diff --git a/src/Server/ZB.MOM.WW.OtOpcUa.AdminUI/Components/Shared/Uns/TagModal.razor b/src/Server/ZB.MOM.WW.OtOpcUa.AdminUI/Components/Shared/Uns/TagModal.razor
index b03337fd..aff7f627 100644
--- a/src/Server/ZB.MOM.WW.OtOpcUa.AdminUI/Components/Shared/Uns/TagModal.razor
+++ b/src/Server/ZB.MOM.WW.OtOpcUa.AdminUI/Components/Shared/Uns/TagModal.razor
@@ -197,6 +197,15 @@
         _error = null;
         try
         {
+            // Client-side per-driver config validation (the typed editor's Validate()), so a blank
+            // required field is caught here rather than silently saving and failing at deploy/connect.
+            var configError = TagConfigValidator.Validate(SelectedDriverType, _form.TagConfig);
+            if (configError is not null)
+            {
+                _error = configError;
+                return;
+            }
+
             var input = new TagInput(
                 _form.TagId,
                 _form.Name,
diff --git a/src/Server/ZB.MOM.WW.OtOpcUa.AdminUI/Uns/TagEditors/TagConfigValidator.cs b/src/Server/ZB.MOM.WW.OtOpcUa.AdminUI/Uns/TagEditors/TagConfigValidator.cs
new file mode 100644
index 00000000..8e5f8722
--- /dev/null
+++ b/src/Server/ZB.MOM.WW.OtOpcUa.AdminUI/Uns/TagEditors/TagConfigValidator.cs
@@ -0,0 +1,29 @@
+namespace ZB.MOM.WW.OtOpcUa.AdminUI.Uns.TagEditors;
+
+/// <summary>
+/// Client-side TagConfig validation dispatched by <c>DriverType</c> (parallel to
+/// <see cref="TagConfigEditorMap"/>). Each entry parses the tag's config JSON into the driver's typed
+/// model and runs its <c>Validate()</c>. Returns an error string to block the TagModal save, or null
+/// when the config is valid — or when no typed validator is registered (unmapped drivers use the raw
+/// textarea and are validated server-side at deploy).
+/// </summary>
+public static class TagConfigValidator
+{
+    private static readonly IReadOnlyDictionary<string, Func<string?, string?>> Validators =
+        new Dictionary<string, Func<string?, string?>>(StringComparer.OrdinalIgnoreCase)
+        {
+            ["ModbusTcp"] = j => ModbusTagConfigModel.FromJson(j).Validate(),
+            ["S7"]        = j => S7TagConfigModel.FromJson(j).Validate(),
+            ["AbCip"]     = j => AbCipTagConfigModel.FromJson(j).Validate(),
+            ["AbLegacy"]  = j => AbLegacyTagConfigModel.FromJson(j).Validate(),
+            ["TwinCat"]   = j => TwinCATTagConfigModel.FromJson(j).Validate(),
+            ["Focas"]     = j => FocasTagConfigModel.FromJson(j).Validate(),
+        };
+
+    /// <summary>
+    /// Validates a tag's <paramref name="configJson"/> for the given <paramref name="driverType"/>.
+    /// Returns an error string to block save, or null when valid / no typed validator is registered.
+    /// </summary>
+    public static string? Validate(string? driverType, string? configJson)
+        => driverType is not null && Validators.TryGetValue(driverType, out var v) ? v(configJson) : null;
+}
diff --git a/tests/Server/ZB.MOM.WW.OtOpcUa.AdminUI.Tests/Uns/TagConfigValidatorTests.cs b/tests/Server/ZB.MOM.WW.OtOpcUa.AdminUI.Tests/Uns/TagConfigValidatorTests.cs
new file mode 100644
index 00000000..328b4f49
--- /dev/null
+++ b/tests/Server/ZB.MOM.WW.OtOpcUa.AdminUI.Tests/Uns/TagConfigValidatorTests.cs
@@ -0,0 +1,49 @@
+using Shouldly;
+using ZB.MOM.WW.OtOpcUa.AdminUI.Uns.TagEditors;
+using Xunit;
+
+namespace ZB.MOM.WW.OtOpcUa.AdminUI.Tests.Uns;
+
+public sealed class TagConfigValidatorTests
+{
+    [Fact]
+    public void No_driver_type_is_valid()
+        => TagConfigValidator.Validate(null, "{}").ShouldBeNull();
+
+    [Fact]
+    public void Unmapped_driver_has_no_typed_validator_so_is_valid()
+        => TagConfigValidator.Validate("OpcUaClient", "{}").ShouldBeNull();
+
+    [Fact]
+    public void Modbus_has_no_required_field_so_empty_config_is_valid()
+        => TagConfigValidator.Validate("ModbusTcp", "{}").ShouldBeNull();
+
+    // Drivers whose Validate() requires a field: blank config must return an error string.
+    [Theory]
+    [InlineData("S7")]
+    [InlineData("AbCip")]
+    [InlineData("AbLegacy")]
+    [InlineData("TwinCat")]
+    [InlineData("Focas")]
+    public void Required_field_blank_is_rejected(string driverType)
+    {
+        TagConfigValidator.Validate(driverType, "{}").ShouldNotBeNullOrEmpty();
+        TagConfigValidator.Validate(driverType, null).ShouldNotBeNullOrEmpty();
+    }
+
+    [Fact]
+    public void S7_with_address_is_valid()
+        => TagConfigValidator.Validate("S7", """{"address":"DB1.DBW0"}""").ShouldBeNull();
+
+    [Fact]
+    public void AbCip_with_tag_path_is_valid()
+        => TagConfigValidator.Validate("AbCip", """{"tagPath":"Program:Main.Speed"}""").ShouldBeNull();
+
+    [Fact]
+    public void TwinCat_with_symbol_path_is_valid()
+        => TagConfigValidator.Validate("TwinCat", """{"symbolPath":"MAIN.bStart"}""").ShouldBeNull();
+
+    [Fact]
+    public void Driver_type_lookup_is_case_insensitive()
+        => TagConfigValidator.Validate("s7", "{}").ShouldNotBeNullOrEmpty();
+}