8 +42,10 @@
     abstract public void addUnigramWord(final String word, final String shortcutTarget,
             final int frequency, final boolean isNotAWord);
 
+    // TODO: Remove lastModifiedTime after making binary dictionary support forgetting curve.
     abstract public void addBigramWords(final String word0, final String word1,
-            final int frequency, final boolean isValid);
+            final int frequency, final boolean isValid,
+            final long lastModifiedTime);
 
     abstract public void removeBigramWords(final String word0, final String word1);
 
diff --git a/java/src/com/android/inputmethod/latin/ContactsBinaryDictionary.java b/java/src/com/android/inputmethod/latin/ContactsBinaryDictionary.java
index c99d0e2..67eb7f3 100644
--- a/java/src/com/android/inputmethod/latin/ContactsBinaryDictionary.java
+++ b/java/src/com/android/inputmethod/latin/ContactsBinaryDictionary.java
@@ -70,7 +70,8 @@
     private final boolean mUseFirstLastBigrams;
 
     public ContactsBinaryDictionary(final Context context, final Locale locale) {
-        super(context, getFilenameWithLocale(NAME, locale.toString()), Dictionary.TYPE_CONTACTS);
+        super(context, getFilenameWithLocale(NAME, locale.toString()), Dictionary.TYPE_CONTACTS,
+                false /* isUpdatable */);
         mLocale = locale;
         mUseFirstLastBigrams = useFirstLastBigramsForLocale(locale);
         registerObserver(context);
@@ -208,7 +209,8 @@
                             false /* isNotAWord */);
                     if (!TextUtils.isEmpty(prevWord)) {
                         if (mUseFirstLastBigrams) {
-                            super.setBigram(prevWord, word, FREQUENCY_FOR_CONTACTS_BIGRAM);
+                            super.addBigram(prevWord, word, FREQUENCY_FOR_CONTACTS_BIGRAM,
+                                    0 /* lastModifiedTime */);
                         }
                     }
                     prevWord = word;
diff --git a/java/src/com/android/inputmethod/latin/DictionaryWriter.java b/java/src/com/android/inputmethod/latin/DictionaryWriter.java
index 1765ce5..1ececd5 100644
--- a/java/src/com/android/inputmethod/latin/DictionaryWriter.java
+++ b/java/src/com/android/inputmethod/latin/DictionaryWriter.java
@@ -75,7 +75,7 @@
 
     @Override
     public void addBigramWords(final String word0, final String word1, final int frequency,
-            final boolean isValid) {
+            final boolean isValid, final long lastModifiedTime) {
         mFusionDictionary.setBigram(word0, word1, frequency);
     }
 
diff --git a/java/src/com/android/inputmethod/latin/ExpandableBinaryDictionary.java b/java/src/com/android/inputmethod/latin/ExpandableBinaryDictionary.java
index b481371..3725677 100644
--- a/java/src/com/android/inputmethod/latin/ExpandableBinaryDictionary.java
+++ b/java/src/com/android/inputmethod/latin/ExpandableBinaryDictionary.java
@@ -20,6 +20,7 @@
 import android.os.SystemClock;
 import android.util.Log;
 
+import com.android.inputmethod.annotations.UsedForTesting;
 import com.android.inputmethod.keyboard.ProximityInfo;
 import com.android.inputmethod.latin.SuggestedWords.SuggestedWordInfo;
 import com.android.inputmethod.latin.utils.CollectionUtils;
@@ -78,6 +79,9 @@
      */
     private final String mFilename;
 
+    /** Whether to support dynamically updating the dictionary */
+    private final boolean mIsUpdatable;
+
     /** Controls access to the shared binary dictionary file across multiple instances. */
     private final DictionaryController mSharedDictionaryController;
 
@@ -113,6 +117,16 @@
         return controller;
     }
 
+    private static AbstractDictionaryWriter getDictionaryWriter(final Context context,
+            final String dictType, final boolean isUpdatable) {
+        if (isUpdatable) {
+            // TODO: Employ dynamically updatable DictionaryWriter.
+            return new DictionaryWriter(context, dictType);
+        } else {
+            return new DictionaryWriter(context, dictType);
+        }
+    }
+
     /**
      * Creates a new expandable binary dictionary.
      *
@@ -120,15 +134,18 @@
      * @param filename The filename for this binary dictionary. Multiple dictionaries with the same
      *        filename is supported.
      * @param dictType the dictionary type, as a human-readable string
+     * @param isUpdatable whether to support dynamically updating the dictionary. Please note that
+     *        dynamic dictionary has negative effects on memory space and computation time.
      */
-    public ExpandableBinaryDictionary(
-            final Context context, final String filename, final String dictType) {
+    public ExpandableBinaryDictionary(final Context context, final String filename,
+            final String dictType, final boolean isUpdatable) {
         super(dictType);
         mFilename = filename;
         mContext = context;
+        mIsUpdatable = isUpdatable;
         mBinaryDictionary = null;
         mSharedDictionaryController = getSharedDictionaryController(filename);
-        mDictionaryWriter = new DictionaryWriter(context, dictType);
+        mDictionaryWriter = getDictionaryWriter(context, dictType, isUpdatable);
     }
 
     protected static String getFilenameWithLocale(final String name, final String localeStr) {
@@ -140,6 +157,16 @@
      */
     @Override
     public void close() {
+        closeBinaryDictionary();
+        mLocalDictionaryController.writeLock().lock();
+        try {
+            mDictionaryWriter.close();
+        } finally {
+            mLocalDictionaryController.writeLock().unlock();
+        }
+    }
+
+    protected void closeBinaryDictionary() {
         // Ensure that no other threads are accessing the local binary dictionary.
         mLocalDictionaryController.writeLock().lock();
         try {
@@ -147,7 +174,6 @@
                 mBinaryDictionary.close();
                 mBinaryDictionary = null;
             }
-            mDictionaryWriter.close();
         } finally {
             mLocalDictionaryController.writeLock().unlock();
         }
@@ -162,35 +188,70 @@
     }
 
     /**
-     * Sets a word bigram in the dictionary. Used for loading a dictionary.
+     * Adds a word bigram in the dictionary. Used for loading a dictionary.
      */
-    protected void setBigram(final String prevWord, final String word, final int frequency) {
-        mDictionaryWriter.addBigramWords(prevWord, word, frequency, true /* isValid */);
+    protected void addBigram(final String prevWord, final String word, final int frequency,
+            final long lastModifiedTime) {
+        mDictionaryWriter.addBigramWords(prevWord, word, frequency, true /* isValid */,
+                lastModifiedTime);
     }
 
     /**
-     * Dynamically adds a word unigram to the dictionary.
+     * Dynamically adds a word unigram to the dictionary. May overwrite an existing entry.
      */
     protected void addWordDynamically(final String word, final String shortcutTarget,
             final int frequency, final boolean isNotAWord) {
-        mLocalDictionaryController.writeLock().lock();
-        try {
-            mDictionaryWriter.addUnigramWord(word, shortcutTarget, frequency, isNotAWord);
-        } finally {
-            mLocalDictionaryController.writeLock().unlock();
+        if (!mIsUpdatable) {
+            Log.w(TAG, "addWordDynamically is called for non-updatable dictionary: " + mFilename);
+            return;
+        }
+        // TODO: Use a queue to reflect what needs to be reflected.
+        if (mLocalDictionaryController.writeLock().tryLock()) {
+            try {
+                mDictionaryWriter.addUnigramWord(word, shortcutTarget, frequency, isNotAWord);
+            } finally {
+                mLocalDictionaryController.writeLock().unlock();
+            }
         }
     }
 
     /**
-     * Dynamically sets a word bigram in the dictionary.
+     * Dynamically adds a word bigram in the dictionary. May overwrite an existing entry.
      */
-    protected void setBigramDynamically(final String prevWord, final String word,
-            final int frequency) {
-        mLocalDictionaryController.writeLock().lock();
-        try {
-            mDictionaryWriter.addBigramWords(prevWord, word, frequency, true /* isValid */);
-        } finally {
-            mLocalDictionaryController.writeLock().unlock();
+    protected void addBigramDynamically(final String word0, final String word1,
+            final int frequency, final boolean isValid) {
+        if (!mIsUpdatable) {
+            Log.w(TAG, "addBigramDynamically is called for non-updatable dictionary: "
+                    + mFilename);
+            return;
+        }
+        // TODO: Use a queue to reflect what needs to be reflected.
+        if (mLocalDictionaryController.writeLock().tryLock()) {
+            try {
+                mDictionaryWriter.addBigramWords(word0, word1, frequency, isValid,
+                        0 /* lastTouchedTime */);
+            } finally {
+                mLocalDictionaryController.writeLock().unlock();
+            }
+        }
+    }
+
+    /**
+     * Dynamically remove a word bigram in the dictionary.
+     */
+    protected void removeBigramDynamically(final String word0, final String word1) {
+        if (!mIsUpdatable) {
+            Log.w(TAG, "removeBigramDynamically is called for non-updatable dictionary: "
+                    + mFilename);
+            return;
+        }
+        // TODO: Use a queue to reflect what needs to be reflected.
+        if (mLocalDictionaryController.writeLock().tryLock()) {
+            try {
+                mDictionaryWriter.removeBigramWords(word0, word1);
+            } finally {
+                mLocalDictionaryController.writeLock().unlock();
+            }
         }
     }
 
@@ -280,7 +341,7 @@
 
         // Build the new binary dictionary
         final BinaryDictionary newBinaryDictionary = new BinaryDictionary(filename, 0, length,
-                true /* useFullEditDistance */, null, mDictType, false /* isUpdatable */);
+                true /* useFullEditDistance */, null, mDictType, mIsUpdatable);
 
         if (mBinaryDictionary != null) {
             // Ensure all threads accessing the current dictionary have finished before swapping in
@@ -305,9 +366,9 @@
     abstract protected boolean needsToReloadBeforeWriting();
 
     /**
-     * Generates and writes a new binary dictionary based on the contents of the fusion dictionary.
+     * Writes a new binary dictionary based on the contents of the fusion dictionary.
      */
-    private void generateBinaryDictionary() {
+    private void writeBinaryDictionary() {
         if (DEBUG) {
             Log.d(TAG, "Generating binary dictionary: " + mFilename + " request="
                     + mSharedDictionaryController.mLastUpdateRequestTime + " update="
@@ -370,41 +431,47 @@
     private final void syncReloadDictionaryInternal() {
         // Ensure that only one thread attempts to read or write to the shared binary dictionary
         // file at the same time.
-        mSharedDictionaryController.writeLock().lock();
+        mLocalDictionaryController.writeLock().lock();
         try {
-            final long time = SystemClock.uptimeMillis();
-            final boolean dictionaryFileExists = dictionaryFileExists();
-            if (mSharedDictionaryController.isOutOfDate() || !dictionaryFileExists) {
-                // If the shared dictionary file does not exist or is out of date, the first
-                // instance that acquires the lock will generate a new one.
-                if (hasContentChanged() || !dictionaryFileExists) {
-                    // If the source content has changed or the dictionary does not exist, rebuild
-                    // the binary dictionary. Empty dictionaries are supported (in the case where
-                    // loadDictionaryAsync() adds nothing) in order to provide a uniform framework.
-                    mSharedDictionaryController.mLastUpdateTime = time;
-                    generateBinaryDictionary();
+            mSharedDictionaryController.writeLock().lock();
+            try {
+                final long time = SystemClock.uptimeMillis();
+                final boolean dictionaryFileExists = dictionaryFileExists();
+                if (mSharedDictionaryController.isOutOfDate() || !dictionaryFileExists) {
+                    // If the shared dictionary file does not exist or is out of date, the first
+                    // instance that acquires the lock will generate a new one.
+                    if (hasContentChanged() || !dictionaryFileExists) {
+                        // If the source content has changed or the dictionary does not exist,
+                        // rebuild the binary dictionary. Empty dictionaries are supported (in the
+                        // case where loadDictionaryAsync() adds nothing) in order to provide a
+                        // uniform framework.
+                        mSharedDictionaryController.mLastUpdateTime = time;
+                        writeBinaryDictionary();
+                        loadBinaryDictionary();
+                    } else {
+                        // If not, the reload request was unnecessary so revert
+                        // LastUpdateRequestTime to LastUpdateTime.
+                        mSharedDictionaryController.mLastUpdateRequestTime =
+                                mSharedDictionaryController.mLastUpdateTime;
+                    }
+                } else if (mBinaryDictionary == null || mLocalDictionaryController.mLastUpdateTime
+                        < mSharedDictionaryController.mLastUpdateTime) {
+                    // Otherwise, if the local dictionary is older than the shared dictionary, load
+                    // the shared dictionary.
                     loadBinaryDictionary();
-                } else {
-                    // If not, the reload request was unnecessary so revert LastUpdateRequestTime
-                    // to LastUpdateTime.
-                    mSharedDictionaryController.mLastUpdateRequestTime =
-                            mSharedDictionaryController.mLastUpdateTime;
                 }
-            } else if (mBinaryDictionary == null || mLocalDictionaryController.mLastUpdateTime
-                    < mSharedDictionaryController.mLastUpdateTime) {
-                // Otherwise, if the local dictionary is older than the shared dictionary, load the
-                // shared dictionary.
-                loadBinaryDictionary();
+                if (mBinaryDictionary != null && !mBinaryDictionary.isValidDictionary()) {
+                    // Binary dictionary is not valid. Regenerate the dictionary file.
+                    mSharedDictionaryController.mLastUpdateTime = time;
+                    writeBinaryDictionary();
+                    loadBinaryDictionary();
+                }
+                mLocalDictionaryController.mLastUpdateTime = time;
+            } finally {
+                mSharedDictionaryController.writeLock().unlock();
             }
-            if (mBinaryDictionary != null && !mBinaryDictionary.isValidDictionary()) {
-                // Binary dictionary is not valid. Regenerate the dictionary file.
-                mSharedDictionaryController.mLastUpdateTime = time;
-                generateBinaryDictionary();
-                loadBinaryDictionary();
-            }
-            mLocalDictionaryController.mLastUpdateTime = time;
         } finally {
-            mSharedDictionaryController.writeLock().unlock();
+            mLocalDictionaryController.writeLock().unlock();
         }
     }
 
@@ -437,4 +504,45 @@
             return (mLastUpdateRequestTime > mLastUpdateTime);
         }
     }
+
+    /**
+     * Dynamically adds a word unigram to the dictionary for testing with blocking-lock.
+     */
+    @UsedForTesting
+    protected void addWordDynamicallyForTests(final String word, final String shortcutTarget,
+            final int frequency, final boolean isNotAWord) {
+        mLocalDictionaryController.writeLock().lock();
+        try {
+            addWordDynamically(word, shortcutTarget, frequency, isNotAWord);
+        } finally {
+            mLocalDictionaryController.writeLock().unlock();
+        }
+    }
+
+    /**
+     * Dynamically adds a word bigram in the dictionary for testing with blocking-lock.
+     */
+    @UsedForTesting
+    protected void addBigramDynamicallyForTests(final String word0, final String word1,
+            final int frequency, final boolean isValid) {
+        mLocalDictionaryController.writeLock().lock();
+        try {
+            addBigramDynamically(word0, word1, frequency, isValid);
+        } finally {
+            mLocalDictionaryController.writeLock().unlock();
+        }
+    }
+
+    /**
+     * Dynamically remove a word bigram in the dictionary for testing with blocking-lock.
+     */
+    @UsedForTesting
+    protected void removeBigramDynamicallyForTests(final String word0, final String word1) {
+        mLocalDictionaryController.writeLock().lock();
+        try {
+            removeBigramDynamically(word0, word1);
+        } finally {
+            mLocalDictionaryController.writeLock().unlock();
+        }
+    }
 }
diff --git a/java/src/com/android/inputmethod/latin/UserBinaryDictionary.java b/java/src/com/android/inputmethod/latin/UserBinaryDictionary.java
index ed6fefa..b2bb615 100644
--- a/java/src/com/android/inputmethod/latin/UserBinaryDictionary.java
+++ b/java/src/com/android/inputmethod/latin/UserBinaryDictionary.java
@@ -75,7 +75,8 @@
 
     public UserBinaryDictionary(final Context context, final String locale,
             final boolean alsoUseMoreRestrictiveLocales) {
-        super(context, getFilenameWithLocale(NAME, locale), Dictionary.TYPE_USER);
+        super(context, getFilenameWithLocale(NAME, locale), Dictionary.TYPE_USER,
+                false /* isUpdatable */);
         if (null == locale) throw new NullPointerException(); // Catch the error earlier
         if (SubtypeLocaleUtils.NO_LANGUAGE.equals(locale)) {
             // If we don't have a locale, insert into the "all locales" user dictionary.
diff --git a/java/src/com/android/inputmethod/latin/personalization/PersonalizationDictionary.java b/java/src/com/android/inputmethod/latin/personalization/PersonalizationDictionary.java
index e38a235..275ce2f 100644
--- a/java/src/com/android/inputmethod/latin/personalization/PersonalizationDictionary.java
+++ b/java/src/com/android/inputmethod/latin/personalization/PersonalizationDictionary.java
@@ -36,7 +36,9 @@
 
     // Singleton
     private PersonalizationDictionary(final Context context, final String locale) {
-        super(context, getFilenameWithLocale(NAME, locale), Dictionary.TYPE_PERSONALIZATION);
+        // TODO: Make isUpdatable true.
+        super(context, getFilenameWithLocale(NAME, locale), Dictionary.TYPE_PERSONALIZATION,
+                false /* isUpdatable */);
         mLocale = locale;
     }
 
diff --git a/java/src/com/android/inputmethod/latin/personalization/PersonalizationDictionarySessionRegister.java b/java/src/com/android/inputmethod/latin/personalization/PersonalizationDictionarySessionRegister.java
index 534d3c5..da59333 100644
--- a/java/src/com/android/inputmethod/latin/personalization/PersonalizationDictionarySessionRegister.java
+++ b/java/src/com/android/inputmethod/latin/personalization/PersonalizationDictionarySessionRegister.java
@@ -25,4 +25,10 @@
 
     public static void onConfigurationChanged(final Context context, final Configuration conf) {
     }
+
+    public static void onUpdateData(Context context, String type) {
+    }
+
+    public static void onRemoveData(Context context, String type) {
+    }
 }
diff --git a/java/src/com/android/inputmethod/latin/personalization/PersonalizationDictionaryUpdateSession.java b/java/src/com/android/inputmethod/latin/personalization/PersonalizationDictionaryUpdateSession.java
index 858aa32..433c69c 100644
--- a/java/src/com/android/inputmethod/latin/personalization/PersonalizationDictionaryUpdateSession.java
+++ b/java/src/com/android/inputmethod/latin/personalization/PersonalizationDictionaryUpdateSession.java
@@ -16,6 +16,8 @@
 
 package com.android.inputmethod.latin.personalization;
 
+import android.content.Context;
+
 import java.lang.ref.WeakReference;
 import java.util.ArrayList;
 
@@ -48,7 +50,7 @@
 
     public abstract void onDictionaryReady();
 
-    public abstract void onDictionaryClosed();
+    public abstract void onDictionaryClosed(Context context);
 
     public void setPredictionDictionary(String locale, DynamicPredictionDictionaryBase dictionary) {
         mPredictionDictionary = new WeakReference<DynamicPredictionDictionaryBase>(dictionary);
@@ -68,9 +70,9 @@
     }
 
 
-    public void closeSession() {
+    public void closeSession(Context context) {
         unsetPredictionDictionary();
-        onDictionaryClosed();
+        onDictionaryClosed(context);
     }
 
     public void addBigramToPersonalizationDictionary(String word0, String word1, boolean isValid,
diff --git a/java/src/com/android/inputmethod/latin/utils/StringUtils.java b/java/src/com/android/inputmethod/latin/utils/StringUtils.java
index 20cc5d8..be41840 100644
--- a/java/src/com/android/inputmethod/latin/utils/StringUtils.java
+++ b/java/src/com/android/inputmethod/latin/utils/StringUtils.java
@@ -370,12 +370,19 @@
         return sb.toString();
     }
 
+    /**
+     * Convert hex string to byte array. The string length must be an even number.
+     */
     @UsedForTesting
     public static byte[] hexStringToByteArray(String hexString) {
         if (TextUtils.isEmpty(hexString)) {
             return null;
         }
         final int N = hexString.length();
+        if (N % 2 != 0) {
+            throw new NumberFormatException("Input hex string length must be an even number."
+                    + " Length = " + N);
+        }
         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)
diff --git a/tests/src/com/android/inputmethod/latin/personalization/UserHistoryDictionaryTests.java b/tests/src/com/android/inputmethod/latin/personalization/UserHistoryDictionaryTests.java
index 304b792..99ccb1a 100644
--- a/tests/src/com/android/inputmethod/latin/personalization/UserHistoryDictionaryTests.java
+++ b/tests/src/com/android/inputmethod/latin/personalization/UserHistoryDictionaryTests.java
@@ -155,7 +155,6 @@
             Log.d(TAG, "testStressTestForSwitchingLanguageAndAddingWords took "
                     + (end - start) + " ms");
         } finally {
-            Log.d(TAG, "waiting for writing ...");
             try {
                 Log.d(TAG, "waiting for writing ...");
                 Thread.sleep(TimeUnit.MILLISECONDS.convert(5L, TimeUnit.SECONDS));