diff --git a/src/com/android/phone/ImsRcsController.java b/src/com/android/phone/ImsRcsController.java
index 7d594d1..3618d58 100644
--- a/src/com/android/phone/ImsRcsController.java
+++ b/src/com/android/phone/ImsRcsController.java
@@ -582,6 +582,7 @@
             throw new SecurityException("Passed in PackageName can not be found on device");
         }
 
+        final int uid = Binder.getCallingUid();
         final long identity = Binder.clearCallingIdentity();
         SipTransportController transport = getRcsFeatureController(subId).getFeature(
                 SipTransportController.class);
@@ -590,7 +591,7 @@
                     "This subscription does not support the creation of SIP delegates");
         }
         try {
-            transport.createSipDelegate(subId, request, packageName, delegateState,
+            transport.createSipDelegate(subId, uid, request, packageName, delegateState,
                     delegateMessage);
         } catch (ImsException e) {
             throw new ServiceSpecificException(e.getCode(), e.getMessage());
diff --git a/src/com/android/services/telephony/rcs/DelegateStateTracker.java b/src/com/android/services/telephony/rcs/DelegateStateTracker.java
index 18aab88..64090d5 100644
--- a/src/com/android/services/telephony/rcs/DelegateStateTracker.java
+++ b/src/com/android/services/telephony/rcs/DelegateStateTracker.java
@@ -16,6 +16,10 @@
 
 package com.android.services.telephony.rcs;
 
+import android.app.compat.CompatChanges;
+import android.compat.annotation.ChangeId;
+import android.compat.annotation.EnabledAfter;
+import android.os.Build;
 import android.os.RemoteException;
 import android.telephony.ims.DelegateRegistrationState;
 import android.telephony.ims.FeatureTagState;
@@ -28,6 +32,7 @@
 import android.util.LocalLog;
 import android.util.Log;
 
+import com.android.internal.annotations.VisibleForTesting;
 import com.android.internal.telephony.metrics.RcsStats;
 
 import java.io.PrintWriter;
@@ -43,25 +48,58 @@
     private static final String LOG_TAG = "DelegateST";
 
     private final int mSubId;
+    private final int mUid;
     private final ISipDelegateConnectionStateCallback mAppStateCallback;
     private final ISipDelegate mLocalDelegateImpl;
 
     private final LocalLog mLocalLog = new LocalLog(SipTransportController.LOG_SIZE);
 
+    private final RcsStats mRcsStats;
+
     private List<FeatureTagState> mDelegateDeniedTags;
     private DelegateRegistrationState mLastRegState;
     private boolean mCreatedCalled = false;
     private int mRegistrationStateOverride = -1;
-
+    private CompatChangesFactory mCompatChangesFactory;
     private Set<String> mDelegateSupportedTags;
-    private final RcsStats mRcsStats;
 
-    public DelegateStateTracker(int subId, ISipDelegateConnectionStateCallback appStateCallback,
+    /**
+     * Interface for checking compatibility of apps
+     */
+    public interface CompatChangesFactory {
+        /**
+         *  @param changeId The ID of the compatibility change.
+         *  @param uid      The UID of the app.
+         *  @return {@code true} if the change is enabled for the current app.
+         */
+        boolean isChangeEnabled(long changeId, int uid);
+    }
+
+    /**
+     * For apps targeting Android T and above, support the REGISTERING state on APIs, such as
+     * {@code DelegateRegistrationState#addRegisteringFeatureTags} and
+     * {@code DelegateRegistrationState#getRegisteringFeatureTags}
+     * @hide
+     */
+    @ChangeId
+    @EnabledAfter(targetSdkVersion = Build.VERSION_CODES.S)
+    @VisibleForTesting
+    public static final long SUPPORT_REGISTERING_DELEGATE_STATE = 205194548;
+
+    public DelegateStateTracker(int subId, int uid,
+            ISipDelegateConnectionStateCallback appStateCallback,
             ISipDelegate localDelegateImpl, RcsStats rcsStats) {
         mSubId = subId;
+        mUid = uid;
         mAppStateCallback = appStateCallback;
         mLocalDelegateImpl = localDelegateImpl;
         mRcsStats = rcsStats;
+        setCompatChangesFactory((changeId, uid1) -> CompatChanges.isChangeEnabled(changeId, uid1));
+    }
+
+    @VisibleForTesting
+    protected void setCompatChangesFactory(CompatChangesFactory factory) {
+        mCompatChangesFactory = factory;
     }
 
     /**
@@ -140,6 +178,9 @@
      */
     @Override
     public void onRegistrationStateChanged(DelegateRegistrationState registrationState) {
+        if (!mCompatChangesFactory.isChangeEnabled(SUPPORT_REGISTERING_DELEGATE_STATE, mUid)) {
+            registrationState = overrideRegistrationForCompatibility(registrationState);
+        }
         if (mRegistrationStateOverride > DelegateRegistrationState.DEREGISTERED_REASON_UNKNOWN) {
             logi("onRegistrationStateChanged: overriding registered state to "
                     + mRegistrationStateOverride);
@@ -204,6 +245,7 @@
     private DelegateRegistrationState overrideRegistrationForDelegateChange(
             int registerOverrideReason, DelegateRegistrationState state) {
         Set<String> registeredFeatures = state.getRegisteredFeatureTags();
+        Set<String> registeringFeatures = state.getRegisteringFeatureTags();
         DelegateRegistrationState.Builder overriddenState = new DelegateRegistrationState.Builder();
         // keep other deregistering/deregistered tags the same.
         for (FeatureTagState dereging : state.getDeregisteringFeatureTags()) {
@@ -214,13 +256,41 @@
             overriddenState.addDeregisteredFeatureTag(dereged.getFeatureTag(),
                     dereged.getState());
         }
-        // Override REGISTERED only
+        // Override REGISTERING/REGISTERED
+        for (String ft : registeringFeatures) {
+            overriddenState.addDeregisteringFeatureTag(ft, registerOverrideReason);
+        }
         for (String ft : registeredFeatures) {
             overriddenState.addDeregisteringFeatureTag(ft, registerOverrideReason);
         }
         return overriddenState.build();
     }
 
+    private DelegateRegistrationState overrideRegistrationForCompatibility(
+            DelegateRegistrationState state) {
+        Set<String> registeredFeatures = state.getRegisteredFeatureTags();
+        Set<String> registeringFeatures = state.getRegisteringFeatureTags();
+        DelegateRegistrationState.Builder overriddenState = new DelegateRegistrationState.Builder();
+        // keep other registered/deregistering/deregistered tags the same.
+        for (FeatureTagState dereging : state.getDeregisteringFeatureTags()) {
+            overriddenState.addDeregisteringFeatureTag(dereging.getFeatureTag(),
+                    dereging.getState());
+        }
+        for (FeatureTagState dereged : state.getDeregisteredFeatureTags()) {
+            overriddenState.addDeregisteredFeatureTag(dereged.getFeatureTag(),
+                    dereged.getState());
+        }
+        overriddenState.addRegisteredFeatureTags(registeredFeatures);
+
+        // move the REGISTERING state to the DEREGISTERED state.
+        for (String tag : registeringFeatures) {
+            overriddenState.addDeregisteredFeatureTag(tag,
+                    DelegateRegistrationState.DEREGISTERED_REASON_NOT_REGISTERED);
+        }
+
+        return overriddenState.build();
+    }
+
     private void notifySipDelegateCreated() {
         try {
             mAppStateCallback.onCreated(mLocalDelegateImpl);
diff --git a/src/com/android/services/telephony/rcs/SipDelegateController.java b/src/com/android/services/telephony/rcs/SipDelegateController.java
index c728141..860a6d9 100644
--- a/src/com/android/services/telephony/rcs/SipDelegateController.java
+++ b/src/com/android/services/telephony/rcs/SipDelegateController.java
@@ -78,6 +78,7 @@
     }
 
     private final int mSubId;
+    private final int mUid;
     private final String mPackageName;
     private final DelegateRequest mInitialRequest;
     private final ScheduledExecutorService mExecutorService;
@@ -89,12 +90,13 @@
     private DelegateBinderStateManager mBinderConnection;
     private Set<String> mTrackedFeatureTags;
 
-    public SipDelegateController(int subId, DelegateRequest initialRequest, String packageName,
-            ISipTransport transportImpl, IImsRegistration registrationImpl,
+    public SipDelegateController(int subId, int uid, DelegateRequest initialRequest,
+            String packageName, ISipTransport transportImpl, IImsRegistration registrationImpl,
             ScheduledExecutorService executorService,
             ISipDelegateConnectionStateCallback stateCallback,
             ISipDelegateMessageCallback messageCallback) {
         mSubId = subId;
+        mUid = uid;
         mPackageName = packageName;
         mInitialRequest = initialRequest;
         mExecutorService = executorService;
@@ -102,7 +104,8 @@
 
         mMessageTransportWrapper = new MessageTransportWrapper(mSubId, executorService,
                 messageCallback);
-        mDelegateStateTracker = new DelegateStateTracker(mSubId, stateCallback,
+
+        mDelegateStateTracker = new DelegateStateTracker(mSubId, mUid, stateCallback,
                 mMessageTransportWrapper.getDelegateConnection(), RcsStats.getInstance());
     }
 
@@ -110,12 +113,13 @@
      * Inject dependencies for testing only.
      */
     @VisibleForTesting
-    public SipDelegateController(int subId, DelegateRequest initialRequest, String packageName,
-            ScheduledExecutorService executorService,
+    public SipDelegateController(int subId, int uid, DelegateRequest initialRequest,
+            String packageName, ScheduledExecutorService executorService,
             MessageTransportWrapper messageTransportWrapper,
             DelegateStateTracker delegateStateTracker,
             DelegateBinderStateManager.Factory connectionFactory) {
         mSubId = subId;
+        mUid = uid;
         mInitialRequest = initialRequest;
         mPackageName = packageName;
         mExecutorService = executorService;
diff --git a/src/com/android/services/telephony/rcs/SipTransportController.java b/src/com/android/services/telephony/rcs/SipTransportController.java
index 709e142..0aa3aa0 100644
--- a/src/com/android/services/telephony/rcs/SipTransportController.java
+++ b/src/com/android/services/telephony/rcs/SipTransportController.java
@@ -243,9 +243,9 @@
     @VisibleForTesting
     public interface SipDelegateControllerFactory {
         /** See {@link SipDelegateController} */
-        SipDelegateController create(int subId, DelegateRequest initialRequest, String packageName,
-                ISipTransport sipTransportImpl,  IImsRegistration registrationImpl,
-                ScheduledExecutorService executorService,
+        SipDelegateController create(int subId, int uid, DelegateRequest initialRequest,
+                String packageName, ISipTransport sipTransportImpl,
+                IImsRegistration registrationImpl, ScheduledExecutorService executorService,
                 ISipDelegateConnectionStateCallback stateCallback,
                 ISipDelegateMessageCallback messageCallback);
     }
@@ -364,17 +364,18 @@
      * {@link ISipDelegateConnectionStateCallback#onCreated(ISipDelegate)} must be called with
      * the AIDL instance corresponding to the remote {@link SipDelegate}.
      * @param subId the subId associated with the request.
+     * @param uid the uid associated with the request
      * @param request The request parameters used to create the {@link SipDelegate}.
      * @param delegateState The {@link DelegateConnectionStateCallback} Binder connection.
      * @param delegateMessage The {@link DelegateConnectionMessageCallback} Binder Connection
      * @throws ImsException if the request to create the {@link SipDelegate} did not complete.
      */
-    public void createSipDelegate(int subId, DelegateRequest request, String packageName,
+    public void createSipDelegate(int subId, int uid, DelegateRequest request, String packageName,
             ISipDelegateConnectionStateCallback delegateState,
             ISipDelegateMessageCallback delegateMessage) throws ImsException {
         logi("createSipDelegate: request= " + request + ", packageName= " + packageName);
         CompletableFuture<ImsException> result = new CompletableFuture<>();
-        mExecutorService.submit(() -> createSipDelegateInternal(subId, request, packageName,
+        mExecutorService.submit(() -> createSipDelegateInternal(subId, uid, request, packageName,
                 delegateState,
                 // Capture any ImsExceptions generated during the process.
                 delegateMessage, result::complete));
@@ -423,8 +424,8 @@
         return result;
     }
 
-    private void createSipDelegateInternal(int subId, DelegateRequest request, String packageName,
-            ISipDelegateConnectionStateCallback delegateState,
+    private void createSipDelegateInternal(int subId, int uid, DelegateRequest request,
+            String packageName, ISipDelegateConnectionStateCallback delegateState,
             ISipDelegateMessageCallback delegateMessage,
             Consumer<ImsException> startedErrorConsumer) {
         ISipTransport transport;
@@ -450,8 +451,9 @@
             return;
         }
 
-        SipDelegateController c = mDelegateControllerFactory.create(subId, request, packageName,
-                transport, registration, mExecutorService, delegateState, delegateMessage);
+        SipDelegateController c = mDelegateControllerFactory.create(subId, uid, request,
+                packageName, transport, registration, mExecutorService, delegateState,
+                delegateMessage);
         logi("createSipDelegateInternal: request= " + request + ", packageName= " + packageName
                 + ", controller created: " + c);
         addPendingCreateAndEvaluate(c);