diff --git a/Android.bp b/Android.bp
index facc741578e07..8df461b54433f 100644
--- a/Android.bp
+++ b/Android.bp
@@ -462,8 +462,6 @@ java_library {
         "telephony/java/android/telephony/ims/internal/aidl/IImsMmTelFeature.aidl",
         "telephony/java/android/telephony/ims/internal/aidl/IImsMmTelListener.aidl",
         "telephony/java/android/telephony/ims/internal/aidl/IImsRcsFeature.aidl",
-        "telephony/java/android/telephony/ims/internal/aidl/IImsRegistration.aidl",
-        "telephony/java/android/telephony/ims/internal/aidl/IImsRegistrationCallback.aidl",
         "telephony/java/android/telephony/ims/internal/aidl/IImsServiceController.aidl",
         "telephony/java/android/telephony/ims/internal/aidl/IImsServiceControllerListener.aidl",
 	"telephony/java/android/telephony/ims/internal/aidl/IImsSmsListener.aidl",
@@ -483,6 +481,8 @@ java_library {
         "telephony/java/com/android/ims/internal/IImsFeatureStatusCallback.aidl",
         "telephony/java/com/android/ims/internal/IImsMMTelFeature.aidl",
         "telephony/java/com/android/ims/internal/IImsMultiEndpoint.aidl",
+        "telephony/java/com/android/ims/internal/IImsRegistration.aidl",
+        "telephony/java/com/android/ims/internal/IImsRegistrationCallback.aidl",
         "telephony/java/com/android/ims/internal/IImsRcsFeature.aidl",
         "telephony/java/com/android/ims/internal/IImsService.aidl",
         "telephony/java/com/android/ims/internal/IImsServiceController.aidl",
diff --git a/telephony/java/android/telephony/TelephonyManager.java b/telephony/java/android/telephony/TelephonyManager.java
index 805fae3533b68..6a683431f0aa4 100644
--- a/telephony/java/android/telephony/TelephonyManager.java
+++ b/telephony/java/android/telephony/TelephonyManager.java
@@ -54,6 +54,7 @@ import android.util.Log;
 
 import com.android.ims.internal.IImsMMTelFeature;
 import com.android.ims.internal.IImsRcsFeature;
+import com.android.ims.internal.IImsRegistration;
 import com.android.ims.internal.IImsServiceFeatureCallback;
 import com.android.internal.annotations.VisibleForTesting;
 import com.android.internal.telecom.ITelecomService;
@@ -4777,6 +4778,25 @@ public class TelephonyManager {
         return null;
     }
 
+    /**
+     * @return the {@IImsRegistration} interface that corresponds with the slot index and feature.
+     * @param slotIndex The SIM slot corresponding to the ImsService ImsRegistration is active for.
+     * @param feature An integer indicating the feature that we wish to get the ImsRegistration for.
+     * Corresponds to features defined in ImsFeature.
+     * @hide
+     */
+    public @Nullable IImsRegistration getImsRegistration(int slotIndex, int feature) {
+        try {
+            ITelephony telephony = getITelephony();
+            if (telephony != null) {
+                return telephony.getImsRegistration(slotIndex, feature);
+            }
+        } catch (RemoteException e) {
+            Rlog.e(TAG, "getImsRegistration, RemoteException: " + e.getMessage());
+        }
+        return null;
+    }
+
     /**
      * Set IMS registration state
      *
diff --git a/telephony/java/android/telephony/ims/ImsService.java b/telephony/java/android/telephony/ims/ImsService.java
index 8230eafc2e4da..aaa0f08594d11 100644
--- a/telephony/java/android/telephony/ims/ImsService.java
+++ b/telephony/java/android/telephony/ims/ImsService.java
@@ -26,12 +26,14 @@ import android.telephony.CarrierConfigManager;
 import android.telephony.ims.feature.ImsFeature;
 import android.telephony.ims.feature.MMTelFeature;
 import android.telephony.ims.feature.RcsFeature;
+import android.telephony.ims.stub.ImsRegistrationImplBase;
 import android.util.Log;
 import android.util.SparseArray;
 
 import com.android.ims.internal.IImsFeatureStatusCallback;
 import com.android.ims.internal.IImsMMTelFeature;
 import com.android.ims.internal.IImsRcsFeature;
+import com.android.ims.internal.IImsRegistration;
 import com.android.ims.internal.IImsServiceController;
 import com.android.internal.annotations.VisibleForTesting;
 
@@ -113,6 +115,12 @@ public class ImsService extends Service {
                 throws RemoteException {
             ImsService.this.removeImsFeature(slotId, featureType, c);
         }
+
+        @Override
+        public IImsRegistration getRegistration(int slotId) throws RemoteException {
+            ImsRegistrationImplBase r = ImsService.this.getRegistration(slotId);
+            return r != null ? r.getBinder() : null;
+        }
     };
 
     /**
@@ -174,6 +182,8 @@ public class ImsService extends Service {
         f.setSlotId(slotId);
         f.addImsFeatureStatusCallback(c);
         addImsFeature(slotId, featureType, f);
+        // TODO: Remove once new onFeatureReady AIDL is merged in.
+        f.onFeatureReady();
     }
 
     private void addImsFeature(int slotId, int featureType, ImsFeature f) {
@@ -236,4 +246,13 @@ public class ImsService extends Service {
     public @Nullable RcsFeature onCreateRcsFeature(int slotId) {
         return null;
     }
+
+    /**
+     * @param slotId The slot that is associated with the IMS Registration.
+     * @return the ImsRegistration implementation associated with the slot.
+     * @hide
+     */
+    public ImsRegistrationImplBase getRegistration(int slotId) {
+        return new ImsRegistrationImplBase();
+    }
 }
diff --git a/telephony/java/android/telephony/ims/feature/ImsFeature.java b/telephony/java/android/telephony/ims/feature/ImsFeature.java
index ca4a210e30cca..d47cea3097f3e 100644
--- a/telephony/java/android/telephony/ims/feature/ImsFeature.java
+++ b/telephony/java/android/telephony/ims/feature/ImsFeature.java
@@ -96,7 +96,7 @@ public abstract class ImsFeature {
             new WeakHashMap<IImsFeatureStatusCallback, Boolean>());
     private @ImsState int mState = STATE_NOT_AVAILABLE;
     private int mSlotId = SubscriptionManager.INVALID_SIM_SLOT_INDEX;
-    private Context mContext;
+    protected Context mContext;
 
     public void setContext(Context context) {
         mContext = context;
diff --git a/telephony/java/android/telephony/ims/internal/ImsService.java b/telephony/java/android/telephony/ims/internal/ImsService.java
index b7c8ca0f97991..afaf33294d8a4 100644
--- a/telephony/java/android/telephony/ims/internal/ImsService.java
+++ b/telephony/java/android/telephony/ims/internal/ImsService.java
@@ -24,7 +24,6 @@ import android.telephony.CarrierConfigManager;
 import android.telephony.ims.internal.aidl.IImsConfig;
 import android.telephony.ims.internal.aidl.IImsMmTelFeature;
 import android.telephony.ims.internal.aidl.IImsRcsFeature;
-import android.telephony.ims.internal.aidl.IImsRegistration;
 import android.telephony.ims.internal.aidl.IImsServiceController;
 import android.telephony.ims.internal.aidl.IImsServiceControllerListener;
 import android.telephony.ims.internal.feature.ImsFeature;
@@ -32,11 +31,12 @@ import android.telephony.ims.internal.feature.MmTelFeature;
 import android.telephony.ims.internal.feature.RcsFeature;
 import android.telephony.ims.internal.stub.ImsConfigImplBase;
 import android.telephony.ims.internal.stub.ImsFeatureConfiguration;
-import android.telephony.ims.internal.stub.ImsRegistrationImplBase;
+import android.telephony.ims.stub.ImsRegistrationImplBase;
 import android.util.Log;
 import android.util.SparseArray;
 
 import com.android.ims.internal.IImsFeatureStatusCallback;
+import com.android.ims.internal.IImsRegistration;
 import com.android.internal.annotations.VisibleForTesting;
 
 /**
diff --git a/telephony/java/android/telephony/ims/internal/aidl/IImsMmTelListener.aidl b/telephony/java/android/telephony/ims/internal/aidl/IImsMmTelListener.aidl
index 8332bc024e374..43f5098af3ca5 100644
--- a/telephony/java/android/telephony/ims/internal/aidl/IImsMmTelListener.aidl
+++ b/telephony/java/android/telephony/ims/internal/aidl/IImsMmTelListener.aidl
@@ -24,4 +24,5 @@ import com.android.ims.internal.IImsCallSession;
  */
 oneway interface IImsMmTelListener {
     void onIncomingCall(IImsCallSession c);
+    void onVoiceMessageCountUpdate(int count);
 }
\ No newline at end of file
diff --git a/telephony/java/android/telephony/ims/internal/aidl/IImsServiceController.aidl b/telephony/java/android/telephony/ims/internal/aidl/IImsServiceController.aidl
index 8afb95588b015..82a85254bbca7 100644
--- a/telephony/java/android/telephony/ims/internal/aidl/IImsServiceController.aidl
+++ b/telephony/java/android/telephony/ims/internal/aidl/IImsServiceController.aidl
@@ -18,12 +18,12 @@ package android.telephony.ims.internal.aidl;
 
 import android.telephony.ims.internal.aidl.IImsMmTelFeature;
 import android.telephony.ims.internal.aidl.IImsRcsFeature;
-import android.telephony.ims.internal.aidl.IImsRegistration;
 import android.telephony.ims.internal.aidl.IImsConfig;
 import android.telephony.ims.internal.aidl.IImsServiceControllerListener;
 import android.telephony.ims.internal.stub.ImsFeatureConfiguration;
 
 import com.android.ims.internal.IImsFeatureStatusCallback;
+import com.android.ims.internal.IImsRegistration;
 
 /**
  * See ImsService and MmTelFeature for more information.
diff --git a/telephony/java/android/telephony/ims/internal/feature/CapabilityChangeRequest.java b/telephony/java/android/telephony/ims/internal/feature/CapabilityChangeRequest.java
index 4d188734c10ed..5dbf077ee7c58 100644
--- a/telephony/java/android/telephony/ims/internal/feature/CapabilityChangeRequest.java
+++ b/telephony/java/android/telephony/ims/internal/feature/CapabilityChangeRequest.java
@@ -18,7 +18,7 @@ package android.telephony.ims.internal.feature;
 
 import android.os.Parcel;
 import android.os.Parcelable;
-import android.telephony.ims.internal.stub.ImsRegistrationImplBase;
+import android.telephony.ims.stub.ImsRegistrationImplBase;
 import android.util.ArraySet;
 
 import java.util.ArrayList;
diff --git a/telephony/java/android/telephony/ims/internal/feature/MmTelFeature.java b/telephony/java/android/telephony/ims/internal/feature/MmTelFeature.java
index 2f350c86a6f63..057c9a86d04e5 100644
--- a/telephony/java/android/telephony/ims/internal/feature/MmTelFeature.java
+++ b/telephony/java/android/telephony/ims/internal/feature/MmTelFeature.java
@@ -28,8 +28,8 @@ import android.telephony.ims.internal.aidl.IImsCallSessionListener;
 import android.telephony.ims.internal.aidl.IImsCapabilityCallback;
 import android.telephony.ims.internal.aidl.IImsMmTelFeature;
 import android.telephony.ims.internal.aidl.IImsMmTelListener;
-import android.telephony.ims.internal.stub.ImsRegistrationImplBase;
 import android.telephony.ims.internal.aidl.IImsSmsListener;
+import android.telephony.ims.stub.ImsRegistrationImplBase;
 import android.telephony.ims.stub.ImsEcbmImplBase;
 import android.telephony.ims.stub.ImsMultiEndpointImplBase;
 import android.telephony.ims.stub.ImsUtImplBase;
@@ -260,6 +260,15 @@ public class MmTelFeature extends ImsFeature {
             onIncomingCall(new ImsCallSession(c));
         }
 
+        /**
+         * Updates the Listener when the voice message count for IMS has changed.
+         * @param count an integer representing the new message count.
+         */
+        @Override
+        public void onVoiceMessageCountUpdate(int count) {
+
+        }
+
         /**
          * Called when the IMS provider receives an incoming call.
          * @param c The {@link ImsCallSession} associated with the new call.
diff --git a/telephony/java/android/telephony/ims/internal/stub/ImsRegistrationImplBase.java b/telephony/java/android/telephony/ims/stub/ImsRegistrationImplBase.java
similarity index 83%
rename from telephony/java/android/telephony/ims/internal/stub/ImsRegistrationImplBase.java
rename to telephony/java/android/telephony/ims/stub/ImsRegistrationImplBase.java
index 558b009ab4c26..42af08365f611 100644
--- a/telephony/java/android/telephony/ims/internal/stub/ImsRegistrationImplBase.java
+++ b/telephony/java/android/telephony/ims/stub/ImsRegistrationImplBase.java
@@ -14,16 +14,19 @@
  * limitations under the License
  */
 
-package android.telephony.ims.internal.stub;
+package android.telephony.ims.stub;
 
 import android.annotation.IntDef;
+import android.net.Uri;
+import android.os.IBinder;
 import android.os.RemoteCallbackList;
 import android.os.RemoteException;
-import android.telephony.ims.internal.aidl.IImsRegistration;
-import android.telephony.ims.internal.aidl.IImsRegistrationCallback;
 import android.util.Log;
 
 import com.android.ims.ImsReasonInfo;
+import com.android.ims.internal.IImsRegistration;
+import com.android.ims.internal.IImsRegistrationCallback;
+import com.android.internal.annotations.VisibleForTesting;
 
 import java.lang.annotation.Retention;
 import java.lang.annotation.RetentionPolicy;
@@ -62,23 +65,25 @@ public class ImsRegistrationImplBase {
 
     // Registration states, used to notify new ImsRegistrationImplBase#Callbacks of the current
     // state.
+    // The unknown state is set as the initialization state. This is so that we do not call back
+    // with NOT_REGISTERED in the case where the ImsService has not updated the registration state
+    // yet.
+    private static final int REGISTRATION_STATE_UNKNOWN = -1;
     private static final int REGISTRATION_STATE_NOT_REGISTERED = 0;
     private static final int REGISTRATION_STATE_REGISTERING = 1;
     private static final int REGISTRATION_STATE_REGISTERED = 2;
 
-
     /**
      * Callback class for receiving Registration callback events.
+     * @hide
      */
-    public static class Callback extends IImsRegistrationCallback.Stub {
-
+    public static class Callback {
         /**
          * Notifies the framework when the IMS Provider is connected to the IMS network.
          *
          * @param imsRadioTech the radio access technology. Valid values are defined in
          * {@link ImsRegistrationTech}.
          */
-        @Override
         public void onRegistered(@ImsRegistrationTech int imsRadioTech) {
         }
 
@@ -88,7 +93,6 @@ public class ImsRegistrationImplBase {
          * @param imsRadioTech the radio access technology. Valid values are defined in
          * {@link ImsRegistrationTech}.
          */
-        @Override
         public void onRegistering(@ImsRegistrationTech int imsRadioTech) {
         }
 
@@ -97,7 +101,6 @@ public class ImsRegistrationImplBase {
          *
          * @param info the {@link ImsReasonInfo} associated with why registration was disconnected.
          */
-        @Override
         public void onDeregistered(ImsReasonInfo info) {
         }
 
@@ -108,10 +111,19 @@ public class ImsRegistrationImplBase {
          * @param imsRadioTech The {@link ImsRegistrationTech} type that has failed
          * @param info A {@link ImsReasonInfo} that identifies the reason for failure.
          */
-        @Override
         public void onTechnologyChangeFailed(@ImsRegistrationTech int imsRadioTech,
                 ImsReasonInfo info) {
         }
+
+        /**
+         * Returns a list of subscriber {@link Uri}s associated with this IMS subscription when
+         * it changes.
+         * @param uris new array of subscriber {@link Uri}s that are associated with this IMS
+         *         subscription.
+         */
+        public void onSubscriberAssociatedUriChanged(Uri[] uris) {
+
+        }
     }
 
     private final IImsRegistration mBinder = new IImsRegistration.Stub() {
@@ -139,9 +151,9 @@ public class ImsRegistrationImplBase {
     private @ImsRegistrationTech
     int mConnectionType = REGISTRATION_TECH_NONE;
     // Locked on mLock
-    private int mRegistrationState = REGISTRATION_STATE_NOT_REGISTERED;
-    // Locked on mLock
-    private ImsReasonInfo mLastDisconnectCause;
+    private int mRegistrationState = REGISTRATION_STATE_UNKNOWN;
+    // Locked on mLock, create unspecified disconnect cause.
+    private ImsReasonInfo mLastDisconnectCause = new ImsReasonInfo();
 
     public final IImsRegistration getBinder() {
         return mBinder;
@@ -221,6 +233,17 @@ public class ImsRegistrationImplBase {
         });
     }
 
+    public final void onSubscriberAssociatedUriChanged(Uri[] uris) {
+        mCallbacks.broadcast((c) -> {
+            try {
+                c.onSubscriberAssociatedUriChanged(uris);
+            } catch (RemoteException e) {
+                Log.w(LOG_TAG, e + " " + "onSubscriberAssociatedUriChanged() - Skipping " +
+                        "callback.");
+            }
+        });
+    }
+
     private void updateToState(@ImsRegistrationTech int connType, int newState) {
         synchronized (mLock) {
             mConnectionType = connType;
@@ -241,7 +264,8 @@ public class ImsRegistrationImplBase {
         }
     }
 
-    private @ImsRegistrationTech int getConnectionType() {
+    @VisibleForTesting
+    public final @ImsRegistrationTech int getConnectionType() {
         synchronized (mLock) {
             return mConnectionType;
         }
@@ -271,6 +295,10 @@ public class ImsRegistrationImplBase {
                 c.onRegistered(getConnectionType());
                 break;
             }
+            case REGISTRATION_STATE_UNKNOWN: {
+                // Do not callback if the state has not been updated yet by the ImsService.
+                break;
+            }
         }
     }
 }
diff --git a/telephony/java/android/telephony/ims/internal/aidl/IImsRegistration.aidl b/telephony/java/com/android/ims/internal/IImsRegistration.aidl
similarity index 83%
rename from telephony/java/android/telephony/ims/internal/aidl/IImsRegistration.aidl
rename to telephony/java/com/android/ims/internal/IImsRegistration.aidl
index 687b7ca408d52..6de264ec90fbf 100644
--- a/telephony/java/android/telephony/ims/internal/aidl/IImsRegistration.aidl
+++ b/telephony/java/com/android/ims/internal/IImsRegistration.aidl
@@ -15,10 +15,9 @@
  */
 
 
-package android.telephony.ims.internal.aidl;
+package com.android.ims.internal;
 
-import android.telephony.ims.internal.aidl.IImsRegistrationCallback;
-import android.telephony.ims.internal.stub.ImsFeatureConfiguration;
+import com.android.ims.internal.IImsRegistrationCallback;
 
 /**
  * See ImsRegistration for more information.
diff --git a/telephony/java/android/telephony/ims/internal/aidl/IImsRegistrationCallback.aidl b/telephony/java/com/android/ims/internal/IImsRegistrationCallback.aidl
similarity index 90%
rename from telephony/java/android/telephony/ims/internal/aidl/IImsRegistrationCallback.aidl
rename to telephony/java/com/android/ims/internal/IImsRegistrationCallback.aidl
index a50575b968655..5f21167422dcf 100644
--- a/telephony/java/android/telephony/ims/internal/aidl/IImsRegistrationCallback.aidl
+++ b/telephony/java/com/android/ims/internal/IImsRegistrationCallback.aidl
@@ -15,8 +15,9 @@
  */
 
 
-package android.telephony.ims.internal.aidl;
+package com.android.ims.internal;
 
+import android.net.Uri;
 import android.telephony.ims.internal.stub.ImsFeatureConfiguration;
 
 import com.android.ims.ImsReasonInfo;
@@ -31,4 +32,5 @@ oneway interface IImsRegistrationCallback {
    void onRegistering(int imsRadioTech);
    void onDeregistered(in ImsReasonInfo info);
    void onTechnologyChangeFailed(int imsRadioTech, in ImsReasonInfo info);
+   void onSubscriberAssociatedUriChanged(in Uri[] uris);
 }
\ No newline at end of file
diff --git a/telephony/java/com/android/ims/internal/IImsServiceController.aidl b/telephony/java/com/android/ims/internal/IImsServiceController.aidl
index 857089fac33aa..7ac25ac13fbe3 100644
--- a/telephony/java/com/android/ims/internal/IImsServiceController.aidl
+++ b/telephony/java/com/android/ims/internal/IImsServiceController.aidl
@@ -18,6 +18,7 @@ package com.android.ims.internal;
 
 import com.android.ims.internal.IImsFeatureStatusCallback;
 import com.android.ims.internal.IImsMMTelFeature;
+import com.android.ims.internal.IImsRegistration;
 import com.android.ims.internal.IImsRcsFeature;
 
 /**
@@ -29,4 +30,5 @@ interface IImsServiceController {
     IImsMMTelFeature createMMTelFeature(int slotId, in IImsFeatureStatusCallback c);
     IImsRcsFeature createRcsFeature(int slotId, in IImsFeatureStatusCallback c);
     void removeImsFeature(int slotId, int featureType, in IImsFeatureStatusCallback c);
+    IImsRegistration getRegistration(int slotId);
 }
diff --git a/telephony/java/com/android/internal/telephony/ITelephony.aidl b/telephony/java/com/android/internal/telephony/ITelephony.aidl
index 416146fcb98ec..fba82ee17f776 100644
--- a/telephony/java/com/android/internal/telephony/ITelephony.aidl
+++ b/telephony/java/com/android/internal/telephony/ITelephony.aidl
@@ -40,6 +40,7 @@ import android.telephony.TelephonyHistogram;
 import android.telephony.VisualVoicemailSmsFilterSettings;
 import com.android.ims.internal.IImsMMTelFeature;
 import com.android.ims.internal.IImsRcsFeature;
+import com.android.ims.internal.IImsRegistration;
 import com.android.ims.internal.IImsServiceFeatureCallback;
 import com.android.internal.telephony.CellNetworkScanResult;
 import com.android.internal.telephony.OperatorInfo;
@@ -807,6 +808,11 @@ interface ITelephony {
      */
     IImsRcsFeature getRcsFeatureAndListen(int slotId, in IImsServiceFeatureCallback callback);
 
+    /**
+    * Returns the IImsRegistration associated with the slot and feature specified.
+    */
+    IImsRegistration getImsRegistration(int slotId, int feature);
+
     /**
      * Set the network selection mode to automatic.
      *