diff --git a/src/Server/ZB.MOM.WW.OtOpcUa.OpcUaServer/Security/SessionAclDecisionCache.cs b/src/Server/ZB.MOM.WW.OtOpcUa.OpcUaServer/Security/SessionAclDecisionCache.cs
index ea44d403..21b40271 100644
--- a/src/Server/ZB.MOM.WW.OtOpcUa.OpcUaServer/Security/SessionAclDecisionCache.cs
+++ b/src/Server/ZB.MOM.WW.OtOpcUa.OpcUaServer/Security/SessionAclDecisionCache.cs
@@ -254,9 +254,9 @@ public sealed class SessionAclDecisionCache
             // paid by every eviction.
             //
             // A shard from a PREVIOUS generation contributes no hint: the fill level it reached belongs to a
-            // set of grants that no longer exists, and it is about to be displaced by the generation check
-            // below in any case. Sizing this generation's storage from the last one's crawl would be a guess
-            // dressed as evidence.
+            // set of grants that no longer exists, and this very Displace replaces it with a fresh shard
+            // stamped to the current generation regardless. Sizing this generation's storage from the last
+            // one's crawl would be a guess dressed as evidence.
             shard = Displace(
                 sessionKey, shard, generation,
                 capacityHint: shard.Generation == generation
diff --git a/tests/Server/ZB.MOM.WW.OtOpcUa.OpcUaServer.Tests/SessionAclDecisionCacheTests.cs b/tests/Server/ZB.MOM.WW.OtOpcUa.OpcUaServer.Tests/SessionAclDecisionCacheTests.cs
index 5bf36a05..4d75d858 100644
--- a/tests/Server/ZB.MOM.WW.OtOpcUa.OpcUaServer.Tests/SessionAclDecisionCacheTests.cs
+++ b/tests/Server/ZB.MOM.WW.OtOpcUa.OpcUaServer.Tests/SessionAclDecisionCacheTests.cs
@@ -295,8 +295,9 @@ public sealed class SessionAclDecisionCacheTests
         cache.TryGet(generation: 1, Session, OpcUaOperation.Read, AddressSpaceRealm.Raw, Node, out _)
             .ShouldBeFalse("a superseded snapshot must recompute rather than read the newer generation");
 
-        // Asserted BEFORE the generation-2 lookup below, which would itself restore a rolled-back stamp and
-        // hide the defect.
+        // Asserted BEFORE the generation-2 lookup below, which would itself restore a rolled-back stamp —
+        // so a stamp assertion made after it could never fail. (The purge half would still surface, as the
+        // last lookup would miss; it is the stamp half that needs its assertion here.)
         cache.Generation.ShouldBe(2, "the straggler must not have rolled the stamp backward");
         cache.Count.ShouldBe(1, "and must not have purged the current generation's entries");