Tweak configuration of JsonSerializerOptions (#49875)

src/Http/Http.Extensions/gen/RequestDelegateGeneratorSources.cs

@@ -188,7 +188,7 @@ internal static class RequestDelegateGeneratorSources
 """;
 
     public static string ResolveJsonBodyOrServiceMethod => """
-        private static Func<HttpContext, bool, ValueTask<(bool, T?)>> ResolveJsonBodyOrService<T>(LogOrThrowExceptionHelper logOrThrowExceptionHelper, string parameterTypeName, string parameterName, JsonOptions jsonOptions, IServiceProviderIsService? serviceProviderIsService = null)
+        private static Func<HttpContext, bool, ValueTask<(bool, T?)>> ResolveJsonBodyOrService<T>(LogOrThrowExceptionHelper logOrThrowExceptionHelper, string parameterTypeName, string parameterName, JsonSerializerOptions jsonSerializerOptions, IServiceProviderIsService? serviceProviderIsService = null)
         {
             if (serviceProviderIsService is not null)
             {
@@ -197,7 +197,7 @@ internal static class RequestDelegateGeneratorSources
                     return static (httpContext, isOptional) => new ValueTask<(bool, T?)>((true, httpContext.RequestServices.GetService<T>()));
                 }
             }
-            var jsonTypeInfo = (JsonTypeInfo<T>)jsonOptions.SerializerOptions.GetTypeInfo(typeof(T));
+            var jsonTypeInfo = (JsonTypeInfo<T>)jsonSerializerOptions.GetTypeInfo(typeof(T));
             return (httpContext, isOptional) => TryResolveBodyAsync<T>(httpContext, logOrThrowExceptionHelper, isOptional, parameterTypeName, parameterName, jsonTypeInfo, isInferred: true);
         }
 """;
@@ -506,6 +506,7 @@ namespace Microsoft.AspNetCore.Http.Generated
     {{GeneratedCodeAttribute}}
     file static class GeneratedRouteBuilderExtensionsCore
     {
+        private static readonly JsonOptions FallbackJsonOptions = new();
         {{GetVerbs(verbs)}}
         {{endpoints}}
 

src/Http/Http.Extensions/gen/StaticRouteHandlerModel/Emitters/EndpointEmitter.cs

@@ -115,7 +115,7 @@ internal static class EndpointEmitter
                 }
                 codeWriter.Write($@"var {parameter.SymbolName}_JsonBodyOrServiceResolver = ");
                 var shortParameterTypeName = parameter.Type.ToDisplayString(SymbolDisplayFormat.CSharpShortErrorMessageFormat);
-                codeWriter.WriteLine($"ResolveJsonBodyOrService<{parameter.Type.ToDisplayString(EmitterConstants.DisplayFormat)}>(logOrThrowExceptionHelper, {SymbolDisplay.FormatLiteral(shortParameterTypeName, true)}, {SymbolDisplay.FormatLiteral(parameter.SymbolName, true)}, jsonOptions, serviceProviderIsService);");
+                codeWriter.WriteLine($"ResolveJsonBodyOrService<{parameter.Type.ToDisplayString(EmitterConstants.DisplayFormat)}>(logOrThrowExceptionHelper, {SymbolDisplay.FormatLiteral(shortParameterTypeName, true)}, {SymbolDisplay.FormatLiteral(parameter.SymbolName, true)}, jsonSerializerOptions, serviceProviderIsService);");
             }
         }
     }

src/Http/Http.Extensions/gen/StaticRouteHandlerModel/Emitters/EndpointJsonPreparationEmitter.cs

@@ -8,13 +8,15 @@ internal static class EndpointJsonPreparationEmitter
 {
     internal static void EmitJsonPreparation(this Endpoint endpoint, CodeWriter codeWriter)
     {
-        codeWriter.WriteLine("var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? new JsonOptions();");
-        codeWriter.WriteLine($"var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonOptions.SerializerOptions.GetTypeInfo(typeof(object));");
+        codeWriter.WriteLine("var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? FallbackJsonOptions;");
+        codeWriter.WriteLine("var jsonSerializerOptions = jsonOptions.SerializerOptions;");
+        codeWriter.WriteLine("jsonSerializerOptions.MakeReadOnly();");
+        codeWriter.WriteLine($"var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonSerializerOptions.GetTypeInfo(typeof(object));");
 
         if (endpoint.Response?.IsSerializableJsonResponse(out var responseType) == true)
         {
             var typeName = responseType.ToDisplayString(EmitterConstants.DisplayFormatWithoutNullability);
-            codeWriter.WriteLine($"var responseJsonTypeInfo =  (JsonTypeInfo<{responseType.ToDisplayString(NullableFlowState.MaybeNull, EmitterConstants.DisplayFormat)}>)jsonOptions.SerializerOptions.GetTypeInfo(typeof({typeName}));");
+            codeWriter.WriteLine($"var responseJsonTypeInfo =  (JsonTypeInfo<{responseType.ToDisplayString(NullableFlowState.MaybeNull, EmitterConstants.DisplayFormat)}>)jsonSerializerOptions.GetTypeInfo(typeof({typeName}));");
         }
 
         foreach (var parameter in endpoint.Parameters)
@@ -36,7 +38,7 @@ internal static class EndpointJsonPreparationEmitter
                 return;
             }
             var typeName = parameter.Type.ToDisplayString(EmitterConstants.DisplayFormat);
-            codeWriter.WriteLine($"var {parameter.SymbolName}_JsonTypeInfo =  (JsonTypeInfo<{typeName}>)jsonOptions.SerializerOptions.GetTypeInfo(typeof({parameter.Type.ToDisplayString(EmitterConstants.DisplayFormatWithoutNullability)}));");
+            codeWriter.WriteLine($"var {parameter.SymbolName}_JsonTypeInfo = (JsonTypeInfo<{typeName}>)jsonSerializerOptions.GetTypeInfo(typeof({parameter.Type.ToDisplayString(EmitterConstants.DisplayFormatWithoutNullability)}));");
         }
 
     }

src/Http/Http.Extensions/src/JsonOptions.cs

@@ -23,8 +23,8 @@ public class JsonOptions
 
         // The JsonSerializerOptions.GetTypeInfo method is called directly and needs a defined resolver
         // setting the default resolver (reflection-based) but the user can overwrite it directly or by modifying
-        // the TypeInfoResolverChain
-        TypeInfoResolver = JsonSerializer.IsReflectionEnabledByDefault ? CreateDefaultTypeResolver() : null
+        // the TypeInfoResolverChain. Use JsonTypeInfoResolver.Combine() to produce an empty TypeInfoResolver.
+        TypeInfoResolver = JsonSerializer.IsReflectionEnabledByDefault ? CreateDefaultTypeResolver() : JsonTypeInfoResolver.Combine()
     };
 
     // Use a copy so the defaults are not modified.

src/Http/Http.Extensions/test/JsonOptionsTests.cs

@@ -12,7 +12,7 @@ public class JsonOptionsTests
 {
     [ConditionalFact]
     [RemoteExecutionSupported]
-    public void DefaultSerializerOptions_SetsTypeInfoResolverNull_WhenJsonIsReflectionEnabledByDefaultFalse()
+    public void DefaultSerializerOptions_SetsTypeInfoResolverEmptyResolver_WhenJsonIsReflectionEnabledByDefaultFalse()
     {
         var options = new RemoteInvokeOptions();
         options.RuntimeConfigurationOptions.Add("System.Text.Json.JsonSerializer.IsReflectionEnabledByDefault", false.ToString());
@@ -23,7 +23,8 @@ public class JsonOptionsTests
             var options = JsonOptions.DefaultSerializerOptions;
 
             // Assert
-            Assert.Null(options.TypeInfoResolver);
+            Assert.NotNull(options.TypeInfoResolver);
+            Assert.IsAssignableFrom<IJsonTypeInfoResolver>(options.TypeInfoResolver);
         }, options);
     }
 

src/Http/Http.Extensions/test/RequestDelegateGenerator/Baselines/HandlesEndpointsWithAndWithoutDiagnostics.generated.txt

@@ -55,6 +55,7 @@ namespace Microsoft.AspNetCore.Http.Generated
     %GENERATEDCODEATTRIBUTE%
     file static class GeneratedRouteBuilderExtensionsCore
     {
+        private static readonly JsonOptions FallbackJsonOptions = new();
         private static readonly string[] GetVerb = new[] { global::Microsoft.AspNetCore.Http.HttpMethods.Get };
 
         [InterceptsLocation(@"TestMapActions.cs", 9, 13)]
@@ -80,8 +81,10 @@ namespace Microsoft.AspNetCore.Http.Generated
                 var handler = Cast(del, global::System.String () => throw null!);
                 EndpointFilterDelegate? filteredInvocation = null;
                 var serviceProvider = options.ServiceProvider ?? options.EndpointBuilder.ApplicationServices;
-                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? new JsonOptions();
-                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonOptions.SerializerOptions.GetTypeInfo(typeof(object));
+                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? FallbackJsonOptions;
+                var jsonSerializerOptions = jsonOptions.SerializerOptions;
+                jsonSerializerOptions.MakeReadOnly();
+                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonSerializerOptions.GetTypeInfo(typeof(object));
 
                 if (options.EndpointBuilder.FilterFactories.Count > 0)
                 {

src/Http/Http.Extensions/test/RequestDelegateGenerator/Baselines/MapAction_BindAsync_NullableReturn.generated.txt

@@ -55,6 +55,7 @@ namespace Microsoft.AspNetCore.Http.Generated
     %GENERATEDCODEATTRIBUTE%
     file static class GeneratedRouteBuilderExtensionsCore
     {
+        private static readonly JsonOptions FallbackJsonOptions = new();
         private static readonly string[] GetVerb = new[] { global::Microsoft.AspNetCore.Http.HttpMethods.Get };
 
         [InterceptsLocation(@"TestMapActions.cs", 25, 13)]
@@ -82,8 +83,10 @@ namespace Microsoft.AspNetCore.Http.Generated
                 EndpointFilterDelegate? filteredInvocation = null;
                 var serviceProvider = options.ServiceProvider ?? options.EndpointBuilder.ApplicationServices;
                 var logOrThrowExceptionHelper = new LogOrThrowExceptionHelper(serviceProvider, options);
-                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? new JsonOptions();
-                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonOptions.SerializerOptions.GetTypeInfo(typeof(object));
+                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? FallbackJsonOptions;
+                var jsonSerializerOptions = jsonOptions.SerializerOptions;
+                jsonSerializerOptions.MakeReadOnly();
+                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonSerializerOptions.GetTypeInfo(typeof(object));
                 var parameters = del.Method.GetParameters();
 
                 if (options.EndpointBuilder.FilterFactories.Count > 0)
@@ -188,8 +191,10 @@ namespace Microsoft.AspNetCore.Http.Generated
                 EndpointFilterDelegate? filteredInvocation = null;
                 var serviceProvider = options.ServiceProvider ?? options.EndpointBuilder.ApplicationServices;
                 var logOrThrowExceptionHelper = new LogOrThrowExceptionHelper(serviceProvider, options);
-                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? new JsonOptions();
-                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonOptions.SerializerOptions.GetTypeInfo(typeof(object));
+                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? FallbackJsonOptions;
+                var jsonSerializerOptions = jsonOptions.SerializerOptions;
+                jsonSerializerOptions.MakeReadOnly();
+                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonSerializerOptions.GetTypeInfo(typeof(object));
                 var parameters = del.Method.GetParameters();
 
                 if (options.EndpointBuilder.FilterFactories.Count > 0)

src/Http/Http.Extensions/test/RequestDelegateGenerator/Baselines/MapAction_BindAsync_Snapshot.generated.txt

@@ -55,6 +55,7 @@ namespace Microsoft.AspNetCore.Http.Generated
     %GENERATEDCODEATTRIBUTE%
     file static class GeneratedRouteBuilderExtensionsCore
     {
+        private static readonly JsonOptions FallbackJsonOptions = new();
         private static readonly string[] GetVerb = new[] { global::Microsoft.AspNetCore.Http.HttpMethods.Get };
 
         [InterceptsLocation(@"TestMapActions.cs", 25, 13)]
@@ -81,8 +82,10 @@ namespace Microsoft.AspNetCore.Http.Generated
                 EndpointFilterDelegate? filteredInvocation = null;
                 var serviceProvider = options.ServiceProvider ?? options.EndpointBuilder.ApplicationServices;
                 var logOrThrowExceptionHelper = new LogOrThrowExceptionHelper(serviceProvider, options);
-                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? new JsonOptions();
-                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonOptions.SerializerOptions.GetTypeInfo(typeof(object));
+                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? FallbackJsonOptions;
+                var jsonSerializerOptions = jsonOptions.SerializerOptions;
+                jsonSerializerOptions.MakeReadOnly();
+                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonSerializerOptions.GetTypeInfo(typeof(object));
                 var parameters = del.Method.GetParameters();
 
                 if (options.EndpointBuilder.FilterFactories.Count > 0)
@@ -188,8 +191,10 @@ namespace Microsoft.AspNetCore.Http.Generated
                 EndpointFilterDelegate? filteredInvocation = null;
                 var serviceProvider = options.ServiceProvider ?? options.EndpointBuilder.ApplicationServices;
                 var logOrThrowExceptionHelper = new LogOrThrowExceptionHelper(serviceProvider, options);
-                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? new JsonOptions();
-                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonOptions.SerializerOptions.GetTypeInfo(typeof(object));
+                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? FallbackJsonOptions;
+                var jsonSerializerOptions = jsonOptions.SerializerOptions;
+                jsonSerializerOptions.MakeReadOnly();
+                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonSerializerOptions.GetTypeInfo(typeof(object));
                 var parameters = del.Method.GetParameters();
 
                 if (options.EndpointBuilder.FilterFactories.Count > 0)
@@ -281,8 +286,10 @@ namespace Microsoft.AspNetCore.Http.Generated
                 EndpointFilterDelegate? filteredInvocation = null;
                 var serviceProvider = options.ServiceProvider ?? options.EndpointBuilder.ApplicationServices;
                 var logOrThrowExceptionHelper = new LogOrThrowExceptionHelper(serviceProvider, options);
-                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? new JsonOptions();
-                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonOptions.SerializerOptions.GetTypeInfo(typeof(object));
+                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? FallbackJsonOptions;
+                var jsonSerializerOptions = jsonOptions.SerializerOptions;
+                jsonSerializerOptions.MakeReadOnly();
+                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonSerializerOptions.GetTypeInfo(typeof(object));
                 var parameters = del.Method.GetParameters();
 
                 if (options.EndpointBuilder.FilterFactories.Count > 0)
@@ -376,8 +383,10 @@ namespace Microsoft.AspNetCore.Http.Generated
                 EndpointFilterDelegate? filteredInvocation = null;
                 var serviceProvider = options.ServiceProvider ?? options.EndpointBuilder.ApplicationServices;
                 var logOrThrowExceptionHelper = new LogOrThrowExceptionHelper(serviceProvider, options);
-                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? new JsonOptions();
-                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonOptions.SerializerOptions.GetTypeInfo(typeof(object));
+                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? FallbackJsonOptions;
+                var jsonSerializerOptions = jsonOptions.SerializerOptions;
+                jsonSerializerOptions.MakeReadOnly();
+                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonSerializerOptions.GetTypeInfo(typeof(object));
                 var parameters = del.Method.GetParameters();
 
                 if (options.EndpointBuilder.FilterFactories.Count > 0)
@@ -469,8 +478,10 @@ namespace Microsoft.AspNetCore.Http.Generated
                 EndpointFilterDelegate? filteredInvocation = null;
                 var serviceProvider = options.ServiceProvider ?? options.EndpointBuilder.ApplicationServices;
                 var logOrThrowExceptionHelper = new LogOrThrowExceptionHelper(serviceProvider, options);
-                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? new JsonOptions();
-                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonOptions.SerializerOptions.GetTypeInfo(typeof(object));
+                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? FallbackJsonOptions;
+                var jsonSerializerOptions = jsonOptions.SerializerOptions;
+                jsonSerializerOptions.MakeReadOnly();
+                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonSerializerOptions.GetTypeInfo(typeof(object));
                 var parameters = del.Method.GetParameters();
 
                 if (options.EndpointBuilder.FilterFactories.Count > 0)
@@ -576,8 +587,10 @@ namespace Microsoft.AspNetCore.Http.Generated
                 EndpointFilterDelegate? filteredInvocation = null;
                 var serviceProvider = options.ServiceProvider ?? options.EndpointBuilder.ApplicationServices;
                 var logOrThrowExceptionHelper = new LogOrThrowExceptionHelper(serviceProvider, options);
-                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? new JsonOptions();
-                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonOptions.SerializerOptions.GetTypeInfo(typeof(object));
+                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? FallbackJsonOptions;
+                var jsonSerializerOptions = jsonOptions.SerializerOptions;
+                jsonSerializerOptions.MakeReadOnly();
+                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonSerializerOptions.GetTypeInfo(typeof(object));
                 var parameters = del.Method.GetParameters();
 
                 if (options.EndpointBuilder.FilterFactories.Count > 0)
@@ -669,8 +682,10 @@ namespace Microsoft.AspNetCore.Http.Generated
                 EndpointFilterDelegate? filteredInvocation = null;
                 var serviceProvider = options.ServiceProvider ?? options.EndpointBuilder.ApplicationServices;
                 var logOrThrowExceptionHelper = new LogOrThrowExceptionHelper(serviceProvider, options);
-                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? new JsonOptions();
-                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonOptions.SerializerOptions.GetTypeInfo(typeof(object));
+                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? FallbackJsonOptions;
+                var jsonSerializerOptions = jsonOptions.SerializerOptions;
+                jsonSerializerOptions.MakeReadOnly();
+                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonSerializerOptions.GetTypeInfo(typeof(object));
                 var parameters = del.Method.GetParameters();
 
                 if (options.EndpointBuilder.FilterFactories.Count > 0)
@@ -764,8 +779,10 @@ namespace Microsoft.AspNetCore.Http.Generated
                 EndpointFilterDelegate? filteredInvocation = null;
                 var serviceProvider = options.ServiceProvider ?? options.EndpointBuilder.ApplicationServices;
                 var logOrThrowExceptionHelper = new LogOrThrowExceptionHelper(serviceProvider, options);
-                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? new JsonOptions();
-                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonOptions.SerializerOptions.GetTypeInfo(typeof(object));
+                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? FallbackJsonOptions;
+                var jsonSerializerOptions = jsonOptions.SerializerOptions;
+                jsonSerializerOptions.MakeReadOnly();
+                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonSerializerOptions.GetTypeInfo(typeof(object));
                 var parameters = del.Method.GetParameters();
 
                 if (options.EndpointBuilder.FilterFactories.Count > 0)
@@ -857,8 +874,10 @@ namespace Microsoft.AspNetCore.Http.Generated
                 EndpointFilterDelegate? filteredInvocation = null;
                 var serviceProvider = options.ServiceProvider ?? options.EndpointBuilder.ApplicationServices;
                 var logOrThrowExceptionHelper = new LogOrThrowExceptionHelper(serviceProvider, options);
-                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? new JsonOptions();
-                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonOptions.SerializerOptions.GetTypeInfo(typeof(object));
+                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? FallbackJsonOptions;
+                var jsonSerializerOptions = jsonOptions.SerializerOptions;
+                jsonSerializerOptions.MakeReadOnly();
+                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonSerializerOptions.GetTypeInfo(typeof(object));
 
                 if (options.EndpointBuilder.FilterFactories.Count > 0)
                 {
@@ -963,8 +982,10 @@ namespace Microsoft.AspNetCore.Http.Generated
                 EndpointFilterDelegate? filteredInvocation = null;
                 var serviceProvider = options.ServiceProvider ?? options.EndpointBuilder.ApplicationServices;
                 var logOrThrowExceptionHelper = new LogOrThrowExceptionHelper(serviceProvider, options);
-                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? new JsonOptions();
-                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonOptions.SerializerOptions.GetTypeInfo(typeof(object));
+                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? FallbackJsonOptions;
+                var jsonSerializerOptions = jsonOptions.SerializerOptions;
+                jsonSerializerOptions.MakeReadOnly();
+                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonSerializerOptions.GetTypeInfo(typeof(object));
 
                 if (options.EndpointBuilder.FilterFactories.Count > 0)
                 {
@@ -1055,8 +1076,10 @@ namespace Microsoft.AspNetCore.Http.Generated
                 EndpointFilterDelegate? filteredInvocation = null;
                 var serviceProvider = options.ServiceProvider ?? options.EndpointBuilder.ApplicationServices;
                 var logOrThrowExceptionHelper = new LogOrThrowExceptionHelper(serviceProvider, options);
-                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? new JsonOptions();
-                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonOptions.SerializerOptions.GetTypeInfo(typeof(object));
+                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? FallbackJsonOptions;
+                var jsonSerializerOptions = jsonOptions.SerializerOptions;
+                jsonSerializerOptions.MakeReadOnly();
+                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonSerializerOptions.GetTypeInfo(typeof(object));
 
                 if (options.EndpointBuilder.FilterFactories.Count > 0)
                 {
@@ -1149,8 +1172,10 @@ namespace Microsoft.AspNetCore.Http.Generated
                 EndpointFilterDelegate? filteredInvocation = null;
                 var serviceProvider = options.ServiceProvider ?? options.EndpointBuilder.ApplicationServices;
                 var logOrThrowExceptionHelper = new LogOrThrowExceptionHelper(serviceProvider, options);
-                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? new JsonOptions();
-                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonOptions.SerializerOptions.GetTypeInfo(typeof(object));
+                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? FallbackJsonOptions;
+                var jsonSerializerOptions = jsonOptions.SerializerOptions;
+                jsonSerializerOptions.MakeReadOnly();
+                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonSerializerOptions.GetTypeInfo(typeof(object));
 
                 if (options.EndpointBuilder.FilterFactories.Count > 0)
                 {
@@ -1241,8 +1266,10 @@ namespace Microsoft.AspNetCore.Http.Generated
                 EndpointFilterDelegate? filteredInvocation = null;
                 var serviceProvider = options.ServiceProvider ?? options.EndpointBuilder.ApplicationServices;
                 var logOrThrowExceptionHelper = new LogOrThrowExceptionHelper(serviceProvider, options);
-                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? new JsonOptions();
-                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonOptions.SerializerOptions.GetTypeInfo(typeof(object));
+                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? FallbackJsonOptions;
+                var jsonSerializerOptions = jsonOptions.SerializerOptions;
+                jsonSerializerOptions.MakeReadOnly();
+                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonSerializerOptions.GetTypeInfo(typeof(object));
                 var parameters = del.Method.GetParameters();
 
                 if (options.EndpointBuilder.FilterFactories.Count > 0)
@@ -1348,8 +1375,10 @@ namespace Microsoft.AspNetCore.Http.Generated
                 EndpointFilterDelegate? filteredInvocation = null;
                 var serviceProvider = options.ServiceProvider ?? options.EndpointBuilder.ApplicationServices;
                 var logOrThrowExceptionHelper = new LogOrThrowExceptionHelper(serviceProvider, options);
-                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? new JsonOptions();
-                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonOptions.SerializerOptions.GetTypeInfo(typeof(object));
+                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? FallbackJsonOptions;
+                var jsonSerializerOptions = jsonOptions.SerializerOptions;
+                jsonSerializerOptions.MakeReadOnly();
+                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonSerializerOptions.GetTypeInfo(typeof(object));
                 var parameters = del.Method.GetParameters();
 
                 if (options.EndpointBuilder.FilterFactories.Count > 0)
@@ -1441,8 +1470,10 @@ namespace Microsoft.AspNetCore.Http.Generated
                 EndpointFilterDelegate? filteredInvocation = null;
                 var serviceProvider = options.ServiceProvider ?? options.EndpointBuilder.ApplicationServices;
                 var logOrThrowExceptionHelper = new LogOrThrowExceptionHelper(serviceProvider, options);
-                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? new JsonOptions();
-                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonOptions.SerializerOptions.GetTypeInfo(typeof(object));
+                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? FallbackJsonOptions;
+                var jsonSerializerOptions = jsonOptions.SerializerOptions;
+                jsonSerializerOptions.MakeReadOnly();
+                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonSerializerOptions.GetTypeInfo(typeof(object));
 
                 if (options.EndpointBuilder.FilterFactories.Count > 0)
                 {
@@ -1547,8 +1578,10 @@ namespace Microsoft.AspNetCore.Http.Generated
                 EndpointFilterDelegate? filteredInvocation = null;
                 var serviceProvider = options.ServiceProvider ?? options.EndpointBuilder.ApplicationServices;
                 var logOrThrowExceptionHelper = new LogOrThrowExceptionHelper(serviceProvider, options);
-                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? new JsonOptions();
-                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonOptions.SerializerOptions.GetTypeInfo(typeof(object));
+                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? FallbackJsonOptions;
+                var jsonSerializerOptions = jsonOptions.SerializerOptions;
+                jsonSerializerOptions.MakeReadOnly();
+                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonSerializerOptions.GetTypeInfo(typeof(object));
 
                 if (options.EndpointBuilder.FilterFactories.Count > 0)
                 {
@@ -1639,8 +1672,10 @@ namespace Microsoft.AspNetCore.Http.Generated
                 EndpointFilterDelegate? filteredInvocation = null;
                 var serviceProvider = options.ServiceProvider ?? options.EndpointBuilder.ApplicationServices;
                 var logOrThrowExceptionHelper = new LogOrThrowExceptionHelper(serviceProvider, options);
-                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? new JsonOptions();
-                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonOptions.SerializerOptions.GetTypeInfo(typeof(object));
+                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? FallbackJsonOptions;
+                var jsonSerializerOptions = jsonOptions.SerializerOptions;
+                jsonSerializerOptions.MakeReadOnly();
+                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonSerializerOptions.GetTypeInfo(typeof(object));
                 var parameters = del.Method.GetParameters();
 
                 if (options.EndpointBuilder.FilterFactories.Count > 0)
@@ -1746,8 +1781,10 @@ namespace Microsoft.AspNetCore.Http.Generated
                 EndpointFilterDelegate? filteredInvocation = null;
                 var serviceProvider = options.ServiceProvider ?? options.EndpointBuilder.ApplicationServices;
                 var logOrThrowExceptionHelper = new LogOrThrowExceptionHelper(serviceProvider, options);
-                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? new JsonOptions();
-                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonOptions.SerializerOptions.GetTypeInfo(typeof(object));
+                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? FallbackJsonOptions;
+                var jsonSerializerOptions = jsonOptions.SerializerOptions;
+                jsonSerializerOptions.MakeReadOnly();
+                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonSerializerOptions.GetTypeInfo(typeof(object));
                 var parameters = del.Method.GetParameters();
 
                 if (options.EndpointBuilder.FilterFactories.Count > 0)
@@ -1839,8 +1876,10 @@ namespace Microsoft.AspNetCore.Http.Generated
                 EndpointFilterDelegate? filteredInvocation = null;
                 var serviceProvider = options.ServiceProvider ?? options.EndpointBuilder.ApplicationServices;
                 var logOrThrowExceptionHelper = new LogOrThrowExceptionHelper(serviceProvider, options);
-                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? new JsonOptions();
-                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonOptions.SerializerOptions.GetTypeInfo(typeof(object));
+                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? FallbackJsonOptions;
+                var jsonSerializerOptions = jsonOptions.SerializerOptions;
+                jsonSerializerOptions.MakeReadOnly();
+                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonSerializerOptions.GetTypeInfo(typeof(object));
 
                 if (options.EndpointBuilder.FilterFactories.Count > 0)
                 {
@@ -1945,8 +1984,10 @@ namespace Microsoft.AspNetCore.Http.Generated
                 EndpointFilterDelegate? filteredInvocation = null;
                 var serviceProvider = options.ServiceProvider ?? options.EndpointBuilder.ApplicationServices;
                 var logOrThrowExceptionHelper = new LogOrThrowExceptionHelper(serviceProvider, options);
-                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? new JsonOptions();
-                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonOptions.SerializerOptions.GetTypeInfo(typeof(object));
+                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? FallbackJsonOptions;
+                var jsonSerializerOptions = jsonOptions.SerializerOptions;
+                jsonSerializerOptions.MakeReadOnly();
+                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonSerializerOptions.GetTypeInfo(typeof(object));
 
                 if (options.EndpointBuilder.FilterFactories.Count > 0)
                 {

src/Http/Http.Extensions/test/RequestDelegateGenerator/Baselines/MapAction_ExplicitBodyParam_ComplexReturn_Snapshot.generated.txt

@@ -55,6 +55,7 @@ namespace Microsoft.AspNetCore.Http.Generated
     %GENERATEDCODEATTRIBUTE%
     file static class GeneratedRouteBuilderExtensionsCore
     {
+        private static readonly JsonOptions FallbackJsonOptions = new();
         private static readonly string[] PostVerb = new[] { global::Microsoft.AspNetCore.Http.HttpMethods.Post };
 
         [InterceptsLocation(@"TestMapActions.cs", 25, 13)]
@@ -82,9 +83,11 @@ namespace Microsoft.AspNetCore.Http.Generated
                 EndpointFilterDelegate? filteredInvocation = null;
                 var serviceProvider = options.ServiceProvider ?? options.EndpointBuilder.ApplicationServices;
                 var logOrThrowExceptionHelper = new LogOrThrowExceptionHelper(serviceProvider, options);
-                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? new JsonOptions();
-                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonOptions.SerializerOptions.GetTypeInfo(typeof(object));
-                var todo_JsonTypeInfo =  (JsonTypeInfo<global::Microsoft.AspNetCore.Http.Generators.Tests.Todo>)jsonOptions.SerializerOptions.GetTypeInfo(typeof(global::Microsoft.AspNetCore.Http.Generators.Tests.Todo));
+                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? FallbackJsonOptions;
+                var jsonSerializerOptions = jsonOptions.SerializerOptions;
+                jsonSerializerOptions.MakeReadOnly();
+                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonSerializerOptions.GetTypeInfo(typeof(object));
+                var todo_JsonTypeInfo = (JsonTypeInfo<global::Microsoft.AspNetCore.Http.Generators.Tests.Todo>)jsonSerializerOptions.GetTypeInfo(typeof(global::Microsoft.AspNetCore.Http.Generators.Tests.Todo));
 
                 if (options.EndpointBuilder.FilterFactories.Count > 0)
                 {
@@ -180,9 +183,11 @@ namespace Microsoft.AspNetCore.Http.Generated
                 EndpointFilterDelegate? filteredInvocation = null;
                 var serviceProvider = options.ServiceProvider ?? options.EndpointBuilder.ApplicationServices;
                 var logOrThrowExceptionHelper = new LogOrThrowExceptionHelper(serviceProvider, options);
-                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? new JsonOptions();
-                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonOptions.SerializerOptions.GetTypeInfo(typeof(object));
-                var todo_JsonTypeInfo =  (JsonTypeInfo<global::Microsoft.AspNetCore.Http.Generators.Tests.Todo?>)jsonOptions.SerializerOptions.GetTypeInfo(typeof(global::Microsoft.AspNetCore.Http.Generators.Tests.Todo));
+                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? FallbackJsonOptions;
+                var jsonSerializerOptions = jsonOptions.SerializerOptions;
+                jsonSerializerOptions.MakeReadOnly();
+                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonSerializerOptions.GetTypeInfo(typeof(object));
+                var todo_JsonTypeInfo = (JsonTypeInfo<global::Microsoft.AspNetCore.Http.Generators.Tests.Todo?>)jsonSerializerOptions.GetTypeInfo(typeof(global::Microsoft.AspNetCore.Http.Generators.Tests.Todo));
 
                 if (options.EndpointBuilder.FilterFactories.Count > 0)
                 {

src/Http/Http.Extensions/test/RequestDelegateGenerator/Baselines/MapAction_ExplicitHeader_ComplexTypeArrayParam.generated.txt

@@ -55,6 +55,7 @@ namespace Microsoft.AspNetCore.Http.Generated
     %GENERATEDCODEATTRIBUTE%
     file static class GeneratedRouteBuilderExtensionsCore
     {
+        private static readonly JsonOptions FallbackJsonOptions = new();
         private static readonly string[] GetVerb = new[] { global::Microsoft.AspNetCore.Http.HttpMethods.Get };
 
         [InterceptsLocation(@"TestMapActions.cs", 25, 13)]
@@ -81,9 +82,11 @@ namespace Microsoft.AspNetCore.Http.Generated
                 EndpointFilterDelegate? filteredInvocation = null;
                 var serviceProvider = options.ServiceProvider ?? options.EndpointBuilder.ApplicationServices;
                 var logOrThrowExceptionHelper = new LogOrThrowExceptionHelper(serviceProvider, options);
-                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? new JsonOptions();
-                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonOptions.SerializerOptions.GetTypeInfo(typeof(object));
-                var responseJsonTypeInfo =  (JsonTypeInfo<global::System.Int32>)jsonOptions.SerializerOptions.GetTypeInfo(typeof(global::System.Int32));
+                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? FallbackJsonOptions;
+                var jsonSerializerOptions = jsonOptions.SerializerOptions;
+                jsonSerializerOptions.MakeReadOnly();
+                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonSerializerOptions.GetTypeInfo(typeof(object));
+                var responseJsonTypeInfo =  (JsonTypeInfo<global::System.Int32>)jsonSerializerOptions.GetTypeInfo(typeof(global::System.Int32));
 
                 if (options.EndpointBuilder.FilterFactories.Count > 0)
                 {

src/Http/Http.Extensions/test/RequestDelegateGenerator/Baselines/MapAction_ExplicitHeader_NullableStringArrayParam.generated.txt

@@ -55,6 +55,7 @@ namespace Microsoft.AspNetCore.Http.Generated
     %GENERATEDCODEATTRIBUTE%
     file static class GeneratedRouteBuilderExtensionsCore
     {
+        private static readonly JsonOptions FallbackJsonOptions = new();
         private static readonly string[] GetVerb = new[] { global::Microsoft.AspNetCore.Http.HttpMethods.Get };
 
         [InterceptsLocation(@"TestMapActions.cs", 25, 13)]
@@ -81,9 +82,11 @@ namespace Microsoft.AspNetCore.Http.Generated
                 EndpointFilterDelegate? filteredInvocation = null;
                 var serviceProvider = options.ServiceProvider ?? options.EndpointBuilder.ApplicationServices;
                 var logOrThrowExceptionHelper = new LogOrThrowExceptionHelper(serviceProvider, options);
-                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? new JsonOptions();
-                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonOptions.SerializerOptions.GetTypeInfo(typeof(object));
-                var responseJsonTypeInfo =  (JsonTypeInfo<global::System.Int32>)jsonOptions.SerializerOptions.GetTypeInfo(typeof(global::System.Int32));
+                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? FallbackJsonOptions;
+                var jsonSerializerOptions = jsonOptions.SerializerOptions;
+                jsonSerializerOptions.MakeReadOnly();
+                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonSerializerOptions.GetTypeInfo(typeof(object));
+                var responseJsonTypeInfo =  (JsonTypeInfo<global::System.Int32>)jsonSerializerOptions.GetTypeInfo(typeof(global::System.Int32));
 
                 if (options.EndpointBuilder.FilterFactories.Count > 0)
                 {

src/Http/Http.Extensions/test/RequestDelegateGenerator/Baselines/MapAction_ExplicitHeader_StringArrayParam.generated.txt

@@ -55,6 +55,7 @@ namespace Microsoft.AspNetCore.Http.Generated
     %GENERATEDCODEATTRIBUTE%
     file static class GeneratedRouteBuilderExtensionsCore
     {
+        private static readonly JsonOptions FallbackJsonOptions = new();
         private static readonly string[] GetVerb = new[] { global::Microsoft.AspNetCore.Http.HttpMethods.Get };
 
         [InterceptsLocation(@"TestMapActions.cs", 25, 13)]
@@ -81,9 +82,11 @@ namespace Microsoft.AspNetCore.Http.Generated
                 EndpointFilterDelegate? filteredInvocation = null;
                 var serviceProvider = options.ServiceProvider ?? options.EndpointBuilder.ApplicationServices;
                 var logOrThrowExceptionHelper = new LogOrThrowExceptionHelper(serviceProvider, options);
-                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? new JsonOptions();
-                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonOptions.SerializerOptions.GetTypeInfo(typeof(object));
-                var responseJsonTypeInfo =  (JsonTypeInfo<global::System.Int32>)jsonOptions.SerializerOptions.GetTypeInfo(typeof(global::System.Int32));
+                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? FallbackJsonOptions;
+                var jsonSerializerOptions = jsonOptions.SerializerOptions;
+                jsonSerializerOptions.MakeReadOnly();
+                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonSerializerOptions.GetTypeInfo(typeof(object));
+                var responseJsonTypeInfo =  (JsonTypeInfo<global::System.Int32>)jsonSerializerOptions.GetTypeInfo(typeof(global::System.Int32));
 
                 if (options.EndpointBuilder.FilterFactories.Count > 0)
                 {

src/Http/Http.Extensions/test/RequestDelegateGenerator/Baselines/MapAction_ExplicitQuery_ComplexTypeArrayParam.generated.txt

@@ -55,6 +55,7 @@ namespace Microsoft.AspNetCore.Http.Generated
     %GENERATEDCODEATTRIBUTE%
     file static class GeneratedRouteBuilderExtensionsCore
     {
+        private static readonly JsonOptions FallbackJsonOptions = new();
         private static readonly string[] GetVerb = new[] { global::Microsoft.AspNetCore.Http.HttpMethods.Get };
 
         [InterceptsLocation(@"TestMapActions.cs", 25, 13)]
@@ -81,9 +82,11 @@ namespace Microsoft.AspNetCore.Http.Generated
                 EndpointFilterDelegate? filteredInvocation = null;
                 var serviceProvider = options.ServiceProvider ?? options.EndpointBuilder.ApplicationServices;
                 var logOrThrowExceptionHelper = new LogOrThrowExceptionHelper(serviceProvider, options);
-                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? new JsonOptions();
-                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonOptions.SerializerOptions.GetTypeInfo(typeof(object));
-                var responseJsonTypeInfo =  (JsonTypeInfo<global::System.Int32>)jsonOptions.SerializerOptions.GetTypeInfo(typeof(global::System.Int32));
+                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? FallbackJsonOptions;
+                var jsonSerializerOptions = jsonOptions.SerializerOptions;
+                jsonSerializerOptions.MakeReadOnly();
+                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonSerializerOptions.GetTypeInfo(typeof(object));
+                var responseJsonTypeInfo =  (JsonTypeInfo<global::System.Int32>)jsonSerializerOptions.GetTypeInfo(typeof(global::System.Int32));
 
                 if (options.EndpointBuilder.FilterFactories.Count > 0)
                 {

src/Http/Http.Extensions/test/RequestDelegateGenerator/Baselines/MapAction_ExplicitQuery_NullableStringArrayParam.generated.txt

@@ -55,6 +55,7 @@ namespace Microsoft.AspNetCore.Http.Generated
     %GENERATEDCODEATTRIBUTE%
     file static class GeneratedRouteBuilderExtensionsCore
     {
+        private static readonly JsonOptions FallbackJsonOptions = new();
         private static readonly string[] GetVerb = new[] { global::Microsoft.AspNetCore.Http.HttpMethods.Get };
 
         [InterceptsLocation(@"TestMapActions.cs", 25, 13)]
@@ -80,9 +81,11 @@ namespace Microsoft.AspNetCore.Http.Generated
                 var handler = Cast(del, global::System.Int32 (global::System.String?[] arg0) => throw null!);
                 EndpointFilterDelegate? filteredInvocation = null;
                 var serviceProvider = options.ServiceProvider ?? options.EndpointBuilder.ApplicationServices;
-                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? new JsonOptions();
-                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonOptions.SerializerOptions.GetTypeInfo(typeof(object));
-                var responseJsonTypeInfo =  (JsonTypeInfo<global::System.Int32>)jsonOptions.SerializerOptions.GetTypeInfo(typeof(global::System.Int32));
+                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? FallbackJsonOptions;
+                var jsonSerializerOptions = jsonOptions.SerializerOptions;
+                jsonSerializerOptions.MakeReadOnly();
+                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonSerializerOptions.GetTypeInfo(typeof(object));
+                var responseJsonTypeInfo =  (JsonTypeInfo<global::System.Int32>)jsonSerializerOptions.GetTypeInfo(typeof(global::System.Int32));
 
                 if (options.EndpointBuilder.FilterFactories.Count > 0)
                 {

src/Http/Http.Extensions/test/RequestDelegateGenerator/Baselines/MapAction_ExplicitQuery_StringArrayParam.generated.txt

@@ -55,6 +55,7 @@ namespace Microsoft.AspNetCore.Http.Generated
     %GENERATEDCODEATTRIBUTE%
     file static class GeneratedRouteBuilderExtensionsCore
     {
+        private static readonly JsonOptions FallbackJsonOptions = new();
         private static readonly string[] GetVerb = new[] { global::Microsoft.AspNetCore.Http.HttpMethods.Get };
 
         [InterceptsLocation(@"TestMapActions.cs", 25, 13)]
@@ -80,9 +81,11 @@ namespace Microsoft.AspNetCore.Http.Generated
                 var handler = Cast(del, global::System.Int32 (global::System.String[] arg0) => throw null!);
                 EndpointFilterDelegate? filteredInvocation = null;
                 var serviceProvider = options.ServiceProvider ?? options.EndpointBuilder.ApplicationServices;
-                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? new JsonOptions();
-                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonOptions.SerializerOptions.GetTypeInfo(typeof(object));
-                var responseJsonTypeInfo =  (JsonTypeInfo<global::System.Int32>)jsonOptions.SerializerOptions.GetTypeInfo(typeof(global::System.Int32));
+                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? FallbackJsonOptions;
+                var jsonSerializerOptions = jsonOptions.SerializerOptions;
+                jsonSerializerOptions.MakeReadOnly();
+                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonSerializerOptions.GetTypeInfo(typeof(object));
+                var responseJsonTypeInfo =  (JsonTypeInfo<global::System.Int32>)jsonSerializerOptions.GetTypeInfo(typeof(global::System.Int32));
 
                 if (options.EndpointBuilder.FilterFactories.Count > 0)
                 {

src/Http/Http.Extensions/test/RequestDelegateGenerator/Baselines/MapAction_ExplicitServiceParam_SimpleReturn_Snapshot.generated.txt

@@ -55,6 +55,7 @@ namespace Microsoft.AspNetCore.Http.Generated
     %GENERATEDCODEATTRIBUTE%
     file static class GeneratedRouteBuilderExtensionsCore
     {
+        private static readonly JsonOptions FallbackJsonOptions = new();
         private static readonly string[] GetVerb = new[] { global::Microsoft.AspNetCore.Http.HttpMethods.Get };
 
         [InterceptsLocation(@"TestMapActions.cs", 25, 13)]
@@ -81,8 +82,10 @@ namespace Microsoft.AspNetCore.Http.Generated
                 EndpointFilterDelegate? filteredInvocation = null;
                 var serviceProvider = options.ServiceProvider ?? options.EndpointBuilder.ApplicationServices;
                 var logOrThrowExceptionHelper = new LogOrThrowExceptionHelper(serviceProvider, options);
-                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? new JsonOptions();
-                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonOptions.SerializerOptions.GetTypeInfo(typeof(object));
+                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? FallbackJsonOptions;
+                var jsonSerializerOptions = jsonOptions.SerializerOptions;
+                jsonSerializerOptions.MakeReadOnly();
+                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonSerializerOptions.GetTypeInfo(typeof(object));
 
                 if (options.EndpointBuilder.FilterFactories.Count > 0)
                 {
@@ -175,8 +178,10 @@ namespace Microsoft.AspNetCore.Http.Generated
                 EndpointFilterDelegate? filteredInvocation = null;
                 var serviceProvider = options.ServiceProvider ?? options.EndpointBuilder.ApplicationServices;
                 var logOrThrowExceptionHelper = new LogOrThrowExceptionHelper(serviceProvider, options);
-                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? new JsonOptions();
-                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonOptions.SerializerOptions.GetTypeInfo(typeof(object));
+                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? FallbackJsonOptions;
+                var jsonSerializerOptions = jsonOptions.SerializerOptions;
+                jsonSerializerOptions.MakeReadOnly();
+                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonSerializerOptions.GetTypeInfo(typeof(object));
 
                 if (options.EndpointBuilder.FilterFactories.Count > 0)
                 {
@@ -269,8 +274,10 @@ namespace Microsoft.AspNetCore.Http.Generated
                 EndpointFilterDelegate? filteredInvocation = null;
                 var serviceProvider = options.ServiceProvider ?? options.EndpointBuilder.ApplicationServices;
                 var logOrThrowExceptionHelper = new LogOrThrowExceptionHelper(serviceProvider, options);
-                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? new JsonOptions();
-                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonOptions.SerializerOptions.GetTypeInfo(typeof(object));
+                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? FallbackJsonOptions;
+                var jsonSerializerOptions = jsonOptions.SerializerOptions;
+                jsonSerializerOptions.MakeReadOnly();
+                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonSerializerOptions.GetTypeInfo(typeof(object));
 
                 if (options.EndpointBuilder.FilterFactories.Count > 0)
                 {

src/Http/Http.Extensions/test/RequestDelegateGenerator/Baselines/MapAction_ExplicitSource_SimpleReturn_Snapshot.generated.txt

@@ -55,6 +55,7 @@ namespace Microsoft.AspNetCore.Http.Generated
     %GENERATEDCODEATTRIBUTE%
     file static class GeneratedRouteBuilderExtensionsCore
     {
+        private static readonly JsonOptions FallbackJsonOptions = new();
         private static readonly string[] GetVerb = new[] { global::Microsoft.AspNetCore.Http.HttpMethods.Get };
 
         [InterceptsLocation(@"TestMapActions.cs", 25, 13)]
@@ -85,8 +86,10 @@ namespace Microsoft.AspNetCore.Http.Generated
                 EndpointFilterDelegate? filteredInvocation = null;
                 var serviceProvider = options.ServiceProvider ?? options.EndpointBuilder.ApplicationServices;
                 var logOrThrowExceptionHelper = new LogOrThrowExceptionHelper(serviceProvider, options);
-                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? new JsonOptions();
-                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonOptions.SerializerOptions.GetTypeInfo(typeof(object));
+                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? FallbackJsonOptions;
+                var jsonSerializerOptions = jsonOptions.SerializerOptions;
+                jsonSerializerOptions.MakeReadOnly();
+                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonSerializerOptions.GetTypeInfo(typeof(object));
 
                 if (options.EndpointBuilder.FilterFactories.Count > 0)
                 {

src/Http/Http.Extensions/test/RequestDelegateGenerator/Baselines/MapAction_ImplicitQuery_ComplexTypeArrayParam.generated.txt

@@ -55,6 +55,7 @@ namespace Microsoft.AspNetCore.Http.Generated
     %GENERATEDCODEATTRIBUTE%
     file static class GeneratedRouteBuilderExtensionsCore
     {
+        private static readonly JsonOptions FallbackJsonOptions = new();
         private static readonly string[] GetVerb = new[] { global::Microsoft.AspNetCore.Http.HttpMethods.Get };
 
         [InterceptsLocation(@"TestMapActions.cs", 25, 13)]
@@ -81,9 +82,11 @@ namespace Microsoft.AspNetCore.Http.Generated
                 EndpointFilterDelegate? filteredInvocation = null;
                 var serviceProvider = options.ServiceProvider ?? options.EndpointBuilder.ApplicationServices;
                 var logOrThrowExceptionHelper = new LogOrThrowExceptionHelper(serviceProvider, options);
-                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? new JsonOptions();
-                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonOptions.SerializerOptions.GetTypeInfo(typeof(object));
-                var responseJsonTypeInfo =  (JsonTypeInfo<global::System.Int32>)jsonOptions.SerializerOptions.GetTypeInfo(typeof(global::System.Int32));
+                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? FallbackJsonOptions;
+                var jsonSerializerOptions = jsonOptions.SerializerOptions;
+                jsonSerializerOptions.MakeReadOnly();
+                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonSerializerOptions.GetTypeInfo(typeof(object));
+                var responseJsonTypeInfo =  (JsonTypeInfo<global::System.Int32>)jsonSerializerOptions.GetTypeInfo(typeof(global::System.Int32));
                 var p_RouteOrQueryResolver = GeneratedRouteBuilderExtensionsCore.ResolveFromRouteOrQuery("p", options.RouteParameterNames);
 
                 if (options.EndpointBuilder.FilterFactories.Count > 0)

src/Http/Http.Extensions/test/RequestDelegateGenerator/Baselines/MapAction_ImplicitQuery_NullableStringArrayParam.generated.txt

@@ -55,6 +55,7 @@ namespace Microsoft.AspNetCore.Http.Generated
     %GENERATEDCODEATTRIBUTE%
     file static class GeneratedRouteBuilderExtensionsCore
     {
+        private static readonly JsonOptions FallbackJsonOptions = new();
         private static readonly string[] GetVerb = new[] { global::Microsoft.AspNetCore.Http.HttpMethods.Get };
 
         [InterceptsLocation(@"TestMapActions.cs", 25, 13)]
@@ -94,9 +95,11 @@ namespace Microsoft.AspNetCore.Http.Generated
                 EndpointFilterDelegate? filteredInvocation = null;
                 var serviceProvider = options.ServiceProvider ?? options.EndpointBuilder.ApplicationServices;
                 var logOrThrowExceptionHelper = new LogOrThrowExceptionHelper(serviceProvider, options);
-                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? new JsonOptions();
-                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonOptions.SerializerOptions.GetTypeInfo(typeof(object));
-                var responseJsonTypeInfo =  (JsonTypeInfo<global::System.Int32>)jsonOptions.SerializerOptions.GetTypeInfo(typeof(global::System.Int32));
+                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? FallbackJsonOptions;
+                var jsonSerializerOptions = jsonOptions.SerializerOptions;
+                jsonSerializerOptions.MakeReadOnly();
+                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonSerializerOptions.GetTypeInfo(typeof(object));
+                var responseJsonTypeInfo =  (JsonTypeInfo<global::System.Int32>)jsonSerializerOptions.GetTypeInfo(typeof(global::System.Int32));
 
                 if (options.EndpointBuilder.FilterFactories.Count > 0)
                 {

src/Http/Http.Extensions/test/RequestDelegateGenerator/Baselines/MapAction_ImplicitQuery_NullableStringArrayParam_EmptyQueryValues.generated.txt

@@ -55,6 +55,7 @@ namespace Microsoft.AspNetCore.Http.Generated
     %GENERATEDCODEATTRIBUTE%
     file static class GeneratedRouteBuilderExtensionsCore
     {
+        private static readonly JsonOptions FallbackJsonOptions = new();
         private static readonly string[] GetVerb = new[] { global::Microsoft.AspNetCore.Http.HttpMethods.Get };
 
         [InterceptsLocation(@"TestMapActions.cs", 25, 13)]
@@ -94,9 +95,11 @@ namespace Microsoft.AspNetCore.Http.Generated
                 EndpointFilterDelegate? filteredInvocation = null;
                 var serviceProvider = options.ServiceProvider ?? options.EndpointBuilder.ApplicationServices;
                 var logOrThrowExceptionHelper = new LogOrThrowExceptionHelper(serviceProvider, options);
-                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? new JsonOptions();
-                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonOptions.SerializerOptions.GetTypeInfo(typeof(object));
-                var responseJsonTypeInfo =  (JsonTypeInfo<global::System.Int32>)jsonOptions.SerializerOptions.GetTypeInfo(typeof(global::System.Int32));
+                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? FallbackJsonOptions;
+                var jsonSerializerOptions = jsonOptions.SerializerOptions;
+                jsonSerializerOptions.MakeReadOnly();
+                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonSerializerOptions.GetTypeInfo(typeof(object));
+                var responseJsonTypeInfo =  (JsonTypeInfo<global::System.Int32>)jsonSerializerOptions.GetTypeInfo(typeof(global::System.Int32));
 
                 if (options.EndpointBuilder.FilterFactories.Count > 0)
                 {

src/Http/Http.Extensions/test/RequestDelegateGenerator/Baselines/MapAction_ImplicitQuery_NullableStringArrayParam_QueryNotPresent.generated.txt

@@ -55,6 +55,7 @@ namespace Microsoft.AspNetCore.Http.Generated
     %GENERATEDCODEATTRIBUTE%
     file static class GeneratedRouteBuilderExtensionsCore
     {
+        private static readonly JsonOptions FallbackJsonOptions = new();
         private static readonly string[] GetVerb = new[] { global::Microsoft.AspNetCore.Http.HttpMethods.Get };
 
         [InterceptsLocation(@"TestMapActions.cs", 25, 13)]
@@ -94,9 +95,11 @@ namespace Microsoft.AspNetCore.Http.Generated
                 EndpointFilterDelegate? filteredInvocation = null;
                 var serviceProvider = options.ServiceProvider ?? options.EndpointBuilder.ApplicationServices;
                 var logOrThrowExceptionHelper = new LogOrThrowExceptionHelper(serviceProvider, options);
-                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? new JsonOptions();
-                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonOptions.SerializerOptions.GetTypeInfo(typeof(object));
-                var responseJsonTypeInfo =  (JsonTypeInfo<global::System.Int32>)jsonOptions.SerializerOptions.GetTypeInfo(typeof(global::System.Int32));
+                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? FallbackJsonOptions;
+                var jsonSerializerOptions = jsonOptions.SerializerOptions;
+                jsonSerializerOptions.MakeReadOnly();
+                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonSerializerOptions.GetTypeInfo(typeof(object));
+                var responseJsonTypeInfo =  (JsonTypeInfo<global::System.Int32>)jsonSerializerOptions.GetTypeInfo(typeof(global::System.Int32));
 
                 if (options.EndpointBuilder.FilterFactories.Count > 0)
                 {

src/Http/Http.Extensions/test/RequestDelegateGenerator/Baselines/MapAction_ImplicitQuery_StringArrayParam.generated.txt

@@ -55,6 +55,7 @@ namespace Microsoft.AspNetCore.Http.Generated
     %GENERATEDCODEATTRIBUTE%
     file static class GeneratedRouteBuilderExtensionsCore
     {
+        private static readonly JsonOptions FallbackJsonOptions = new();
         private static readonly string[] GetVerb = new[] { global::Microsoft.AspNetCore.Http.HttpMethods.Get };
 
         [InterceptsLocation(@"TestMapActions.cs", 25, 13)]
@@ -94,9 +95,11 @@ namespace Microsoft.AspNetCore.Http.Generated
                 EndpointFilterDelegate? filteredInvocation = null;
                 var serviceProvider = options.ServiceProvider ?? options.EndpointBuilder.ApplicationServices;
                 var logOrThrowExceptionHelper = new LogOrThrowExceptionHelper(serviceProvider, options);
-                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? new JsonOptions();
-                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonOptions.SerializerOptions.GetTypeInfo(typeof(object));
-                var responseJsonTypeInfo =  (JsonTypeInfo<global::System.Int32>)jsonOptions.SerializerOptions.GetTypeInfo(typeof(global::System.Int32));
+                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? FallbackJsonOptions;
+                var jsonSerializerOptions = jsonOptions.SerializerOptions;
+                jsonSerializerOptions.MakeReadOnly();
+                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonSerializerOptions.GetTypeInfo(typeof(object));
+                var responseJsonTypeInfo =  (JsonTypeInfo<global::System.Int32>)jsonSerializerOptions.GetTypeInfo(typeof(global::System.Int32));
 
                 if (options.EndpointBuilder.FilterFactories.Count > 0)
                 {

src/Http/Http.Extensions/test/RequestDelegateGenerator/Baselines/MapAction_JsonBodyOrService_HandlesBothJsonAndService.generated.txt

@@ -55,6 +55,7 @@ namespace Microsoft.AspNetCore.Http.Generated
     %GENERATEDCODEATTRIBUTE%
     file static class GeneratedRouteBuilderExtensionsCore
     {
+        private static readonly JsonOptions FallbackJsonOptions = new();
         private static readonly string[] PostVerb = new[] { global::Microsoft.AspNetCore.Http.HttpMethods.Post };
 
         [InterceptsLocation(@"TestMapActions.cs", 25, 13)]
@@ -95,11 +96,13 @@ namespace Microsoft.AspNetCore.Http.Generated
                 EndpointFilterDelegate? filteredInvocation = null;
                 var serviceProvider = options.ServiceProvider ?? options.EndpointBuilder.ApplicationServices;
                 var logOrThrowExceptionHelper = new LogOrThrowExceptionHelper(serviceProvider, options);
-                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? new JsonOptions();
-                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonOptions.SerializerOptions.GetTypeInfo(typeof(object));
+                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? FallbackJsonOptions;
+                var jsonSerializerOptions = jsonOptions.SerializerOptions;
+                jsonSerializerOptions.MakeReadOnly();
+                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonSerializerOptions.GetTypeInfo(typeof(object));
                 var serviceProviderIsService = serviceProvider?.GetService<IServiceProviderIsService>();
-                var todo_JsonBodyOrServiceResolver = ResolveJsonBodyOrService<global::Microsoft.AspNetCore.Http.Generators.Tests.Todo>(logOrThrowExceptionHelper, "Todo", "todo", jsonOptions, serviceProviderIsService);
-                var svc_JsonBodyOrServiceResolver = ResolveJsonBodyOrService<global::Microsoft.AspNetCore.Http.Generators.Tests.TestService>(logOrThrowExceptionHelper, "TestService", "svc", jsonOptions, serviceProviderIsService);
+                var todo_JsonBodyOrServiceResolver = ResolveJsonBodyOrService<global::Microsoft.AspNetCore.Http.Generators.Tests.Todo>(logOrThrowExceptionHelper, "Todo", "todo", jsonSerializerOptions, serviceProviderIsService);
+                var svc_JsonBodyOrServiceResolver = ResolveJsonBodyOrService<global::Microsoft.AspNetCore.Http.Generators.Tests.TestService>(logOrThrowExceptionHelper, "TestService", "svc", jsonSerializerOptions, serviceProviderIsService);
 
                 if (options.EndpointBuilder.FilterFactories.Count > 0)
                 {
@@ -319,7 +322,7 @@ namespace Microsoft.AspNetCore.Http.Generated
 
             return (true, bodyValue);
         }
-        private static Func<HttpContext, bool, ValueTask<(bool, T?)>> ResolveJsonBodyOrService<T>(LogOrThrowExceptionHelper logOrThrowExceptionHelper, string parameterTypeName, string parameterName, JsonOptions jsonOptions, IServiceProviderIsService? serviceProviderIsService = null)
+        private static Func<HttpContext, bool, ValueTask<(bool, T?)>> ResolveJsonBodyOrService<T>(LogOrThrowExceptionHelper logOrThrowExceptionHelper, string parameterTypeName, string parameterName, JsonSerializerOptions jsonSerializerOptions, IServiceProviderIsService? serviceProviderIsService = null)
         {
             if (serviceProviderIsService is not null)
             {
@@ -328,7 +331,7 @@ namespace Microsoft.AspNetCore.Http.Generated
                     return static (httpContext, isOptional) => new ValueTask<(bool, T?)>((true, httpContext.RequestServices.GetService<T>()));
                 }
             }
-            var jsonTypeInfo = (JsonTypeInfo<T>)jsonOptions.SerializerOptions.GetTypeInfo(typeof(T));
+            var jsonTypeInfo = (JsonTypeInfo<T>)jsonSerializerOptions.GetTypeInfo(typeof(T));
             return (httpContext, isOptional) => TryResolveBodyAsync<T>(httpContext, logOrThrowExceptionHelper, isOptional, parameterTypeName, parameterName, jsonTypeInfo, isInferred: true);
         }
 

src/Http/Http.Extensions/test/RequestDelegateGenerator/Baselines/MapAction_MultipleSpecialTypeParam_StringReturn.generated.txt

@@ -55,6 +55,7 @@ namespace Microsoft.AspNetCore.Http.Generated
     %GENERATEDCODEATTRIBUTE%
     file static class GeneratedRouteBuilderExtensionsCore
     {
+        private static readonly JsonOptions FallbackJsonOptions = new();
         private static readonly string[] GetVerb = new[] { global::Microsoft.AspNetCore.Http.HttpMethods.Get };
 
         [InterceptsLocation(@"TestMapActions.cs", 25, 13)]
@@ -80,8 +81,10 @@ namespace Microsoft.AspNetCore.Http.Generated
                 var handler = Cast(del, global::System.String (global::Microsoft.AspNetCore.Http.HttpRequest arg0, global::Microsoft.AspNetCore.Http.HttpResponse arg1) => throw null!);
                 EndpointFilterDelegate? filteredInvocation = null;
                 var serviceProvider = options.ServiceProvider ?? options.EndpointBuilder.ApplicationServices;
-                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? new JsonOptions();
-                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonOptions.SerializerOptions.GetTypeInfo(typeof(object));
+                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? FallbackJsonOptions;
+                var jsonSerializerOptions = jsonOptions.SerializerOptions;
+                jsonSerializerOptions.MakeReadOnly();
+                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonSerializerOptions.GetTypeInfo(typeof(object));
 
                 if (options.EndpointBuilder.FilterFactories.Count > 0)
                 {

src/Http/Http.Extensions/test/RequestDelegateGenerator/Baselines/MapAction_MultipleStringParam_StringReturn.generated.txt

@@ -55,6 +55,7 @@ namespace Microsoft.AspNetCore.Http.Generated
     %GENERATEDCODEATTRIBUTE%
     file static class GeneratedRouteBuilderExtensionsCore
     {
+        private static readonly JsonOptions FallbackJsonOptions = new();
         private static readonly string[] GetVerb = new[] { global::Microsoft.AspNetCore.Http.HttpMethods.Get };
 
         [InterceptsLocation(@"TestMapActions.cs", 25, 13)]
@@ -81,8 +82,10 @@ namespace Microsoft.AspNetCore.Http.Generated
                 EndpointFilterDelegate? filteredInvocation = null;
                 var serviceProvider = options.ServiceProvider ?? options.EndpointBuilder.ApplicationServices;
                 var logOrThrowExceptionHelper = new LogOrThrowExceptionHelper(serviceProvider, options);
-                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? new JsonOptions();
-                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonOptions.SerializerOptions.GetTypeInfo(typeof(object));
+                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? FallbackJsonOptions;
+                var jsonSerializerOptions = jsonOptions.SerializerOptions;
+                jsonSerializerOptions.MakeReadOnly();
+                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonSerializerOptions.GetTypeInfo(typeof(object));
 
                 if (options.EndpointBuilder.FilterFactories.Count > 0)
                 {

src/Http/Http.Extensions/test/RequestDelegateGenerator/Baselines/MapAction_NoParam_StringReturn_WithFilter.generated.txt

@@ -55,6 +55,7 @@ namespace Microsoft.AspNetCore.Http.Generated
     %GENERATEDCODEATTRIBUTE%
     file static class GeneratedRouteBuilderExtensionsCore
     {
+        private static readonly JsonOptions FallbackJsonOptions = new();
         private static readonly string[] GetVerb = new[] { global::Microsoft.AspNetCore.Http.HttpMethods.Get };
 
         [InterceptsLocation(@"TestMapActions.cs", 25, 13)]
@@ -80,8 +81,10 @@ namespace Microsoft.AspNetCore.Http.Generated
                 var handler = Cast(del, global::System.String () => throw null!);
                 EndpointFilterDelegate? filteredInvocation = null;
                 var serviceProvider = options.ServiceProvider ?? options.EndpointBuilder.ApplicationServices;
-                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? new JsonOptions();
-                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonOptions.SerializerOptions.GetTypeInfo(typeof(object));
+                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? FallbackJsonOptions;
+                var jsonSerializerOptions = jsonOptions.SerializerOptions;
+                jsonSerializerOptions.MakeReadOnly();
+                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonSerializerOptions.GetTypeInfo(typeof(object));
 
                 if (options.EndpointBuilder.FilterFactories.Count > 0)
                 {

src/Http/Http.Extensions/test/RequestDelegateGenerator/Baselines/MapAction_ReturnsString_Has_Metadata.generated.txt

@@ -55,6 +55,7 @@ namespace Microsoft.AspNetCore.Http.Generated
     %GENERATEDCODEATTRIBUTE%
     file static class GeneratedRouteBuilderExtensionsCore
     {
+        private static readonly JsonOptions FallbackJsonOptions = new();
         private static readonly string[] GetVerb = new[] { global::Microsoft.AspNetCore.Http.HttpMethods.Get };
 
         [InterceptsLocation(@"TestMapActions.cs", 25, 13)]
@@ -80,8 +81,10 @@ namespace Microsoft.AspNetCore.Http.Generated
                 var handler = Cast(del, global::System.String () => throw null!);
                 EndpointFilterDelegate? filteredInvocation = null;
                 var serviceProvider = options.ServiceProvider ?? options.EndpointBuilder.ApplicationServices;
-                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? new JsonOptions();
-                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonOptions.SerializerOptions.GetTypeInfo(typeof(object));
+                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? FallbackJsonOptions;
+                var jsonSerializerOptions = jsonOptions.SerializerOptions;
+                jsonSerializerOptions.MakeReadOnly();
+                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonSerializerOptions.GetTypeInfo(typeof(object));
 
                 if (options.EndpointBuilder.FilterFactories.Count > 0)
                 {

src/Http/Http.Extensions/test/RequestDelegateGenerator/Baselines/MapAction_ReturnsTodo_Has_Metadata.generated.txt

@@ -55,6 +55,7 @@ namespace Microsoft.AspNetCore.Http.Generated
     %GENERATEDCODEATTRIBUTE%
     file static class GeneratedRouteBuilderExtensionsCore
     {
+        private static readonly JsonOptions FallbackJsonOptions = new();
         private static readonly string[] GetVerb = new[] { global::Microsoft.AspNetCore.Http.HttpMethods.Get };
 
         [InterceptsLocation(@"TestMapActions.cs", 25, 13)]
@@ -80,9 +81,11 @@ namespace Microsoft.AspNetCore.Http.Generated
                 var handler = Cast(del, global::Microsoft.AspNetCore.Http.Generators.Tests.Todo () => throw null!);
                 EndpointFilterDelegate? filteredInvocation = null;
                 var serviceProvider = options.ServiceProvider ?? options.EndpointBuilder.ApplicationServices;
-                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? new JsonOptions();
-                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonOptions.SerializerOptions.GetTypeInfo(typeof(object));
-                var responseJsonTypeInfo =  (JsonTypeInfo<global::Microsoft.AspNetCore.Http.Generators.Tests.Todo?>)jsonOptions.SerializerOptions.GetTypeInfo(typeof(global::Microsoft.AspNetCore.Http.Generators.Tests.Todo));
+                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? FallbackJsonOptions;
+                var jsonSerializerOptions = jsonOptions.SerializerOptions;
+                jsonSerializerOptions.MakeReadOnly();
+                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonSerializerOptions.GetTypeInfo(typeof(object));
+                var responseJsonTypeInfo =  (JsonTypeInfo<global::Microsoft.AspNetCore.Http.Generators.Tests.Todo?>)jsonSerializerOptions.GetTypeInfo(typeof(global::Microsoft.AspNetCore.Http.Generators.Tests.Todo));
 
                 if (options.EndpointBuilder.FilterFactories.Count > 0)
                 {

src/Http/Http.Extensions/test/RequestDelegateGenerator/Baselines/MapAction_ReturnsValidationProblemResult_Has_Metadata.generated.txt

@@ -55,6 +55,7 @@ namespace Microsoft.AspNetCore.Http.Generated
     %GENERATEDCODEATTRIBUTE%
     file static class GeneratedRouteBuilderExtensionsCore
     {
+        private static readonly JsonOptions FallbackJsonOptions = new();
         private static readonly string[] GetVerb = new[] { global::Microsoft.AspNetCore.Http.HttpMethods.Get };
 
         [InterceptsLocation(@"TestMapActions.cs", 25, 13)]
@@ -80,8 +81,10 @@ namespace Microsoft.AspNetCore.Http.Generated
                 var handler = Cast(del, global::Microsoft.AspNetCore.Http.HttpResults.ValidationProblem () => throw null!);
                 EndpointFilterDelegate? filteredInvocation = null;
                 var serviceProvider = options.ServiceProvider ?? options.EndpointBuilder.ApplicationServices;
-                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? new JsonOptions();
-                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonOptions.SerializerOptions.GetTypeInfo(typeof(object));
+                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? FallbackJsonOptions;
+                var jsonSerializerOptions = jsonOptions.SerializerOptions;
+                jsonSerializerOptions.MakeReadOnly();
+                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonSerializerOptions.GetTypeInfo(typeof(object));
 
                 if (options.EndpointBuilder.FilterFactories.Count > 0)
                 {

src/Http/Http.Extensions/test/RequestDelegateGenerator/Baselines/MapAction_ReturnsVoid_Has_No_Metadata.generated.txt

@@ -55,6 +55,7 @@ namespace Microsoft.AspNetCore.Http.Generated
     %GENERATEDCODEATTRIBUTE%
     file static class GeneratedRouteBuilderExtensionsCore
     {
+        private static readonly JsonOptions FallbackJsonOptions = new();
         private static readonly string[] GetVerb = new[] { global::Microsoft.AspNetCore.Http.HttpMethods.Get };
 
         [InterceptsLocation(@"TestMapActions.cs", 25, 13)]
@@ -79,8 +80,10 @@ namespace Microsoft.AspNetCore.Http.Generated
                 var handler = Cast(del, void () => throw null!);
                 EndpointFilterDelegate? filteredInvocation = null;
                 var serviceProvider = options.ServiceProvider ?? options.EndpointBuilder.ApplicationServices;
-                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? new JsonOptions();
-                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonOptions.SerializerOptions.GetTypeInfo(typeof(object));
+                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? FallbackJsonOptions;
+                var jsonSerializerOptions = jsonOptions.SerializerOptions;
+                jsonSerializerOptions.MakeReadOnly();
+                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonSerializerOptions.GetTypeInfo(typeof(object));
 
                 if (options.EndpointBuilder.FilterFactories.Count > 0)
                 {

src/Http/Http.Extensions/test/RequestDelegateGenerator/Baselines/MapAction_SingleComplexTypeParam_StringReturn.generated.txt

@@ -55,6 +55,7 @@ namespace Microsoft.AspNetCore.Http.Generated
     %GENERATEDCODEATTRIBUTE%
     file static class GeneratedRouteBuilderExtensionsCore
     {
+        private static readonly JsonOptions FallbackJsonOptions = new();
         private static readonly string[] GetVerb = new[] { global::Microsoft.AspNetCore.Http.HttpMethods.Get };
 
         [InterceptsLocation(@"TestMapActions.cs", 25, 13)]
@@ -81,8 +82,10 @@ namespace Microsoft.AspNetCore.Http.Generated
                 EndpointFilterDelegate? filteredInvocation = null;
                 var serviceProvider = options.ServiceProvider ?? options.EndpointBuilder.ApplicationServices;
                 var logOrThrowExceptionHelper = new LogOrThrowExceptionHelper(serviceProvider, options);
-                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? new JsonOptions();
-                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonOptions.SerializerOptions.GetTypeInfo(typeof(object));
+                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? FallbackJsonOptions;
+                var jsonSerializerOptions = jsonOptions.SerializerOptions;
+                jsonSerializerOptions.MakeReadOnly();
+                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonSerializerOptions.GetTypeInfo(typeof(object));
 
                 if (options.EndpointBuilder.FilterFactories.Count > 0)
                 {

src/Http/Http.Extensions/test/RequestDelegateGenerator/Baselines/MapAction_SingleEnumParam_StringReturn.generated.txt

@@ -55,6 +55,7 @@ namespace Microsoft.AspNetCore.Http.Generated
     %GENERATEDCODEATTRIBUTE%
     file static class GeneratedRouteBuilderExtensionsCore
     {
+        private static readonly JsonOptions FallbackJsonOptions = new();
         private static readonly string[] GetVerb = new[] { global::Microsoft.AspNetCore.Http.HttpMethods.Get };
 
         [InterceptsLocation(@"TestMapActions.cs", 25, 13)]
@@ -81,8 +82,10 @@ namespace Microsoft.AspNetCore.Http.Generated
                 EndpointFilterDelegate? filteredInvocation = null;
                 var serviceProvider = options.ServiceProvider ?? options.EndpointBuilder.ApplicationServices;
                 var logOrThrowExceptionHelper = new LogOrThrowExceptionHelper(serviceProvider, options);
-                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? new JsonOptions();
-                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonOptions.SerializerOptions.GetTypeInfo(typeof(object));
+                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? FallbackJsonOptions;
+                var jsonSerializerOptions = jsonOptions.SerializerOptions;
+                jsonSerializerOptions.MakeReadOnly();
+                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonSerializerOptions.GetTypeInfo(typeof(object));
 
                 if (options.EndpointBuilder.FilterFactories.Count > 0)
                 {

src/Http/Http.Extensions/test/RequestDelegateGenerator/Baselines/MapAction_SingleNullableStringParam_WithEmptyQueryStringValueProvided_StringReturn.generated.txt

@@ -55,6 +55,7 @@ namespace Microsoft.AspNetCore.Http.Generated
     %GENERATEDCODEATTRIBUTE%
     file static class GeneratedRouteBuilderExtensionsCore
     {
+        private static readonly JsonOptions FallbackJsonOptions = new();
         private static readonly string[] GetVerb = new[] { global::Microsoft.AspNetCore.Http.HttpMethods.Get };
 
         [InterceptsLocation(@"TestMapActions.cs", 25, 13)]
@@ -81,8 +82,10 @@ namespace Microsoft.AspNetCore.Http.Generated
                 EndpointFilterDelegate? filteredInvocation = null;
                 var serviceProvider = options.ServiceProvider ?? options.EndpointBuilder.ApplicationServices;
                 var logOrThrowExceptionHelper = new LogOrThrowExceptionHelper(serviceProvider, options);
-                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? new JsonOptions();
-                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonOptions.SerializerOptions.GetTypeInfo(typeof(object));
+                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? FallbackJsonOptions;
+                var jsonSerializerOptions = jsonOptions.SerializerOptions;
+                jsonSerializerOptions.MakeReadOnly();
+                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonSerializerOptions.GetTypeInfo(typeof(object));
 
                 if (options.EndpointBuilder.FilterFactories.Count > 0)
                 {

src/Http/Http.Extensions/test/RequestDelegateGenerator/Baselines/MapAction_TakesCustomMetadataEmitter_Has_Metadata.generated.txt

@@ -55,6 +55,7 @@ namespace Microsoft.AspNetCore.Http.Generated
     %GENERATEDCODEATTRIBUTE%
     file static class GeneratedRouteBuilderExtensionsCore
     {
+        private static readonly JsonOptions FallbackJsonOptions = new();
         private static readonly string[] PostVerb = new[] { global::Microsoft.AspNetCore.Http.HttpMethods.Post };
 
         [InterceptsLocation(@"TestMapActions.cs", 25, 13)]
@@ -97,10 +98,12 @@ namespace Microsoft.AspNetCore.Http.Generated
                 EndpointFilterDelegate? filteredInvocation = null;
                 var serviceProvider = options.ServiceProvider ?? options.EndpointBuilder.ApplicationServices;
                 var logOrThrowExceptionHelper = new LogOrThrowExceptionHelper(serviceProvider, options);
-                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? new JsonOptions();
-                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonOptions.SerializerOptions.GetTypeInfo(typeof(object));
+                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? FallbackJsonOptions;
+                var jsonSerializerOptions = jsonOptions.SerializerOptions;
+                jsonSerializerOptions.MakeReadOnly();
+                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonSerializerOptions.GetTypeInfo(typeof(object));
                 var serviceProviderIsService = serviceProvider?.GetService<IServiceProviderIsService>();
-                var x_JsonBodyOrServiceResolver = ResolveJsonBodyOrService<global::Microsoft.AspNetCore.Http.Generators.Tests.CustomMetadataEmitter>(logOrThrowExceptionHelper, "CustomMetadataEmitter", "x", jsonOptions, serviceProviderIsService);
+                var x_JsonBodyOrServiceResolver = ResolveJsonBodyOrService<global::Microsoft.AspNetCore.Http.Generators.Tests.CustomMetadataEmitter>(logOrThrowExceptionHelper, "CustomMetadataEmitter", "x", jsonSerializerOptions, serviceProviderIsService);
 
                 if (options.EndpointBuilder.FilterFactories.Count > 0)
                 {
@@ -298,7 +301,7 @@ namespace Microsoft.AspNetCore.Http.Generated
 
             return (true, bodyValue);
         }
-        private static Func<HttpContext, bool, ValueTask<(bool, T?)>> ResolveJsonBodyOrService<T>(LogOrThrowExceptionHelper logOrThrowExceptionHelper, string parameterTypeName, string parameterName, JsonOptions jsonOptions, IServiceProviderIsService? serviceProviderIsService = null)
+        private static Func<HttpContext, bool, ValueTask<(bool, T?)>> ResolveJsonBodyOrService<T>(LogOrThrowExceptionHelper logOrThrowExceptionHelper, string parameterTypeName, string parameterName, JsonSerializerOptions jsonSerializerOptions, IServiceProviderIsService? serviceProviderIsService = null)
         {
             if (serviceProviderIsService is not null)
             {
@@ -307,7 +310,7 @@ namespace Microsoft.AspNetCore.Http.Generated
                     return static (httpContext, isOptional) => new ValueTask<(bool, T?)>((true, httpContext.RequestServices.GetService<T>()));
                 }
             }
-            var jsonTypeInfo = (JsonTypeInfo<T>)jsonOptions.SerializerOptions.GetTypeInfo(typeof(T));
+            var jsonTypeInfo = (JsonTypeInfo<T>)jsonSerializerOptions.GetTypeInfo(typeof(T));
             return (httpContext, isOptional) => TryResolveBodyAsync<T>(httpContext, logOrThrowExceptionHelper, isOptional, parameterTypeName, parameterName, jsonTypeInfo, isInferred: true);
         }
         private static void PopulateMetadataForEndpoint<T>(MethodInfo method, EndpointBuilder builder)

src/Http/Http.Extensions/test/RequestDelegateGenerator/Baselines/MapMethods_Get_WithArrayQueryString_AndBody_ShouldUseQueryString.generated.txt

@@ -55,6 +55,7 @@ namespace Microsoft.AspNetCore.Http.Generated
     %GENERATEDCODEATTRIBUTE%
     file static class GeneratedRouteBuilderExtensionsCore
     {
+        private static readonly JsonOptions FallbackJsonOptions = new();
         
         [InterceptsLocation(@"TestMapActions.cs", 25, 13)]
         internal static RouteHandlerBuilder MapMethods0(
@@ -94,8 +95,10 @@ namespace Microsoft.AspNetCore.Http.Generated
                 EndpointFilterDelegate? filteredInvocation = null;
                 var serviceProvider = options.ServiceProvider ?? options.EndpointBuilder.ApplicationServices;
                 var logOrThrowExceptionHelper = new LogOrThrowExceptionHelper(serviceProvider, options);
-                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? new JsonOptions();
-                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonOptions.SerializerOptions.GetTypeInfo(typeof(object));
+                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? FallbackJsonOptions;
+                var jsonSerializerOptions = jsonOptions.SerializerOptions;
+                jsonSerializerOptions.MakeReadOnly();
+                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonSerializerOptions.GetTypeInfo(typeof(object));
 
                 if (options.EndpointBuilder.FilterFactories.Count > 0)
                 {

src/Http/Http.Extensions/test/RequestDelegateGenerator/Baselines/MapMethods_PostAndGet_WithArrayQueryString_AndBody_ShouldUseQueryString.generated.txt

@@ -55,6 +55,7 @@ namespace Microsoft.AspNetCore.Http.Generated
     %GENERATEDCODEATTRIBUTE%
     file static class GeneratedRouteBuilderExtensionsCore
     {
+        private static readonly JsonOptions FallbackJsonOptions = new();
         
         [InterceptsLocation(@"TestMapActions.cs", 25, 13)]
         internal static RouteHandlerBuilder MapMethods0(
@@ -94,8 +95,10 @@ namespace Microsoft.AspNetCore.Http.Generated
                 EndpointFilterDelegate? filteredInvocation = null;
                 var serviceProvider = options.ServiceProvider ?? options.EndpointBuilder.ApplicationServices;
                 var logOrThrowExceptionHelper = new LogOrThrowExceptionHelper(serviceProvider, options);
-                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? new JsonOptions();
-                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonOptions.SerializerOptions.GetTypeInfo(typeof(object));
+                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? FallbackJsonOptions;
+                var jsonSerializerOptions = jsonOptions.SerializerOptions;
+                jsonSerializerOptions.MakeReadOnly();
+                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonSerializerOptions.GetTypeInfo(typeof(object));
 
                 if (options.EndpointBuilder.FilterFactories.Count > 0)
                 {

src/Http/Http.Extensions/test/RequestDelegateGenerator/Baselines/MapMethods_PostAndPut_WithArrayQueryString_AndBody_ShouldUseBody.generated.txt

@@ -55,6 +55,7 @@ namespace Microsoft.AspNetCore.Http.Generated
     %GENERATEDCODEATTRIBUTE%
     file static class GeneratedRouteBuilderExtensionsCore
     {
+        private static readonly JsonOptions FallbackJsonOptions = new();
         
         [InterceptsLocation(@"TestMapActions.cs", 25, 13)]
         internal static RouteHandlerBuilder MapMethods0(
@@ -94,8 +95,10 @@ namespace Microsoft.AspNetCore.Http.Generated
                 EndpointFilterDelegate? filteredInvocation = null;
                 var serviceProvider = options.ServiceProvider ?? options.EndpointBuilder.ApplicationServices;
                 var logOrThrowExceptionHelper = new LogOrThrowExceptionHelper(serviceProvider, options);
-                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? new JsonOptions();
-                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonOptions.SerializerOptions.GetTypeInfo(typeof(object));
+                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? FallbackJsonOptions;
+                var jsonSerializerOptions = jsonOptions.SerializerOptions;
+                jsonSerializerOptions.MakeReadOnly();
+                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonSerializerOptions.GetTypeInfo(typeof(object));
 
                 if (options.EndpointBuilder.FilterFactories.Count > 0)
                 {

src/Http/Http.Extensions/test/RequestDelegateGenerator/Baselines/MapMethods_Post_WithArrayQueryString_AndBody_ShouldUseBody.generated.txt

@@ -55,6 +55,7 @@ namespace Microsoft.AspNetCore.Http.Generated
     %GENERATEDCODEATTRIBUTE%
     file static class GeneratedRouteBuilderExtensionsCore
     {
+        private static readonly JsonOptions FallbackJsonOptions = new();
         
         [InterceptsLocation(@"TestMapActions.cs", 25, 13)]
         internal static RouteHandlerBuilder MapMethods0(
@@ -94,8 +95,10 @@ namespace Microsoft.AspNetCore.Http.Generated
                 EndpointFilterDelegate? filteredInvocation = null;
                 var serviceProvider = options.ServiceProvider ?? options.EndpointBuilder.ApplicationServices;
                 var logOrThrowExceptionHelper = new LogOrThrowExceptionHelper(serviceProvider, options);
-                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? new JsonOptions();
-                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonOptions.SerializerOptions.GetTypeInfo(typeof(object));
+                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? FallbackJsonOptions;
+                var jsonSerializerOptions = jsonOptions.SerializerOptions;
+                jsonSerializerOptions.MakeReadOnly();
+                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonSerializerOptions.GetTypeInfo(typeof(object));
 
                 if (options.EndpointBuilder.FilterFactories.Count > 0)
                 {

src/Http/Http.Extensions/test/RequestDelegateGenerator/Baselines/MapPost_WithArrayQueryString_AndBody_ShouldUseBody.generated.txt

@@ -55,6 +55,7 @@ namespace Microsoft.AspNetCore.Http.Generated
     %GENERATEDCODEATTRIBUTE%
     file static class GeneratedRouteBuilderExtensionsCore
     {
+        private static readonly JsonOptions FallbackJsonOptions = new();
         private static readonly string[] PostVerb = new[] { global::Microsoft.AspNetCore.Http.HttpMethods.Post };
 
         [InterceptsLocation(@"TestMapActions.cs", 25, 13)]
@@ -94,8 +95,10 @@ namespace Microsoft.AspNetCore.Http.Generated
                 EndpointFilterDelegate? filteredInvocation = null;
                 var serviceProvider = options.ServiceProvider ?? options.EndpointBuilder.ApplicationServices;
                 var logOrThrowExceptionHelper = new LogOrThrowExceptionHelper(serviceProvider, options);
-                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? new JsonOptions();
-                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonOptions.SerializerOptions.GetTypeInfo(typeof(object));
+                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? FallbackJsonOptions;
+                var jsonSerializerOptions = jsonOptions.SerializerOptions;
+                jsonSerializerOptions.MakeReadOnly();
+                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonSerializerOptions.GetTypeInfo(typeof(object));
 
                 if (options.EndpointBuilder.FilterFactories.Count > 0)
                 {

src/Http/Http.Extensions/test/RequestDelegateGenerator/Baselines/MapPost_WithArrayQueryString_ShouldFail.generated.txt

@@ -55,6 +55,7 @@ namespace Microsoft.AspNetCore.Http.Generated
     %GENERATEDCODEATTRIBUTE%
     file static class GeneratedRouteBuilderExtensionsCore
     {
+        private static readonly JsonOptions FallbackJsonOptions = new();
         private static readonly string[] PostVerb = new[] { global::Microsoft.AspNetCore.Http.HttpMethods.Post };
 
         [InterceptsLocation(@"TestMapActions.cs", 25, 13)]
@@ -94,9 +95,11 @@ namespace Microsoft.AspNetCore.Http.Generated
                 EndpointFilterDelegate? filteredInvocation = null;
                 var serviceProvider = options.ServiceProvider ?? options.EndpointBuilder.ApplicationServices;
                 var logOrThrowExceptionHelper = new LogOrThrowExceptionHelper(serviceProvider, options);
-                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? new JsonOptions();
-                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonOptions.SerializerOptions.GetTypeInfo(typeof(object));
-                var responseJsonTypeInfo =  (JsonTypeInfo<global::System.Int32>)jsonOptions.SerializerOptions.GetTypeInfo(typeof(global::System.Int32));
+                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? FallbackJsonOptions;
+                var jsonSerializerOptions = jsonOptions.SerializerOptions;
+                jsonSerializerOptions.MakeReadOnly();
+                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonSerializerOptions.GetTypeInfo(typeof(object));
+                var responseJsonTypeInfo =  (JsonTypeInfo<global::System.Int32>)jsonSerializerOptions.GetTypeInfo(typeof(global::System.Int32));
 
                 if (options.EndpointBuilder.FilterFactories.Count > 0)
                 {

src/Http/Http.Extensions/test/RequestDelegateGenerator/Baselines/Multiple_MapAction_NoParam_StringReturn.generated.txt

@@ -55,6 +55,7 @@ namespace Microsoft.AspNetCore.Http.Generated
     %GENERATEDCODEATTRIBUTE%
     file static class GeneratedRouteBuilderExtensionsCore
     {
+        private static readonly JsonOptions FallbackJsonOptions = new();
         private static readonly string[] GetVerb = new[] { global::Microsoft.AspNetCore.Http.HttpMethods.Get };
 
         [InterceptsLocation(@"TestMapActions.cs", 25, 13)]
@@ -81,8 +82,10 @@ namespace Microsoft.AspNetCore.Http.Generated
                 var handler = Cast(del, global::System.String () => throw null!);
                 EndpointFilterDelegate? filteredInvocation = null;
                 var serviceProvider = options.ServiceProvider ?? options.EndpointBuilder.ApplicationServices;
-                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? new JsonOptions();
-                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonOptions.SerializerOptions.GetTypeInfo(typeof(object));
+                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? FallbackJsonOptions;
+                var jsonSerializerOptions = jsonOptions.SerializerOptions;
+                jsonSerializerOptions.MakeReadOnly();
+                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonSerializerOptions.GetTypeInfo(typeof(object));
 
                 if (options.EndpointBuilder.FilterFactories.Count > 0)
                 {
@@ -168,8 +171,10 @@ namespace Microsoft.AspNetCore.Http.Generated
                 var handler = Cast(del, global::System.Threading.Tasks.Task<global::System.String> () => throw null!);
                 EndpointFilterDelegate? filteredInvocation = null;
                 var serviceProvider = options.ServiceProvider ?? options.EndpointBuilder.ApplicationServices;
-                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? new JsonOptions();
-                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonOptions.SerializerOptions.GetTypeInfo(typeof(object));
+                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? FallbackJsonOptions;
+                var jsonSerializerOptions = jsonOptions.SerializerOptions;
+                jsonSerializerOptions.MakeReadOnly();
+                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonSerializerOptions.GetTypeInfo(typeof(object));
 
                 if (options.EndpointBuilder.FilterFactories.Count > 0)
                 {
@@ -256,8 +261,10 @@ namespace Microsoft.AspNetCore.Http.Generated
                 var handler = Cast(del, global::System.Threading.Tasks.ValueTask<global::System.String> () => throw null!);
                 EndpointFilterDelegate? filteredInvocation = null;
                 var serviceProvider = options.ServiceProvider ?? options.EndpointBuilder.ApplicationServices;
-                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? new JsonOptions();
-                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonOptions.SerializerOptions.GetTypeInfo(typeof(object));
+                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? FallbackJsonOptions;
+                var jsonSerializerOptions = jsonOptions.SerializerOptions;
+                jsonSerializerOptions.MakeReadOnly();
+                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonSerializerOptions.GetTypeInfo(typeof(object));
 
                 if (options.EndpointBuilder.FilterFactories.Count > 0)
                 {

src/Http/Http.Extensions/test/RequestDelegateGenerator/Baselines/Multiple_MapAction_WithParams_StringReturn.generated.txt

@@ -55,6 +55,7 @@ namespace Microsoft.AspNetCore.Http.Generated
     %GENERATEDCODEATTRIBUTE%
     file static class GeneratedRouteBuilderExtensionsCore
     {
+        private static readonly JsonOptions FallbackJsonOptions = new();
         private static readonly string[] GetVerb = new[] { global::Microsoft.AspNetCore.Http.HttpMethods.Get };
 
         [InterceptsLocation(@"TestMapActions.cs", 25, 13)]
@@ -80,8 +81,10 @@ namespace Microsoft.AspNetCore.Http.Generated
                 var handler = Cast(del, global::System.String (global::Microsoft.AspNetCore.Http.HttpRequest arg0) => throw null!);
                 EndpointFilterDelegate? filteredInvocation = null;
                 var serviceProvider = options.ServiceProvider ?? options.EndpointBuilder.ApplicationServices;
-                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? new JsonOptions();
-                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonOptions.SerializerOptions.GetTypeInfo(typeof(object));
+                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? FallbackJsonOptions;
+                var jsonSerializerOptions = jsonOptions.SerializerOptions;
+                jsonSerializerOptions.MakeReadOnly();
+                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonSerializerOptions.GetTypeInfo(typeof(object));
 
                 if (options.EndpointBuilder.FilterFactories.Count > 0)
                 {
@@ -171,8 +174,10 @@ namespace Microsoft.AspNetCore.Http.Generated
                 var handler = Cast(del, global::System.String (global::Microsoft.AspNetCore.Http.HttpResponse arg0) => throw null!);
                 EndpointFilterDelegate? filteredInvocation = null;
                 var serviceProvider = options.ServiceProvider ?? options.EndpointBuilder.ApplicationServices;
-                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? new JsonOptions();
-                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonOptions.SerializerOptions.GetTypeInfo(typeof(object));
+                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? FallbackJsonOptions;
+                var jsonSerializerOptions = jsonOptions.SerializerOptions;
+                jsonSerializerOptions.MakeReadOnly();
+                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonSerializerOptions.GetTypeInfo(typeof(object));
 
                 if (options.EndpointBuilder.FilterFactories.Count > 0)
                 {
@@ -262,8 +267,10 @@ namespace Microsoft.AspNetCore.Http.Generated
                 var handler = Cast(del, global::System.String (global::Microsoft.AspNetCore.Http.HttpRequest arg0, global::Microsoft.AspNetCore.Http.HttpResponse arg1) => throw null!);
                 EndpointFilterDelegate? filteredInvocation = null;
                 var serviceProvider = options.ServiceProvider ?? options.EndpointBuilder.ApplicationServices;
-                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? new JsonOptions();
-                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonOptions.SerializerOptions.GetTypeInfo(typeof(object));
+                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? FallbackJsonOptions;
+                var jsonSerializerOptions = jsonOptions.SerializerOptions;
+                jsonSerializerOptions.MakeReadOnly();
+                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonSerializerOptions.GetTypeInfo(typeof(object));
 
                 if (options.EndpointBuilder.FilterFactories.Count > 0)
                 {

src/Http/Http.Extensions/test/RequestDelegateGenerator/Baselines/RequestDelegateValidateGeneratedFormCode.generated.txt

@@ -55,6 +55,7 @@ namespace Microsoft.AspNetCore.Http.Generated
     %GENERATEDCODEATTRIBUTE%
     file static class GeneratedRouteBuilderExtensionsCore
     {
+        private static readonly JsonOptions FallbackJsonOptions = new();
         private static readonly string[] PostVerb = new[] { global::Microsoft.AspNetCore.Http.HttpMethods.Post };
 
         [InterceptsLocation(@"TestMapActions.cs", 29, 5)]
@@ -82,8 +83,10 @@ namespace Microsoft.AspNetCore.Http.Generated
                 EndpointFilterDelegate? filteredInvocation = null;
                 var serviceProvider = options.ServiceProvider ?? options.EndpointBuilder.ApplicationServices;
                 var logOrThrowExceptionHelper = new LogOrThrowExceptionHelper(serviceProvider, options);
-                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? new JsonOptions();
-                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonOptions.SerializerOptions.GetTypeInfo(typeof(object));
+                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? FallbackJsonOptions;
+                var jsonSerializerOptions = jsonOptions.SerializerOptions;
+                jsonSerializerOptions.MakeReadOnly();
+                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonSerializerOptions.GetTypeInfo(typeof(object));
 
                 if (options.EndpointBuilder.FilterFactories.Count > 0)
                 {

src/Http/Http.Extensions/test/RequestDelegateGenerator/Baselines/SupportsDifferentInterceptorsFromSameLocation.generated.txt

@@ -55,6 +55,7 @@ namespace Microsoft.AspNetCore.Http.Generated
     %GENERATEDCODEATTRIBUTE%
     file static class GeneratedRouteBuilderExtensionsCore
     {
+        private static readonly JsonOptions FallbackJsonOptions = new();
         private static readonly string[] GetVerb = new[] { global::Microsoft.AspNetCore.Http.HttpMethods.Get };
 
         [InterceptsLocation(@"TestMapActions.cs", 25, 13)]
@@ -81,8 +82,10 @@ namespace Microsoft.AspNetCore.Http.Generated
                 EndpointFilterDelegate? filteredInvocation = null;
                 var serviceProvider = options.ServiceProvider ?? options.EndpointBuilder.ApplicationServices;
                 var logOrThrowExceptionHelper = new LogOrThrowExceptionHelper(serviceProvider, options);
-                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? new JsonOptions();
-                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonOptions.SerializerOptions.GetTypeInfo(typeof(object));
+                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? FallbackJsonOptions;
+                var jsonSerializerOptions = jsonOptions.SerializerOptions;
+                jsonSerializerOptions.MakeReadOnly();
+                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonSerializerOptions.GetTypeInfo(typeof(object));
                 var name_RouteOrQueryResolver = GeneratedRouteBuilderExtensionsCore.ResolveFromRouteOrQuery("name", options.RouteParameterNames);
 
                 if (options.EndpointBuilder.FilterFactories.Count > 0)
@@ -190,8 +193,10 @@ namespace Microsoft.AspNetCore.Http.Generated
                 EndpointFilterDelegate? filteredInvocation = null;
                 var serviceProvider = options.ServiceProvider ?? options.EndpointBuilder.ApplicationServices;
                 var logOrThrowExceptionHelper = new LogOrThrowExceptionHelper(serviceProvider, options);
-                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? new JsonOptions();
-                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonOptions.SerializerOptions.GetTypeInfo(typeof(object));
+                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? FallbackJsonOptions;
+                var jsonSerializerOptions = jsonOptions.SerializerOptions;
+                jsonSerializerOptions.MakeReadOnly();
+                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonSerializerOptions.GetTypeInfo(typeof(object));
                 var age_RouteOrQueryResolver = GeneratedRouteBuilderExtensionsCore.ResolveFromRouteOrQuery("age", options.RouteParameterNames);
 
                 if (options.EndpointBuilder.FilterFactories.Count > 0)

src/Http/Http.Extensions/test/RequestDelegateGenerator/Baselines/SupportsSameInterceptorsFromDifferentFiles.generated.txt

@@ -55,6 +55,7 @@ namespace Microsoft.AspNetCore.Http.Generated
     %GENERATEDCODEATTRIBUTE%
     file static class GeneratedRouteBuilderExtensionsCore
     {
+        private static readonly JsonOptions FallbackJsonOptions = new();
         private static readonly string[] GetVerb = new[] { global::Microsoft.AspNetCore.Http.HttpMethods.Get };
 
         [InterceptsLocation(@"TestMapActions.cs", 25, 13)]
@@ -83,8 +84,10 @@ namespace Microsoft.AspNetCore.Http.Generated
                 EndpointFilterDelegate? filteredInvocation = null;
                 var serviceProvider = options.ServiceProvider ?? options.EndpointBuilder.ApplicationServices;
                 var logOrThrowExceptionHelper = new LogOrThrowExceptionHelper(serviceProvider, options);
-                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? new JsonOptions();
-                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonOptions.SerializerOptions.GetTypeInfo(typeof(object));
+                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? FallbackJsonOptions;
+                var jsonSerializerOptions = jsonOptions.SerializerOptions;
+                jsonSerializerOptions.MakeReadOnly();
+                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonSerializerOptions.GetTypeInfo(typeof(object));
                 var name_RouteOrQueryResolver = GeneratedRouteBuilderExtensionsCore.ResolveFromRouteOrQuery("name", options.RouteParameterNames);
 
                 if (options.EndpointBuilder.FilterFactories.Count > 0)

src/Http/Http.Extensions/test/RequestDelegateGenerator/Baselines/VerifyAsParametersBaseline.generated.txt

@@ -55,6 +55,7 @@ namespace Microsoft.AspNetCore.Http.Generated
     %GENERATEDCODEATTRIBUTE%
     file static class GeneratedRouteBuilderExtensionsCore
     {
+        private static readonly JsonOptions FallbackJsonOptions = new();
         private static readonly string[] GetVerb = new[] { global::Microsoft.AspNetCore.Http.HttpMethods.Get };
         private static readonly string[] PatchVerb = new[] { global::Microsoft.AspNetCore.Http.HttpMethods.Patch };
         private static readonly string[] PostVerb = new[] { global::Microsoft.AspNetCore.Http.HttpMethods.Post };
@@ -83,8 +84,10 @@ namespace Microsoft.AspNetCore.Http.Generated
                 EndpointFilterDelegate? filteredInvocation = null;
                 var serviceProvider = options.ServiceProvider ?? options.EndpointBuilder.ApplicationServices;
                 var logOrThrowExceptionHelper = new LogOrThrowExceptionHelper(serviceProvider, options);
-                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? new JsonOptions();
-                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonOptions.SerializerOptions.GetTypeInfo(typeof(object));
+                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? FallbackJsonOptions;
+                var jsonSerializerOptions = jsonOptions.SerializerOptions;
+                jsonSerializerOptions.MakeReadOnly();
+                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonSerializerOptions.GetTypeInfo(typeof(object));
 
                 if (options.EndpointBuilder.FilterFactories.Count > 0)
                 {
@@ -215,8 +218,10 @@ namespace Microsoft.AspNetCore.Http.Generated
                 EndpointFilterDelegate? filteredInvocation = null;
                 var serviceProvider = options.ServiceProvider ?? options.EndpointBuilder.ApplicationServices;
                 var logOrThrowExceptionHelper = new LogOrThrowExceptionHelper(serviceProvider, options);
-                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? new JsonOptions();
-                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonOptions.SerializerOptions.GetTypeInfo(typeof(object));
+                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? FallbackJsonOptions;
+                var jsonSerializerOptions = jsonOptions.SerializerOptions;
+                jsonSerializerOptions.MakeReadOnly();
+                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonSerializerOptions.GetTypeInfo(typeof(object));
                 var Value_RouteOrQueryResolver = GeneratedRouteBuilderExtensionsCore.ResolveFromRouteOrQuery("Value", options.RouteParameterNames);
 
                 if (options.EndpointBuilder.FilterFactories.Count > 0)
@@ -340,8 +345,10 @@ namespace Microsoft.AspNetCore.Http.Generated
                 EndpointFilterDelegate? filteredInvocation = null;
                 var serviceProvider = options.ServiceProvider ?? options.EndpointBuilder.ApplicationServices;
                 var logOrThrowExceptionHelper = new LogOrThrowExceptionHelper(serviceProvider, options);
-                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? new JsonOptions();
-                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonOptions.SerializerOptions.GetTypeInfo(typeof(object));
+                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? FallbackJsonOptions;
+                var jsonSerializerOptions = jsonOptions.SerializerOptions;
+                jsonSerializerOptions.MakeReadOnly();
+                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonSerializerOptions.GetTypeInfo(typeof(object));
 
                 if (options.EndpointBuilder.FilterFactories.Count > 0)
                 {
@@ -438,10 +445,12 @@ namespace Microsoft.AspNetCore.Http.Generated
                 EndpointFilterDelegate? filteredInvocation = null;
                 var serviceProvider = options.ServiceProvider ?? options.EndpointBuilder.ApplicationServices;
                 var logOrThrowExceptionHelper = new LogOrThrowExceptionHelper(serviceProvider, options);
-                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? new JsonOptions();
-                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonOptions.SerializerOptions.GetTypeInfo(typeof(object));
+                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? FallbackJsonOptions;
+                var jsonSerializerOptions = jsonOptions.SerializerOptions;
+                jsonSerializerOptions.MakeReadOnly();
+                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonSerializerOptions.GetTypeInfo(typeof(object));
                 var serviceProviderIsService = serviceProvider?.GetService<IServiceProviderIsService>();
-                var Todo_JsonBodyOrServiceResolver = ResolveJsonBodyOrService<global::Microsoft.AspNetCore.Http.Generators.Tests.TodoStruct>(logOrThrowExceptionHelper, "TodoStruct", "Todo", jsonOptions, serviceProviderIsService);
+                var Todo_JsonBodyOrServiceResolver = ResolveJsonBodyOrService<global::Microsoft.AspNetCore.Http.Generators.Tests.TodoStruct>(logOrThrowExceptionHelper, "TodoStruct", "Todo", jsonSerializerOptions, serviceProviderIsService);
 
                 if (options.EndpointBuilder.FilterFactories.Count > 0)
                 {
@@ -556,10 +565,12 @@ namespace Microsoft.AspNetCore.Http.Generated
                 EndpointFilterDelegate? filteredInvocation = null;
                 var serviceProvider = options.ServiceProvider ?? options.EndpointBuilder.ApplicationServices;
                 var logOrThrowExceptionHelper = new LogOrThrowExceptionHelper(serviceProvider, options);
-                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? new JsonOptions();
-                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonOptions.SerializerOptions.GetTypeInfo(typeof(object));
+                var jsonOptions = serviceProvider?.GetService<IOptions<JsonOptions>>()?.Value ?? FallbackJsonOptions;
+                var jsonSerializerOptions = jsonOptions.SerializerOptions;
+                jsonSerializerOptions.MakeReadOnly();
+                var objectJsonTypeInfo = (JsonTypeInfo<object?>)jsonSerializerOptions.GetTypeInfo(typeof(object));
                 var serviceProviderIsService = serviceProvider?.GetService<IServiceProviderIsService>();
-                var Value_JsonBodyOrServiceResolver = ResolveJsonBodyOrService<global::Microsoft.AspNetCore.Http.Generators.Tests.AddsCustomParameterMetadataAsProperty>(logOrThrowExceptionHelper, "AddsCustomParameterMetadataAsProperty", "Value", jsonOptions, serviceProviderIsService);
+                var Value_JsonBodyOrServiceResolver = ResolveJsonBodyOrService<global::Microsoft.AspNetCore.Http.Generators.Tests.AddsCustomParameterMetadataAsProperty>(logOrThrowExceptionHelper, "AddsCustomParameterMetadataAsProperty", "Value", jsonSerializerOptions, serviceProviderIsService);
 
                 if (options.EndpointBuilder.FilterFactories.Count > 0)
                 {
@@ -771,7 +782,7 @@ namespace Microsoft.AspNetCore.Http.Generated
 
             return (true, bodyValue);
         }
-        private static Func<HttpContext, bool, ValueTask<(bool, T?)>> ResolveJsonBodyOrService<T>(LogOrThrowExceptionHelper logOrThrowExceptionHelper, string parameterTypeName, string parameterName, JsonOptions jsonOptions, IServiceProviderIsService? serviceProviderIsService = null)
+        private static Func<HttpContext, bool, ValueTask<(bool, T?)>> ResolveJsonBodyOrService<T>(LogOrThrowExceptionHelper logOrThrowExceptionHelper, string parameterTypeName, string parameterName, JsonSerializerOptions jsonSerializerOptions, IServiceProviderIsService? serviceProviderIsService = null)
         {
             if (serviceProviderIsService is not null)
             {
@@ -780,7 +791,7 @@ namespace Microsoft.AspNetCore.Http.Generated
                     return static (httpContext, isOptional) => new ValueTask<(bool, T?)>((true, httpContext.RequestServices.GetService<T>()));
                 }
             }
-            var jsonTypeInfo = (JsonTypeInfo<T>)jsonOptions.SerializerOptions.GetTypeInfo(typeof(T));
+            var jsonTypeInfo = (JsonTypeInfo<T>)jsonSerializerOptions.GetTypeInfo(typeof(T));
             return (httpContext, isOptional) => TryResolveBodyAsync<T>(httpContext, logOrThrowExceptionHelper, isOptional, parameterTypeName, parameterName, jsonTypeInfo, isInferred: true);
         }
         private static bool TryParseExplicit<T>(string? s, IFormatProvider? provider, [MaybeNullWhen(returnValue: false)] out T result) where T: IParsable<T>

src/Http/Http.Extensions/test/RequestDelegateGenerator/CompileTimeCreationTests.cs

@@ -6,6 +6,7 @@ using Microsoft.CodeAnalysis;
 using Microsoft.AspNetCore.Http.RequestDelegateGenerator;
 using Microsoft.CodeAnalysis.CSharp;
 using Microsoft.CodeAnalysis.Text;
+using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.Logging;
 
 namespace Microsoft.AspNetCore.Http.Generators.Tests;
@@ -358,4 +359,19 @@ app.MapGet("/optional-struct-with-filter", (BindableStruct? param) => $"Hello {p
             await VerifyResponseBodyAsync(httpContext, $"Hello {endpoint.DisplayName}!");
         }
     }
+
+    [Fact]
+    public async Task MapAction_NoJsonTypeInfoResolver_ThrowsException()
+    {
+        var source = """
+app.MapGet("/", () => "Hello world!");
+""";
+        var (_, compilation) = await RunGeneratorAsync(source);
+        var serviceProvider = CreateServiceProvider(serviceCollection =>
+        {
+            serviceCollection.ConfigureHttpJsonOptions(o => o.SerializerOptions.TypeInfoResolver = null);
+        });
+        var exception = Assert.Throws<InvalidOperationException>(() => GetEndpointFromCompilation(compilation, serviceProvider: serviceProvider));
+        Assert.Equal("JsonSerializerOptions instance must specify a TypeInfoResolver setting before being marked as read-only.", exception.Message);
+    }
 }

src/Mvc/Mvc.Core/src/Formatters/SystemTextJsonOutputFormatter.cs

@@ -23,8 +23,6 @@ public class SystemTextJsonOutputFormatter : TextOutputFormatter
     {
         SerializerOptions = jsonSerializerOptions;
 
-        // Use JsonTypeInfoResolver.Combine() to produce an empty TypeInfoResolver
-        jsonSerializerOptions.TypeInfoResolver ??= JsonTypeInfoResolver.Combine();
         jsonSerializerOptions.MakeReadOnly();
 
         SupportedEncodings.Add(Encoding.UTF8);

src/Mvc/Mvc.Core/src/JsonOptions.cs

@@ -41,8 +41,8 @@ public class JsonOptions
 
         // The JsonSerializerOptions.GetTypeInfo method is called directly and needs a defined resolver
         // setting the default resolver (reflection-based) but the user can overwrite it directly or by modifying
-        // the TypeInfoResolverChain
-        TypeInfoResolver = JsonSerializer.IsReflectionEnabledByDefault ? CreateDefaultTypeResolver() : null
+        // the TypeInfoResolverChain. Use JsonTypeInfoResolver.Combine() to produce an empty TypeInfoResolver.
+        TypeInfoResolver = JsonSerializer.IsReflectionEnabledByDefault ? CreateDefaultTypeResolver() : JsonTypeInfoResolver.Combine()
     };
 
     private static IJsonTypeInfoResolver CreateDefaultTypeResolver()

src/Mvc/Mvc.Core/test/Formatters/SystemTextJsonOutputFormatterTest.cs

@@ -262,8 +262,8 @@ public partial class SystemTextJsonOutputFormatterTest : JsonOutputFormatterTest
         var jsonOptions = new JsonOptions();
         jsonOptions.JsonSerializerOptions.TypeInfoResolver = null;
 
-        var stjOutputFormatter = SystemTextJsonOutputFormatter.CreateFormatter(jsonOptions);
-        Assert.IsAssignableFrom<IJsonTypeInfoResolver>(stjOutputFormatter.SerializerOptions.TypeInfoResolver);
+        var exception = Assert.Throws<InvalidOperationException>(() => SystemTextJsonOutputFormatter.CreateFormatter(jsonOptions));
+        Assert.Equal("JsonSerializerOptions instance must specify a TypeInfoResolver setting before being marked as read-only.", exception.Message);
     }
 
     [ConditionalTheory]

src/Mvc/Mvc.Core/test/JsonOptionsTest.cs

@@ -22,7 +22,8 @@ public class JsonOptionsTest
             var options = new JsonOptions().JsonSerializerOptions;
 
             // Assert
-            Assert.Null(options.TypeInfoResolver);
+            Assert.NotNull(options.TypeInfoResolver);
+            Assert.IsAssignableFrom<IJsonTypeInfoResolver>(options.TypeInfoResolver);
         }, options);
     }
 

src/Shared/Json/JsonSerializerExtensions.cs

@@ -18,8 +18,6 @@ internal static class JsonSerializerExtensions
 
     public static JsonTypeInfo GetReadOnlyTypeInfo(this JsonSerializerOptions options, Type type)
     {
-        // Use JsonTypeInfoResolver.Combine() to produce an empty TypeInfoResolver
-        options.TypeInfoResolver ??= JsonTypeInfoResolver.Combine();
         options.MakeReadOnly();
         return options.GetTypeInfo(type);
     }