diff --git a/src/ZB.MOM.WW.ScadaBridge.ManagementService/ManagementActor.cs b/src/ZB.MOM.WW.ScadaBridge.ManagementService/ManagementActor.cs
index 34571956..17493d6e 100644
--- a/src/ZB.MOM.WW.ScadaBridge.ManagementService/ManagementActor.cs
+++ b/src/ZB.MOM.WW.ScadaBridge.ManagementService/ManagementActor.cs
@@ -590,9 +590,23 @@ public class ManagementActor : ReceiveActor
         var schemaLibrary = sharedSchemas.ToDictionary(s => s.Name, s => s.SchemaJson, StringComparer.Ordinal);
         Func<string, string?> resolveSchemaRef = name => schemaLibrary.GetValueOrDefault(name);
 
+        // #259: also pass shared scripts so a dangling $ref in a SHARED script's schema is
+        // caught at design-time (not only on the deploy path). Mirror the deploy-path mapping
+        // in FlatteningPipeline: SharedScript entity → ResolvedScript (name + schema fields).
+        var sharedScriptEntities = await repo.GetAllSharedScriptsAsync();
+        var resolvedSharedScripts = sharedScriptEntities
+            .Select(s => new Commons.Types.Flattening.ResolvedScript
+            {
+                CanonicalName = s.Name,
+                Code = s.Code,
+                ParameterDefinitions = s.ParameterDefinitions,
+                ReturnDefinition = s.ReturnDefinition
+            })
+            .ToList();
+
         // Run full validation pipeline (collisions, script compilation, trigger refs, bindings)
         var validationService = new TemplateEngine.Validation.ValidationService();
-        var validationResult = validationService.Validate(flatConfig, resolveSchemaRef: resolveSchemaRef);
+        var validationResult = validationService.Validate(flatConfig, resolvedSharedScripts, resolveSchemaRef: resolveSchemaRef);
 
         // Also detect naming collisions across the inheritance/composition graph
         var svc = sp.GetRequiredService<TemplateService>();
diff --git a/tests/ZB.MOM.WW.ScadaBridge.ManagementService.Tests/ManagementActorTests.cs b/tests/ZB.MOM.WW.ScadaBridge.ManagementService.Tests/ManagementActorTests.cs
index 9ab96d9d..16c79746 100644
--- a/tests/ZB.MOM.WW.ScadaBridge.ManagementService.Tests/ManagementActorTests.cs
+++ b/tests/ZB.MOM.WW.ScadaBridge.ManagementService.Tests/ManagementActorTests.cs
@@ -5,6 +5,8 @@ using Microsoft.Extensions.Logging.Abstractions;
 using NSubstitute;
 using NSubstitute.ExceptionExtensions;
 using ZB.MOM.WW.ScadaBridge.Commons.Entities.Instances;
+using ZB.MOM.WW.ScadaBridge.Commons.Entities.Schemas;
+using ZB.MOM.WW.ScadaBridge.Commons.Entities.Scripts;
 using ZB.MOM.WW.ScadaBridge.Commons.Entities.Templates;
 using ZB.MOM.WW.ScadaBridge.Commons.Interfaces.Repositories;
 using ZB.MOM.WW.ScadaBridge.Commons.Interfaces.Services;
@@ -2378,4 +2380,66 @@ public class ManagementActorTests : TestKit, IDisposable
         // The off-site template (42) must never be scanned.
         _templateRepo.DidNotReceive().GetTemplateByIdAsync(42, Arg.Any<CancellationToken>());
     }
+
+    // ========================================================================
+    // #259: design-time ValidateTemplateCommand passes sharedScripts so a
+    // dangling $ref in a SHARED script's schema is caught at design time, not
+    // only on the deploy path.
+    // ========================================================================
+
+    [Fact]
+    public void ValidateTemplate_DanglingRefInSharedScript_ReturnsInvalidResult()
+    {
+        // Arrange
+        var template = new Template("T1") { Id = 1 };
+
+        _templateRepo.GetTemplateWithChildrenAsync(1, Arg.Any<CancellationToken>())
+            .Returns(template);
+        _templateRepo.GetAttributesByTemplateIdAsync(1, Arg.Any<CancellationToken>())
+            .Returns(new List<TemplateAttribute>());
+        _templateRepo.GetAlarmsByTemplateIdAsync(1, Arg.Any<CancellationToken>())
+            .Returns(new List<TemplateAlarm>());
+        _templateRepo.GetScriptsByTemplateIdAsync(1, Arg.Any<CancellationToken>())
+            .Returns(new List<TemplateScript>());
+
+        // Shared script whose parameter schema contains a dangling $ref.
+        _templateRepo.GetAllSharedScriptsAsync(Arg.Any<CancellationToken>())
+            .Returns(new List<SharedScript>
+            {
+                new SharedScript("ComputeOrder", "var x = 1;")
+                {
+                    ParameterDefinitions = """{"$ref":"lib:MissingSharedSchema"}"""
+                }
+            });
+
+        // Schema library is empty → the $ref cannot be resolved and dangles.
+        var schemaRepo = Substitute.For<ISharedSchemaRepository>();
+        schemaRepo.ListAsync(Arg.Any<CancellationToken>())
+            .Returns(new List<SharedSchema>());
+        _services.AddScoped(_ => schemaRepo);
+
+        // TemplateService is required by the collision-detection step inside HandleValidateTemplate.
+        _templateRepo.GetTemplateByIdAsync(1, Arg.Any<CancellationToken>())
+            .Returns(template);
+        _templateRepo.GetAllTemplatesAsync(Arg.Any<CancellationToken>())
+            .Returns(new List<Template> { template });
+        _services.AddScoped<TemplateService>();
+
+        var actor = CreateActor();
+        var envelope = Envelope(new ValidateTemplateCommand(1), "Designer");
+
+        // Act
+        actor.Tell(envelope);
+
+        // Assert: the handler returns ManagementSuccess whose JSON payload signals an invalid
+        // ValidationResult with a SchemaReference error naming the missing library entry.
+        var msg = ExpectMsg<ManagementSuccess>(TimeSpan.FromSeconds(10));
+        Assert.Equal(envelope.CorrelationId, msg.CorrelationId);
+        // The ValidationResult is JSON-serialised into JsonData; check key fields in the raw JSON
+        // (consistent with how other ManagementActorTests verify structured payloads).
+        // ValidationCategory is serialised as an integer; SchemaReference is ordinal 15.
+        Assert.Contains("\"isValid\":false", msg.JsonData, StringComparison.Ordinal);
+        Assert.Contains("MissingSharedSchema", msg.JsonData, StringComparison.Ordinal);
+        Assert.Contains("\"category\":15", msg.JsonData, StringComparison.Ordinal);
+    }
 }