diff --git a/core/api/current.txt b/core/api/current.txt
index d3d754c0d8a5a..7da1b14adbd89 100644
--- a/core/api/current.txt
+++ b/core/api/current.txt
@@ -51530,6 +51530,7 @@ package android.view.inputmethod {
     method public int describeContents();
     method public void dump(android.util.Printer, String);
     method public android.content.ComponentName getComponent();
+    method public int getConfigChanges();
     method public String getId();
     method public int getIsDefaultResourceId();
     method public String getPackageName();
diff --git a/core/api/test-current.txt b/core/api/test-current.txt
index ff96f92da2f58..7ccb967aac211 100644
--- a/core/api/test-current.txt
+++ b/core/api/test-current.txt
@@ -2554,6 +2554,10 @@ package android.view.inputmethod {
     method @NonNull public static android.view.inputmethod.InlineSuggestionsResponse newInlineSuggestionsResponse(@NonNull java.util.List<android.view.inputmethod.InlineSuggestion>);
   }
 
+  public final class InputMethodInfo implements android.os.Parcelable {
+    ctor public InputMethodInfo(@NonNull String, @NonNull String, @NonNull CharSequence, @NonNull String, int);
+  }
+
   public final class InputMethodManager {
     method public int getDisplayId();
     method public boolean hasActiveInputConnection(@Nullable android.view.View);
diff --git a/core/java/android/inputmethodservice/IInputMethodWrapper.java b/core/java/android/inputmethodservice/IInputMethodWrapper.java
index 5cfcd667632b0..9198eb74d1f84 100644
--- a/core/java/android/inputmethodservice/IInputMethodWrapper.java
+++ b/core/java/android/inputmethodservice/IInputMethodWrapper.java
@@ -171,7 +171,7 @@ class IInputMethodWrapper extends IInputMethod.Stub
                 SomeArgs args = (SomeArgs) msg.obj;
                 try {
                     inputMethod.initializeInternal((IBinder) args.arg1, msg.arg1,
-                            (IInputMethodPrivilegedOperations) args.arg2);
+                            (IInputMethodPrivilegedOperations) args.arg2, (int) args.arg3);
                 } finally {
                     args.recycle();
                 }
@@ -280,9 +280,10 @@ class IInputMethodWrapper extends IInputMethod.Stub
     @BinderThread
     @Override
     public void initializeInternal(IBinder token, int displayId,
-            IInputMethodPrivilegedOperations privOps) {
+            IInputMethodPrivilegedOperations privOps, int configChanges) {
         mCaller.executeOrSendMessage(
-                mCaller.obtainMessageIOO(DO_INITIALIZE_INTERNAL, displayId, token, privOps));
+                mCaller.obtainMessageIOOO(DO_INITIALIZE_INTERNAL, displayId, token, privOps,
+                        configChanges));
     }
 
     @BinderThread
diff --git a/core/java/android/inputmethodservice/InputMethodService.java b/core/java/android/inputmethodservice/InputMethodService.java
index 7e2be01feb014..03dd3067e64eb 100644
--- a/core/java/android/inputmethodservice/InputMethodService.java
+++ b/core/java/android/inputmethodservice/InputMethodService.java
@@ -70,6 +70,7 @@ import android.compat.annotation.ChangeId;
 import android.compat.annotation.EnabledSince;
 import android.compat.annotation.UnsupportedAppUsage;
 import android.content.Context;
+import android.content.pm.ActivityInfo;
 import android.content.pm.PackageManager;
 import android.content.res.Configuration;
 import android.content.res.Resources;
@@ -131,6 +132,7 @@ import android.widget.TextView;
 import android.window.WindowMetricsHelper;
 
 import com.android.internal.annotations.GuardedBy;
+import com.android.internal.annotations.VisibleForTesting;
 import com.android.internal.inputmethod.IInputContentUriToken;
 import com.android.internal.inputmethod.IInputMethodPrivilegedOperations;
 import com.android.internal.inputmethod.InputMethodPrivilegedOperations;
@@ -513,6 +515,8 @@ public class InputMethodService extends AbstractInputMethodService {
     private boolean mIsAutomotive;
     private Handler mHandler;
     private boolean mImeSurfaceScheduledForRemoval;
+    private Configuration mLastKnownConfig;
+    private int mHandledConfigChanges;
 
     /**
      * An opaque {@link Binder} token of window requesting {@link InputMethodImpl#showSoftInput}
@@ -588,12 +592,14 @@ public class InputMethodService extends AbstractInputMethodService {
         @MainThread
         @Override
         public final void initializeInternal(@NonNull IBinder token, int displayId,
-                IInputMethodPrivilegedOperations privilegedOperations) {
+                IInputMethodPrivilegedOperations privilegedOperations,
+                int configChanges) {
             if (InputMethodPrivilegedOperationsRegistry.isRegistered(token)) {
                 Log.w(TAG, "The token has already registered, ignore this initialization.");
                 return;
             }
             Trace.traceBegin(TRACE_TAG_WINDOW_MANAGER, "IMS.initializeInternal");
+            mHandledConfigChanges = configChanges;
             mPrivOps.set(privilegedOperations);
             InputMethodPrivilegedOperationsRegistry.put(token, mPrivOps);
             updateInputMethodDisplay(displayId);
@@ -821,6 +827,9 @@ public class InputMethodService extends AbstractInputMethodService {
                 setImeWindowStatus(mapToImeWindowStatus(), mBackDisposition);
             }
             final boolean isVisible = isInputViewShown();
+            if (isVisible && getResources() != null) {
+                mLastKnownConfig = getResources().getConfiguration();
+            }
             final boolean visibilityChanged = isVisible != wasVisible;
             if (resultReceiver != null) {
                 resultReceiver.send(visibilityChanged
@@ -1428,10 +1437,37 @@ public class InputMethodService extends AbstractInputMethodService {
      * state: {@link #onStartInput} if input is active, and
      * {@link #onCreateInputView} and {@link #onStartInputView} and related
      * appropriate functions if the UI is displayed.
+     * <p>Starting with {@link Build.VERSION_CODES#S}, IMEs can opt into handling configuration
+     * changes themselves instead of being restarted with
+     * {@link android.R.styleable#InputMethod_configChanges}.
      */
     @Override public void onConfigurationChanged(Configuration newConfig) {
         super.onConfigurationChanged(newConfig);
-        resetStateForNewConfiguration();
+        if (shouldImeRestartForConfig(newConfig)) {
+            resetStateForNewConfiguration();
+        }
+    }
+
+    /**
+     * @return {@code true} if {@link InputMethodService} needs to restart to handle
+     * .{@link #onConfigurationChanged(Configuration)}
+     */
+    @VisibleForTesting
+    boolean shouldImeRestartForConfig(@NonNull Configuration newConfig) {
+        if (mLastKnownConfig == null) {
+            return true;
+        }
+        // If the new config is the same as the config this Service is already running with,
+        // then don't bother calling resetStateForNewConfiguration.
+        int diff = mLastKnownConfig.diffPublicOnly(newConfig);
+        if (diff != 0) {
+            // remove attrs not-relevant to IME service.
+            diff &= ActivityInfo.CONFIG_KEYBOARD_HIDDEN;
+            diff &= ActivityInfo.CONFIG_KEYBOARD;
+            diff &= ActivityInfo.CONFIG_NAVIGATION;
+        }
+        int unhandledDiff = (diff & ~mHandledConfigChanges);
+        return unhandledDiff != 0;
     }
 
     private void resetStateForNewConfiguration() {
@@ -3181,7 +3217,17 @@ public class InputMethodService extends AbstractInputMethodService {
             requestHideSelf(InputMethodManager.HIDE_NOT_ALWAYS);
         }
     }
-    
+
+    @VisibleForTesting
+    void setLastKnownConfig(@NonNull Configuration config) {
+        mLastKnownConfig = config;
+    }
+
+    @VisibleForTesting
+    void setHandledConfigChanges(int configChanges) {
+        mHandledConfigChanges = configChanges;
+    }
+
     void startExtractingText(boolean inputChanged) {
         final ExtractEditText eet = mExtractEditText;
         if (eet != null && getCurrentInputStarted()
diff --git a/core/java/android/view/inputmethod/InputMethod.java b/core/java/android/view/inputmethod/InputMethod.java
index de4554b9e6249..6ade5e622eab6 100644
--- a/core/java/android/view/inputmethod/InputMethod.java
+++ b/core/java/android/view/inputmethod/InputMethod.java
@@ -105,7 +105,7 @@ public interface InputMethod {
      */
     @MainThread
     default void initializeInternal(IBinder token, int displayId,
-            IInputMethodPrivilegedOperations privilegedOperations) {
+            IInputMethodPrivilegedOperations privilegedOperations, int configChanges) {
         updateInputMethodDisplay(displayId);
         attachToken(token);
     }
diff --git a/core/java/android/view/inputmethod/InputMethodInfo.java b/core/java/android/view/inputmethod/InputMethodInfo.java
index 5d876a6f62d35..25712f8bf9b87 100644
--- a/core/java/android/view/inputmethod/InputMethodInfo.java
+++ b/core/java/android/view/inputmethod/InputMethodInfo.java
@@ -18,19 +18,23 @@ package android.view.inputmethod;
 
 import android.annotation.NonNull;
 import android.annotation.Nullable;
+import android.annotation.TestApi;
 import android.compat.annotation.UnsupportedAppUsage;
 import android.content.ComponentName;
 import android.content.Context;
+import android.content.pm.ActivityInfo;
 import android.content.pm.ApplicationInfo;
 import android.content.pm.PackageManager;
 import android.content.pm.PackageManager.NameNotFoundException;
 import android.content.pm.ResolveInfo;
 import android.content.pm.ServiceInfo;
+import android.content.res.Configuration;
 import android.content.res.Resources;
 import android.content.res.Resources.NotFoundException;
 import android.content.res.TypedArray;
 import android.content.res.XmlResourceParser;
 import android.graphics.drawable.Drawable;
+import android.inputmethodservice.InputMethodService;
 import android.os.Parcel;
 import android.os.Parcelable;
 import android.util.AttributeSet;
@@ -60,6 +64,7 @@ import java.util.List;
  * @attr ref android.R.styleable#InputMethod_isDefault
  * @attr ref android.R.styleable#InputMethod_supportsSwitchingToNextInputMethod
  * @attr ref android.R.styleable#InputMethod_supportsInlineSuggestions
+ * @attr ref android.R.styleable#InputMethod_configChanges
  */
 public final class InputMethodInfo implements Parcelable {
     static final String TAG = "InputMethodInfo";
@@ -117,6 +122,12 @@ public final class InputMethodInfo implements Parcelable {
      */
     private final boolean mInlineSuggestionsEnabled;
 
+    /**
+     * The flag for configurations IME assumes the responsibility for handling in
+     * {@link InputMethodService#onConfigurationChanged(Configuration)}}.
+     */
+    private final int mHandledConfigChanges;
+
     /**
      * @param service the {@link ResolveInfo} corresponds in which the IME is implemented.
      * @return a unique ID to be returned by {@link #getId()}. We have used
@@ -203,6 +214,8 @@ public final class InputMethodInfo implements Parcelable {
                     false);
             inlineSuggestionsEnabled = sa.getBoolean(
                     com.android.internal.R.styleable.InputMethod_supportsInlineSuggestions, false);
+            mHandledConfigChanges = sa.getInt(
+                    com.android.internal.R.styleable.InputMethod_configChanges, 0);
             sa.recycle();
 
             final int depth = parser.getDepth();
@@ -287,6 +300,7 @@ public final class InputMethodInfo implements Parcelable {
         mIsVrOnly = source.readBoolean();
         mService = ResolveInfo.CREATOR.createFromParcel(source);
         mSubtypes = new InputMethodSubtypeArray(source);
+        mHandledConfigChanges = source.readInt();
         mForceDefault = false;
     }
 
@@ -298,7 +312,22 @@ public final class InputMethodInfo implements Parcelable {
         this(buildFakeResolveInfo(packageName, className, label), false /* isAuxIme */,
                 settingsActivity, null /* subtypes */, 0 /* isDefaultResId */,
                 false /* forceDefault */, true /* supportsSwitchingToNextInputMethod */,
-                false /* inlineSuggestionsEnabled */, false /* isVrOnly */);
+                false /* inlineSuggestionsEnabled */, false /* isVrOnly */,
+                0 /* handledConfigChanges */);
+    }
+
+    /**
+     * Temporary API for creating a built-in input method for test.
+     * @hide
+     */
+    @TestApi
+    public InputMethodInfo(@NonNull String packageName, @NonNull String className,
+            @NonNull CharSequence label, @NonNull String settingsActivity,
+            int handledConfigChanges) {
+        this(buildFakeResolveInfo(packageName, className, label), false /* isAuxIme */,
+                settingsActivity, null /* subtypes */, 0 /* isDefaultResId */,
+                false /* forceDefault */, true /* supportsSwitchingToNextInputMethod */,
+                false /* inlineSuggestionsEnabled */, false /* isVrOnly */, handledConfigChanges);
     }
 
     /**
@@ -310,7 +339,7 @@ public final class InputMethodInfo implements Parcelable {
             boolean forceDefault) {
         this(ri, isAuxIme, settingsActivity, subtypes, isDefaultResId, forceDefault,
                 true /* supportsSwitchingToNextInputMethod */, false /* inlineSuggestionsEnabled */,
-                false /* isVrOnly */);
+                false /* isVrOnly */, 0 /* handledconfigChanges */);
     }
 
     /**
@@ -321,7 +350,8 @@ public final class InputMethodInfo implements Parcelable {
             List<InputMethodSubtype> subtypes, int isDefaultResId, boolean forceDefault,
             boolean supportsSwitchingToNextInputMethod, boolean isVrOnly) {
         this(ri, isAuxIme, settingsActivity, subtypes, isDefaultResId, forceDefault,
-                supportsSwitchingToNextInputMethod, false /* inlineSuggestionsEnabled */, isVrOnly);
+                supportsSwitchingToNextInputMethod, false /* inlineSuggestionsEnabled */, isVrOnly,
+                0 /* handledConfigChanges */);
     }
 
     /**
@@ -331,7 +361,7 @@ public final class InputMethodInfo implements Parcelable {
     public InputMethodInfo(ResolveInfo ri, boolean isAuxIme, String settingsActivity,
             List<InputMethodSubtype> subtypes, int isDefaultResId, boolean forceDefault,
             boolean supportsSwitchingToNextInputMethod, boolean inlineSuggestionsEnabled,
-            boolean isVrOnly) {
+            boolean isVrOnly, int handledConfigChanges) {
         final ServiceInfo si = ri.serviceInfo;
         mService = ri;
         mId = new ComponentName(si.packageName, si.name).flattenToShortString();
@@ -343,6 +373,7 @@ public final class InputMethodInfo implements Parcelable {
         mSupportsSwitchingToNextInputMethod = supportsSwitchingToNextInputMethod;
         mInlineSuggestionsEnabled = inlineSuggestionsEnabled;
         mIsVrOnly = isVrOnly;
+        mHandledConfigChanges = handledConfigChanges;
     }
 
     private static ResolveInfo buildFakeResolveInfo(String packageName, String className,
@@ -489,6 +520,17 @@ public final class InputMethodInfo implements Parcelable {
         }
     }
 
+    /**
+     * Returns the bit mask of kinds of configuration changes that this IME
+     * can handle itself (without being restarted by the system).
+     *
+     * @attr ref android.R.styleable#InputMethod_configChanges
+     */
+    @ActivityInfo.Config
+    public int getConfigChanges() {
+        return mHandledConfigChanges;
+    }
+
     public void dump(Printer pw, String prefix) {
         pw.println(prefix + "mId=" + mId
                 + " mSettingsActivityName=" + mSettingsActivityName
@@ -579,6 +621,7 @@ public final class InputMethodInfo implements Parcelable {
         dest.writeBoolean(mIsVrOnly);
         mService.writeToParcel(dest, flags);
         mSubtypes.writeToParcel(dest);
+        dest.writeInt(mHandledConfigChanges);
     }
 
     /**
diff --git a/core/java/com/android/internal/view/IInputMethod.aidl b/core/java/com/android/internal/view/IInputMethod.aidl
index c336373539844..8d82e33dc29ff 100644
--- a/core/java/com/android/internal/view/IInputMethod.aidl
+++ b/core/java/com/android/internal/view/IInputMethod.aidl
@@ -35,7 +35,8 @@ import com.android.internal.view.InlineSuggestionsRequestInfo;
  * {@hide}
  */
 oneway interface IInputMethod {
-    void initializeInternal(IBinder token, int displayId, IInputMethodPrivilegedOperations privOps);
+    void initializeInternal(IBinder token, int displayId, IInputMethodPrivilegedOperations privOps,
+             int configChanges);
 
     void onCreateInlineSuggestionsRequest(in InlineSuggestionsRequestInfo requestInfo,
             in IInlineSuggestionsRequestCallback cb);
diff --git a/core/res/res/values/attrs.xml b/core/res/res/values/attrs.xml
index 69bb20cf9c1ee..99f58ee1f8a63 100644
--- a/core/res/res/values/attrs.xml
+++ b/core/res/res/values/attrs.xml
@@ -3564,6 +3564,16 @@
         <attr name="__removed2" format="boolean" />
         <!-- Specifies whether the IME supports showing inline suggestions. -->
         <attr name="supportsInlineSuggestions" format="boolean" />
+        <!-- Specify one or more configuration changes that the IME will handle itself. If not
+             specified, the IME will be restarted if any of these configuration changes happen in
+              the system.  Otherwise, the IME will remain running and its
+             {@link android.inputmethodservice.InputMethodService#onConfigurationChanged}
+             method is called with the new configuration.
+             <p>Note that all of these configuration changes can impact the
+             resource values seen by the application, so you will generally need
+             to re-retrieve all resources (including view layouts, drawables, etc)
+             to correctly handle any configuration change.-->
+        <attr name="configChanges" />
     </declare-styleable>
 
     <!-- This is the subtype of InputMethod. Subtype can describe locales (for example, en_US and
diff --git a/core/tests/coretests/src/android/inputmethodservice/InputMethodServiceTest.java b/core/tests/coretests/src/android/inputmethodservice/InputMethodServiceTest.java
new file mode 100644
index 0000000000000..890614982ba5a
--- /dev/null
+++ b/core/tests/coretests/src/android/inputmethodservice/InputMethodServiceTest.java
@@ -0,0 +1,80 @@
+/*
+ * Copyright (C) 2021 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 android.inputmethodservice;
+
+import static androidx.test.platform.app.InstrumentationRegistry.getInstrumentation;
+
+
+import static junit.framework.Assert.assertFalse;
+
+import static org.junit.Assert.assertTrue;
+
+import android.content.Context;
+import android.content.pm.ActivityInfo;
+import android.content.res.Configuration;
+import android.os.Build;
+
+import androidx.test.filters.SmallTest;
+import androidx.test.rule.ServiceTestRule;
+import androidx.test.runner.AndroidJUnit4;
+
+import org.junit.Before;
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+
+import java.util.concurrent.TimeoutException;
+
+@SmallTest
+@RunWith(AndroidJUnit4.class)
+public class InputMethodServiceTest {
+    private InputMethodService mService;
+    private Context mContext;
+    @Rule
+    public final ServiceTestRule serviceRule = new ServiceTestRule();
+
+    @Before
+    public void setUp() throws TimeoutException {
+        mContext = getInstrumentation().getContext();
+        mService = new InputMethodService();
+    }
+
+    @Test
+    public void testShouldImeRestartForConfig() throws Exception {
+        // Make sure we preserve Pre-S behavior i.e. Service restarts.
+        mContext.getApplicationInfo().targetSdkVersion = Build.VERSION_CODES.R;
+        Configuration config = mContext.getResources().getConfiguration();
+        mService.setLastKnownConfig(config);
+        assertTrue("IME should restart for Pre-S",
+                mService.shouldImeRestartForConfig(config));
+
+        // IME shouldn't restart on targetSdk S+ (with no config changes).
+        mContext.getApplicationInfo().targetSdkVersion = Build.VERSION_CODES.S;
+        assertFalse("IME shouldn't restart for S+",
+                mService.shouldImeRestartForConfig(config));
+
+        // Screen density changed but IME doesn't handle congfigChanges
+        config.densityDpi = 99;
+        assertTrue("IME should restart for unhandled configChanges",
+                mService.shouldImeRestartForConfig(config));
+
+        // opt-in IME to handle config changes.
+        mService.setHandledConfigChanges(ActivityInfo.CONFIG_DENSITY);
+        assertFalse("IME shouldn't restart for S+ since it handles configChanges",
+                mService.shouldImeRestartForConfig(config));
+    }
+}
diff --git a/services/core/java/com/android/server/inputmethod/InputMethodManagerService.java b/services/core/java/com/android/server/inputmethod/InputMethodManagerService.java
index 0754df0e6b9f5..1e66589308404 100644
--- a/services/core/java/com/android/server/inputmethod/InputMethodManagerService.java
+++ b/services/core/java/com/android/server/inputmethod/InputMethodManagerService.java
@@ -2620,8 +2620,9 @@ public class InputMethodManagerService extends IInputMethodManager.Stub
                 }
                 if (DEBUG) Slog.v(TAG, "Initiating attach with token: " + mCurToken);
                 // Dispatch display id for InputMethodService to update context display.
-                executeOrSendMessage(mCurMethod, mCaller.obtainMessageIOO(
-                        MSG_INITIALIZE_IME, mCurTokenDisplayId, mCurMethod, mCurToken));
+                executeOrSendMessage(mCurMethod, mCaller.obtainMessageIOOO(
+                        MSG_INITIALIZE_IME, mCurTokenDisplayId, mCurMethod, mCurToken,
+                        mMethodMap.get(mCurMethodId).getConfigChanges()));
                 scheduleNotifyImeUidToAudioService(mCurMethodUid);
                 if (mCurClient != null) {
                     clearClientSessionLocked(mCurClient);
@@ -4466,7 +4467,8 @@ public class InputMethodManagerService extends IInputMethodManager.Stub
                     }
                     final IBinder token = (IBinder) args.arg2;
                     ((IInputMethod) args.arg1).initializeInternal(token, msg.arg1,
-                            new InputMethodPrivilegedOperationsImpl(this, token));
+                            new InputMethodPrivilegedOperationsImpl(this, token),
+                            (int) args.arg3);
                 } catch (RemoteException e) {
                 }
                 args.recycle();