diff --git a/telecomm/java/android/telecom/Conference.java b/telecomm/java/android/telecom/Conference.java
index a39e885..7d1f8ce 100644
--- a/telecomm/java/android/telecom/Conference.java
+++ b/telecomm/java/android/telecom/Conference.java
@@ -19,6 +19,7 @@
 import android.annotation.NonNull;
 import android.annotation.Nullable;
 import android.annotation.SystemApi;
+import android.net.Uri;
 import android.os.Bundle;
 import android.os.SystemClock;
 import android.telecom.Connection.VideoProvider;
@@ -64,6 +65,10 @@
         public void onStatusHintsChanged(Conference conference, StatusHints statusHints) {}
         public void onExtrasChanged(Conference c, Bundle extras) {}
         public void onExtrasRemoved(Conference c, List<String> keys) {}
+        public void onConferenceStateChanged(Conference c, boolean isConference) {}
+        public void onAddressChanged(Conference c, Uri newAddress, int presentation) {}
+        public void onCallerDisplayNameChanged(
+                Conference c, String callerDisplayName, int presentation) {}
     }
 
     private final Set<Listener> mListeners = new CopyOnWriteArraySet<>();
@@ -946,6 +951,62 @@
     public void onExtrasChanged(Bundle extras) {}
 
     /**
+     * Set whether Telecom should treat this {@link Conference} as a conference call or if it
+     * should treat it as a single-party call.
+     * This method is used as part of a workaround regarding IMS conference calls and user
+     * expectation.  In IMS, once a conference is formed, the UE is connected to an IMS conference
+     * server.  If all participants of the conference drop out of the conference except for one, the
+     * UE is still connected to the IMS conference server.  At this point, the user logically
+     * assumes they're no longer in a conference, yet the underlying network actually is.
+     * To help provide a better user experiece, IMS conference calls can pretend to actually be a
+     * single-party call when the participant count drops to 1.  Although the dialer/phone app
+     * could perform this trickery, it makes sense to do this in Telephony since a fix there will
+     * ensure that bluetooth head units, auto and wearable apps all behave consistently.
+     *
+     * @param isConference {@code true} if this {@link Conference} should be treated like a
+     *      conference call, {@code false} if it should be treated like a single-party call.
+     * @hide
+     */
+    public void setConferenceState(boolean isConference) {
+        for (Listener l : mListeners) {
+            l.onConferenceStateChanged(this, isConference);
+        }
+    }
+
+    /**
+     * Sets the address of this {@link Conference}.  Used when {@link #setConferenceState(boolean)}
+     * is called to mark a conference temporarily as NOT a conference.
+     *
+     * @param address The new address.
+     * @param presentation The presentation requirements for the address.
+     *        See {@link TelecomManager} for valid values.
+     * @hide
+     */
+    public final void setAddress(Uri address, int presentation) {
+        Log.d(this, "setAddress %s", address);
+        for (Listener l : mListeners) {
+            l.onAddressChanged(this, address, presentation);
+        }
+    }
+
+    /**
+     * Sets the caller display name (CNAP) of this {@link Conference}.  Used when
+     * {@link #setConferenceState(boolean)} is called to mark a conference temporarily as NOT a
+     * conference.
+     *
+     * @param callerDisplayName The new display name.
+     * @param presentation The presentation requirements for the handle.
+     *        See {@link TelecomManager} for valid values.
+     * @hide
+     */
+    public final void setCallerDisplayName(String callerDisplayName, int presentation) {
+        Log.d(this, "setCallerDisplayName %s", callerDisplayName);
+        for (Listener l : mListeners) {
+            l.onCallerDisplayNameChanged(this, callerDisplayName, presentation);
+        }
+    }
+
+    /**
      * Handles a change to extras received from Telecom.
      *
      * @param extras The new extras.
diff --git a/telecomm/java/android/telecom/ConnectionService.java b/telecomm/java/android/telecom/ConnectionService.java
index 4c2d22f..82db0d2 100644
--- a/telecomm/java/android/telecom/ConnectionService.java
+++ b/telecomm/java/android/telecom/ConnectionService.java
@@ -1254,6 +1254,31 @@
                 mAdapter.removeExtras(id, keys);
             }
         }
+
+        @Override
+        public void onConferenceStateChanged(Conference c, boolean isConference) {
+            String id = mIdByConference.get(c);
+            if (id != null) {
+                mAdapter.setConferenceState(id, isConference);
+            }
+        }
+
+        @Override
+        public void onAddressChanged(Conference c, Uri newAddress, int presentation) {
+            String id = mIdByConference.get(c);
+            if (id != null) {
+                mAdapter.setAddress(id, newAddress, presentation);
+            }
+        }
+
+        @Override
+        public void onCallerDisplayNameChanged(Conference c, String callerDisplayName,
+                int presentation) {
+            String id = mIdByConference.get(c);
+            if (id != null) {
+                mAdapter.setCallerDisplayName(id, callerDisplayName, presentation);
+            }
+        }
     };
 
     private final Connection.Listener mConnectionListener = new Connection.Listener() {
diff --git a/telecomm/java/android/telecom/ConnectionServiceAdapter.java b/telecomm/java/android/telecom/ConnectionServiceAdapter.java
index 520e7ed..6c3f4f3 100644
--- a/telecomm/java/android/telecom/ConnectionServiceAdapter.java
+++ b/telecomm/java/android/telecom/ConnectionServiceAdapter.java
@@ -653,4 +653,22 @@
             }
         }
     }
+
+    /**
+     * Sets whether a conference is treated as a conference or a single party call.
+     * See {@link Conference#setConferenceState(boolean)} for more information.
+     *
+     * @param callId The ID of the telecom call.
+     * @param isConference {@code true} if this call should be treated as a conference,
+     * {@code false} otherwise.
+     */
+    void setConferenceState(String callId, boolean isConference) {
+        Log.v(this, "setConferenceState: %s %b", callId, isConference);
+        for (IConnectionServiceAdapter adapter : mAdapters) {
+            try {
+                adapter.setConferenceState(callId, isConference, Log.getExternalSession());
+            } catch (RemoteException ignored) {
+            }
+        }
+    }
 }
diff --git a/telecomm/java/android/telecom/ConnectionServiceAdapterServant.java b/telecomm/java/android/telecom/ConnectionServiceAdapterServant.java
index 78d65e6..f99b218 100644
--- a/telecomm/java/android/telecom/ConnectionServiceAdapterServant.java
+++ b/telecomm/java/android/telecom/ConnectionServiceAdapterServant.java
@@ -74,6 +74,7 @@
     private static final int MSG_ON_RTT_UPGRADE_REQUEST = 33;
     private static final int MSG_SET_PHONE_ACCOUNT_CHANGED = 34;
     private static final int MSG_CONNECTION_SERVICE_FOCUS_RELEASED = 35;
+    private static final int MSG_SET_CONFERENCE_STATE = 36;
 
     private final IConnectionServiceAdapter mDelegate;
 
@@ -333,6 +334,14 @@
                 case MSG_CONNECTION_SERVICE_FOCUS_RELEASED:
                     mDelegate.onConnectionServiceFocusReleased(null /*Session.Info*/);
                     break;
+                case MSG_SET_CONFERENCE_STATE:
+                    SomeArgs args = (SomeArgs) msg.obj;
+                    try {
+                        mDelegate.setConferenceState((String) args.arg1, (Boolean) args.arg2,
+                                (Session.Info) args.arg3);
+                    } finally {
+                        args.recycle();
+                    }
             }
         }
     };
@@ -615,6 +624,16 @@
         public void resetConnectionTime(String callId, Session.Info sessionInfo) {
             // Do nothing
         }
+
+        @Override
+        public void setConferenceState(String callId, boolean isConference,
+                Session.Info sessionInfo) {
+            SomeArgs args = SomeArgs.obtain();
+            args.arg1 = callId;
+            args.arg2 = isConference;
+            args.arg3 = sessionInfo;
+            mHandler.obtainMessage(MSG_SET_CONFERENCE_STATE, args).sendToTarget();
+        }
     };
 
     public ConnectionServiceAdapterServant(IConnectionServiceAdapter delegate) {
diff --git a/telecomm/java/android/telecom/RemoteConnectionService.java b/telecomm/java/android/telecom/RemoteConnectionService.java
index 9821dcb..744544e 100644
--- a/telecomm/java/android/telecom/RemoteConnectionService.java
+++ b/telecomm/java/android/telecom/RemoteConnectionService.java
@@ -471,6 +471,12 @@
         public void resetConnectionTime(String callId, Session.Info sessionInfo) {
             // Do nothing
         }
+
+        @Override
+        public void setConferenceState(String callId, boolean isConference,
+                Session.Info sessionInfo) {
+            // Do nothing
+        }
     };
 
     private final ConnectionServiceAdapterServant mServant =
diff --git a/telecomm/java/com/android/internal/telecom/IConnectionServiceAdapter.aidl b/telecomm/java/com/android/internal/telecom/IConnectionServiceAdapter.aidl
index 0157a58..76ac88e 100644
--- a/telecomm/java/com/android/internal/telecom/IConnectionServiceAdapter.aidl
+++ b/telecomm/java/com/android/internal/telecom/IConnectionServiceAdapter.aidl
@@ -123,4 +123,6 @@
     void onConnectionServiceFocusReleased(in Session.Info sessionInfo);
 
     void resetConnectionTime(String callIdi, in Session.Info sessionInfo);
+
+    void setConferenceState(String callId, boolean isConference, in Session.Info sessionInfo);
 }