diff --git a/src/ZB.MOM.WW.ScadaBridge.CentralUI/Components/Pages/Admin/ApiKeyForm.razor b/src/ZB.MOM.WW.ScadaBridge.CentralUI/Components/Pages/Admin/ApiKeyForm.razor
index a0287807..66d4fe3f 100644
--- a/src/ZB.MOM.WW.ScadaBridge.CentralUI/Components/Pages/Admin/ApiKeyForm.razor
+++ b/src/ZB.MOM.WW.ScadaBridge.CentralUI/Components/Pages/Admin/ApiKeyForm.razor
@@ -170,6 +170,12 @@
     {
         _formError = null;
 
+        if (!IsEditMode && string.IsNullOrWhiteSpace(_formName))
+        {
+            _formError = "Name is required.";
+            return;
+        }
+
         // The seam/server reject empty scope sets; validate in the UI for a clear message.
         if (_selectedMethodNames.Count == 0)
         {
@@ -182,13 +188,16 @@
             if (_editingKey != null)
             {
                 // Edit: name is fixed; only the method-scope set is mutable.
-                await ApiKeyAdmin.SetMethodsAsync(_editingKey.KeyId, _selectedMethodNames.ToList());
+                var ok = await ApiKeyAdmin.SetMethodsAsync(_editingKey.KeyId, _selectedMethodNames.ToList());
+                if (!ok)
+                {
+                    _formError = $"API key '{_editingKey.Name}' was not found. Reload and retry.";
+                    return;
+                }
                 NavigationManager.NavigateTo("/admin/api-keys");
             }
             else
             {
-                if (string.IsNullOrWhiteSpace(_formName)) { _formError = "Name is required."; return; }
-
                 var created = await ApiKeyAdmin.CreateAsync(_formName.Trim(), _selectedMethodNames.ToList());
                 _newlyCreatedKeyId = created.KeyId;
                 _newlyCreatedToken = created.Token;  // shown once; never persisted client-side.
diff --git a/src/ZB.MOM.WW.ScadaBridge.CentralUI/Components/Pages/Admin/ApiKeys.razor b/src/ZB.MOM.WW.ScadaBridge.CentralUI/Components/Pages/Admin/ApiKeys.razor
index b06700de..a0adf48a 100644
--- a/src/ZB.MOM.WW.ScadaBridge.CentralUI/Components/Pages/Admin/ApiKeys.razor
+++ b/src/ZB.MOM.WW.ScadaBridge.CentralUI/Components/Pages/Admin/ApiKeys.razor
@@ -146,7 +146,13 @@
         {
             var newEnabled = !key.Enabled;
             // The seam persists; there is no separate SaveChangesAsync.
-            await ApiKeyAdmin.SetEnabledAsync(key.KeyId, newEnabled);
+            var ok = await ApiKeyAdmin.SetEnabledAsync(key.KeyId, newEnabled);
+            if (!ok)
+            {
+                _toast.ShowError($"API key '{key.Name}' was not found — it may have been removed. Refreshing.");
+                await LoadDataAsync();
+                return;
+            }
             _toast.ShowSuccess($"API key '{key.Name}' {(newEnabled ? "enabled" : "disabled")}.");
             await LoadDataAsync();
         }
@@ -166,7 +172,13 @@
 
         try
         {
-            await ApiKeyAdmin.DeleteAsync(key.KeyId);
+            var ok = await ApiKeyAdmin.DeleteAsync(key.KeyId);
+            if (!ok)
+            {
+                _toast.ShowError($"API key '{key.Name}' was not found — it may have been removed. Refreshing.");
+                await LoadDataAsync();
+                return;
+            }
             _toast.ShowSuccess($"API key '{key.Name}' deleted.");
             await LoadDataAsync();
         }
diff --git a/src/ZB.MOM.WW.ScadaBridge.CentralUI/Components/Pages/Design/ApiMethodForm.razor b/src/ZB.MOM.WW.ScadaBridge.CentralUI/Components/Pages/Design/ApiMethodForm.razor
index 1d3f0d9f..67067d8e 100644
--- a/src/ZB.MOM.WW.ScadaBridge.CentralUI/Components/Pages/Design/ApiMethodForm.razor
+++ b/src/ZB.MOM.WW.ScadaBridge.CentralUI/Components/Pages/Design/ApiMethodForm.razor
@@ -331,9 +331,21 @@
             return false;
         }
 
-        foreach (var update in plan.Updates)
+        try
         {
-            await ApiKeyAdmin.SetMethodsAsync(update.KeyId, update.NewMethods);
+            foreach (var update in plan.Updates)
+            {
+                var ok = await ApiKeyAdmin.SetMethodsAsync(update.KeyId, update.NewMethods);
+                if (!ok)
+                    throw new InvalidOperationException(
+                        $"Key '{NameFor(update.KeyId)}' was not found in the key store.");
+            }
+        }
+        catch (Exception ex)
+        {
+            throw new InvalidOperationException(
+                $"Method '{methodName}' was saved, but updating approved-key scopes failed partway: {ex.Message} " +
+                "Some keys may be partially updated — review them on the API Keys page and retry.", ex);
         }
 
         // Selection is now the baseline (matters if save is retried without reload).
@@ -341,6 +353,10 @@
         return true;
     }
 
+    // Returns the display name for a keyId if available from the loaded key list, else the id itself.
+    private string NameFor(string keyId) =>
+        _allKeys.FirstOrDefault(k => string.Equals(k.KeyId, keyId, StringComparison.Ordinal))?.Name ?? keyId;
+
     private void GoBack() => NavigationManager.NavigateTo("/design/external-systems");
 
     private void ToggleTestRunPanel() => _showTestRun = !_showTestRun;
diff --git a/tests/ZB.MOM.WW.ScadaBridge.CentralUI.Tests/Services/ApiMethodKeyScopeReconcilerTests.cs b/tests/ZB.MOM.WW.ScadaBridge.CentralUI.Tests/Services/ApiMethodKeyScopeReconcilerTests.cs
index 929acddf..7459ea00 100644
--- a/tests/ZB.MOM.WW.ScadaBridge.CentralUI.Tests/Services/ApiMethodKeyScopeReconcilerTests.cs
+++ b/tests/ZB.MOM.WW.ScadaBridge.CentralUI.Tests/Services/ApiMethodKeyScopeReconcilerTests.cs
@@ -115,4 +115,28 @@ public sealed class ApiMethodKeyScopeReconcilerTests
         Assert.Empty(result.Updates);
         Assert.Empty(result.EmptyScopeKeyNames);
     }
+
+    /// <summary>
+    /// Concurrent-edit guard: if selected == initial (no diff), the reconciler must produce
+    /// ZERO updates even when the live store shows different scopes on that key. The reconciler
+    /// only acts on keys that appear in the diff (added or removed relative to <c>initialKeyIds</c>)
+    /// — it must never touch keys that are not in the diff, regardless of what their current
+    /// live scopes look like.
+    /// </summary>
+    [Fact]
+    public void NoDiff_ProducesNoUpdates_EvenWhenLiveScopesDiffer()
+    {
+        // k1 was approved at load time and is still approved — no diff.
+        // However, a concurrent edit changed k1's live scopes to include an extra method.
+        var result = ApiMethodKeyScopeReconciler.Reconcile(
+            methodName: "PlaceOrder",
+            selectedKeyIds: new HashSet<string> { "k1" },
+            initialKeyIds: new HashSet<string> { "k1" },
+            currentMethodsByKey: Current(("k1", new[] { "PlaceOrder", "OtherMethod" })),
+            keyNamesById: Names(("k1", "Key One")));
+
+        // k1 is not in the diff → reconciler must not touch it.
+        Assert.Empty(result.Updates);
+        Assert.Empty(result.EmptyScopeKeyNames);
+    }
 }