diff --git a/crates/rpc/proto/zed.proto b/crates/rpc/proto/zed.proto
index d0c9d73fc4..0f289edcf8 100644
--- a/crates/rpc/proto/zed.proto
+++ b/crates/rpc/proto/zed.proto
@@ -155,6 +155,7 @@ message Envelope {
         UpdateChannelBufferCollaborators update_channel_buffer_collaborators = 128;
         RejoinChannelBuffers rejoin_channel_buffers = 129;
         RejoinChannelBuffersResponse rejoin_channel_buffers_response = 130;
+        AckBufferOperation ack_buffer_operation = 143;
 
         JoinChannelChat join_channel_chat = 131;
         JoinChannelChatResponse join_channel_chat_response = 132;
@@ -165,10 +166,11 @@ message Envelope {
         GetChannelMessages get_channel_messages = 137;
         GetChannelMessagesResponse get_channel_messages_response = 138;
         RemoveChannelMessage remove_channel_message = 139;
+        AckChannelMessage ack_channel_message = 144;
 
         LinkChannel link_channel = 140;
         UnlinkChannel unlink_channel = 141;
-        MoveChannel move_channel = 142;
+        MoveChannel move_channel = 142; // current max: 144
     }
 }
 
@@ -1062,6 +1064,11 @@ message RemoveChannelMessage {
     uint64 message_id = 2;
 }
 
+message AckChannelMessage {
+    uint64 channel_id = 1;
+    uint64 message_id = 2;
+}
+
 message SendChannelMessageResponse {
     ChannelMessage message = 1;
 }
@@ -1117,6 +1124,13 @@ message RejoinChannelBuffersResponse {
     repeated RejoinedChannelBuffer buffers = 1;
 }
 
+message AckBufferOperation {
+    uint64 buffer_id = 1;
+    uint64 epoch = 2;
+    uint64 lamport_timestamp = 3;
+    uint64 replica_id = 4;
+}
+
 message JoinChannelBufferResponse {
     uint64 buffer_id = 1;
     uint32 replica_id = 2;
diff --git a/crates/rpc/src/proto.rs b/crates/rpc/src/proto.rs
index 6d0a0f85d1..f0d7937f6f 100644
--- a/crates/rpc/src/proto.rs
+++ b/crates/rpc/src/proto.rs
@@ -271,6 +271,8 @@ messages!(
     (LeaveChannelBuffer, Background),
     (UpdateChannelBuffer, Foreground),
     (UpdateChannelBufferCollaborators, Foreground),
+    (AckBufferOperation, Background),
+    (AckChannelMessage, Background),
 );
 
 request_messages!(
@@ -406,7 +408,7 @@ entity_messages!(
     ChannelMessageSent,
     UpdateChannelBuffer,
     RemoveChannelMessage,
-    UpdateChannelBufferCollaborators
+    UpdateChannelBufferCollaborators,
 );
 
 const KIB: usize = 1024;