diff --git a/transport/manager/1.2/Android.bp b/transport/manager/1.2/Android.bp
index 564fb8a..3f02f78 100644
--- a/transport/manager/1.2/Android.bp
+++ b/transport/manager/1.2/Android.bp
@@ -7,6 +7,7 @@
         enabled: true,
     },
     srcs: [
+        "IClientCallback.hal",
         "IServiceManager.hal",
     ],
     interfaces: [
diff --git a/transport/manager/1.2/IClientCallback.hal b/transport/manager/1.2/IClientCallback.hal
new file mode 100644
index 0000000..030bcd0
--- /dev/null
+++ b/transport/manager/1.2/IClientCallback.hal
@@ -0,0 +1,26 @@
+/*
+ * Copyright (C) 2018 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package android.hidl.manager@1.2;
+
+interface IClientCallback {
+    /**
+     * Called when there are no clients remaining for the HAL registered with this service.
+     *
+     * @param registered binder 'server' registered with IServiceManager's registerClientCallback
+     */
+    oneway onNoClients(interface registered);
+};
diff --git a/transport/manager/1.2/IServiceManager.hal b/transport/manager/1.2/IServiceManager.hal
index 1ef4ed8..af72dcc 100644
--- a/transport/manager/1.2/IServiceManager.hal
+++ b/transport/manager/1.2/IServiceManager.hal
@@ -18,11 +18,40 @@
 
 import @1.1::IServiceManager;
 
+import IClientCallback;
+
 interface IServiceManager extends @1.1::IServiceManager {
     // TODO(b/66921961): additional functionality for the next release:
     // - Better notifications (onRegistration will contain the interface)
-    // - Callbacks to support lazy hal shutdown when there are no clients (b/79983843)
     // - Method to list interfaces in the manifest (for b/76108617, since if they are
     //     lazy, they will no longer show up in listByInterface)
     // - Register w/o it having to call interface chain (b/36424585)
+
+    /**
+     * Adds a callback that must be called when the specified server has no clients.
+     *
+     * This must only be called after the first time the service has no clients.
+     *
+     * @param server non-null service waiting to have no clients
+     * @param cb non-null callback to call when there are no clients
+     * @return success
+     *     true on success
+     *     false if either
+     *      - the server or cb parameters are null
+     *      - this is called by a process other than the server process
+     */
+    registerClientCallback(interface server, IClientCallback cb) generates (bool success);
+
+    /**
+     * Removes a callback previously registered with registerClientCallback.
+     *
+     * If server is null, then this must remove the cb from all matching services.
+     *
+     * @param server service registered with registerClientCallback
+     * @param cb non-null callback to remove
+     * @return success
+     *     true if the server(s) have been removed
+     *     false if cb is null or if the client callback or server could not be found
+     */
+    unregisterClientCallback(interface server, IClientCallback cb) generates (bool success);
 };