diff --git a/.github/workflows/dotnet.yml b/.github/workflows/dotnet.yml
index a98a0e1..07f9959 100644
--- a/.github/workflows/dotnet.yml
+++ b/.github/workflows/dotnet.yml
@@ -36,6 +36,8 @@ jobs:
       run: |
         echo "=== Starting test services with docker-compose ==="
         docker compose -f docker-compose.test.yml up -d
+      env:
+        LOCALSTACK_AUTH_TOKEN: ${{ secrets.LOCALSTACK_AUTH_TOKEN }}
 
     - name: Wait for services to be ready
       if: matrix.os == 'ubuntu-latest'
diff --git a/docker-compose.test.yml b/docker-compose.test.yml
index 08a0bf7..841c9fb 100644
--- a/docker-compose.test.yml
+++ b/docker-compose.test.yml
@@ -36,9 +36,7 @@ services:
     ports:
       - "4566:4566"
     environment:
-      SERVICES: s3
-      DEBUG: 0
-      EDGE_PORT: 4566
+      LOCALSTACK_AUTH_TOKEN: ${LOCALSTACK_AUTH_TOKEN:-}
     healthcheck:
       test: ["CMD", "curl", "-f", "http://localhost:4566/_localstack/health"]
       interval: 15s
diff --git a/src/SharpSync/SharpSync.csproj b/src/SharpSync/SharpSync.csproj
index 7ac6cdc..cbbd6ac 100644
--- a/src/SharpSync/SharpSync.csproj
+++ b/src/SharpSync/SharpSync.csproj
@@ -52,7 +52,7 @@
     <PackageReference Include="WebDav.Client" Version="2.9.0" />
     <PackageReference Include="SSH.NET" Version="2025.1.0" />
     <PackageReference Include="AWSSDK.S3" Version="4.0.19.2" />
-    <PackageReference Include="FluentFTP" Version="53.0.2" />
+    <PackageReference Include="FluentFTP" Version="54.0.2" />
     <PackageReference Include="Microsoft.CodeAnalysis.Analyzers" Version="5.3.0" PrivateAssets="all" />
     <PackageReference Include="Microsoft.CodeAnalysis.NetAnalyzers" Version="10.0.201" PrivateAssets="all" />
   </ItemGroup>
diff --git a/src/SharpSync/Sync/SyncEngine.cs b/src/SharpSync/Sync/SyncEngine.cs
index b067f65..33d1e8b 100644
--- a/src/SharpSync/Sync/SyncEngine.cs
+++ b/src/SharpSync/Sync/SyncEngine.cs
@@ -752,6 +752,9 @@ private async Task ProcessChangesAsync(ChangeSet changes, SyncOptions? options,
         await ProcessPhase1_DirectoriesAndSmallFilesAsync(actionGroups, threadSafeResult, progressCounter, totalChanges, cancellationToken).ConfigureAwait(false);
         await ProcessPhase2_LargeFilesAsync(actionGroups, threadSafeResult, progressCounter, totalChanges, cancellationToken).ConfigureAwait(false);
         await ProcessPhase3_DeletesAndConflictsAsync(actionGroups, threadSafeResult, progressCounter, totalChanges, cancellationToken).ConfigureAwait(false);
+
+        // Write final atomic counter values to the result
+        threadSafeResult.Flush();
     }
 
     /// <summary>
diff --git a/src/SharpSync/Sync/ThreadSafeSyncResult.cs b/src/SharpSync/Sync/ThreadSafeSyncResult.cs
index 23bc585..d477f45 100644
--- a/src/SharpSync/Sync/ThreadSafeSyncResult.cs
+++ b/src/SharpSync/Sync/ThreadSafeSyncResult.cs
@@ -3,7 +3,9 @@
 namespace Oire.SharpSync.Sync;
 
 /// <summary>
-/// Thread-safe wrapper for SyncResult counters
+/// Thread-safe wrapper for SyncResult counters.
+/// Call <see cref="Flush"/> after all parallel processing completes
+/// to write the final values to the underlying <see cref="SyncResult"/>.
 /// </summary>
 internal sealed class ThreadSafeSyncResult {
     private readonly SyncResult _result;
@@ -16,23 +18,22 @@ public ThreadSafeSyncResult(SyncResult result) {
         _result = result;
     }
 
-    public void IncrementFilesSynchronized() {
-        var newValue = Interlocked.Increment(ref _filesSynchronized);
-        _result.FilesSynchronized = newValue;
-    }
+    public void IncrementFilesSynchronized() => Interlocked.Increment(ref _filesSynchronized);
 
-    public void IncrementFilesSkipped() {
-        var newValue = Interlocked.Increment(ref _filesSkipped);
-        _result.FilesSkipped = newValue;
-    }
+    public void IncrementFilesSkipped() => Interlocked.Increment(ref _filesSkipped);
 
-    public void IncrementFilesConflicted() {
-        var newValue = Interlocked.Increment(ref _filesConflicted);
-        _result.FilesConflicted = newValue;
-    }
+    public void IncrementFilesConflicted() => Interlocked.Increment(ref _filesConflicted);
+
+    public void IncrementFilesDeleted() => Interlocked.Increment(ref _filesDeleted);
 
-    public void IncrementFilesDeleted() {
-        var newValue = Interlocked.Increment(ref _filesDeleted);
-        _result.FilesDeleted = newValue;
+    /// <summary>
+    /// Writes the final atomic counter values to the underlying <see cref="SyncResult"/>.
+    /// Must be called after all parallel processing has completed.
+    /// </summary>
+    public void Flush() {
+        _result.FilesSynchronized = Interlocked.Read(ref _filesSynchronized);
+        _result.FilesSkipped = Interlocked.Read(ref _filesSkipped);
+        _result.FilesConflicted = Interlocked.Read(ref _filesConflicted);
+        _result.FilesDeleted = Interlocked.Read(ref _filesDeleted);
     }
 }