diff --git a/src/ZB.MOM.WW.ScadaBridge.Commons/Validation/GrpcEndpointRules.cs b/src/ZB.MOM.WW.ScadaBridge.Commons/Validation/GrpcEndpointRules.cs
new file mode 100644
index 00000000..7dc75b32
--- /dev/null
+++ b/src/ZB.MOM.WW.ScadaBridge.Commons/Validation/GrpcEndpointRules.cs
@@ -0,0 +1,37 @@
+namespace ZB.MOM.WW.ScadaBridge.Commons.Validation;
+
+/// <summary>
+/// Validation for site gRPC endpoint addresses (<c>Site.GrpcNodeAAddress</c>/<c>GrpcNodeBAddress</c>).
+/// A bare host or <c>host:port</c> is rejected because the gRPC channel needs an absolute http(s) URI.
+/// </summary>
+public static class GrpcEndpointRules
+{
+    /// <summary>
+    /// Validates a gRPC endpoint. Null/whitespace is "not configured": valid only when
+    /// <paramref name="allowEmpty"/> is true.
+    /// </summary>
+    public static bool TryValidate(string? value, bool allowEmpty, out string? error)
+    {
+        error = null;
+        if (string.IsNullOrWhiteSpace(value))
+        {
+            if (allowEmpty)
+            {
+                return true;
+            }
+
+            error = "gRPC endpoint is required (e.g. http://host:8083).";
+            return false;
+        }
+
+        if (!Uri.TryCreate(value.Trim(), UriKind.Absolute, out var uri)
+            || (uri.Scheme != Uri.UriSchemeHttp && uri.Scheme != Uri.UriSchemeHttps)
+            || string.IsNullOrEmpty(uri.Host))
+        {
+            error = $"gRPC endpoint '{value}' must be an absolute http:// or https:// URL with a host (e.g. http://host:8083).";
+            return false;
+        }
+
+        return true;
+    }
+}
diff --git a/tests/ZB.MOM.WW.ScadaBridge.Commons.Tests/Validation/GrpcEndpointRulesTests.cs b/tests/ZB.MOM.WW.ScadaBridge.Commons.Tests/Validation/GrpcEndpointRulesTests.cs
new file mode 100644
index 00000000..a356953e
--- /dev/null
+++ b/tests/ZB.MOM.WW.ScadaBridge.Commons.Tests/Validation/GrpcEndpointRulesTests.cs
@@ -0,0 +1,37 @@
+using ZB.MOM.WW.ScadaBridge.Commons.Validation;
+
+namespace ZB.MOM.WW.ScadaBridge.Commons.Tests.Validation;
+
+public class GrpcEndpointRulesTests
+{
+    [Theory]
+    [InlineData("scadabridge-site-a-node-a")]
+    [InlineData("site-a-node-a:8083")]
+    [InlineData("ftp://x:1")]
+    public void TryValidate_RejectsNonHttpEndpoints(string value)
+    {
+        Assert.False(GrpcEndpointRules.TryValidate(value, false, out var error));
+        Assert.NotNull(error);
+    }
+
+    [Theory]
+    [InlineData("http://site-a-node-a:8083")]
+    [InlineData("https://h")]
+    public void TryValidate_AcceptsHttpEndpoints(string value)
+    {
+        Assert.True(GrpcEndpointRules.TryValidate(value, false, out var error));
+        Assert.Null(error);
+    }
+
+    [Theory]
+    [InlineData(null)]
+    [InlineData("")]
+    [InlineData("  ")]
+    public void TryValidate_EmptyHonoursAllowEmpty(string? value)
+    {
+        Assert.True(GrpcEndpointRules.TryValidate(value, true, out var ok));
+        Assert.Null(ok);
+        Assert.False(GrpcEndpointRules.TryValidate(value, false, out var err));
+        Assert.NotNull(err);
+    }
+}