diff --git a/api/current.txt b/api/current.txt
index 81088ab85ba6c..dbbdce9b61b0d 100644
--- a/api/current.txt
+++ b/api/current.txt
@@ -46086,6 +46086,7 @@ package android.telecom {
     field public static final int MISSED = 5; // 0x5
     field public static final int OTHER = 9; // 0x9
     field public static final String REASON_EMERGENCY_CALL_PLACED = "REASON_EMERGENCY_CALL_PLACED";
+    field public static final String REASON_EMULATING_SINGLE_CALL = "EMULATING_SINGLE_CALL";
     field public static final String REASON_IMS_ACCESS_BLOCKED = "REASON_IMS_ACCESS_BLOCKED";
     field public static final String REASON_WIFI_ON_BUT_WFC_OFF = "REASON_WIFI_ON_BUT_WFC_OFF";
     field public static final int REJECTED = 6; // 0x6
diff --git a/api/system-current.txt b/api/system-current.txt
index c4f9067b507d1..a02f393aeceff 100644
--- a/api/system-current.txt
+++ b/api/system-current.txt
@@ -10437,10 +10437,6 @@ package android.telecom {
     method public final void addExistingConnection(@NonNull android.telecom.PhoneAccountHandle, @NonNull android.telecom.Connection, @NonNull android.telecom.Conference);
   }
 
-  public final class DisconnectCause implements android.os.Parcelable {
-    field public static final String REASON_EMULATING_SINGLE_CALL = "EMULATING_SINGLE_CALL";
-  }
-
   public abstract class InCallService extends android.app.Service {
     method @Deprecated public android.telecom.Phone getPhone();
     method @Deprecated public void onPhoneCreated(android.telecom.Phone);
diff --git a/non-updatable-api/current.txt b/non-updatable-api/current.txt
index bcc239f35afee..db5cd150a0799 100644
--- a/non-updatable-api/current.txt
+++ b/non-updatable-api/current.txt
@@ -44223,6 +44223,7 @@ package android.telecom {
     field public static final int MISSED = 5; // 0x5
     field public static final int OTHER = 9; // 0x9
     field public static final String REASON_EMERGENCY_CALL_PLACED = "REASON_EMERGENCY_CALL_PLACED";
+    field public static final String REASON_EMULATING_SINGLE_CALL = "EMULATING_SINGLE_CALL";
     field public static final String REASON_IMS_ACCESS_BLOCKED = "REASON_IMS_ACCESS_BLOCKED";
     field public static final String REASON_WIFI_ON_BUT_WFC_OFF = "REASON_WIFI_ON_BUT_WFC_OFF";
     field public static final int REJECTED = 6; // 0x6
diff --git a/non-updatable-api/system-current.txt b/non-updatable-api/system-current.txt
index 10fe058bb76f2..215078a82c176 100644
--- a/non-updatable-api/system-current.txt
+++ b/non-updatable-api/system-current.txt
@@ -9299,10 +9299,6 @@ package android.telecom {
     method public final void addExistingConnection(@NonNull android.telecom.PhoneAccountHandle, @NonNull android.telecom.Connection, @NonNull android.telecom.Conference);
   }
 
-  public final class DisconnectCause implements android.os.Parcelable {
-    field public static final String REASON_EMULATING_SINGLE_CALL = "EMULATING_SINGLE_CALL";
-  }
-
   public abstract class InCallService extends android.app.Service {
     method @Deprecated public android.telecom.Phone getPhone();
     method @Deprecated public void onPhoneCreated(android.telecom.Phone);
diff --git a/telecomm/java/android/telecom/DisconnectCause.java b/telecomm/java/android/telecom/DisconnectCause.java
index f7fe1ba1f998b..1472a4ac27bc1 100644
--- a/telecomm/java/android/telecom/DisconnectCause.java
+++ b/telecomm/java/android/telecom/DisconnectCause.java
@@ -16,7 +16,6 @@
 
 package android.telecom;
 
-import android.annotation.SystemApi;
 import android.media.ToneGenerator;
 import android.os.Parcel;
 import android.os.Parcelable;
@@ -97,10 +96,7 @@ public final class DisconnectCause implements Parcelable {
      *
      * This reason code is only used for communication between a {@link ConnectionService} and
      * Telecom and should not be surfaced to the user.
-     *
-     * @hide
      */
-    @SystemApi
     public static final String REASON_EMULATING_SINGLE_CALL = "EMULATING_SINGLE_CALL";
 
     /**
diff --git a/telecomm/java/android/telecom/PhoneAccount.java b/telecomm/java/android/telecom/PhoneAccount.java
index c20e5ad8ce7c5..4a3561b5d509e 100644
--- a/telecomm/java/android/telecom/PhoneAccount.java
+++ b/telecomm/java/android/telecom/PhoneAccount.java
@@ -28,6 +28,7 @@ import android.net.Uri;
 import android.os.Bundle;
 import android.os.Parcel;
 import android.os.Parcelable;
+import android.telephony.TelephonyManager;
 import android.text.TextUtils;
 
 import java.util.ArrayList;
@@ -52,8 +53,17 @@ public final class PhoneAccount implements Parcelable {
      *
      * This is an extras key set via {@link Builder#setExtras} which determines the order in which
      * {@link PhoneAccount}s from the same {@link ConnectionService} are sorted. The accounts
-     * are sorted by this key via standard lexicographical order, and this ordering is used to
+     * are sorted by this key via standard lexicographical order, (as implemented in
+     * {@link String#compareTo}), and this ordering is used to
      * determine priority when a call can be placed via multiple accounts.
+     *
+     * When multiple {@link PhoneAccount}s are supplied with the same sort order key, no ordering is
+     * guaranteed between those {@link PhoneAccount}s. Additionally, no ordering is guaranteed
+     * between {@link PhoneAccount}s that do not supply this extra, and all such accounts
+     * will be sorted after the accounts that do supply this extra.
+     *
+     * An example of a sort order key is slot index (see {@link TelephonyManager#getSlotIndex()}),
+     * which is the one used by the cell Telephony stack.
      * @hide
      */
     @SystemApi