diff --git a/init/subcontext.proto b/init/subcontext.proto
new file mode 100644
index 0000000..0d89734
--- /dev/null
+++ b/init/subcontext.proto
@@ -0,0 +1,33 @@
+/*
+ * Copyright (C) 2017 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.
+ */
+
+syntax = "proto2";
+option optimize_for = LITE_RUNTIME;
+
+message SubcontextCommand {
+    message ExecuteCommand { repeated string args = 1; }
+    oneof command { ExecuteCommand execute_command = 1; }
+}
+
+message SubcontextReply {
+    message ResultMessage {
+        optional bool success = 1;
+        optional string error_string = 2;
+        optional int32 error_errno = 3;
+    }
+
+    oneof reply { ResultMessage result = 1; }
+}
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