diff --git a/buffet/commands/command_proxy_interface.h b/buffet/commands/command_proxy_interface.h
new file mode 100644
index 0000000..f9e78d6
--- /dev/null
+++ b/buffet/commands/command_proxy_interface.h
@@ -0,0 +1,25 @@
+// Copyright 2014 The Chromium OS Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef BUFFET_COMMANDS_COMMAND_PROXY_INTERFACE_H_
+#define BUFFET_COMMANDS_COMMAND_PROXY_INTERFACE_H_
+
+#include <string>
+
+namespace buffet {
+
+// This interface lets the command instance to update its proxy of command
+// state changes, so that the proxy can then notify clients of the changes over
+// their supported protocol (e.g. D-Bus).
+class CommandProxyInterface {
+ public:
+  virtual ~CommandProxyInterface() = default;
+
+  virtual void OnStatusChanged(const std::string& status) = 0;
+  virtual void OnProgressChanged(int progress) = 0;
+};
+
+}  // namespace buffet
+
+#endif  // BUFFET_COMMANDS_COMMAND_PROXY_INTERFACE_H_