diff --git a/proto/mls/api/v1/mls.proto b/proto/mls/api/v1/mls.proto
index 94e02d02..08827337 100644
--- a/proto/mls/api/v1/mls.proto
+++ b/proto/mls/api/v1/mls.proto
@@ -218,7 +218,8 @@ message GroupMessage {
     bytes data = 4;
     bytes sender_hmac = 5;
     bool should_push = 6;
-    bool is_commit = 7;
+    bool is_commit = 7 [deprecated = true];
+    MessageType message_type = 8;
   }
 
   oneof version {
@@ -226,6 +227,15 @@ message GroupMessage {
   }
 }
 
+// Enum to specify the type of a message.
+// Primarily used for ordering while retaining some metadata.
+enum MessageType {
+  MESSAGE_TYPE_UNSPECIFIED = 0;
+  MESSAGE_TYPE_APPLICATION = 1;
+  MESSAGE_TYPE_COMMIT = 2;
+  MESSAGE_TYPE_FORK_ADMIN_CHANGE = 3;
+}
+
 // Input type for a group message
 message GroupMessageInput {
   // Version 1 of the GroupMessageInput payload format
diff --git a/proto/mls/message_contents/commit_log.proto b/proto/mls/message_contents/commit_log.proto
index 29eb42c3..8b614dff 100644
--- a/proto/mls/message_contents/commit_log.proto
+++ b/proto/mls/message_contents/commit_log.proto
@@ -22,17 +22,34 @@ message PlaintextCommitLogEntry {
   // The sequence ID of the commit payload being validated.
   uint64 commit_sequence_id = 2;
   // The encryption state before the commit was applied.
-  bytes last_epoch_authenticator = 3;
+  bytes last_epoch_authenticator = 3 [deprecated = true];
   // Indicates whether the commit was successful, or why it failed.
   CommitResult commit_result = 4;
   // The epoch number after the commit was applied, if successful.
   uint64 applied_epoch_number = 5;
   // The encryption state after the commit was applied, if successful.
   bytes applied_epoch_authenticator = 6;
+  
+  // The hmac of the installation_id that published this commit log entry.
+  // Value: hmac-sha256(salt, installation_id)
+  bytes installation_hmac = 7;
 }
 
 message CommitLogEntry {
   uint64 sequence_id = 1;
   bytes serialized_commit_log_entry = 2;
-  xmtp.identity.associations.RecoverableEd25519Signature signature = 3;
+  xmtp.identity.associations.RecoverableEd25519Signature deprecated_signature = 3 [deprecated = true];
+
+  // Installation cred signature on field 2 + group salt
+  bytes signature = 4;
+}
+
+message ForkAdminChange {
+  // Used to protect against replays, and against replays for new members.
+	int64 sequence_id = 1;
+	// value: hmac-sha256(group salt, installation_id)
+	bytes fork_admin_hmac = 2;
+	// Installation cred signature on fields 1 + 2 + 4 + group salt
+	bytes signature = 3;
+	bytes group_id = 4;
 }
diff --git a/proto/mls_validation/v1/service.proto b/proto/mls_validation/v1/service.proto
index ae921cf3..8af7ebd0 100644
--- a/proto/mls_validation/v1/service.proto
+++ b/proto/mls_validation/v1/service.proto
@@ -5,6 +5,7 @@ package xmtp.mls_validation.v1;
 import "identity/api/v1/identity.proto";
 import "identity/associations/association.proto";
 import "identity/credential.proto";
+import "mls/api/v1/mls.proto";
 
 option go_package = "github.com/xmtp/proto/v3/go/mls_validation/v1";
 
@@ -98,7 +99,8 @@ message ValidateGroupMessagesResponse {
     bool is_ok = 1;
     string error_message = 2;
     string group_id = 3;
-    bool is_commit = 4;
+    bool is_commit = 4 [deprecated = true];
+    xmtp.mls.api.v1.MessageType message_type = 5;
   }
 
   repeated ValidationResponse responses = 1;