diff --git a/framework/src/android/net/NetworkCapabilities.java b/framework/src/android/net/NetworkCapabilities.java
index 17fc3b4..ae5cfda 100644
--- a/framework/src/android/net/NetworkCapabilities.java
+++ b/framework/src/android/net/NetworkCapabilities.java
@@ -1055,6 +1055,14 @@
         return isValidTransport(transportType) && ((mTransportTypes & (1 << transportType)) != 0);
     }
 
+    /**
+     * Returns true iff this NetworkCapabilities has the specified transport and no other.
+     * @hide
+     */
+    public boolean hasSingleTransport(@Transport int transportType) {
+        return mTransportTypes == (1 << transportType);
+    }
+
     private void combineTransportTypes(NetworkCapabilities nc) {
         this.mTransportTypes |= nc.mTransportTypes;
     }
diff --git a/service/ServiceConnectivityResources/res/values/config.xml b/service/ServiceConnectivityResources/res/values/config.xml
index b22457a..f8f86a2 100644
--- a/service/ServiceConnectivityResources/res/values/config.xml
+++ b/service/ServiceConnectivityResources/res/values/config.xml
@@ -125,4 +125,15 @@
          details on what is happening. -->
     <bool name="config_partialConnectivityNotifiedAsNoInternet">false</bool>
 
+    <!-- Whether the cell radio of the device is capable of timesharing.
+
+         Whether the cell radio is capable of timesharing between two different networks
+         even for a few seconds. When this is false, the networking stack will ask telephony
+         networks to disconnect immediately, instead of lingering, when outscored by some
+         other telephony network (typically on another subscription). This deprives apps
+         of a chance to gracefully migrate to the new network and degrades the experience
+         for apps, so it should only be set to false when timesharing on the cell radio has
+         extreme adverse effects on performance of the new network.
+    -->
+    <bool translatable="false" name="config_cellular_radio_timesharing_capable">true</bool>
 </resources>
diff --git a/service/ServiceConnectivityResources/res/values/overlayable.xml b/service/ServiceConnectivityResources/res/values/overlayable.xml
index 5af13d7..e5010d7 100644
--- a/service/ServiceConnectivityResources/res/values/overlayable.xml
+++ b/service/ServiceConnectivityResources/res/values/overlayable.xml
@@ -36,6 +36,7 @@
             <item type="bool" name="config_partialConnectivityNotifiedAsNoInternet"/>
             <item type="drawable" name="stat_notify_wifi_in_range"/>
             <item type="drawable" name="stat_notify_rssi_in_range"/>
+            <item type="bool" name="config_cellular_radio_timesharing_capable" />
         </policy>
     </overlayable>
 </resources>
diff --git a/service/src/com/android/server/ConnectivityService.java b/service/src/com/android/server/ConnectivityService.java
index 9f63191..c69af06 100644
--- a/service/src/com/android/server/ConnectivityService.java
+++ b/service/src/com/android/server/ConnectivityService.java
@@ -80,6 +80,7 @@
 import static android.net.NetworkCapabilities.TRANSPORT_VPN;
 import static android.net.NetworkCapabilities.TRANSPORT_WIFI;
 import static android.net.NetworkRequest.Type.LISTEN_FOR_BEST;
+import static android.net.NetworkScore.POLICY_TRANSPORT_PRIMARY;
 import static android.net.OemNetworkPreferences.OEM_NETWORK_PREFERENCE_TEST;
 import static android.net.OemNetworkPreferences.OEM_NETWORK_PREFERENCE_TEST_ONLY;
 import static android.net.shared.NetworkMonitorUtils.isPrivateDnsValidationRequired;
@@ -335,6 +336,9 @@
     protected int mLingerDelayMs;  // Can't be final, or test subclass constructors can't change it.
     @VisibleForTesting
     protected int mNascentDelayMs;
+    // True if the cell radio of the device is capable of time-sharing.
+    @VisibleForTesting
+    protected boolean mCellularRadioTimesharingCapable = true;
 
     // How long to delay to removal of a pending intent based request.
     // See ConnectivitySettingsManager.CONNECTIVITY_RELEASE_PENDING_INTENT_DELAY_MS
@@ -1375,6 +1379,12 @@
                 NetworkCapabilities.NET_CAPABILITY_VEHICLE_INTERNAL,
                 NetworkRequest.Type.BACKGROUND_REQUEST);
 
+        mLingerDelayMs = mSystemProperties.getInt(LINGER_DELAY_PROPERTY, DEFAULT_LINGER_DELAY_MS);
+        // TODO: Consider making the timer customizable.
+        mNascentDelayMs = DEFAULT_NASCENT_DELAY_MS;
+        mCellularRadioTimesharingCapable =
+                mResources.get().getBoolean(R.bool.config_cellular_radio_timesharing_capable);
+
         mHandlerThread = mDeps.makeHandlerThread();
         mHandlerThread.start();
         mHandler = new InternalHandler(mHandlerThread.getLooper());
@@ -1385,10 +1395,6 @@
         mReleasePendingIntentDelayMs = Settings.Secure.getInt(context.getContentResolver(),
                 ConnectivitySettingsManager.CONNECTIVITY_RELEASE_PENDING_INTENT_DELAY_MS, 5_000);
 
-        mLingerDelayMs = mSystemProperties.getInt(LINGER_DELAY_PROPERTY, DEFAULT_LINGER_DELAY_MS);
-        // TODO: Consider making the timer customizable.
-        mNascentDelayMs = DEFAULT_NASCENT_DELAY_MS;
-
         mStatsManager = mContext.getSystemService(NetworkStatsManager.class);
         mPolicyManager = mContext.getSystemService(NetworkPolicyManager.class);
         mDnsResolver = Objects.requireNonNull(dnsresolver, "missing IDnsResolver");
@@ -7824,6 +7830,30 @@
         bundle.putParcelable(t.getClass().getSimpleName(), t);
     }
 
+    /**
+     * Returns whether reassigning a request from an NAI to another can be done gracefully.
+     *
+     * When a request should be assigned to a new network, it is normally lingered to give
+     * time for apps to gracefully migrate their connections. When both networks are on the same
+     * radio, but that radio can't do time-sharing efficiently, this may end up being
+     * counter-productive because any traffic on the old network may drastically reduce the
+     * performance of the new network.
+     * The stack supports a configuration to let modem vendors state that their radio can't
+     * do time-sharing efficiently. If this configuration is set, the stack assumes moving
+     * from one cell network to another can't be done gracefully.
+     *
+     * @param oldNai the old network serving the request
+     * @param newNai the new network serving the request
+     * @return whether the switch can be graceful
+     */
+    private boolean canSupportGracefulNetworkSwitch(@NonNull final NetworkAgentInfo oldSatisfier,
+            @NonNull final NetworkAgentInfo newSatisfier) {
+        if (mCellularRadioTimesharingCapable) return true;
+        return !oldSatisfier.networkCapabilities.hasSingleTransport(TRANSPORT_CELLULAR)
+                || !newSatisfier.networkCapabilities.hasSingleTransport(TRANSPORT_CELLULAR)
+                || !newSatisfier.getScore().hasPolicy(POLICY_TRANSPORT_PRIMARY);
+    }
+
     private void teardownUnneededNetwork(NetworkAgentInfo nai) {
         if (nai.numRequestNetworkRequests() != 0) {
             for (int i = 0; i < nai.numNetworkRequests(); i++) {
@@ -8084,7 +8114,13 @@
                     log("   accepting network in place of " + previousSatisfier.toShortString());
                 }
                 previousSatisfier.removeRequest(previousRequest.requestId);
-                previousSatisfier.lingerRequest(previousRequest.requestId, now);
+                if (canSupportGracefulNetworkSwitch(previousSatisfier, newSatisfier)) {
+                    // If this network switch can't be supported gracefully, the request is not
+                    // lingered. This allows letting go of the network sooner to reclaim some
+                    // performance on the new network, since the radio can't do both at the same
+                    // time while preserving good performance.
+                    previousSatisfier.lingerRequest(previousRequest.requestId, now);
+                }
             } else {
                 if (VDBG || DDBG) log("   accepting network in place of null");
             }
diff --git a/tests/integration/util/com/android/server/NetworkAgentWrapper.java b/tests/integration/util/com/android/server/NetworkAgentWrapper.java
index 970b7d2..4dc86ff 100644
--- a/tests/integration/util/com/android/server/NetworkAgentWrapper.java
+++ b/tests/integration/util/com/android/server/NetworkAgentWrapper.java
@@ -27,6 +27,7 @@
 
 import static com.android.server.ConnectivityServiceTestUtils.transportToLegacyType;
 
+import static junit.framework.Assert.assertFalse;
 import static junit.framework.Assert.assertTrue;
 
 import static org.junit.Assert.assertEquals;
@@ -310,6 +311,10 @@
         assertTrue(mDisconnected.block(timeoutMs));
     }
 
+    public void assertNotDisconnected(long timeoutMs) {
+        assertFalse(mDisconnected.block(timeoutMs));
+    }
+
     public void sendLinkProperties(LinkProperties lp) {
         mNetworkAgent.sendLinkProperties(lp);
     }
diff --git a/tests/unit/java/com/android/server/ConnectivityServiceTest.java b/tests/unit/java/com/android/server/ConnectivityServiceTest.java
index 2aba0b4..1c7ac44 100644
--- a/tests/unit/java/com/android/server/ConnectivityServiceTest.java
+++ b/tests/unit/java/com/android/server/ConnectivityServiceTest.java
@@ -1792,6 +1792,8 @@
         doReturn(R.integer.config_networkAvoidBadWifi).when(mResources)
                 .getIdentifier(eq("config_networkAvoidBadWifi"), eq("integer"), any());
         doReturn(1).when(mResources).getInteger(R.integer.config_networkAvoidBadWifi);
+        doReturn(true).when(mResources)
+                .getBoolean(R.bool.config_cellular_radio_timesharing_capable);
 
         final ConnectivityResources connRes = mock(ConnectivityResources.class);
         doReturn(mResources).when(connRes).get();
@@ -2273,8 +2275,22 @@
         // After waitForIdle(), the message was processed and the service didn't crash.
     }
 
+    // TODO : migrate to @Parameterized
     @Test
-    public void testValidatedCellularOutscoresUnvalidatedWiFi() throws Exception {
+    public void testValidatedCellularOutscoresUnvalidatedWiFi_CanTimeShare() throws Exception {
+        // The behavior of this test should be the same whether the radio can time share or not.
+        doTestValidatedCellularOutscoresUnvalidatedWiFi(true);
+    }
+
+    // TODO : migrate to @Parameterized
+    @Test
+    public void testValidatedCellularOutscoresUnvalidatedWiFi_CannotTimeShare() throws Exception {
+        doTestValidatedCellularOutscoresUnvalidatedWiFi(false);
+    }
+
+    public void doTestValidatedCellularOutscoresUnvalidatedWiFi(
+            final boolean cellRadioTimesharingCapable) throws Exception {
+        mService.mCellularRadioTimesharingCapable = cellRadioTimesharingCapable;
         // Test bringing up unvalidated WiFi
         mWiFiNetworkAgent = new TestNetworkAgentWrapper(TRANSPORT_WIFI);
         ExpectedBroadcast b = registerConnectivityBroadcast(1);
@@ -2308,8 +2324,21 @@
         verifyNoNetwork();
     }
 
+    // TODO : migrate to @Parameterized
     @Test
-    public void testUnvalidatedWifiOutscoresUnvalidatedCellular() throws Exception {
+    public void testUnvalidatedWifiOutscoresUnvalidatedCellular_CanTimeShare() throws Exception {
+        doTestUnvalidatedWifiOutscoresUnvalidatedCellular(true);
+    }
+
+    // TODO : migrate to @Parameterized
+    @Test
+    public void testUnvalidatedWifiOutscoresUnvalidatedCellular_CannotTimeShare() throws Exception {
+        doTestUnvalidatedWifiOutscoresUnvalidatedCellular(false);
+    }
+
+    public void doTestUnvalidatedWifiOutscoresUnvalidatedCellular(
+            final boolean cellRadioTimesharingCapable) throws Exception {
+        mService.mCellularRadioTimesharingCapable = cellRadioTimesharingCapable;
         // Test bringing up unvalidated cellular.
         mCellNetworkAgent = new TestNetworkAgentWrapper(TRANSPORT_CELLULAR);
         ExpectedBroadcast b = registerConnectivityBroadcast(1);
@@ -2334,8 +2363,21 @@
         verifyNoNetwork();
     }
 
+    // TODO : migrate to @Parameterized
     @Test
-    public void testUnlingeringDoesNotValidate() throws Exception {
+    public void testUnlingeringDoesNotValidate_CanTimeShare() throws Exception {
+        doTestUnlingeringDoesNotValidate(true);
+    }
+
+    // TODO : migrate to @Parameterized
+    @Test
+    public void testUnlingeringDoesNotValidate_CannotTimeShare() throws Exception {
+        doTestUnlingeringDoesNotValidate(false);
+    }
+
+    public void doTestUnlingeringDoesNotValidate(
+            final boolean cellRadioTimesharingCapable) throws Exception {
+        mService.mCellularRadioTimesharingCapable = cellRadioTimesharingCapable;
         // Test bringing up unvalidated WiFi.
         mWiFiNetworkAgent = new TestNetworkAgentWrapper(TRANSPORT_WIFI);
         ExpectedBroadcast b = registerConnectivityBroadcast(1);
@@ -2362,8 +2404,134 @@
                 NET_CAPABILITY_VALIDATED));
     }
 
+    // TODO : migrate to @Parameterized
     @Test
-    public void testCellularOutscoresWeakWifi() throws Exception {
+    public void testRequestMigrationToSameTransport_CanTimeShare() throws Exception {
+        // Simulate a device where the cell radio is capable of time sharing
+        mService.mCellularRadioTimesharingCapable = true;
+        doTestRequestMigrationToSameTransport(TRANSPORT_CELLULAR, true);
+        doTestRequestMigrationToSameTransport(TRANSPORT_WIFI, true);
+        doTestRequestMigrationToSameTransport(TRANSPORT_ETHERNET, true);
+    }
+
+    // TODO : migrate to @Parameterized
+    @Test
+    public void testRequestMigrationToSameTransport_CannotTimeShare() throws Exception {
+        // Simulate a device where the cell radio is not capable of time sharing
+        mService.mCellularRadioTimesharingCapable = false;
+        doTestRequestMigrationToSameTransport(TRANSPORT_CELLULAR, false);
+        doTestRequestMigrationToSameTransport(TRANSPORT_WIFI, true);
+        doTestRequestMigrationToSameTransport(TRANSPORT_ETHERNET, true);
+    }
+
+    public void doTestRequestMigrationToSameTransport(final int transport,
+            final boolean expectLingering) throws Exception {
+        // To speed up tests the linger delay is very short by default in tests but this
+        // test needs to make sure the delay is not incurred so a longer value is safer (it
+        // reduces the risk that a bug exists but goes undetected). The alarm manager in the test
+        // throws and crashes CS if this is set to anything more than the below constant though.
+        mService.mLingerDelayMs = UNREASONABLY_LONG_ALARM_WAIT_MS;
+
+        final TestNetworkCallback generalCb = new TestNetworkCallback();
+        final TestNetworkCallback defaultCb = new TestNetworkCallback();
+        mCm.registerNetworkCallback(
+                new NetworkRequest.Builder().addTransportType(transport | transport).build(),
+                generalCb);
+        mCm.registerDefaultNetworkCallback(defaultCb);
+
+        // Bring up net agent 1
+        final TestNetworkAgentWrapper net1 = new TestNetworkAgentWrapper(transport);
+        net1.connect(true);
+        // Make sure the default request is on net 1
+        generalCb.expectAvailableThenValidatedCallbacks(net1);
+        defaultCb.expectAvailableThenValidatedCallbacks(net1);
+
+        // Bring up net 2 with primary and mms
+        final TestNetworkAgentWrapper net2 = new TestNetworkAgentWrapper(transport);
+        net2.addCapability(NET_CAPABILITY_MMS);
+        net2.setScore(new NetworkScore.Builder().setTransportPrimary(true).build());
+        net2.connect(true);
+
+        // Make sure the default request goes to net 2
+        generalCb.expectAvailableCallbacksUnvalidated(net2);
+        if (expectLingering) {
+            generalCb.expectCallback(CallbackEntry.LOSING, net1);
+        }
+        generalCb.expectCapabilitiesWith(NET_CAPABILITY_VALIDATED, net2);
+        defaultCb.expectAvailableDoubleValidatedCallbacks(net2);
+
+        // Make sure cell 1 is unwanted immediately if the radio can't time share, but only
+        // after some delay if it can.
+        if (expectLingering) {
+            net1.assertNotDisconnected(TEST_CALLBACK_TIMEOUT_MS); // always incurs the timeout
+            generalCb.assertNoCallback();
+            // assertNotDisconnected waited for TEST_CALLBACK_TIMEOUT_MS, so waiting for the
+            // linger period gives TEST_CALLBACK_TIMEOUT_MS time for the event to process.
+            net1.expectDisconnected(UNREASONABLY_LONG_ALARM_WAIT_MS);
+        } else {
+            net1.expectDisconnected(TEST_CALLBACK_TIMEOUT_MS);
+        }
+        net1.disconnect();
+        generalCb.expectCallback(CallbackEntry.LOST, net1);
+
+        // Remove primary from net 2
+        net2.setScore(new NetworkScore.Builder().build());
+        // Request MMS
+        final TestNetworkCallback mmsCallback = new TestNetworkCallback();
+        mCm.requestNetwork(new NetworkRequest.Builder().addCapability(NET_CAPABILITY_MMS).build(),
+                mmsCallback);
+        mmsCallback.expectAvailableCallbacksValidated(net2);
+
+        // Bring up net 3 with primary but without MMS
+        final TestNetworkAgentWrapper net3 = new TestNetworkAgentWrapper(transport);
+        net3.setScore(new NetworkScore.Builder().setTransportPrimary(true).build());
+        net3.connect(true);
+
+        // Make sure default goes to net 3, but the MMS request doesn't
+        generalCb.expectAvailableThenValidatedCallbacks(net3);
+        defaultCb.expectAvailableDoubleValidatedCallbacks(net3);
+        mmsCallback.assertNoCallback();
+        net2.assertNotDisconnected(TEST_CALLBACK_TIMEOUT_MS); // Always incurs the timeout
+
+        // Revoke MMS request and make sure net 2 is torn down with the appropriate delay
+        mCm.unregisterNetworkCallback(mmsCallback);
+        if (expectLingering) {
+            // If the radio can time share, the linger delay hasn't elapsed yet, so apps will
+            // get LOSING. If the radio can't time share, this is a hard loss, since the last
+            // request keeping up this network has been removed and the network isn't lingering
+            // for any other request.
+            generalCb.expectCallback(CallbackEntry.LOSING, net2);
+            net2.assertNotDisconnected(TEST_CALLBACK_TIMEOUT_MS);
+            generalCb.assertNoCallback();
+            net2.expectDisconnected(UNREASONABLY_LONG_ALARM_WAIT_MS);
+        } else {
+            net2.expectDisconnected(TEST_CALLBACK_TIMEOUT_MS);
+        }
+        net2.disconnect();
+        generalCb.expectCallback(CallbackEntry.LOST, net2);
+        defaultCb.assertNoCallback();
+
+        net3.disconnect();
+        mCm.unregisterNetworkCallback(defaultCb);
+        mCm.unregisterNetworkCallback(generalCb);
+    }
+
+    // TODO : migrate to @Parameterized
+    @Test
+    public void testCellularOutscoresWeakWifi_CanTimeShare() throws Exception {
+        // The behavior of this test should be the same whether the radio can time share or not.
+        doTestCellularOutscoresWeakWifi(true);
+    }
+
+    // TODO : migrate to @Parameterized
+    @Test
+    public void testCellularOutscoresWeakWifi_CannotTimeShare() throws Exception {
+        doTestCellularOutscoresWeakWifi(false);
+    }
+
+    public void doTestCellularOutscoresWeakWifi(
+            final boolean cellRadioTimesharingCapable) throws Exception {
+        mService.mCellularRadioTimesharingCapable = cellRadioTimesharingCapable;
         // Test bringing up validated cellular.
         mCellNetworkAgent = new TestNetworkAgentWrapper(TRANSPORT_CELLULAR);
         ExpectedBroadcast b = registerConnectivityBroadcast(1);
@@ -2388,8 +2556,21 @@
         verifyActiveNetwork(TRANSPORT_WIFI);
     }
 
+    // TODO : migrate to @Parameterized
     @Test
-    public void testReapingNetwork() throws Exception {
+    public void testReapingNetwork_CanTimeShare() throws Exception {
+        doTestReapingNetwork(true);
+    }
+
+    // TODO : migrate to @Parameterized
+    @Test
+    public void testReapingNetwork_CannotTimeShare() throws Exception {
+        doTestReapingNetwork(false);
+    }
+
+    public void doTestReapingNetwork(
+            final boolean cellRadioTimesharingCapable) throws Exception {
+        mService.mCellularRadioTimesharingCapable = cellRadioTimesharingCapable;
         // Test bringing up WiFi without NET_CAPABILITY_INTERNET.
         // Expect it to be torn down immediately because it satisfies no requests.
         mWiFiNetworkAgent = new TestNetworkAgentWrapper(TRANSPORT_WIFI);
@@ -2417,8 +2598,21 @@
         mWiFiNetworkAgent.expectDisconnected();
     }
 
+    // TODO : migrate to @Parameterized
     @Test
-    public void testCellularFallback() throws Exception {
+    public void testCellularFallback_CanTimeShare() throws Exception {
+        doTestCellularFallback(true);
+    }
+
+    // TODO : migrate to @Parameterized
+    @Test
+    public void testCellularFallback_CannotTimeShare() throws Exception {
+        doTestCellularFallback(false);
+    }
+
+    public void doTestCellularFallback(
+            final boolean cellRadioTimesharingCapable) throws Exception {
+        mService.mCellularRadioTimesharingCapable = cellRadioTimesharingCapable;
         // Test bringing up validated cellular.
         mCellNetworkAgent = new TestNetworkAgentWrapper(TRANSPORT_CELLULAR);
         ExpectedBroadcast b = registerConnectivityBroadcast(1);
@@ -2455,8 +2649,21 @@
         verifyActiveNetwork(TRANSPORT_WIFI);
     }
 
+    // TODO : migrate to @Parameterized
     @Test
-    public void testWiFiFallback() throws Exception {
+    public void testWiFiFallback_CanTimeShare() throws Exception {
+        doTestWiFiFallback(true);
+    }
+
+    // TODO : migrate to @Parameterized
+    @Test
+    public void testWiFiFallback_CannotTimeShare() throws Exception {
+        doTestWiFiFallback(false);
+    }
+
+    public void doTestWiFiFallback(
+            final boolean cellRadioTimesharingCapable) throws Exception {
+        mService.mCellularRadioTimesharingCapable = cellRadioTimesharingCapable;
         // Test bringing up unvalidated WiFi.
         mWiFiNetworkAgent = new TestNetworkAgentWrapper(TRANSPORT_WIFI);
         ExpectedBroadcast b = registerConnectivityBroadcast(1);