diff --git a/java/src/com/android/inputmethod/latin/utils/CapsModeUtils.java b/java/src/com/android/inputmethod/latin/utils/CapsModeUtils.java
index 0db63fd..0dbc7c8 100644
--- a/java/src/com/android/inputmethod/latin/utils/CapsModeUtils.java
+++ b/java/src/com/android/inputmethod/latin/utils/CapsModeUtils.java
@@ -24,6 +24,7 @@
 import com.android.inputmethod.latin.common.StringUtils;
 import com.android.inputmethod.latin.settings.SpacingAndPunctuations;
 
+import java.util.ArrayList;
 import java.util.Locale;
 
 public final class CapsModeUtils {
@@ -326,4 +327,31 @@
         // Here we arrived at the start of the line. This should behave exactly like whitespace.
         return (START == state || LETTER == state) ? noCaps : caps;
     }
+
+    /**
+     * Convert capitalize mode flags into human readable text.
+     *
+     * @param capsFlags The modes flags to be converted. It may be any combination of
+     * {@link TextUtils#CAP_MODE_CHARACTERS}, {@link TextUtils#CAP_MODE_WORDS}, and
+     * {@link TextUtils#CAP_MODE_SENTENCES}.
+     * @return the text that describe the <code>capsMode</code>.
+     */
+    public static String flagsToString(final int capsFlags) {
+        final int capsFlagsMask = TextUtils.CAP_MODE_CHARACTERS | TextUtils.CAP_MODE_WORDS
+                | TextUtils.CAP_MODE_SENTENCES;
+        if ((capsFlags & ~capsFlagsMask) != 0) {
+            return "unknown<0x" + Integer.toHexString(capsFlags) + ">";
+        }
+        final ArrayList<String> builder = new ArrayList<>();
+        if ((capsFlags & android.text.TextUtils.CAP_MODE_CHARACTERS) != 0) {
+            builder.add("characters");
+        }
+        if ((capsFlags & android.text.TextUtils.CAP_MODE_WORDS) != 0) {
+            builder.add("words");
+        }
+        if ((capsFlags & android.text.TextUtils.CAP_MODE_SENTENCES) != 0) {
+            builder.add("sentences");
+        }
+        return builder.isEmpty() ? "none" : TextUtils.join("|", builder);
+    }
 }
diff --git a/java/src/com/android/inputmethod/latin/utils/RecapitalizeStatus.java b/java/src/com/android/inputmethod/latin/utils/RecapitalizeStatus.java
index 21daddc..a381649 100644
--- a/java/src/com/android/inputmethod/latin/utils/RecapitalizeStatus.java
+++ b/java/src/com/android/inputmethod/latin/utils/RecapitalizeStatus.java
@@ -51,6 +51,17 @@
         }
     }
 
+    public static String modeToString(final int recapitalizeMode) {
+        switch (recapitalizeMode) {
+        case NOT_A_RECAPITALIZE_MODE: return "undefined";
+        case CAPS_MODE_ORIGINAL_MIXED_CASE: return "mixedCase";
+        case CAPS_MODE_ALL_LOWER: return "allLower";
+        case CAPS_MODE_FIRST_WORD_UPPER: return "firstWordUpper";
+        case CAPS_MODE_ALL_UPPER: return "allUpper";
+        default: return "unknown<" + recapitalizeMode + ">";
+        }
+    }
+
     /**
      * We store the location of the cursor and the string that was there before the recapitalize
      * action was done, and the location of the cursor and the string that was there after.
diff --git a/native/dicttoolkit/Android.mk b/native/dicttoolkit/Android.mk
new file mode 100644
index 0000000..118682d
--- /dev/null
+++ b/native/dicttoolkit/Android.mk
@@ -0,0 +1,67 @@
+# Copyright (C) 2014 The Android Open Source Project
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+ifeq (,$(TARGET_BUILD_APPS))
+
+# Only build if it's explicitly requested, or running mm/mmm.
+ifneq ($(ONE_SHOT_MAKEFILE)$(filter $(MAKECMDGOALS),dicttoolkit),)
+
+# HACK: Temporarily disable host tool build on Mac until the build system is ready for C++11.
+LATINIME_HOST_OSNAME := $(shell uname -s)
+ifneq ($(LATINIME_HOST_OSNAME), Darwin) # TODO: Remove this
+
+LOCAL_PATH := $(call my-dir)
+
+include $(CLEAR_VARS)
+
+LATIN_IME_CORE_PATH := $(LOCAL_PATH)/../jni
+
+LATIN_IME_DICT_TOOLKIT_SRC_DIR := src
+LATIN_IME_CORE_SRC_DIR := ../jni/src
+
+LOCAL_CFLAGS += -Werror -Wall -Wextra -Weffc++ -Wformat=2 -Wcast-qual -Wcast-align \
+    -Wwrite-strings -Wfloat-equal -Wpointer-arith -Winit-self -Wredundant-decls \
+    -Woverloaded-virtual -Wsign-promo -Wno-system-headers
+
+# To suppress compiler warnings for unused variables/functions used for debug features etc.
+LOCAL_CFLAGS += -Wno-unused-parameter -Wno-unused-function
+LOCAL_CFLAGS += -std=c++11 -Wno-unused-parameter -Wno-unused-function
+
+include $(LOCAL_PATH)/NativeFileList.mk
+include $(LATIN_IME_CORE_PATH)/NativeFileList.mk
+
+LOCAL_C_INCLUDES += $(LOCAL_PATH)/$(LATIN_IME_DICT_TOOLKIT_SRC_DIR) \
+    $(LATIN_IME_CORE_PATH)/$(LATIN_IME_CORE_SRC_DIR)
+
+LOCAL_SRC_FILES := $(LATIN_IME_DICT_TOOLKIT_MAIN_SRC_FILES) \
+    $(addprefix $(LATIN_IME_DICT_TOOLKIT_SRC_DIR)/, $(LATIN_IME_DICT_TOOLKIT_SRC_FILES)) \
+    $(addprefix $(LATIN_IME_CORE_SRC_DIR)/, $(LATIN_IME_CORE_SRC_FILES))
+
+LOCAL_MODULE := dicttoolkit
+LOCAL_MODULE_TAGS := optional
+
+LOCAL_CLANG := true
+LOCAL_CXX_STL := libc++
+
+include $(BUILD_HOST_EXECUTABLE)
+#################### Clean up the tmp vars
+include $(LOCAL_PATH)/CleanupNativeFileList.mk
+#################### Unit test
+include $(LOCAL_PATH)/UnitTests.mk
+
+endif # Darwin - TODO: Remove this
+
+endif
+
+endif # TARGET_BUILD_APPS
diff --git a/native/dicttoolkit/CleanupNativeFileList.mk b/native/dicttoolkit/CleanupNativeFileList.mk
new file mode 100644
index 0000000..b804b41
--- /dev/null
+++ b/native/dicttoolkit/CleanupNativeFileList.mk
@@ -0,0 +1,17 @@
+# Copyright (C) 2014 The Android Open Source Project
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+LATIN_IME_DICT_TOOLKIT_MAIN_SRC_FILES :=
+LATIN_IME_DICT_TOOLKIT_SRC_FILES :=
+LATIN_IME_DICT_TOOLKIT_TEST_FILES :=
diff --git a/native/dicttoolkit/NativeFileList.mk b/native/dicttoolkit/NativeFileList.mk
new file mode 100644
index 0000000..b6be9c5
--- /dev/null
+++ b/native/dicttoolkit/NativeFileList.mk
@@ -0,0 +1,21 @@
+# Copyright (C) 2014 The Android Open Source Project
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+LATIN_IME_DICT_TOOLKIT_MAIN_SRC_FILES := \
+    dict_toolkit_main.cpp
+
+LATIN_IME_DICT_TOOLKIT_SRC_FILES :=
+
+LATIN_IME_DICT_TOOLKIT_TEST_FILES := \
+    dict_toolkit_defines_test.cpp
diff --git a/native/dicttoolkit/UnitTests.mk b/native/dicttoolkit/UnitTests.mk
new file mode 100644
index 0000000..d568db4
--- /dev/null
+++ b/native/dicttoolkit/UnitTests.mk
@@ -0,0 +1,68 @@
+# Copyright (C) 2014 The Android Open Source Project
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+ifeq (,$(TARGET_BUILD_APPS))
+
+LOCAL_PATH := $(call my-dir)
+
+######################################
+include $(CLEAR_VARS)
+
+LATIN_IME_CORE_PATH := $(LOCAL_PATH)/../jni
+
+LATIN_IME_DICT_TOOLKIT_SRC_DIR := src
+LATIN_IME_CORE_SRC_DIR := ../jni/src
+LATIN_DICT_TOOLKIT_TEST_SRC_DIR := tests
+
+include $(LOCAL_PATH)/NativeFileList.mk
+include $(LATIN_IME_CORE_PATH)/NativeFileList.mk
+
+# TODO: Remove -std=c++11 once it is set by default on host build.
+LATIN_IME_SRC_DIR := src
+LOCAL_ADDRESS_SANITIZER := true
+LOCAL_CFLAGS += -std=c++11 -Wno-unused-parameter -Wno-unused-function
+LOCAL_CLANG := true
+LOCAL_CXX_STL := libc++
+LOCAL_C_INCLUDES += $(LOCAL_PATH)/$(LATIN_IME_DICT_TOOLKIT_SRC_DIR) \
+    $(LATIN_IME_CORE_PATH)/$(LATIN_IME_CORE_SRC_DIR)
+LOCAL_MODULE := liblatinime_dicttoolkit_host_static_for_unittests
+LOCAL_MODULE_TAGS := optional
+LOCAL_SRC_FILES := \
+    $(addprefix $(LATIN_IME_DICT_TOOLKIT_SRC_DIR)/, $(LATIN_IME_DICT_TOOLKIT_SRC_FILES)) \
+    $(addprefix $(LATIN_IME_CORE_SRC_DIR)/, $(LATIN_IME_CORE_SRC_FILES))
+include $(BUILD_HOST_STATIC_LIBRARY)
+
+include $(CLEAR_VARS)
+
+# TODO: Remove -std=c++11 once it is set by default on host build.
+LOCAL_CFLAGS += -std=c++11 -Wno-unused-parameter -Wno-unused-function
+LOCAL_CLANG := true
+LOCAL_CXX_STL := libc++
+LOCAL_C_INCLUDES += $(LOCAL_PATH)/$(LATIN_IME_DICT_TOOLKIT_SRC_DIR) \
+    $(LATIN_IME_CORE_PATH)/$(LATIN_IME_CORE_SRC_DIR)
+LOCAL_MODULE := dicttoolkit_unittests
+LOCAL_MODULE_TAGS := tests
+LOCAL_SRC_FILES := \
+    $(addprefix $(LATIN_DICT_TOOLKIT_TEST_SRC_DIR)/, $(LATIN_IME_DICT_TOOLKIT_TEST_FILES))
+LOCAL_STATIC_LIBRARIES += liblatinime_dicttoolkit_host_static_for_unittests
+include $(BUILD_HOST_NATIVE_TEST)
+
+include $(LOCAL_PATH)/CleanupNativeFileList.mk
+
+#################### Clean up the tmp vars
+LATINIME_HOST_OSNAME :=
+LATIN_IME_SRC_DIR :=
+LATIN_IME_TEST_SRC_DIR :=
+
+endif # TARGET_BUILD_APPS
diff --git a/native/dicttoolkit/dict_toolkit_main.cpp b/native/dicttoolkit/dict_toolkit_main.cpp
new file mode 100644
index 0000000..d71b50e
--- /dev/null
+++ b/native/dicttoolkit/dict_toolkit_main.cpp
@@ -0,0 +1,23 @@
+/*
+ * Copyright (C) 2014 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <cstdio>
+
+int main(int argc, char **argv) {
+    // TODO: Implement.
+    printf("%s\n", argv[0]);
+    return 0;
+}
diff --git a/native/dicttoolkit/run_tests.sh b/native/dicttoolkit/run_tests.sh
new file mode 100755
index 0000000..44c99c1
--- /dev/null
+++ b/native/dicttoolkit/run_tests.sh
@@ -0,0 +1,34 @@
+#!/bin/bash
+# Copyright 2014, The Android Open Source Project
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# check script arguments
+if [[ $(type -t mmm) != function ]]; then
+if [[ ${BASH_SOURCE[0]} != $0 ]]; then return; else exit 1; fi
+fi
+
+# Host build is never supported in unbundled (NDK/tapas) build
+if [[ -n $TARGET_BUILD_APPS ]]; then
+  echo "Host build is never supported in tapas build."  1>&2
+  echo "Use lunch command instead."  1>&2
+  if [[ ${BASH_SOURCE[0]} != $0 ]]; then return; else exit 1; fi
+fi
+
+test_name=dicttoolkit_unittests
+
+pushd $PWD > /dev/null
+cd $(gettop)
+(mmm -j16 packages/inputmethods/LatinIME/native/dicttoolkit) || (make -j16 $test_name)
+$ANDROID_HOST_OUT/bin/$test_name
+popd > /dev/null
diff --git a/native/dicttoolkit/src/dict_toolkit_defines.h b/native/dicttoolkit/src/dict_toolkit_defines.h
new file mode 100644
index 0000000..2a2104e
--- /dev/null
+++ b/native/dicttoolkit/src/dict_toolkit_defines.h
@@ -0,0 +1,22 @@
+/*
+ * Copyright (C) 2014 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef LATINIME_DICT_TOOLKIT_DEFINES_H
+#define LATINIME_DICT_TOOLKIT_DEFINES_H
+
+#include "defines.h"
+
+#endif // LATINIME_DICT_TOOLKIT_DEFINES_H
diff --git a/native/dicttoolkit/tests/dict_toolkit_defines_test.cpp b/native/dicttoolkit/tests/dict_toolkit_defines_test.cpp
new file mode 100644
index 0000000..3445bd0
--- /dev/null
+++ b/native/dicttoolkit/tests/dict_toolkit_defines_test.cpp
@@ -0,0 +1,32 @@
+/*
+ * Copyright (C) 2014 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "dict_toolkit_defines.h"
+
+#include <gtest/gtest.h>
+
+namespace latinime {
+namespace dicttoolkit {
+namespace {
+
+// Initial trivial test case.
+TEST(DictToolkitDefinesTest, TestKeycodeSpace) {
+    EXPECT_EQ(' ', KEYCODE_SPACE);
+}
+
+} // namespace
+} // namespace dicttoolkit
+} // namespace latinime
diff --git a/native/jni/src/suggest/core/dictionary/error_type_utils.cpp b/native/jni/src/suggest/core/dictionary/error_type_utils.cpp
index 1e2494e..8f07ce2 100644
--- a/native/jni/src/suggest/core/dictionary/error_type_utils.cpp
+++ b/native/jni/src/suggest/core/dictionary/error_type_utils.cpp
@@ -31,6 +31,7 @@
 
 const ErrorTypeUtils::ErrorType ErrorTypeUtils::ERRORS_TREATED_AS_AN_EXACT_MATCH =
         NOT_AN_ERROR | MATCH_WITH_WRONG_CASE | MATCH_WITH_MISSING_ACCENT | MATCH_WITH_DIGRAPH;
+const ErrorTypeUtils::ErrorType ErrorTypeUtils::ERRORS_TREATED_AS_A_PERFECT_MATCH = NOT_AN_ERROR;
 
 const ErrorTypeUtils::ErrorType
         ErrorTypeUtils::ERRORS_TREATED_AS_AN_EXACT_MATCH_WITH_INTENTIONAL_OMISSION =
diff --git a/native/jni/src/suggest/core/dictionary/error_type_utils.h b/native/jni/src/suggest/core/dictionary/error_type_utils.h
index fd1d5fc..e92c509 100644
--- a/native/jni/src/suggest/core/dictionary/error_type_utils.h
+++ b/native/jni/src/suggest/core/dictionary/error_type_utils.h
@@ -52,6 +52,10 @@
         return (containedErrorTypes & ~ERRORS_TREATED_AS_AN_EXACT_MATCH) == 0;
     }
 
+    static bool isPerfectMatch(const ErrorType containedErrorTypes) {
+        return (containedErrorTypes & ~ERRORS_TREATED_AS_A_PERFECT_MATCH) == 0;
+    }
+
     static bool isExactMatchWithIntentionalOmission(const ErrorType containedErrorTypes) {
         return (containedErrorTypes
                 & ~ERRORS_TREATED_AS_AN_EXACT_MATCH_WITH_INTENTIONAL_OMISSION) == 0;
@@ -73,6 +77,7 @@
     DISALLOW_IMPLICIT_CONSTRUCTORS(ErrorTypeUtils);
 
     static const ErrorType ERRORS_TREATED_AS_AN_EXACT_MATCH;
+    static const ErrorType ERRORS_TREATED_AS_A_PERFECT_MATCH;
     static const ErrorType ERRORS_TREATED_AS_AN_EXACT_MATCH_WITH_INTENTIONAL_OMISSION;
 };
 } // namespace latinime
diff --git a/native/jni/src/suggest/core/policy/scoring.h b/native/jni/src/suggest/core/policy/scoring.h
index ce3684a..b9dda83 100644
--- a/native/jni/src/suggest/core/policy/scoring.h
+++ b/native/jni/src/suggest/core/policy/scoring.h
@@ -30,7 +30,7 @@
  public:
     virtual int calculateFinalScore(const float compoundDistance, const int inputSize,
             const ErrorTypeUtils::ErrorType containedErrorTypes, const bool forceCommit,
-            const bool boostExactMatches) const = 0;
+            const bool boostExactMatches, const bool hasProbabilityZero) const = 0;
     virtual void getMostProbableString(const DicTraverseSession *const traverseSession,
             const float weightOfLangModelVsSpatialModel,
             SuggestionResults *const outSuggestionResults) const = 0;
diff --git a/native/jni/src/suggest/core/result/suggestions_output_utils.cpp b/native/jni/src/suggest/core/result/suggestions_output_utils.cpp
index 23103b9..74db959 100644
--- a/native/jni/src/suggest/core/result/suggestions_output_utils.cpp
+++ b/native/jni/src/suggest/core/result/suggestions_output_utils.cpp
@@ -161,7 +161,7 @@
             compoundDistance, traverseSession->getInputSize(),
             terminalDicNode->getContainedErrorTypes(),
             (forceCommitMultiWords && terminalDicNode->hasMultipleWords()),
-            boostExactMatches);
+            boostExactMatches, wordAttributes.getProbability() == 0);
 
     // Don't output invalid or blocked offensive words. However, we still need to submit their
     // shortcuts if any.
diff --git a/native/jni/src/suggest/policyimpl/typing/scoring_params.cpp b/native/jni/src/suggest/policyimpl/typing/scoring_params.cpp
index a6f9a8b..856808a 100644
--- a/native/jni/src/suggest/policyimpl/typing/scoring_params.cpp
+++ b/native/jni/src/suggest/policyimpl/typing/scoring_params.cpp
@@ -24,6 +24,7 @@
 const float ScoringParams::AUTOCORRECT_OUTPUT_THRESHOLD = 1.0f;
 
 const float ScoringParams::EXACT_MATCH_PROMOTION = 1.1f;
+const float ScoringParams::PERFECT_MATCH_PROMOTION = 1.1f;
 const float ScoringParams::CASE_ERROR_PENALTY_FOR_EXACT_MATCH = 0.01f;
 const float ScoringParams::ACCENT_ERROR_PENALTY_FOR_EXACT_MATCH = 0.02f;
 const float ScoringParams::DIGRAPH_PENALTY_FOR_EXACT_MATCH = 0.03f;
diff --git a/native/jni/src/suggest/policyimpl/typing/scoring_params.h b/native/jni/src/suggest/policyimpl/typing/scoring_params.h
index b8f8895..6f327a3 100644
--- a/native/jni/src/suggest/policyimpl/typing/scoring_params.h
+++ b/native/jni/src/suggest/policyimpl/typing/scoring_params.h
@@ -34,6 +34,7 @@
     static const int THRESHOLD_SHORT_WORD_LENGTH;
 
     static const float EXACT_MATCH_PROMOTION;
+    static const float PERFECT_MATCH_PROMOTION;
     static const float CASE_ERROR_PENALTY_FOR_EXACT_MATCH;
     static const float ACCENT_ERROR_PENALTY_FOR_EXACT_MATCH;
     static const float DIGRAPH_PENALTY_FOR_EXACT_MATCH;
diff --git a/native/jni/src/suggest/policyimpl/typing/typing_scoring.h b/native/jni/src/suggest/policyimpl/typing/typing_scoring.h
index 0240bcf..6acd767 100644
--- a/native/jni/src/suggest/policyimpl/typing/typing_scoring.h
+++ b/native/jni/src/suggest/policyimpl/typing/typing_scoring.h
@@ -44,23 +44,50 @@
 
     AK_FORCE_INLINE int calculateFinalScore(const float compoundDistance, const int inputSize,
             const ErrorTypeUtils::ErrorType containedErrorTypes, const bool forceCommit,
-            const bool boostExactMatches) const {
+            const bool boostExactMatches, const bool hasProbabilityZero) const {
         const float maxDistance = ScoringParams::DISTANCE_WEIGHT_LANGUAGE
                 + static_cast<float>(inputSize) * ScoringParams::TYPING_MAX_OUTPUT_SCORE_PER_INPUT;
         float score = ScoringParams::TYPING_BASE_OUTPUT_SCORE - compoundDistance / maxDistance;
         if (forceCommit) {
             score += ScoringParams::AUTOCORRECT_OUTPUT_THRESHOLD;
         }
-        if (boostExactMatches && ErrorTypeUtils::isExactMatch(containedErrorTypes)) {
-            score += ScoringParams::EXACT_MATCH_PROMOTION;
-            if ((ErrorTypeUtils::MATCH_WITH_WRONG_CASE & containedErrorTypes) != 0) {
-                score -= ScoringParams::CASE_ERROR_PENALTY_FOR_EXACT_MATCH;
+        if (hasProbabilityZero) {
+            // Previously, when both legitimate 0-frequency words (such as distracters) and
+            // offensive words were encoded in the same way, distracters would never show up
+            // when the user blocked offensive words (the default setting, as well as the
+            // setting for regression tests).
+            //
+            // When b/11031090 was fixed and a separate encoding was used for offensive words,
+            // 0-frequency words would no longer be blocked when they were an "exact match"
+            // (where case mismatches and accent mismatches would be considered an "exact
+            // match"). The exact match boosting functionality meant that, for example, when
+            // the user typed "mt" they would be suggested the word "Mt", although they most
+            // probably meant to type "my".
+            //
+            // For this reason, we introduced this change, which does the following:
+            // * Defines the "perfect match" as a really exact match, with no room for case or
+            // accent mismatches
+            // * When the target word has probability zero (as "Mt" does, because it is a
+            // distracter), ONLY boost its score if it is a perfect match.
+            //
+            // By doing this, when the user types "mt", the word "Mt" will NOT be boosted, and
+            // they will get "my". However, if the user makes an explicit effort to type "Mt",
+            // we do boost the word "Mt" so that the user's input is not autocorrected to "My".
+            if (boostExactMatches && ErrorTypeUtils::isPerfectMatch(containedErrorTypes)) {
+                score += ScoringParams::PERFECT_MATCH_PROMOTION;
             }
-            if ((ErrorTypeUtils::MATCH_WITH_MISSING_ACCENT & containedErrorTypes) != 0) {
-                score -= ScoringParams::ACCENT_ERROR_PENALTY_FOR_EXACT_MATCH;
-            }
-            if ((ErrorTypeUtils::MATCH_WITH_DIGRAPH & containedErrorTypes) != 0) {
-                score -= ScoringParams::DIGRAPH_PENALTY_FOR_EXACT_MATCH;
+        } else {
+            if (boostExactMatches && ErrorTypeUtils::isExactMatch(containedErrorTypes)) {
+                score += ScoringParams::EXACT_MATCH_PROMOTION;
+                if ((ErrorTypeUtils::MATCH_WITH_WRONG_CASE & containedErrorTypes) != 0) {
+                    score -= ScoringParams::CASE_ERROR_PENALTY_FOR_EXACT_MATCH;
+                }
+                if ((ErrorTypeUtils::MATCH_WITH_MISSING_ACCENT & containedErrorTypes) != 0) {
+                    score -= ScoringParams::ACCENT_ERROR_PENALTY_FOR_EXACT_MATCH;
+                }
+                if ((ErrorTypeUtils::MATCH_WITH_DIGRAPH & containedErrorTypes) != 0) {
+                    score -= ScoringParams::DIGRAPH_PENALTY_FOR_EXACT_MATCH;
+                }
             }
         }
         return static_cast<int>(score * SUGGEST_INTERFACE_OUTPUT_SCALE);
diff --git a/tools/dicttool/Android.mk b/tools/dicttool/Android.mk
index 13d7c37..4265925 100644
--- a/tools/dicttool/Android.mk
+++ b/tools/dicttool/Android.mk
@@ -42,8 +42,6 @@
 # a significant part of the dependencies are mocked in the compat/ directory, with empty or
 # nearly-empty implementations, for parts that we don't use in Dicttool.
 LATINIME_SRC_FILES_FOR_DICTTOOL := \
-        event/Combiner.java \
-        event/Event.java \
         latin/BinaryDictionary.java \
         latin/DicTraverseSession.java \
         latin/Dictionary.java \
diff --git a/tools/dicttool/compat/com/android/inputmethod/event/CombinerChain.java b/tools/dicttool/compat/com/android/inputmethod/event/CombinerChain.java
deleted file mode 100644
index c4457a1..0000000
--- a/tools/dicttool/compat/com/android/inputmethod/event/CombinerChain.java
+++ /dev/null
@@ -1,54 +0,0 @@
-/*
- * Copyright (C) 2014 The Android Open Source Project
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *      http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-package com.android.inputmethod.event;
-
-import java.util.ArrayList;
-
-/**
- * Compatibility class that stands in for the combiner chain in LatinIME.
- *
- * This is not used by dicttool, it's just needed by the dependency chain.
- */
-// TODO: there should not be a dependency to this in dicttool, so there
-// should be a sensible way to separate them cleanly.
-public class CombinerChain {
-    private StringBuilder mComposingWord;
-    public CombinerChain(final String initialText, final Combiner... combinerList) {
-        mComposingWord = new StringBuilder(initialText);
-    }
-
-    public Event processEvent(final ArrayList<Event> previousEvents, final Event newEvent) {
-        return newEvent;
-    }
-
-    public void applyProcessedEvent(final Event event) {
-        mComposingWord.append(event.getTextToCommit());
-    }
-
-    public CharSequence getComposingWordWithCombiningFeedback() {
-        return mComposingWord;
-    }
-
-    public void reset() {
-        mComposingWord.setLength(0);
-    }
-
-    public static Combiner[] createCombiners(final String spec) {
-        // Dicttool never uses a combiner at all, so we just return a zero-sized array.
-        return new Combiner[0];
-    }
-}
diff --git a/tools/dicttool/src/com/android/inputmethod/latin/dicttool/CommandList.java b/tools/dicttool/src/com/android/inputmethod/latin/dicttool/CommandList.java
index 0d93c7f..07450ca 100644
--- a/tools/dicttool/src/com/android/inputmethod/latin/dicttool/CommandList.java
+++ b/tools/dicttool/src/com/android/inputmethod/latin/dicttool/CommandList.java
@@ -18,6 +18,7 @@
 
 public class CommandList {
     public static void populate() {
+        // TODO: Move some commands to native code.
         Dicttool.addCommand("info", Info.class);
         Dicttool.addCommand("diff", Diff.class);
         Dicttool.addCommand("compress", Compress.Compressor.class);