diff --git a/native/cpp/CommonCpp/grpc/protos/tunnelbroker.proto b/native/cpp/CommonCpp/grpc/protos/tunnelbroker.proto
--- a/native/cpp/CommonCpp/grpc/protos/tunnelbroker.proto
+++ b/native/cpp/CommonCpp/grpc/protos/tunnelbroker.proto
@@ -22,7 +22,7 @@
   rpc Get(GetRequest) returns (stream GetResponse) {}
 
   // Replacing Send and Get with a single bidirectional streaming RPC
-  rpc OpenStream(stream OutboundMessage) returns (stream InboundMessage) {}
+  rpc MessagesStream(stream InboundMessage) returns (stream OutboundMessage) {}
 }
 
 // Session
@@ -76,19 +76,53 @@
   repeated string blobHashes = 3;
 }
 
-message OutboundMessage {
-  string toDeviceID = 1;
-  string payload = 2;
-  repeated string blobHashes = 3;
+// Common messages structures for the MessagesStream
+
+message ProcessedMessages {
+  repeated string messageID = 1;
+}
+
+// The messages from the Client to the Tunnelbroker
+
+message InboundMessageStruct {
+  string messageID = 1;
+  string toDeviceID = 2;
+  string payload = 3;
+  repeated string blobHashes = 4;
+}
+
+message MessagesToSent {
+  repeated InboundMessageStruct messages = 1;
 }
 
 message InboundMessage {
-  string fromDeviceID = 1;
-  string fromConnectionID = 2;
+  string sessionID = 1;
+  oneof data {
+    MessagesToSent messagesToSent = 2;
+    ProcessedMessages processedMessages = 3;
+  }
+}
+
+// The messages from the Tunnelbroker to the Client
+
+message OutboundMessageStruct {
+  string messageID = 1;
+  string fromDeviceID = 2;
   string payload = 3;
   repeated string blobHashes = 4;
 }
 
+message MessagesToDeliver {
+  repeated OutboundMessageStruct messages = 1;
+}
+
+message OutboundMessage {
+  oneof data {
+    MessagesToDeliver messagesToDeliver = 1;
+    ProcessedMessages processedMessages = 2;
+  }
+}
+
 // Old API structures
 
 enum CheckResponseType {