diff --git a/Refit.HttpClientFactory/HttpClientFactoryCore.cs b/Refit.HttpClientFactory/HttpClientFactoryCore.cs
new file mode 100644
index 000000000..5684070da
--- /dev/null
+++ b/Refit.HttpClientFactory/HttpClientFactoryCore.cs
@@ -0,0 +1,291 @@
+
+using System;
+using System.Linq;
+using System.Net.Http;
+using System.Reflection;
+using System.Runtime.CompilerServices;
+
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Http;
+
+namespace Refit
+{
+    /// <summary>
+    /// HttpClientFactoryExtensions
+    /// </summary>
+    internal static class HttpClientFactoryCore
+    {
+
+        internal static IHttpClientBuilder AddRefitClientCore(
+             IServiceCollection services,
+             Type refitInterfaceType,
+             Func<IServiceProvider, RefitSettings?>? settings,
+             string? httpClientName
+         )
+        {
+            if (services == null) throw new ArgumentNullException(nameof(services));
+            if (refitInterfaceType == null) throw new ArgumentNullException(nameof(refitInterfaceType));
+
+            // register settings
+            var settingsType = typeof(SettingsFor<>).MakeGenericType(refitInterfaceType);
+            services.AddSingleton(
+                settingsType,
+                provider => Activator.CreateInstance(
+                    typeof(SettingsFor<>).MakeGenericType(refitInterfaceType)!,
+                    settings?.Invoke(provider)
+                )!
+            );
+
+            // register RequestBuilder
+            var requestBuilderType = typeof(IRequestBuilder<>).MakeGenericType(refitInterfaceType);
+            services.AddSingleton(
+                requestBuilderType,
+                provider => RequestBuilderGenericForTypeMethod
+                    .MakeGenericMethod(refitInterfaceType)
+                    .Invoke(
+                        null,
+                        [((ISettingsFor)provider.GetRequiredService(settingsType)).Settings]
+                    )!
+            );
+
+            // create HttpClientBuilder
+            var builder = services.AddHttpClient(httpClientName ?? UniqueName.ForType(refitInterfaceType));
+
+            // configure message handler
+            builder.ConfigureHttpMessageHandlerBuilder(builderConfig =>
+            {
+                var handler = CreateInnerHandlerIfProvided(
+                    ((ISettingsFor)builderConfig.Services.GetRequiredService(settingsType)).Settings
+                );
+                if (handler != null)
+                {
+                    builderConfig.PrimaryHandler = handler;
+                }
+            });
+
+            // add typed client (register transient that resolves HttpClient from IHttpClientFactory and creates Refit client)
+            builder.Services.AddTransient(
+                refitInterfaceType,
+                s =>
+                {
+                    var httpClientFactory = s.GetRequiredService<IHttpClientFactory>();
+                    var httpClient = httpClientFactory.CreateClient(builder.Name);
+                    return RestService.For(
+                        refitInterfaceType,
+                        httpClient,
+                        (IRequestBuilder)s.GetRequiredService(requestBuilderType)
+                    );
+                }
+            );
+
+            return builder;
+        }
+
+        internal static IHttpClientBuilder AddKeyedRefitClientCore(
+            IServiceCollection services,
+            Type refitInterfaceType,
+            object? serviceKey,
+            Func<IServiceProvider, RefitSettings?>? settings,
+            string? httpClientName
+        )
+        {
+            if (services == null) throw new ArgumentNullException(nameof(services));
+            if (refitInterfaceType == null) throw new ArgumentNullException(nameof(refitInterfaceType));
+            if (serviceKey == null) throw new ArgumentNullException(nameof(serviceKey));
+
+            // register settings
+            var settingsType = typeof(SettingsFor<>).MakeGenericType(refitInterfaceType);
+            services.AddKeyedSingleton(
+                settingsType,
+                serviceKey,
+                (provider, _) => Activator.CreateInstance(
+                    typeof(SettingsFor<>).MakeGenericType(refitInterfaceType)!,
+                    settings?.Invoke(provider)
+                )!
+            );
+
+            // register RequestBuilder
+            var requestBuilderType = typeof(IRequestBuilder<>).MakeGenericType(refitInterfaceType);
+            services.AddKeyedSingleton(
+                requestBuilderType,
+                serviceKey,
+                (provider, _) => RequestBuilderGenericForTypeMethod
+                    .MakeGenericMethod(refitInterfaceType)
+                    .Invoke(
+                        null,
+                        [((ISettingsFor)provider.GetRequiredKeyedService(settingsType, serviceKey)).Settings]
+                    )!
+            );
+
+            // create HttpClientBuilder
+            var builder = services.AddHttpClient(httpClientName ?? UniqueName.ForType(refitInterfaceType, serviceKey));
+
+            // configure primary handler
+            builder.ConfigurePrimaryHttpMessageHandler(serviceProvider =>
+            {
+                var settingsInstance = (ISettingsFor)serviceProvider.GetRequiredKeyedService(settingsType, serviceKey);
+                return settingsInstance.Settings?.HttpMessageHandlerFactory?.Invoke() ?? new HttpClientHandler();
+            });
+
+            // configure additional handlers
+            builder.ConfigureAdditionalHttpMessageHandlers((handlers, serviceProvider) =>
+            {
+                var settingsInstance = (ISettingsFor)serviceProvider.GetRequiredKeyedService(settingsType, serviceKey);
+                if (settingsInstance.Settings?.AuthorizationHeaderValueGetter is { } getToken)
+                {
+                    handlers.Add(new AuthenticatedHttpClientHandler(null, getToken));
+                }
+            });
+
+            // add keyed typed client (register keyed transient that resolves HttpClient and creates Refit client)
+            builder.Services.AddKeyedTransient(
+                refitInterfaceType,
+                serviceKey,
+                (s, _) =>
+                {
+                    var httpClientFactory = s.GetRequiredService<IHttpClientFactory>();
+                    var httpClient = httpClientFactory.CreateClient(builder.Name);
+                    return RestService.For(
+                        refitInterfaceType,
+                        httpClient,
+                        (IRequestBuilder)s.GetRequiredKeyedService(requestBuilderType, serviceKey)
+                    );
+                }
+            );
+
+            return builder;
+        }
+
+        internal static IHttpClientBuilder AddRefitClientCore<T>(
+            IServiceCollection services,
+            Type refitInterfaceType,
+            Func<IServiceProvider, RefitSettings?>? settings,
+            string? httpClientName
+        ) where T : class
+        {
+            if (services == null) throw new ArgumentNullException(nameof(services));
+
+            // register settings
+            services.AddSingleton(provider => new SettingsFor<T>(settings?.Invoke(provider)));
+
+            // register RequestBuilder
+            services.AddSingleton(provider =>
+                RequestBuilder.ForType<T>(provider.GetRequiredService<SettingsFor<T>>().Settings)
+            );
+
+            // create HttpClientBuilder
+            var builder = services.AddHttpClient(httpClientName ?? UniqueName.ForType<T>());
+
+            // configure message handler
+            builder.ConfigureHttpMessageHandlerBuilder(builderConfig =>
+            {
+                var handler = CreateInnerHandlerIfProvided(
+                    builderConfig.Services.GetRequiredService<SettingsFor<T>>().Settings
+                );
+                if (handler != null)
+                {
+                    builderConfig.PrimaryHandler = handler;
+                }
+            });
+
+            // add typed client using framework AddTypedClient
+            return builder.AddTypedClient((client, serviceProvider) =>
+                RestService.For<T>(
+                    client,
+                    serviceProvider.GetRequiredService<IRequestBuilder<T>>()
+                )
+            );
+        }
+
+        internal static IHttpClientBuilder AddKeyedRefitClientCore<T>(
+            IServiceCollection services,
+            Type refitInterfaceType,
+            object? serviceKey,
+            Func<IServiceProvider, RefitSettings?>? settings,
+            string? httpClientName
+        ) where T : class
+        {
+            if (services == null) throw new ArgumentNullException(nameof(services));
+            if (serviceKey == null) throw new ArgumentNullException(nameof(serviceKey));
+
+            // register settings
+            services.AddKeyedSingleton(
+                serviceKey,
+                (provider, _) => new SettingsFor<T>(settings?.Invoke(provider))
+            );
+
+            // register RequestBuilder
+            services.AddKeyedSingleton(
+                serviceKey,
+                (provider, _) =>
+                    RequestBuilder.ForType<T>(
+                        provider.GetRequiredKeyedService<SettingsFor<T>>(serviceKey).Settings
+                    )
+            );
+
+            // create HttpClientBuilder
+            var builder = services.AddHttpClient(httpClientName ?? UniqueName.ForType<T>(serviceKey));
+
+            // configure primary handler
+            builder.ConfigurePrimaryHttpMessageHandler(serviceProvider =>
+            {
+                var settingsInstance = serviceProvider.GetRequiredKeyedService<SettingsFor<T>>(serviceKey).Settings;
+                return settingsInstance?.HttpMessageHandlerFactory?.Invoke() ?? new HttpClientHandler();
+            });
+
+            // configure additional handlers
+            builder.ConfigureAdditionalHttpMessageHandlers((handlers, serviceProvider) =>
+            {
+                var settingsInstance = serviceProvider.GetRequiredKeyedService<SettingsFor<T>>(serviceKey).Settings;
+                if (settingsInstance?.AuthorizationHeaderValueGetter is { } getToken)
+                {
+                    handlers.Add(new AuthenticatedHttpClientHandler(null, getToken));
+                }
+            });
+
+            // add keyed typed client (inline keyed registration)
+            builder.Services.AddKeyedTransient(
+                serviceKey,
+                (s, _) =>
+                {
+                    var httpClientFactory = s.GetRequiredService<IHttpClientFactory>();
+                    var httpClient = httpClientFactory.CreateClient(builder.Name);
+                    return RestService.For<T>(
+                        httpClient,
+                        s.GetRequiredKeyedService<IRequestBuilder<T>>(serviceKey)
+                    );
+                }
+            );
+
+            return builder;
+        }
+
+        // helper - used by AddRefitClientCore and AddRefitClientCore<T>
+        private static HttpMessageHandler? CreateInnerHandlerIfProvided(RefitSettings? settings)
+        {
+            HttpMessageHandler? innerHandler = null;
+            if (settings != null)
+            {
+                if (settings.HttpMessageHandlerFactory != null)
+                {
+                    innerHandler = settings.HttpMessageHandlerFactory();
+                }
+
+                if (settings.AuthorizationHeaderValueGetter != null)
+                {
+                    innerHandler = new AuthenticatedHttpClientHandler(
+                        settings.AuthorizationHeaderValueGetter,
+                        innerHandler
+                    );
+                }
+            }
+
+            return innerHandler;
+        }
+
+        private static readonly MethodInfo RequestBuilderGenericForTypeMethod =
+            typeof(RequestBuilder)
+                .GetMethods(BindingFlags.Public | BindingFlags.Static)
+                .Single(z => z.IsGenericMethodDefinition && z.GetParameters().Length == 1);
+    }
+}
diff --git a/Refit.HttpClientFactory/HttpClientFactoryExtensions.cs b/Refit.HttpClientFactory/HttpClientFactoryExtensions.cs
index ff188bf9c..348e2d023 100644
--- a/Refit.HttpClientFactory/HttpClientFactoryExtensions.cs
+++ b/Refit.HttpClientFactory/HttpClientFactoryExtensions.cs
@@ -12,183 +12,185 @@ namespace Refit
     /// </summary>
     public static class HttpClientFactoryExtensions
     {
+        /// <summary>
+        /// Adds a Refit client to the DI container
+        /// </summary>
+        /// <param name="refitInterfaceType">Type of the Refit interface</param>
+        /// <param name="services">container</param>
+        /// <param name="settings">Optional. Settings to configure the instance with</param>
+        /// <param name="httpClientName">Optional. Allows users to change the HttpClient name.</param>
+        /// <returns></returns>
+        public static IHttpClientBuilder AddRefitClient(
+            this IServiceCollection services,
+            Type refitInterfaceType,
+            RefitSettings? settings = null,
+            string? httpClientName = null
+        )
+        {
+            if (services == null) throw new ArgumentNullException(nameof(services));
+            if (refitInterfaceType == null) throw new ArgumentNullException(nameof(refitInterfaceType));
+
+            return HttpClientFactoryCore.AddRefitClientCore(services, refitInterfaceType, _ => settings, httpClientName);
+        }
+
+        /// <summary>
+        /// Adds a Refit client to the DI container with a specified service key
+        /// </summary>
+        /// <param name="refitInterfaceType">Type of the Refit interface</param>
+        /// <param name="services">container</param>
+        /// <param name="serviceKey">An optional key to associate with the specific Refit client instance</param>
+        /// <param name="settings">Optional. Settings to configure the instance with</param>
+        /// <param name="httpClientName">Optional. Allows users to change the HttpClient name.</param>
+        /// <returns></returns>
+        public static IHttpClientBuilder AddKeyedRefitClient(
+            this IServiceCollection services,
+            Type refitInterfaceType,
+            object? serviceKey,
+            RefitSettings? settings = null,
+            string? httpClientName = null
+        )
+        {
+            if (services == null) throw new ArgumentNullException(nameof(services));
+            if (refitInterfaceType == null) throw new ArgumentNullException(nameof(refitInterfaceType));
+            if (serviceKey == null) throw new ArgumentNullException(nameof(serviceKey));
+
+            return HttpClientFactoryCore.AddKeyedRefitClientCore(services, refitInterfaceType, serviceKey, _ => settings, httpClientName);
+        }
+
         /// <summary>
         /// Adds a Refit client to the DI container
         /// </summary>
         /// <typeparam name="T">Type of the Refit interface</typeparam>
         /// <param name="services">container</param>
         /// <param name="settings">Optional. Settings to configure the instance with</param>
+        /// <param name="httpClientName">Optional. Allows users to change the HttpClient name.</param>
         /// <returns></returns>
         public static IHttpClientBuilder AddRefitClient<T>(
             this IServiceCollection services,
-            RefitSettings? settings = null
+            RefitSettings? settings = null,
+            string? httpClientName = null
         )
             where T : class
         {
-            return AddRefitClient<T>(services, _ => settings);
+            if (services == null) throw new ArgumentNullException(nameof(services));
+
+            return HttpClientFactoryCore.AddRefitClientCore<T>(services, typeof(T), _ => settings, httpClientName);
         }
 
         /// <summary>
-        /// Adds a Refit client to the DI container
+        /// Adds a Refit client to the DI container with a specified service key
         /// </summary>
         /// <typeparam name="T">Type of the Refit interface</typeparam>
         /// <param name="services">container</param>
         /// <param name="serviceKey">An optional key to associate with the specific Refit client instance</param>
         /// <param name="settings">Optional. Settings to configure the instance with</param>
+        /// <param name="httpClientName">Optional. Allows users to change the HttpClient name.</param>
         /// <returns></returns>
         public static IHttpClientBuilder AddKeyedRefitClient<T>(
             this IServiceCollection services,
             object? serviceKey,
-            RefitSettings? settings = null
+            RefitSettings? settings = null,
+            string? httpClientName = null
         )
             where T : class
         {
-            return AddKeyedRefitClient<T>(services, serviceKey, _ => settings);
+            if (services == null) throw new ArgumentNullException(nameof(services));
+            if (serviceKey == null) throw new ArgumentNullException(nameof(serviceKey));
+
+            return HttpClientFactoryCore.AddKeyedRefitClientCore<T>(services, typeof(T), serviceKey, _ => settings, httpClientName);
         }
 
         /// <summary>
         /// Adds a Refit client to the DI container
         /// </summary>
-        /// <param name="services">container</param>
         /// <param name="refitInterfaceType">Type of the Refit interface</param>
+        /// <param name="builder">The HTTP client builder</param>
         /// <param name="settings">Optional. Settings to configure the instance with</param>
         /// <returns></returns>
         public static IHttpClientBuilder AddRefitClient(
-            this IServiceCollection services,
+            this IHttpClientBuilder builder,
             Type refitInterfaceType,
             RefitSettings? settings = null
         )
         {
-            return AddRefitClient(services, refitInterfaceType, _ => settings);
+            if (builder == null) throw new ArgumentNullException(nameof(builder));
+            if (refitInterfaceType == null) throw new ArgumentNullException(nameof(refitInterfaceType));
+
+            return HttpClientFactoryCore.AddRefitClientCore(builder.Services, refitInterfaceType, _ => settings, builder.Name);
         }
 
         /// <summary>
-        /// Adds a Refit client to the DI container
+        /// Adds a Refit client to the DI container with a specified service key
         /// </summary>
-        /// <param name="services">container</param>
         /// <param name="refitInterfaceType">Type of the Refit interface</param>
+        /// <param name="builder">The HTTP client builder</param>
         /// <param name="serviceKey">An optional key to associate with the specific Refit client instance</param>
         /// <param name="settings">Optional. Settings to configure the instance with</param>
         /// <returns></returns>
         public static IHttpClientBuilder AddKeyedRefitClient(
-            this IServiceCollection services,
+            this IHttpClientBuilder builder,
             Type refitInterfaceType,
             object? serviceKey,
             RefitSettings? settings = null
         )
         {
-            return AddKeyedRefitClient(services, refitInterfaceType, serviceKey, _ => settings);
+            if (builder == null) throw new ArgumentNullException(nameof(builder));
+            if (refitInterfaceType == null) throw new ArgumentNullException(nameof(refitInterfaceType));
+            if (serviceKey == null) throw new ArgumentNullException(nameof(serviceKey));
+
+            return HttpClientFactoryCore.AddKeyedRefitClientCore(builder.Services, refitInterfaceType, serviceKey, _ => settings, builder.Name);
         }
 
         /// <summary>
         /// Adds a Refit client to the DI container
         /// </summary>
         /// <typeparam name="T">Type of the Refit interface</typeparam>
-        /// <param name="services">container</param>
-        /// <param name="settingsAction">Optional. Action to configure refit settings.  This method is called once and only once, avoid using any scoped dependencies that maybe be disposed automatically.</param>
-        /// <param name="httpClientName">Optional. Allows users to change the HttpClient name as provided to IServiceCollection.AddHttpClient. Useful for logging scenarios.</param>
+        /// <param name="builder">The HTTP client builder</param>
+        /// <param name="settings">Optional. Settings to configure the instance with</param>
         /// <returns></returns>
         public static IHttpClientBuilder AddRefitClient<T>(
-            this IServiceCollection services,
-            Func<IServiceProvider, RefitSettings?>? settingsAction,
-            string? httpClientName = null
+            this IHttpClientBuilder builder,
+            RefitSettings? settings = null
         )
             where T : class
         {
-            services.AddSingleton(provider => new SettingsFor<T>(settingsAction?.Invoke(provider)));
-            services.AddSingleton(
-                provider =>
-                    RequestBuilder.ForType<T>(
-                        provider.GetRequiredService<SettingsFor<T>>().Settings
-                    )
-            );
-
-            return services
-                .AddHttpClient(httpClientName ?? UniqueName.ForType<T>())
-                .ConfigureHttpMessageHandlerBuilder(builder =>
-                {
-                    // check to see if user provided custom auth token
-                    if (
-                        CreateInnerHandlerIfProvided(
-                            builder.Services.GetRequiredService<SettingsFor<T>>().Settings
-                        ) is
-                        { } innerHandler
-                    )
-                    {
-                        builder.PrimaryHandler = innerHandler;
-                    }
-                })
-                .AddTypedClient(
-                    (client, serviceProvider) =>
-                        RestService.For<T>(
-                            client,
-                            serviceProvider.GetService<IRequestBuilder<T>>()!
-                        )
-                );
+            if (builder == null) throw new ArgumentNullException(nameof(builder));
+
+            return HttpClientFactoryCore.AddRefitClientCore<T>(builder.Services, typeof(T), _ => settings, builder.Name);
         }
 
         /// <summary>
         /// Adds a Refit client to the DI container with a specified service key
         /// </summary>
         /// <typeparam name="T">Type of the Refit interface</typeparam>
-        /// <param name="services">container</param>
+        /// <param name="builder">The HTTP client builder</param>
         /// <param name="serviceKey">An optional key to associate with the specific Refit client instance</param>
-        /// <param name="settingsAction">Optional. Action to configure refit settings.  This method is called once and only once, avoid using any scoped dependencies that maybe be disposed automatically.</param>
-        /// <param name="httpClientName">Optional. Allows users to change the HttpClient name as provided to IServiceCollection.AddHttpClient. Useful for logging scenarios.</param>
+        /// <param name="settings">Optional. Settings to configure the instance with</param>
         /// <returns></returns>
         public static IHttpClientBuilder AddKeyedRefitClient<T>(
-            this IServiceCollection services,
+            this IHttpClientBuilder builder,
             object? serviceKey,
-            Func<IServiceProvider, RefitSettings?>? settingsAction,
-            string? httpClientName = null
+            RefitSettings? settings = null
         )
             where T : class
         {
-            services.AddKeyedSingleton(serviceKey,
-                (provider, _) => new SettingsFor<T>(settingsAction?.Invoke(provider)));
-            services.AddKeyedSingleton(
-                serviceKey,
-                (provider, _) =>
-                    RequestBuilder.ForType<T>(
-                        provider.GetRequiredKeyedService<SettingsFor<T>>(serviceKey).Settings
-                    )
-            );
-
-            return services
-                .AddHttpClient(httpClientName ?? UniqueName.ForType<T>(serviceKey))
-                .ConfigurePrimaryHttpMessageHandler(serviceProvider =>
-                {
-                    var settings = serviceProvider.GetRequiredKeyedService<SettingsFor<T>>(serviceKey).Settings;
-                    return
-                        settings?.HttpMessageHandlerFactory?.Invoke()
-                        ?? new HttpClientHandler();
-                })
-                .ConfigureAdditionalHttpMessageHandlers((handlers, serviceProvider) =>
-                {
-                    var settings = serviceProvider.GetRequiredKeyedService<SettingsFor<T>>(serviceKey).Settings;
-                    if (settings?.AuthorizationHeaderValueGetter is { } getToken)
-                    {
-                        handlers.Add(new AuthenticatedHttpClientHandler(null, getToken));
-                    }
-                })
-                .AddKeyedTypedClient(
-                    serviceKey,
-                    (client, serviceProvider) =>
-                        RestService.For<T>(
-                            client,
-                            serviceProvider.GetKeyedService<IRequestBuilder<T>>(serviceKey)!
-                        )
-                );
+            if (builder == null) throw new ArgumentNullException(nameof(builder));
+            if (serviceKey == null) throw new ArgumentNullException(nameof(serviceKey));
+
+            return HttpClientFactoryCore.AddKeyedRefitClientCore<T>(builder.Services, typeof(T), serviceKey, _ => settings, builder.Name);
         }
 
         /// <summary>
         /// Adds a Refit client to the DI container
         /// </summary>
-        /// <param name="services">container</param>
         /// <param name="refitInterfaceType">Type of the Refit interface</param>
-        /// <param name="settingsAction">Optional. Action to configure refit settings.  This method is called once and only once, avoid using any scoped dependencies that maybe be disposed automatically.</param>
-        /// <param name="httpClientName">Optional. Allows users to change the HttpClient name as provided to IServiceCollection.AddHttpClient. Useful for logging scenarios.</param>
+        /// <param name="services">container</param>
+        /// <param name="settingsAction">Optional. Action to configure refit settings.</param>
+        /// <param name="httpClientName">Optional. Allows users to change the HttpClient name.</param>
         /// <returns></returns>
+#if NET9_0_OR_GREATER
+        [System.Runtime.CompilerServices.OverloadResolutionPriority(1)]
+#endif
         public static IHttpClientBuilder AddRefitClient(
             this IServiceCollection services,
             Type refitInterfaceType,
@@ -196,66 +198,24 @@ public static IHttpClientBuilder AddRefitClient(
             string? httpClientName = null
         )
         {
-            var settingsType = typeof(SettingsFor<>).MakeGenericType(refitInterfaceType);
-            var requestBuilderType = typeof(IRequestBuilder<>).MakeGenericType(refitInterfaceType);
-            services.AddSingleton(
-                settingsType,
-                provider =>
-                    Activator.CreateInstance(
-                        typeof(SettingsFor<>).MakeGenericType(refitInterfaceType)!,
-                        settingsAction?.Invoke(provider)
-                    )!
-            );
-            services.AddSingleton(
-                requestBuilderType,
-                provider =>
-                    RequestBuilderGenericForTypeMethod
-                        .MakeGenericMethod(refitInterfaceType)
-                        .Invoke(
-                            null,
-                            [
-                                ((ISettingsFor)provider.GetRequiredService(settingsType)).Settings
-                            ]
-                        )!
-            );
-
-            return services
-                .AddHttpClient(httpClientName ?? UniqueName.ForType(refitInterfaceType))
-                .ConfigureHttpMessageHandlerBuilder(builder =>
-                {
-                    // check to see if user provided custom auth token
-                    if (
-                        CreateInnerHandlerIfProvided(
-                            (
-                                (ISettingsFor)builder.Services.GetRequiredService(settingsType)
-                            ).Settings
-                        ) is
-                        { } innerHandler
-                    )
-                    {
-                        builder.PrimaryHandler = innerHandler;
-                    }
-                })
-                .AddTypedClient(
-                    refitInterfaceType,
-                    (client, serviceProvider) =>
-                        RestService.For(
-                            refitInterfaceType,
-                            client,
-                            (IRequestBuilder)serviceProvider.GetRequiredService(requestBuilderType)
-                        )
-                );
+            if (services == null) throw new ArgumentNullException(nameof(services));
+            if (refitInterfaceType == null) throw new ArgumentNullException(nameof(refitInterfaceType));
+
+            return HttpClientFactoryCore.AddRefitClientCore(services, refitInterfaceType, settingsAction, httpClientName);
         }
 
         /// <summary>
         /// Adds a Refit client to the DI container with a specified service key
         /// </summary>
-        /// <param name="services">container</param>
         /// <param name="refitInterfaceType">Type of the Refit interface</param>
+        /// <param name="services">container</param>
         /// <param name="serviceKey">An optional key to associate with the specific Refit client instance</param>
-        /// <param name="settingsAction">Optional. Action to configure refit settings.  This method is called once and only once, avoid using any scoped dependencies that maybe be disposed automatically.</param>
-        /// <param name="httpClientName">Optional. Allows users to change the HttpClient name as provided to IServiceCollection.AddHttpClient. Useful for logging scenarios.</param>
+        /// <param name="settingsAction">Optional. Action to configure refit settings.</param>
+        /// <param name="httpClientName">Optional. Allows users to change the HttpClient name.</param>
         /// <returns></returns>
+#if NET9_0_OR_GREATER
+        [System.Runtime.CompilerServices.OverloadResolutionPriority(1)]
+#endif
         public static IHttpClientBuilder AddKeyedRefitClient(
             this IServiceCollection services,
             Type refitInterfaceType,
@@ -264,178 +224,153 @@ public static IHttpClientBuilder AddKeyedRefitClient(
             string? httpClientName = null
         )
         {
-            var settingsType = typeof(SettingsFor<>).MakeGenericType(refitInterfaceType);
-            var requestBuilderType = typeof(IRequestBuilder<>).MakeGenericType(refitInterfaceType);
-            services.AddKeyedSingleton(
-                settingsType,
-                serviceKey,
-                (provider, _) =>
-                    Activator.CreateInstance(
-                        typeof(SettingsFor<>).MakeGenericType(refitInterfaceType)!,
-                        settingsAction?.Invoke(provider)
-                    )!
-            );
-            services.AddKeyedSingleton(
-                requestBuilderType,
-                serviceKey,
-                (provider, _) =>
-                    RequestBuilderGenericForTypeMethod
-                        .MakeGenericMethod(refitInterfaceType)
-                        .Invoke(
-                            null,
-                            [
-                                ((ISettingsFor)provider.GetRequiredKeyedService(settingsType, serviceKey)).Settings
-                            ]
-                        )!
-            );
-
-            return services
-                .AddHttpClient(httpClientName ?? UniqueName.ForType(refitInterfaceType, serviceKey))
-                .ConfigurePrimaryHttpMessageHandler(serviceProvider =>
-                {
-                    var settings = (ISettingsFor)serviceProvider.GetRequiredKeyedService(settingsType, serviceKey);
-                    return
-                        settings.Settings?.HttpMessageHandlerFactory?.Invoke()
-                        ?? new HttpClientHandler();
-                })
-                .ConfigureAdditionalHttpMessageHandlers((handlers, serviceProvider) =>
-                {
-                    var settings = (ISettingsFor)serviceProvider.GetRequiredKeyedService(settingsType, serviceKey);
-                    if (settings.Settings?.AuthorizationHeaderValueGetter is { } getToken)
-                    {
-                        handlers.Add(new AuthenticatedHttpClientHandler(null, getToken));
-                    }
-                })
-                .AddKeyedTypedClient(
-                    refitInterfaceType,
-                    serviceKey,
-                    (client, serviceProvider) =>
-                        RestService.For(
-                            refitInterfaceType,
-                            client,
-                            (IRequestBuilder)serviceProvider.GetRequiredKeyedService(requestBuilderType, serviceKey)
-                        )
-                );
+            if (services == null) throw new ArgumentNullException(nameof(services));
+            if (refitInterfaceType == null) throw new ArgumentNullException(nameof(refitInterfaceType));
+            if (serviceKey == null) throw new ArgumentNullException(nameof(serviceKey));
+
+            return HttpClientFactoryCore.AddKeyedRefitClientCore(services, refitInterfaceType, serviceKey, settingsAction, httpClientName);
         }
 
-        private static readonly MethodInfo RequestBuilderGenericForTypeMethod =
-            typeof(RequestBuilder)
-                .GetMethods(BindingFlags.Public | BindingFlags.Static)
-                .Single(z => z.IsGenericMethodDefinition && z.GetParameters().Length == 1);
+        /// <summary>
+        /// Adds a Refit client to the DI container
+        /// </summary>
+        /// <typeparam name="T">Type of the Refit interface</typeparam>
+        /// <param name="services">container</param>
+        /// <param name="settingsAction">Optional. Action to configure refit settings.</param>
+        /// <param name="httpClientName">Optional. Allows users to change the HttpClient name.</param>
+        /// <returns></returns>
+#if NET9_0_OR_GREATER
+        [System.Runtime.CompilerServices.OverloadResolutionPriority(1)]
+#endif
+        public static IHttpClientBuilder AddRefitClient<T>(
+            this IServiceCollection services,
+            Func<IServiceProvider, RefitSettings?>? settingsAction,
+            string? httpClientName = null
+        )
+            where T : class
+        {
+            if (services == null) throw new ArgumentNullException(nameof(services));
+
+            return HttpClientFactoryCore.AddRefitClientCore<T>(services, typeof(T), settingsAction, httpClientName);
+        }
 
-        static HttpMessageHandler? CreateInnerHandlerIfProvided(RefitSettings? settings)
+        /// <summary>
+        /// Adds a Refit client to the DI container with a specified service key
+        /// </summary>
+        /// <typeparam name="T">Type of the Refit interface</typeparam>
+        /// <param name="services">container</param>
+        /// <param name="serviceKey">An optional key to associate with the specific Refit client instance</param>
+        /// <param name="settingsAction">Optional. Action to configure refit settings.</param>
+        /// <param name="httpClientName">Optional. Allows users to change the HttpClient name.</param>
+        /// <returns></returns>
+#if NET9_0_OR_GREATER
+        [System.Runtime.CompilerServices.OverloadResolutionPriority(1)]
+#endif
+        public static IHttpClientBuilder AddKeyedRefitClient<T>(
+            this IServiceCollection services,
+            object? serviceKey,
+            Func<IServiceProvider, RefitSettings?>? settingsAction,
+            string? httpClientName = null
+        )
+            where T : class
         {
-            HttpMessageHandler? innerHandler = null;
-            if (settings != null)
-            {
-                if (settings.HttpMessageHandlerFactory != null)
-                {
-                    innerHandler = settings.HttpMessageHandlerFactory();
-                }
-
-                if (settings.AuthorizationHeaderValueGetter != null)
-                {
-                    innerHandler = new AuthenticatedHttpClientHandler(
-                        settings.AuthorizationHeaderValueGetter,
-                        innerHandler
-                    );
-                }
-            }
-
-            return innerHandler;
+            if (services == null) throw new ArgumentNullException(nameof(services));
+            if (serviceKey == null) throw new ArgumentNullException(nameof(serviceKey));
+
+            return HttpClientFactoryCore.AddKeyedRefitClientCore<T>(services, typeof(T), serviceKey, settingsAction, httpClientName);
         }
 
-        static IHttpClientBuilder AddTypedClient(
+        /// <summary>
+        /// Adds a Refit client to the DI container
+        /// </summary>
+        /// <param name="refitInterfaceType">Type of the Refit interface</param>
+        /// <param name="builder">The HTTP client builder</param>
+        /// <param name="settingsAction">Optional. Action to configure refit settings.</param>
+        /// <returns></returns>
+#if NET9_0_OR_GREATER
+        [System.Runtime.CompilerServices.OverloadResolutionPriority(1)]
+#endif
+        public static IHttpClientBuilder AddRefitClient(
             this IHttpClientBuilder builder,
-            Type type,
-            Func<HttpClient, IServiceProvider, object> factory
+            Type refitInterfaceType,
+            Func<IServiceProvider, RefitSettings?>? settingsAction
         )
         {
-            if (builder == null)
-            {
-                throw new ArgumentNullException(nameof(builder));
-            }
-
-            if (factory == null)
-            {
-                throw new ArgumentNullException(nameof(factory));
-            }
-
-            builder.Services.AddTransient(
-                type,
-                s =>
-                {
-                    var httpClientFactory = s.GetRequiredService<IHttpClientFactory>();
-                    var httpClient = httpClientFactory.CreateClient(builder.Name);
-
-                    return factory(httpClient, s);
-                }
-            );
-
-            return builder;
+            if (builder == null) throw new ArgumentNullException(nameof(builder));
+            if (refitInterfaceType == null) throw new ArgumentNullException(nameof(refitInterfaceType));
+
+            return HttpClientFactoryCore.AddRefitClientCore(builder.Services, refitInterfaceType, settingsAction, builder.Name);
         }
 
-        static IHttpClientBuilder AddKeyedTypedClient(
+        /// <summary>
+        /// Adds a Refit client to the DI container with a specified service key
+        /// </summary>
+        /// <param name="refitInterfaceType">Type of the Refit interface</param>
+        /// <param name="builder">The HTTP client builder</param>
+        /// <param name="serviceKey">An optional key to associate with the specific Refit client instance</param>
+        /// <param name="settingsAction">Optional. Action to configure refit settings.</param>
+        /// <returns></returns>
+#if NET9_0_OR_GREATER
+        [System.Runtime.CompilerServices.OverloadResolutionPriority(1)]
+#endif
+        public static IHttpClientBuilder AddKeyedRefitClient(
             this IHttpClientBuilder builder,
-            Type type,
+            Type refitInterfaceType,
             object? serviceKey,
-            Func<HttpClient, IServiceProvider, object> factory
+            Func<IServiceProvider, RefitSettings?>? settingsAction
         )
         {
-            if (builder == null)
-            {
-                throw new ArgumentNullException(nameof(builder));
-            }
-
-            if (factory == null)
-            {
-                throw new ArgumentNullException(nameof(factory));
-            }
-
-            builder.Services.AddKeyedTransient(
-                type,
-                serviceKey,
-                (s, _) =>
-                {
-                    var httpClientFactory = s.GetRequiredService<IHttpClientFactory>();
-                    var httpClient = httpClientFactory.CreateClient(builder.Name);
-
-                    return factory(httpClient, s);
-                }
-            );
-
-            return builder;
+            if (builder == null) throw new ArgumentNullException(nameof(builder));
+            if (refitInterfaceType == null) throw new ArgumentNullException(nameof(refitInterfaceType));
+            if (serviceKey == null) throw new ArgumentNullException(nameof(serviceKey));
+
+            return HttpClientFactoryCore.AddKeyedRefitClientCore(builder.Services, refitInterfaceType, serviceKey, settingsAction, builder.Name);
         }
 
-        static IHttpClientBuilder AddKeyedTypedClient<T>(
+        /// <summary>
+        /// Adds a Refit client to the DI container
+        /// </summary>
+        /// <typeparam name="T">Type of the Refit interface</typeparam>
+        /// <param name="builder">The HTTP client builder</param>
+        /// <param name="settingsAction">Optional. Action to configure refit settings.</param>
+        /// <returns></returns>
+#if NET9_0_OR_GREATER
+        [System.Runtime.CompilerServices.OverloadResolutionPriority(1)]
+#endif
+        public static IHttpClientBuilder AddRefitClient<T>(
+            this IHttpClientBuilder builder,
+            Func<IServiceProvider, RefitSettings?>? settingsAction
+        )
+            where T : class
+        {
+            if (builder == null) throw new ArgumentNullException(nameof(builder));
+
+            return HttpClientFactoryCore.AddRefitClientCore<T>(builder.Services, typeof(T), settingsAction, builder.Name);
+        }
+
+        /// <summary>
+        /// Adds a Refit client to the DI container with a specified service key
+        /// </summary>
+        /// <typeparam name="T">Type of the Refit interface</typeparam>
+        /// <param name="builder">The HTTP client builder</param>
+        /// <param name="serviceKey">An optional key to associate with the specific Refit client instance</param>
+        /// <param name="settingsAction">Optional. Action to configure refit settings.</param>
+        /// <returns></returns>
+#if NET9_0_OR_GREATER
+        [System.Runtime.CompilerServices.OverloadResolutionPriority(1)]
+#endif
+        public static IHttpClientBuilder AddKeyedRefitClient<T>(
             this IHttpClientBuilder builder,
             object? serviceKey,
-            Func<HttpClient, IServiceProvider, T> factory
+            Func<IServiceProvider, RefitSettings?>? settingsAction
         )
             where T : class
         {
-            if (builder == null)
-            {
-                throw new ArgumentNullException(nameof(builder));
-            }
-
-            if (factory == null)
-            {
-                throw new ArgumentNullException(nameof(factory));
-            }
-
-            builder.Services.AddKeyedTransient(
-                serviceKey,
-                (s, _) =>
-                {
-                    var httpClientFactory = s.GetRequiredService<IHttpClientFactory>();
-                    var httpClient = httpClientFactory.CreateClient(builder.Name);
-
-                    return factory(httpClient, s);
-                }
-            );
-
-            return builder;
+            if (builder == null) throw new ArgumentNullException(nameof(builder));
+            if (serviceKey == null) throw new ArgumentNullException(nameof(serviceKey));
+
+            return HttpClientFactoryCore.AddKeyedRefitClientCore<T>(builder.Services, typeof(T), serviceKey, settingsAction, builder.Name);
         }
+
     }
-}
+}
\ No newline at end of file
diff --git a/Refit.HttpClientFactory/HttpClientFactoryExtensions.tt b/Refit.HttpClientFactory/HttpClientFactoryExtensions.tt
new file mode 100644
index 000000000..b4992f3c4
--- /dev/null
+++ b/Refit.HttpClientFactory/HttpClientFactoryExtensions.tt
@@ -0,0 +1,181 @@
+<#@ template debug="false" hostspecific="false" language="C#" #>
+<#@ output extension=".cs" #>
+using System;
+using System.Linq;
+using System.Net.Http;
+using System.Reflection;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Http;
+
+namespace Refit
+{
+    /// <summary>
+    /// HttpClientFactoryExtensions.
+    /// </summary>
+    public static class HttpClientFactoryExtensions
+    {
+<#
+    // 位运算控制组合
+    for (int bits = 0; bits < 16; bits++)
+    {
+        bool hasKeyed = (bits & 1) != 0;      // 0001: 是否有Keyed
+        bool hasGeneric = (bits & 2) != 0;    // 0010: 是否泛型
+        bool isBuilder = (bits & 4) != 0;     // 0100: 是否builder扩展
+        bool hasAction = (bits & 8) != 0;     // 1000: 是否有settingsAction
+        
+        // 生成XML注释
+#>
+        /// <summary>
+<# if (hasKeyed) { #>
+        /// Adds a Refit client to the DI container with a specified service key
+<# } else { #>
+        /// Adds a Refit client to the DI container
+<# } #>
+        /// </summary>
+<# if (hasGeneric) { #>
+        /// <typeparam name="T">Type of the Refit interface</typeparam>
+<# } else { #>
+        /// <param name="refitInterfaceType">Type of the Refit interface</param>
+<# } #>
+<# if (isBuilder) { #>
+        /// <param name="builder">The HTTP client builder</param>
+<# } else { #>
+        /// <param name="services">container</param>
+<# } #>
+<# if (hasKeyed) { #>
+        /// <param name="serviceKey">An optional key to associate with the specific Refit client instance</param>
+<# } #>
+<# if (hasAction) { #>
+        /// <param name="settingsAction">Optional. Action to configure refit settings.</param>
+<# } else { #>
+        /// <param name="settings">Optional. Settings to configure the instance with</param>
+<# } #>
+<# if (!isBuilder) { #>
+        /// <param name="httpClientName">Optional. Allows users to change the HttpClient name.</param>
+<# } #>
+        /// <returns></returns>
+<# if(hasAction) { #>
+#if NET9_0_OR_GREATER
+        [System.Runtime.CompilerServices.OverloadResolutionPriority(1)]
+#endif
+<# } #>
+<# 
+        // 生成方法签名
+        string methodName = (hasKeyed ? "AddKeyedRefitClient" : "AddRefitClient"); 
+#>
+        public static IHttpClientBuilder <#= methodName #><#= hasGeneric ? "<T>" : "" #>(
+            this <#= isBuilder ? "IHttpClientBuilder" : "IServiceCollection" #> <#= isBuilder ? "builder" : "services" #>,
+<# if (!hasGeneric) { #>
+            Type refitInterfaceType,
+<# } #>
+<# if (hasKeyed) { #>
+            object? serviceKey,
+<# } #>
+<# if (hasAction) { #>
+            Func<IServiceProvider, RefitSettings?>? settingsAction<#= !isBuilder ? "," : "" #>
+<# } else { #>
+            RefitSettings? settings = null<#= !isBuilder ? "," : "" #>
+<# } #>
+<# if (!isBuilder) { #>
+            string? httpClientName = null
+<# } #>
+        )
+<# if (hasGeneric) { #>
+            where T : class
+<# } #>
+        {
+<# 
+        // 生成参数验证
+        if (isBuilder) 
+        { 
+#>
+            if (builder == null) throw new ArgumentNullException(nameof(builder));
+<# 
+        } 
+        else 
+        { 
+#>
+            if (services == null) throw new ArgumentNullException(nameof(services));
+<# 
+        } 
+        
+        if (!hasGeneric) 
+        { 
+#>
+            if (refitInterfaceType == null) throw new ArgumentNullException(nameof(refitInterfaceType));
+<# 
+        } 
+        
+        if (hasKeyed) 
+        { 
+#>
+            if (serviceKey == null) throw new ArgumentNullException(nameof(serviceKey));
+<# 
+        }  
+#>
+
+<# 
+        // 生成Core方法调用
+        string coreMethod = "HttpClientFactoryCore.";
+        coreMethod += (hasKeyed ? "AddKeyedRefitClient" : "AddRefitClient") + "Core";
+        coreMethod += hasGeneric ? "<T>" : "";
+        coreMethod += "(";
+        
+        // 第一个参数：services
+        if (isBuilder)
+        {
+            coreMethod += "builder.Services";
+        }
+        else
+        {
+            coreMethod += "services";
+        }
+        
+        // 第二个参数：Type
+        if (hasGeneric)
+        {
+            coreMethod += ", typeof(T)";
+        }
+        else
+        {
+            coreMethod += ", refitInterfaceType";
+        }
+        
+        // 第三个参数：serviceKey
+        if (hasKeyed)
+        {
+            coreMethod += ", serviceKey";
+        }
+        
+        // 第四个参数：settingsAction
+        if (hasAction)
+        {
+            coreMethod += ", settingsAction";
+        }
+        else
+        {
+            coreMethod += ", _ => settings";
+        }
+        
+        // 第五个参数：httpClientName
+        if (isBuilder)
+        {
+            // IHttpClientBuilder 版本使用 builder.Name
+            coreMethod += ", builder.Name";
+        }
+        else
+        {
+            // IServiceCollection 版本使用传入的 httpClientName
+            coreMethod += ", httpClientName";
+        }
+        
+        coreMethod += ")";
+#>
+            return <#= coreMethod #>;
+        }
+
+<#
+    }
+#>
+    }
+}
\ No newline at end of file
diff --git a/Refit.HttpClientFactory/Refit.HttpClientFactory.csproj b/Refit.HttpClientFactory/Refit.HttpClientFactory.csproj
index a6f6558f2..4920d7e0d 100644
--- a/Refit.HttpClientFactory/Refit.HttpClientFactory.csproj
+++ b/Refit.HttpClientFactory/Refit.HttpClientFactory.csproj
@@ -13,4 +13,23 @@
     <PackageReference Include="Microsoft.Extensions.Http" Version="9.0.3" />
   </ItemGroup>
 
+  <ItemGroup>
+    <None Update="HttpClientFactoryExtensions.tt">
+      <Generator>TextTemplatingFileGenerator</Generator>
+      <LastGenOutput>HttpClientFactoryExtensions.cs</LastGenOutput>
+    </None>
+  </ItemGroup>
+
+  <ItemGroup>
+    <Service Include="{508349b6-6b84-4df5-91f0-309beebad82d}" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <Compile Update="HttpClientFactoryExtensions.cs">
+      <DesignTime>True</DesignTime>
+      <AutoGen>True</AutoGen>
+      <DependentUpon>HttpClientFactoryExtensions.tt</DependentUpon>
+    </Compile>
+  </ItemGroup>
+
 </Project>
diff --git a/Refit.Tests/HttpClientFactoryExtensionsTests.cs b/Refit.Tests/HttpClientFactoryExtensionsTests.cs
index ec64b65d0..0f903a2f9 100644
--- a/Refit.Tests/HttpClientFactoryExtensionsTests.cs
+++ b/Refit.Tests/HttpClientFactoryExtensionsTests.cs
@@ -190,11 +190,12 @@ public void ProvidedHttpClientIsUsedAsNamedClient()
         var baseUri = new Uri("https://0:1337");
         var services = new ServiceCollection();
 
-        services.AddHttpClient("MyHttpClient", client => {
+        services.AddHttpClient("MyHttpClient", client =>
+        {
             client.BaseAddress = baseUri;
             client.DefaultRequestHeaders.Add("X-Powered-By", Environment.OSVersion.VersionString);
         });
-        services.AddRefitClient<IGitHubApi>(null, "MyHttpClient");
+        services.AddRefitClient<IGitHubApi>(settingsAction: null, "MyHttpClient");
 
         var sp = services.BuildServiceProvider();
         var httpClientFactory = sp.GetRequiredService<IHttpClientFactory>();