diff --git a/src/ZB.MOM.WW.ScadaBridge.Transport/Import/BundleImporter.cs b/src/ZB.MOM.WW.ScadaBridge.Transport/Import/BundleImporter.cs
index a93d34bc..f05852d9 100644
--- a/src/ZB.MOM.WW.ScadaBridge.Transport/Import/BundleImporter.cs
+++ b/src/ZB.MOM.WW.ScadaBridge.Transport/Import/BundleImporter.cs
@@ -1040,7 +1040,7 @@ public sealed class BundleImporter : IBundleImporter
         {
             t.Attributes.Add(new TemplateAttribute(a.Name)
             {
-                Value = a.Value,
+                Value = ImportValueNormalizer.NormalizeListValue(a.Value, a.DataType, a.ElementDataType),
                 DataType = a.DataType,
                 IsLocked = a.IsLocked,
                 Description = a.Description,
@@ -1115,11 +1115,17 @@ public sealed class BundleImporter : IBundleImporter
         // Adds + Updates.
         foreach (var attrDto in dto.Attributes)
         {
+            // Normalise List values to the native-typed JSON form on import so the
+            // comparison (and the persisted value) match what the target already
+            // stores natively — otherwise an idempotent re-import of an old-form
+            // bundle would spuriously report a Value change.
+            var normalizedValue = ImportValueNormalizer.NormalizeListValue(
+                attrDto.Value, attrDto.DataType, attrDto.ElementDataType);
             if (existingByName.TryGetValue(attrDto.Name, out var current))
             {
                 // Update only if any field actually changed.
                 bool changed =
-                    !string.Equals(current.Value, attrDto.Value, StringComparison.Ordinal) ||
+                    !string.Equals(current.Value, normalizedValue, StringComparison.Ordinal) ||
                     current.DataType != attrDto.DataType ||
                     current.IsLocked != attrDto.IsLocked ||
                     !string.Equals(current.Description, attrDto.Description, StringComparison.Ordinal) ||
@@ -1127,7 +1133,7 @@ public sealed class BundleImporter : IBundleImporter
                     current.ElementDataType != attrDto.ElementDataType;
                 if (!changed) continue;
 
-                current.Value = attrDto.Value;
+                current.Value = normalizedValue;
                 current.DataType = attrDto.DataType;
                 current.IsLocked = attrDto.IsLocked;
                 current.Description = attrDto.Description;
@@ -1157,7 +1163,7 @@ public sealed class BundleImporter : IBundleImporter
             {
                 var newAttr = new TemplateAttribute(attrDto.Name)
                 {
-                    Value = attrDto.Value,
+                    Value = normalizedValue,
                     DataType = attrDto.DataType,
                     IsLocked = attrDto.IsLocked,
                     Description = attrDto.Description,
diff --git a/src/ZB.MOM.WW.ScadaBridge.Transport/Serialization/EntitySerializer.cs b/src/ZB.MOM.WW.ScadaBridge.Transport/Serialization/EntitySerializer.cs
index 22c7c31b..88b66573 100644
--- a/src/ZB.MOM.WW.ScadaBridge.Transport/Serialization/EntitySerializer.cs
+++ b/src/ZB.MOM.WW.ScadaBridge.Transport/Serialization/EntitySerializer.cs
@@ -199,7 +199,7 @@ public sealed class EntitySerializer
                     t.Attributes.Add(new TemplateAttribute(a.Name)
                     {
                         TemplateId = t.Id,
-                        Value = a.Value,
+                        Value = ImportValueNormalizer.NormalizeListValue(a.Value, a.DataType, a.ElementDataType),
                         DataType = a.DataType,
                         IsLocked = a.IsLocked,
                         Description = a.Description,
diff --git a/src/ZB.MOM.WW.ScadaBridge.Transport/Serialization/ImportValueNormalizer.cs b/src/ZB.MOM.WW.ScadaBridge.Transport/Serialization/ImportValueNormalizer.cs
new file mode 100644
index 00000000..e4211ae1
--- /dev/null
+++ b/src/ZB.MOM.WW.ScadaBridge.Transport/Serialization/ImportValueNormalizer.cs
@@ -0,0 +1,51 @@
+using ZB.MOM.WW.ScadaBridge.Commons.Types;
+using ZB.MOM.WW.ScadaBridge.Commons.Types.Enums;
+
+namespace ZB.MOM.WW.ScadaBridge.Transport.Serialization;
+
+/// <summary>
+/// Import-time normalization of attribute values to the native-typed JSON form.
+/// <para>
+/// Bundles exported before the native-typed-JSON change carry List attribute
+/// values in the old quoted-element form (e.g. <c>["10","20"]</c> for an
+/// <see cref="DataType.Int32"/> list). Already-exported bundle files can't be
+/// rewritten, so List values are normalised on import: every DTO→entity write
+/// site routes the value through <see cref="NormalizeListValue"/> so imported
+/// data lands native (<c>[10,20]</c>). The central DB normalizer remains the
+/// backstop for anything that slips through.
+/// </para>
+/// <para>
+/// Non-List attributes and null/empty values pass through unchanged. A value
+/// that fails to decode (malformed JSON / un-parseable element) is left exactly
+/// as-is so the import still succeeds — the DB normalizer is the backstop.
+/// </para>
+/// </summary>
+internal static class ImportValueNormalizer
+{
+    /// <summary>
+    /// Returns the native-typed JSON form of a List attribute value, or the
+    /// value unchanged for non-List / null / empty / malformed inputs.
+    /// </summary>
+    /// <param name="value">The attribute value as carried by the bundle DTO.</param>
+    /// <param name="dataType">The attribute's declared data type.</param>
+    /// <param name="elementType">The List element type (null for scalars).</param>
+    public static string? NormalizeListValue(string? value, DataType dataType, DataType? elementType)
+    {
+        if (dataType != DataType.List || string.IsNullOrEmpty(value))
+        {
+            return value;
+        }
+
+        try
+        {
+            return AttributeValueCodec.Encode(
+                AttributeValueCodec.Decode(value, DataType.List, elementType));
+        }
+        catch (FormatException)
+        {
+            // Leave malformed values exactly as imported; the DB normalizer is
+            // the backstop. Never abort the import for a single bad value.
+            return value;
+        }
+    }
+}
diff --git a/tests/ZB.MOM.WW.ScadaBridge.Transport.Tests/Serialization/EntitySerializerTests.cs b/tests/ZB.MOM.WW.ScadaBridge.Transport.Tests/Serialization/EntitySerializerTests.cs
index b4fefbb0..51f8ab0c 100644
--- a/tests/ZB.MOM.WW.ScadaBridge.Transport.Tests/Serialization/EntitySerializerTests.cs
+++ b/tests/ZB.MOM.WW.ScadaBridge.Transport.Tests/Serialization/EntitySerializerTests.cs
@@ -259,6 +259,122 @@ public sealed class EntitySerializerTests
         Assert.Equal("[\"a\",\"b\"]", rtAttr.Value);
     }
 
+    private static BundleContentDto MakeContentWithListAttribute(
+        string value, DataType elementType)
+    {
+        var template = new TemplateDto(
+            Name: "Pump",
+            FolderName: null,
+            BaseTemplateName: null,
+            Description: null,
+            Attributes: new[]
+            {
+                new TemplateAttributeDto(
+                    Name: "Tags",
+                    Value: value,
+                    DataType: DataType.List,
+                    IsLocked: false,
+                    Description: null,
+                    DataSourceReference: null,
+                    ElementDataType: elementType),
+            },
+            Alarms: Array.Empty<TemplateAlarmDto>(),
+            Scripts: Array.Empty<TemplateScriptDto>(),
+            Compositions: Array.Empty<TemplateCompositionDto>());
+
+        return new BundleContentDto(
+            TemplateFolders: Array.Empty<TemplateFolderDto>(),
+            Templates: new[] { template },
+            SharedScripts: Array.Empty<SharedScriptDto>(),
+            ExternalSystems: Array.Empty<ExternalSystemDto>(),
+            DatabaseConnections: Array.Empty<DatabaseConnectionDto>(),
+            NotificationLists: Array.Empty<NotificationListDto>(),
+            SmtpConfigs: Array.Empty<SmtpConfigDto>(),
+            ApiMethods: Array.Empty<ApiMethodDto>());
+    }
+
+    [Fact]
+    public void Import_normalizes_old_form_Int32_list_value_to_native_json()
+    {
+        // Pre-native bundle: quoted Int32 list elements.
+        var dto = MakeContentWithListAttribute("[\"10\",\"20\"]", DataType.Int32);
+
+        var aggregate = new EntitySerializer().FromBundleContent(dto);
+
+        var attr = Assert.Single(Assert.Single(aggregate.Templates).Attributes);
+        Assert.Equal(DataType.List, attr.DataType);
+        Assert.Equal(DataType.Int32, attr.ElementDataType);
+        // Imported native: numbers unquoted.
+        Assert.Equal("[10,20]", attr.Value);
+    }
+
+    [Fact]
+    public void Import_leaves_string_list_value_quoted()
+    {
+        var dto = MakeContentWithListAttribute("[\"a\",\"b\"]", DataType.String);
+
+        var aggregate = new EntitySerializer().FromBundleContent(dto);
+
+        var attr = Assert.Single(Assert.Single(aggregate.Templates).Attributes);
+        Assert.Equal(DataType.List, attr.DataType);
+        Assert.Equal(DataType.String, attr.ElementDataType);
+        // Strings stay quoted in native form.
+        Assert.Equal("[\"a\",\"b\"]", attr.Value);
+    }
+
+    [Fact]
+    public void Import_leaves_malformed_list_value_unchanged_without_throwing()
+    {
+        // Truncated JSON array — Decode throws FormatException; the import must
+        // still succeed and carry the value through verbatim (DB normalizer is
+        // the backstop).
+        var dto = MakeContentWithListAttribute("[\"a\"", DataType.String);
+
+        var aggregate = new EntitySerializer().FromBundleContent(dto);
+
+        var attr = Assert.Single(Assert.Single(aggregate.Templates).Attributes);
+        Assert.Equal("[\"a\"", attr.Value);
+    }
+
+    [Fact]
+    public void Import_leaves_scalar_attribute_value_unchanged()
+    {
+        var template = new TemplateDto(
+            Name: "Sensor",
+            FolderName: null,
+            BaseTemplateName: null,
+            Description: null,
+            Attributes: new[]
+            {
+                new TemplateAttributeDto(
+                    Name: "Pressure",
+                    Value: "42.0",
+                    DataType: DataType.Double,
+                    IsLocked: false,
+                    Description: null,
+                    DataSourceReference: null,
+                    ElementDataType: null),
+            },
+            Alarms: Array.Empty<TemplateAlarmDto>(),
+            Scripts: Array.Empty<TemplateScriptDto>(),
+            Compositions: Array.Empty<TemplateCompositionDto>());
+        var dto = new BundleContentDto(
+            TemplateFolders: Array.Empty<TemplateFolderDto>(),
+            Templates: new[] { template },
+            SharedScripts: Array.Empty<SharedScriptDto>(),
+            ExternalSystems: Array.Empty<ExternalSystemDto>(),
+            DatabaseConnections: Array.Empty<DatabaseConnectionDto>(),
+            NotificationLists: Array.Empty<NotificationListDto>(),
+            SmtpConfigs: Array.Empty<SmtpConfigDto>(),
+            ApiMethods: Array.Empty<ApiMethodDto>());
+
+        var aggregate = new EntitySerializer().FromBundleContent(dto);
+
+        var attr = Assert.Single(Assert.Single(aggregate.Templates).Attributes);
+        Assert.Equal(DataType.Double, attr.DataType);
+        Assert.Equal("42.0", attr.Value);
+    }
+
     [Fact]
     public void Roundtrip_scalar_attribute_with_null_ElementDataType_remains_null()
     {