diff --git a/src/ZB.MOM.WW.ScadaBridge.ConfigurationDatabase/Repositories/NotificationOutboxRepository.cs b/src/ZB.MOM.WW.ScadaBridge.ConfigurationDatabase/Repositories/NotificationOutboxRepository.cs
index 6845bb73..f55d3837 100644
--- a/src/ZB.MOM.WW.ScadaBridge.ConfigurationDatabase/Repositories/NotificationOutboxRepository.cs
+++ b/src/ZB.MOM.WW.ScadaBridge.ConfigurationDatabase/Repositories/NotificationOutboxRepository.cs
@@ -61,6 +61,39 @@ public class NotificationOutboxRepository : INotificationOutboxRepository
         var type = n.Type.ToString();
         var status = n.Status.ToString();
 
+        // Provider-aware idempotent insert. The production path is SQL Server; the
+        // NotificationOutbox integration tests run over an in-memory SQLite database,
+        // and SQLite does not understand the T-SQL `IF NOT EXISTS … INSERT` form
+        // (it raises 'near "IF": syntax error'). Detect SQLite by provider name so
+        // ConfigurationDatabase needs no Sqlite package reference; the SQL Server
+        // path below stays byte-identical.
+        if (_context.Database.ProviderName == "Microsoft.EntityFrameworkCore.Sqlite")
+        {
+            // SQLite's idempotent insert: INSERT OR IGNORE skips the row when the
+            // NotificationId primary key already exists (no schema prefix in SQLite).
+            // Same parameterised columns/values as the SQL Server branch — the
+            // FormattableString interpolation still parameterises every value
+            // (no concatenation), so this is injection-safe.
+            var sqliteRowsAffected = await _context.Database.ExecuteSqlInterpolatedAsync(
+                $@"INSERT OR IGNORE INTO Notifications
+    (NotificationId, Type, ListName, Subject, Body, TypeData, Status, RetryCount, LastError,
+     ResolvedTargets, SourceSiteId, SourceNode, SourceInstanceId, SourceScript,
+     OriginExecutionId, OriginParentExecutionId,
+     SiteEnqueuedAt, CreatedAt, LastAttemptAt, NextAttemptAt, DeliveredAt)
+VALUES
+    ({n.NotificationId}, {type}, {n.ListName}, {n.Subject}, {n.Body}, {n.TypeData}, {status}, {n.RetryCount}, {n.LastError},
+     {n.ResolvedTargets}, {n.SourceSiteId}, {n.SourceNode}, {n.SourceInstanceId}, {n.SourceScript},
+     {n.OriginExecutionId}, {n.OriginParentExecutionId},
+     {n.SiteEnqueuedAt}, {n.CreatedAt}, {n.LastAttemptAt}, {n.NextAttemptAt}, {n.DeliveredAt});",
+                cancellationToken);
+
+            // rowsAffected == 1 -> we inserted; 0 -> the row was IGNOREd because the
+            // NotificationId already existed. Preserves the true=inserted / false=already-existed
+            // contract. No SqlException catch needed — INSERT OR IGNORE never raises a
+            // unique-constraint violation.
+            return sqliteRowsAffected == 1;
+        }
+
         // FormattableString interpolation parameterises every value (no concatenation),
         // so this is safe against injection even for the string columns.
         try
diff --git a/tests/ZB.MOM.WW.ScadaBridge.IntegrationTests/ScadaBridgeWebApplicationFactory.cs b/tests/ZB.MOM.WW.ScadaBridge.IntegrationTests/ScadaBridgeWebApplicationFactory.cs
index e95c210a..9aaada52 100644
--- a/tests/ZB.MOM.WW.ScadaBridge.IntegrationTests/ScadaBridgeWebApplicationFactory.cs
+++ b/tests/ZB.MOM.WW.ScadaBridge.IntegrationTests/ScadaBridgeWebApplicationFactory.cs
@@ -38,6 +38,10 @@ public class ScadaBridgeWebApplicationFactory : WebApplicationFactory<Program>
             ["ScadaBridge__Database__MachineDataDb"] = "Server=localhost;Database=ScadaBridge_MachineData_Test;TrustServerCertificate=True",
             ["ScadaBridge__Database__SkipMigrations"] = "true",
             ["ScadaBridge__Security__JwtSigningKey"] = "integration-test-signing-key-must-be-at-least-32-chars-long",
+            // The inbound API-key pepper is a REQUIRED Central config value (StartupValidator
+            // enforces a >=16-char floor; it backs the peppered-HMAC verifier). Supply a fixed
+            // test pepper so host boot passes validation in the test environment.
+            ["ScadaBridge__InboundApi__ApiKeyPepper"] = "integration-test-api-key-pepper-0123456789",
             // Task 1.4: LDAP settings nest under Security:Ldap (shared LdapOptions) and use
             // the renamed keys (Transport replaces LdapUseTls; None == plaintext for the
             // GLAuth dev directory, paired with AllowInsecure=true).