diff --git a/src/ZB.MOM.WW.MxGateway.Contracts/Generated/MxaccessGateway.cs b/src/ZB.MOM.WW.MxGateway.Contracts/Generated/MxaccessGateway.cs
index 4b033b5..48601e2 100644
--- a/src/ZB.MOM.WW.MxGateway.Contracts/Generated/MxaccessGateway.cs
+++ b/src/ZB.MOM.WW.MxGateway.Contracts/Generated/MxaccessGateway.cs
@@ -23592,6 +23592,9 @@ namespace ZB.MOM.WW.MxGateway.Contracts.Proto {
     /// clients MUST treat a present `replay_gap` as "you missed events — discard
     /// local state and re-snapshot" and read `requested_after_sequence` /
     /// `oldest_available_sequence` from it. Unset on every normal MXAccess event.
+    /// This field is ONLY ever set on events returned from the StreamEvents server
+    /// stream; it is ALWAYS unset on events in DrainEventsReply (the diagnostic
+    /// drain path never emits the sentinel).
     /// Additive (proto3): existing clients that ignore this field continue to
     /// deserialize the stream unchanged. (Reconnect/replay logic is Task 12; this
     /// is the contract surface only.)
@@ -24491,9 +24494,14 @@ namespace ZB.MOM.WW.MxGateway.Contracts.Proto {
     public const int OldestAvailableSequenceFieldNumber = 2;
     private ulong oldestAvailableSequence_;
     /// <summary>
-    /// The oldest worker_sequence still retained in the replay ring. Events with
-    /// worker_sequence in (requested_after_sequence, oldest_available_sequence)
-    /// were evicted and are unrecoverable.
+    /// The oldest worker_sequence still retained in the replay ring and available
+    /// for replay. Events with worker_sequence in the open interval
+    /// (requested_after_sequence, oldest_available_sequence) were evicted and are
+    /// unrecoverable. oldest_available_sequence itself IS still retained: a client
+    /// that wishes to resume without incurring another gap MUST set
+    /// after_worker_sequence = oldest_available_sequence - 1 in the next
+    /// StreamEventsRequest, which will cause the server to replay starting at
+    /// oldest_available_sequence (the first retained event).
     /// </summary>
     [global::System.Diagnostics.DebuggerNonUserCodeAttribute]
     [global::System.CodeDom.Compiler.GeneratedCode("protoc", null)]
diff --git a/src/ZB.MOM.WW.MxGateway.Contracts/Protos/mxaccess_gateway.proto b/src/ZB.MOM.WW.MxGateway.Contracts/Protos/mxaccess_gateway.proto
index a56fb3c..3c9d587 100644
--- a/src/ZB.MOM.WW.MxGateway.Contracts/Protos/mxaccess_gateway.proto
+++ b/src/ZB.MOM.WW.MxGateway.Contracts/Protos/mxaccess_gateway.proto
@@ -725,6 +725,9 @@ message MxEvent {
   // clients MUST treat a present `replay_gap` as "you missed events — discard
   // local state and re-snapshot" and read `requested_after_sequence` /
   // `oldest_available_sequence` from it. Unset on every normal MXAccess event.
+  // This field is ONLY ever set on events returned from the StreamEvents server
+  // stream; it is ALWAYS unset on events in DrainEventsReply (the diagnostic
+  // drain path never emits the sentinel).
   // Additive (proto3): existing clients that ignore this field continue to
   // deserialize the stream unchanged. (Reconnect/replay logic is Task 12; this
   // is the contract surface only.)
@@ -750,9 +753,14 @@ message ReplayGap {
   // The worker_sequence the client asked to resume after
   // (StreamEventsRequest.after_worker_sequence).
   uint64 requested_after_sequence = 1;
-  // The oldest worker_sequence still retained in the replay ring. Events with
-  // worker_sequence in (requested_after_sequence, oldest_available_sequence)
-  // were evicted and are unrecoverable.
+  // The oldest worker_sequence still retained in the replay ring and available
+  // for replay. Events with worker_sequence in the open interval
+  // (requested_after_sequence, oldest_available_sequence) were evicted and are
+  // unrecoverable. oldest_available_sequence itself IS still retained: a client
+  // that wishes to resume without incurring another gap MUST set
+  // after_worker_sequence = oldest_available_sequence - 1 in the next
+  // StreamEventsRequest, which will cause the server to replay starting at
+  // oldest_available_sequence (the first retained event).
   uint64 oldest_available_sequence = 2;
 }