diff --git a/src/Core/ZB.MOM.WW.OtOpcUa.Configuration/Entities/Tag.cs b/src/Core/ZB.MOM.WW.OtOpcUa.Configuration/Entities/Tag.cs
index 889e9d7f..e6517171 100644
--- a/src/Core/ZB.MOM.WW.OtOpcUa.Configuration/Entities/Tag.cs
+++ b/src/Core/ZB.MOM.WW.OtOpcUa.Configuration/Entities/Tag.cs
@@ -3,9 +3,11 @@ using ZB.MOM.WW.OtOpcUa.Configuration.Enums;
 namespace ZB.MOM.WW.OtOpcUa.Configuration.Entities;
 
 /// <summary>
-///     One canonical tag (signal) in a cluster's generation. Per decision #110:
-///     <see cref="EquipmentId"/> is REQUIRED when the driver is in an Equipment-kind namespace
-///     and NULL when in SystemPlatform-kind namespace (Galaxy hierarchy preserved).
+///     One canonical tag (signal) in a cluster's generation. <see cref="EquipmentId"/> set ⟺ the
+///     tag participates in the Equipment tree, regardless of the driver's namespace kind. A
+///     <c>GalaxyMxGateway</c>-bound equipment tag is an <em>alias</em> — a Galaxy attribute surfaced
+///     under a UNS name, with its Galaxy reference carried in <c>TagConfig.FullName</c>.
+///     <see cref="EquipmentId"/> is NULL for SystemPlatform mirror tags (FolderPath-scoped).
 /// </summary>
 public sealed class Tag
 {
@@ -30,8 +32,8 @@ public sealed class Tag
     public string? DeviceId { get; set; }
 
     /// <summary>
-    ///     Required when driver is in Equipment-kind namespace; NULL when in SystemPlatform-kind.
-    ///     Cross-table invariant enforced by sp_ValidateDraft (decision #110).
+    ///     Set when the tag belongs to an Equipment (driver tag OR Galaxy alias); NULL for
+    ///     SystemPlatform mirror tags.
     /// </summary>
     public string? EquipmentId { get; set; }
 
diff --git a/src/Core/ZB.MOM.WW.OtOpcUa.Configuration/Validation/DraftValidator.cs b/src/Core/ZB.MOM.WW.OtOpcUa.Configuration/Validation/DraftValidator.cs
index 16dc5f21..88db5322 100644
--- a/src/Core/ZB.MOM.WW.OtOpcUa.Configuration/Validation/DraftValidator.cs
+++ b/src/Core/ZB.MOM.WW.OtOpcUa.Configuration/Validation/DraftValidator.cs
@@ -33,10 +33,43 @@ public static class DraftValidator
         ValidateEquipmentIdDerivation(draft, errors);
         ValidateDriverNamespaceCompatibility(draft, errors);
         ValidateNoEquipmentSignalNameCollision(draft, errors);
+        ValidateAliasTagFullName(draft, errors);
 
         return errors;
     }
 
+    private static void ValidateAliasTagFullName(DraftSnapshot draft, List<ValidationError> errors)
+    {
+        var typeByDriver = draft.DriverInstances
+            .ToDictionary(d => d.DriverInstanceId, d => d.DriverType, StringComparer.Ordinal);
+        foreach (var t in draft.Tags)
+        {
+            if (t.EquipmentId is null) continue;
+            if (!typeByDriver.TryGetValue(t.DriverInstanceId, out var dtype) || dtype != "GalaxyMxGateway")
+                continue;
+            if (string.IsNullOrWhiteSpace(ExtractTagConfigFullName(t.TagConfig)))
+                errors.Add(new("AliasTagMissingReference",
+                    $"Alias tag '{t.TagId}' on equipment '{t.EquipmentId}' is missing a Galaxy reference (TagConfig.FullName)",
+                    t.TagId));
+        }
+    }
+
+    // Minimal reader for the top-level "FullName" string in a tag's schemaless TagConfig JSON
+    // (mirrors Phase7Composer.ExtractTagFullName — a small local copy, consistent with this codebase
+    // where the composer keeps its own).
+    private static string? ExtractTagConfigFullName(string? tagConfig)
+    {
+        if (string.IsNullOrWhiteSpace(tagConfig)) return null;
+        try
+        {
+            using var doc = System.Text.Json.JsonDocument.Parse(tagConfig);
+            return doc.RootElement.ValueKind == System.Text.Json.JsonValueKind.Object
+                && doc.RootElement.TryGetProperty("FullName", out var fn)
+                && fn.ValueKind == System.Text.Json.JsonValueKind.String ? fn.GetString() : null;
+        }
+        catch (System.Text.Json.JsonException) { return null; }
+    }
+
     private static void ValidateNoEquipmentSignalNameCollision(DraftSnapshot draft, List<ValidationError> errors)
     {
         // Materialiser NodeId key: "{EquipmentId}[/{FolderPath}]/{Name}". Tag (EquipmentId != null) and
diff --git a/tests/Core/ZB.MOM.WW.OtOpcUa.Configuration.Tests/DraftValidatorTests.cs b/tests/Core/ZB.MOM.WW.OtOpcUa.Configuration.Tests/DraftValidatorTests.cs
index 6e98af3b..5452884b 100644
--- a/tests/Core/ZB.MOM.WW.OtOpcUa.Configuration.Tests/DraftValidatorTests.cs
+++ b/tests/Core/ZB.MOM.WW.OtOpcUa.Configuration.Tests/DraftValidatorTests.cs
@@ -405,16 +405,21 @@ public sealed class DraftValidatorTests
         DraftValidator.Validate(draft).ShouldNotContain(e => e.Code == "EquipmentSignalNameCollision");
     }
 
-    private static Tag BuildTag(string? equipmentId, string name, string? folderPath) => new()
+    private static Tag BuildTag(
+        string? equipmentId,
+        string name,
+        string? folderPath,
+        string driverInstanceId = "d",
+        string tagConfig = "{}") => new()
     {
         TagId = $"tag-{name}",
-        DriverInstanceId = "d",
+        DriverInstanceId = driverInstanceId,
         EquipmentId = equipmentId,
         Name = name,
         FolderPath = folderPath,
         DataType = "Float",
         AccessLevel = TagAccessLevel.Read,
-        TagConfig = "{}",
+        TagConfig = tagConfig,
     };
 
     private static VirtualTag BuildVirtualTag(string equipmentId, string name) => new()
@@ -426,6 +431,57 @@ public sealed class DraftValidatorTests
         ScriptId = "s-1",
     };
 
+    // ------------------------------------------------------------------------------------
+    // ValidateAliasTagFullName — Galaxy alias tags must carry TagConfig.FullName
+    // ------------------------------------------------------------------------------------
+
+    /// <summary>Verifies that an equipment-scoped Tag bound to a GalaxyMxGateway driver whose
+    /// TagConfig has no FullName (an alias with no Galaxy reference) is rejected — it would
+    /// subscribe to nothing.</summary>
+    [Fact]
+    public void AliasTag_missing_FullName_is_rejected()
+    {
+        var draft = new DraftSnapshot
+        {
+            GenerationId = 1, ClusterId = "c",
+            DriverInstances = [new DriverInstance { DriverInstanceId = "d-galaxy", ClusterId = "c", NamespaceId = "ns-1", Name = "Galaxy", DriverType = "GalaxyMxGateway", DriverConfig = "{}" }],
+            Tags = [BuildTag(equipmentId: "eq-1", name: "alias", folderPath: null, driverInstanceId: "d-galaxy", tagConfig: "{}")],
+        };
+
+        DraftValidator.Validate(draft).ShouldContain(e => e.Code == "AliasTagMissingReference" && e.Context == "tag-alias");
+    }
+
+    /// <summary>Verifies that an equipment-scoped Galaxy alias tag carrying a TagConfig.FullName
+    /// reference is accepted.</summary>
+    [Fact]
+    public void AliasTag_with_FullName_is_accepted()
+    {
+        var draft = new DraftSnapshot
+        {
+            GenerationId = 1, ClusterId = "c",
+            DriverInstances = [new DriverInstance { DriverInstanceId = "d-galaxy", ClusterId = "c", NamespaceId = "ns-1", Name = "Galaxy", DriverType = "GalaxyMxGateway", DriverConfig = "{}" }],
+            Tags = [BuildTag(equipmentId: "eq-1", name: "alias", folderPath: null, driverInstanceId: "d-galaxy", tagConfig: "{\"FullName\":\"X.Y\"}")],
+        };
+
+        DraftValidator.Validate(draft).ShouldNotContain(e => e.Code == "AliasTagMissingReference");
+    }
+
+    /// <summary>Verifies that an equipment-scoped Tag bound to a NON-Galaxy driver with an empty
+    /// TagConfig is NOT flagged as an alias missing its reference — only GalaxyMxGateway-bound
+    /// equipment tags are aliases.</summary>
+    [Fact]
+    public void AliasTag_check_skips_nonGalaxy_equipment_tag()
+    {
+        var draft = new DraftSnapshot
+        {
+            GenerationId = 1, ClusterId = "c",
+            DriverInstances = [new DriverInstance { DriverInstanceId = "d-modbus", ClusterId = "c", NamespaceId = "ns-1", Name = "Modbus", DriverType = "Modbus", DriverConfig = "{}" }],
+            Tags = [BuildTag(equipmentId: "eq-1", name: "alias", folderPath: null, driverInstanceId: "d-modbus", tagConfig: "{}")],
+        };
+
+        DraftValidator.Validate(draft).ShouldNotContain(e => e.Code == "AliasTagMissingReference");
+    }
+
     // ------------------------------------------------------------------------------------
     // Phase 6.3 task #148 part 2 — ValidateClusterTopology
     // ------------------------------------------------------------------------------------