diff --git a/src/Cli.Tests/EndToEndTests.cs b/src/Cli.Tests/EndToEndTests.cs
index a23f7823d2..c0a0acb56b 100644
--- a/src/Cli.Tests/EndToEndTests.cs
+++ b/src/Cli.Tests/EndToEndTests.cs
@@ -729,7 +729,7 @@ public void TestUpdateEntity()
 
         Assert.IsTrue(_runtimeConfigLoader!.TryLoadConfig(TEST_RUNTIME_CONFIG_FILE, out RuntimeConfig? updateRuntimeConfig));
         Assert.IsNotNull(updateRuntimeConfig);
-        Assert.AreEqual(TEST_ENV_CONN_STRING, updateRuntimeConfig.DataSource.ConnectionString);
+        Assert.AreEqual(TEST_ENV_CONN_STRING, updateRuntimeConfig.DataSource!.ConnectionString);
         Assert.AreEqual(2, updateRuntimeConfig.Entities.Count()); // No new entity added
 
         Assert.IsTrue(updateRuntimeConfig.Entities.ContainsKey("todo"));
diff --git a/src/Cli.Tests/ValidateConfigTests.cs b/src/Cli.Tests/ValidateConfigTests.cs
index e1bbc02e11..953485017d 100644
--- a/src/Cli.Tests/ValidateConfigTests.cs
+++ b/src/Cli.Tests/ValidateConfigTests.cs
@@ -944,7 +944,7 @@ private static Entity BuildSimpleEntity(string source)
     {
         return new Entity(
             Source: new EntitySource(Object: source, Type: EntitySourceType.Table, Parameters: null, KeyFields: null),
-            GraphQL: new(Singular: null, Plural: null),
+            GraphQL: new(Singular: string.Empty, Plural: string.Empty),
             Fields: null,
             Rest: new(EntityRestOptions.DEFAULT_SUPPORTED_VERBS),
             Permissions: new[] { new EntityPermission("anonymous", new[] { new EntityAction(EntityActionOperation.Read, null, null) }) },
diff --git a/src/Service.Tests/Configuration/RuntimeConfigLoaderTests.cs b/src/Service.Tests/Configuration/RuntimeConfigLoaderTests.cs
index 7c972a2d43..d4470a0017 100644
--- a/src/Service.Tests/Configuration/RuntimeConfigLoaderTests.cs
+++ b/src/Service.Tests/Configuration/RuntimeConfigLoaderTests.cs
@@ -191,9 +191,9 @@ public async Task ChildConfigWithMissingEnvVarsLoadsSuccessfully()
         }";
 
         // Save original env var values and clear them to ensure they don't exist.
-        string? origEndpoint = Environment.GetEnvironmentVariable("NONEXISTENT_OTEL_ENDPOINT");
-        string? origHeaders = Environment.GetEnvironmentVariable("NONEXISTENT_OTEL_HEADERS");
-        string? origServiceName = Environment.GetEnvironmentVariable("NONEXISTENT_OTEL_SERVICE_NAME");
+        string origEndpoint = Environment.GetEnvironmentVariable("NONEXISTENT_OTEL_ENDPOINT");
+        string origHeaders = Environment.GetEnvironmentVariable("NONEXISTENT_OTEL_HEADERS");
+        string origServiceName = Environment.GetEnvironmentVariable("NONEXISTENT_OTEL_SERVICE_NAME");
         Environment.SetEnvironmentVariable("NONEXISTENT_OTEL_ENDPOINT", null);
         Environment.SetEnvironmentVariable("NONEXISTENT_OTEL_HEADERS", null);
         Environment.SetEnvironmentVariable("NONEXISTENT_OTEL_SERVICE_NAME", null);
diff --git a/src/Service.Tests/UnitTests/RequestParserUnitTests.cs b/src/Service.Tests/UnitTests/RequestParserUnitTests.cs
index 4da3266271..0aeb309c61 100644
--- a/src/Service.Tests/UnitTests/RequestParserUnitTests.cs
+++ b/src/Service.Tests/UnitTests/RequestParserUnitTests.cs
@@ -35,7 +35,7 @@ public class RequestParserUnitTests
         public void ExtractRawQueryParameter_PreservesEncoding(string queryString, string parameterName, string expectedValue)
         {
             // Call the internal method directly (no reflection needed)
-            string? result = RequestParser.ExtractRawQueryParameter(queryString, parameterName);
+            string result = RequestParser.ExtractRawQueryParameter(queryString, parameterName);
 
             Assert.AreEqual(expectedValue, result,
                 $"Expected '{expectedValue}' but got '{result}' for parameter '{parameterName}' in query '{queryString}'");
@@ -49,10 +49,10 @@ public void ExtractRawQueryParameter_PreservesEncoding(string queryString, strin
         [DataRow("", "$filter", DisplayName = "Empty query string")]
         [DataRow(null, "$filter", DisplayName = "Null query string")]
         [DataRow("?otherParam=value", "$filter", DisplayName = "Different parameter")]
-        public void ExtractRawQueryParameter_ReturnsNull_WhenParameterNotFound(string? queryString, string parameterName)
+        public void ExtractRawQueryParameter_ReturnsNull_WhenParameterNotFound(string queryString, string parameterName)
         {
             // Call the internal method directly (no reflection needed)
-            string? result = RequestParser.ExtractRawQueryParameter(queryString, parameterName);
+            string result = RequestParser.ExtractRawQueryParameter(queryString, parameterName);
 
             Assert.IsNull(result,
                 $"Expected null but got '{result}' for parameter '{parameterName}' in query '{queryString}'");
@@ -71,7 +71,7 @@ public void ExtractRawQueryParameter_ReturnsNull_WhenParameterNotFound(string? q
         public void ExtractRawQueryParameter_HandlesEdgeCases(string queryString, string parameterName, string expectedValue)
         {
             // Call the internal method directly (no reflection needed)
-            string? result = RequestParser.ExtractRawQueryParameter(queryString, parameterName);
+            string result = RequestParser.ExtractRawQueryParameter(queryString, parameterName);
 
             Assert.AreEqual(expectedValue, result,
                 $"Expected '{expectedValue}' but got '{result}' for parameter '{parameterName}' in query '{queryString}'");
diff --git a/src/Service.Tests/UnitTests/SqlQueryExecutorUnitTests.cs b/src/Service.Tests/UnitTests/SqlQueryExecutorUnitTests.cs
index 778144c6d2..18d039b23b 100644
--- a/src/Service.Tests/UnitTests/SqlQueryExecutorUnitTests.cs
+++ b/src/Service.Tests/UnitTests/SqlQueryExecutorUnitTests.cs
@@ -950,8 +950,8 @@ public void TestOboNoUserContext_UsesBaseConnectionString()
         [DataRow(null, null, "iss and oid/sub",
             DisplayName = "Authenticated user with no claims throws OboAuthenticationFailure")]
         public void TestOboEnabled_AuthenticatedUserMissingClaims_ThrowsException(
-            string? issuer,
-            string? objectId,
+            string issuer,
+            string objectId,
             string missingClaimDescription)
         {
             // Arrange - Create an authenticated HttpContext with incomplete claims
@@ -986,8 +986,8 @@ public void TestOboEnabled_AuthenticatedUserMissingClaims_ThrowsException(
         /// <param name="objectId">The oid claim value, or null to omit.</param>
         /// <returns>A configured HttpContextAccessor mock with authenticated user.</returns>
         private static Mock<IHttpContextAccessor> CreateHttpContextAccessorWithAuthenticatedUserMissingClaims(
-            string? issuer,
-            string? objectId)
+            string issuer,
+            string objectId)
         {
             Mock<IHttpContextAccessor> httpContextAccessor = new();
             DefaultHttpContext context = new();