diff --git a/src/ZB.MOM.WW.MxGateway.Worker/MxAccess/MxAccessSession.cs b/src/ZB.MOM.WW.MxGateway.Worker/MxAccess/MxAccessSession.cs
index a82e0a6..0bc4690 100644
--- a/src/ZB.MOM.WW.MxGateway.Worker/MxAccess/MxAccessSession.cs
+++ b/src/ZB.MOM.WW.MxGateway.Worker/MxAccess/MxAccessSession.cs
@@ -13,6 +13,7 @@ public sealed class MxAccessSession : IDisposable
     private readonly IMxAccessEventSink eventSink;
     private readonly MxAccessHandleRegistry handleRegistry;
     private readonly MxAccessValueCache valueCache;
+    private readonly MxAccessWriteCompletionCache writeCompletionCache;
     private bool disposed;
 
     private MxAccessSession(
@@ -21,6 +22,7 @@ public sealed class MxAccessSession : IDisposable
         IMxAccessEventSink eventSink,
         MxAccessHandleRegistry handleRegistry,
         MxAccessValueCache valueCache,
+        MxAccessWriteCompletionCache writeCompletionCache,
         int creationThreadId)
     {
         this.mxAccessComObject = mxAccessComObject ?? throw new ArgumentNullException(nameof(mxAccessComObject));
@@ -28,6 +30,7 @@ public sealed class MxAccessSession : IDisposable
         this.eventSink = eventSink ?? throw new ArgumentNullException(nameof(eventSink));
         this.handleRegistry = handleRegistry ?? throw new ArgumentNullException(nameof(handleRegistry));
         this.valueCache = valueCache ?? throw new ArgumentNullException(nameof(valueCache));
+        this.writeCompletionCache = writeCompletionCache ?? throw new ArgumentNullException(nameof(writeCompletionCache));
         CreationThreadId = creationThreadId;
     }
 
@@ -45,6 +48,14 @@ public sealed class MxAccessSession : IDisposable
     /// </summary>
     public MxAccessValueCache ValueCache => valueCache;
 
+    /// <summary>
+    ///     Per-session OnWriteComplete completion cache populated by the event
+    ///     sink. The write command executor consults it after a
+    ///     WriteSecured/WriteSecured2 COM call so the unary reply can carry
+    ///     the correlated completion outcome.
+    /// </summary>
+    public MxAccessWriteCompletionCache WriteCompletionCache => writeCompletionCache;
+
     /// <summary>Creates a WorkerReady message with session metadata.</summary>
     /// <param name="workerProcessId">Process ID of the worker.</param>
     /// <returns>The populated <see cref="WorkerReady"/> message.</returns>
@@ -149,12 +160,22 @@ public sealed class MxAccessSession : IDisposable
                 ? baseSink.ValueCache
                 : new MxAccessValueCache();
 
+            // Share the sink's completion cache the same way (the production
+            // sink and completion-aware test sinks implement the provider
+            // seam); fall back to a fresh cache for other fakes — the write
+            // executor then simply never observes a completion and replies
+            // unconfirmed.
+            MxAccessWriteCompletionCache writeCompletionCache = eventSink is IWriteCompletionCacheProvider provider
+                ? provider.WriteCompletionCache
+                : new MxAccessWriteCompletionCache();
+
             return new MxAccessSession(
                 mxAccessComObject,
                 new MxAccessComServer(mxAccessComObject),
                 eventSink,
                 new MxAccessHandleRegistry(),
                 valueCache,
+                writeCompletionCache,
                 Environment.CurrentManagedThreadId);
         }
         catch (Exception exception)