diff --git a/src/Application.php b/src/Application.php
index d1804bd..fcffeda 100644
--- a/src/Application.php
+++ b/src/Application.php
@@ -28,17 +28,14 @@
  */
 final class Application
 {
-    /** @var Application\Implementation<I, O> */
-    private Application\Implementation $app;
-
     /**
      * @psalm-mutation-free
      *
      * @param Application\Implementation<I, O> $app
      */
-    private function __construct(Application\Implementation $app)
-    {
-        $this->app = $app;
+    private function __construct(
+        private Application\Implementation $app,
+    ) {
     }
 
     /**
diff --git a/src/Application/Async/Http.php b/src/Application/Async/Http.php
index cc2e27f..9658bc7 100644
--- a/src/Application/Async/Http.php
+++ b/src/Application/Async/Http.php
@@ -40,41 +40,23 @@
  */
 final class Http implements Implementation
 {
-    private OperatingSystem $os;
-    /** @var callable(OperatingSystem, Environment): array{OperatingSystem, Environment} */
-    private $map;
-    /** @var callable(OperatingSystem, Environment): Builder */
-    private $container;
-    /** @var Sequence<callable(Routes, Container, OperatingSystem, Environment): Routes> */
-    private Sequence $routes;
-    /** @var callable(RequestHandler, Container, OperatingSystem, Environment): RequestHandler */
-    private $mapRequestHandler;
-    /** @var Maybe<callable(ServerRequest, Container, OperatingSystem, Environment): Response> */
-    private Maybe $notFound;
-
     /**
      * @psalm-mutation-free
      *
-     * @param callable(OperatingSystem, Environment): array{OperatingSystem, Environment} $map
-     * @param callable(OperatingSystem, Environment): Builder $container
+     * @param \Closure(OperatingSystem, Environment): array{OperatingSystem, Environment} $map
+     * @param \Closure(OperatingSystem, Environment): Builder $container
      * @param Sequence<callable(Routes, Container, OperatingSystem, Environment): Routes> $routes
-     * @param callable(RequestHandler, Container, OperatingSystem, Environment): RequestHandler $mapRequestHandler
+     * @param \Closure(RequestHandler, Container, OperatingSystem, Environment): RequestHandler $mapRequestHandler
      * @param Maybe<callable(ServerRequest, Container, OperatingSystem, Environment): Response> $notFound
      */
     private function __construct(
-        OperatingSystem $os,
-        callable $map,
-        callable $container,
-        Sequence $routes,
-        callable $mapRequestHandler,
-        Maybe $notFound,
+        private OperatingSystem $os,
+        private \Closure $map,
+        private \Closure $container,
+        private Sequence $routes,
+        private \Closure $mapRequestHandler,
+        private Maybe $notFound,
     ) {
-        $this->os = $os;
-        $this->map = $map;
-        $this->container = $container;
-        $this->routes = $routes;
-        $this->mapRequestHandler = $mapRequestHandler;
-        $this->notFound = $notFound;
     }
 
     /**
diff --git a/src/Application/Cli.php b/src/Application/Cli.php
index 1d87ec6..c707a9b 100644
--- a/src/Application/Cli.php
+++ b/src/Application/Cli.php
@@ -29,34 +29,20 @@
  */
 final class Cli implements Implementation
 {
-    private OperatingSystem $os;
-    private Environment $env;
-    /** @var callable(OperatingSystem, Environment): Builder */
-    private $container;
-    /** @var Sequence<callable(Container, OperatingSystem, Environment): Command> */
-    private Sequence $commands;
-    /** @var callable(Command, Container, OperatingSystem, Environment): Command */
-    private $mapCommand;
-
     /**
      * @psalm-mutation-free
      *
-     * @param callable(OperatingSystem, Environment): Builder $container
+     * @param \Closure(OperatingSystem, Environment): Builder $container
      * @param Sequence<callable(Container, OperatingSystem, Environment): Command> $commands
-     * @param callable(Command, Container, OperatingSystem, Environment): Command $mapCommand
+     * @param \Closure(Command, Container, OperatingSystem, Environment): Command $mapCommand
      */
     private function __construct(
-        OperatingSystem $os,
-        Environment $env,
-        callable $container,
-        Sequence $commands,
-        callable $mapCommand,
+        private OperatingSystem $os,
+        private Environment $env,
+        private \Closure $container,
+        private Sequence $commands,
+        private \Closure $mapCommand,
     ) {
-        $this->os = $os;
-        $this->env = $env;
-        $this->container = $container;
-        $this->commands = $commands;
-        $this->mapCommand = $mapCommand;
     }
 
     /**
@@ -217,7 +203,7 @@ public function run($input)
             $env,
         );
         $commands = $this->commands->map(static fn($command) => new Defer(
-            $command,
+            \Closure::fromCallable($command),
             $container,
             $os,
             $env,
diff --git a/src/Application/Http.php b/src/Application/Http.php
index b7f3a02..9508942 100644
--- a/src/Application/Http.php
+++ b/src/Application/Http.php
@@ -31,39 +31,22 @@
  */
 final class Http implements Implementation
 {
-    private OperatingSystem $os;
-    private Environment $env;
-    /** @var callable(OperatingSystem, Environment): Builder */
-    private $container;
-    /** @var Sequence<callable(Routes, Container, OperatingSystem, Environment): Routes> */
-    private Sequence $routes;
-    /** @var callable(RequestHandler, Container, OperatingSystem, Environment): RequestHandler */
-    private $mapRequestHandler;
-    /** @var Maybe<callable(ServerRequest, Container, OperatingSystem, Environment): Response> */
-    private Maybe $notFound;
-
     /**
      * @psalm-mutation-free
      *
-     * @param callable(OperatingSystem, Environment): Builder $container
+     * @param \Closure(OperatingSystem, Environment): Builder $container
      * @param Sequence<callable(Routes, Container, OperatingSystem, Environment): Routes> $routes
-     * @param callable(RequestHandler, Container, OperatingSystem, Environment): RequestHandler $mapRequestHandler
+     * @param \Closure(RequestHandler, Container, OperatingSystem, Environment): RequestHandler $mapRequestHandler
      * @param Maybe<callable(ServerRequest, Container, OperatingSystem, Environment): Response> $notFound
      */
     private function __construct(
-        OperatingSystem $os,
-        Environment $env,
-        callable $container,
-        Sequence $routes,
-        callable $mapRequestHandler,
-        Maybe $notFound,
+        private OperatingSystem $os,
+        private Environment $env,
+        private \Closure $container,
+        private Sequence $routes,
+        private \Closure $mapRequestHandler,
+        private Maybe $notFound,
     ) {
-        $this->os = $os;
-        $this->env = $env;
-        $this->container = $container;
-        $this->routes = $routes;
-        $this->mapRequestHandler = $mapRequestHandler;
-        $this->notFound = $notFound;
     }
 
     /**
diff --git a/src/Cli/Command/Defer.php b/src/Cli/Command/Defer.php
index 03d2f76..6438792 100644
--- a/src/Cli/Command/Defer.php
+++ b/src/Cli/Command/Defer.php
@@ -16,31 +16,19 @@
  */
 final class Defer implements Command
 {
-    /** @var callable(Container, OperatingSystem, Environment): Command */
-    private $build;
-    private Container $locate;
-    private OperatingSystem $os;
-    private Environment $env;
-    /** @var callable(Command): Command */
-    private $map;
     private ?Command $command = null;
 
     /**
-     * @param callable(Container, OperatingSystem, Environment): Command $build
-     * @param callable(Command): Command $map
+     * @param \Closure(Container, OperatingSystem, Environment): Command $build
+     * @param \Closure(Command): Command $map
      */
     public function __construct(
-        callable $build,
-        Container $locate,
-        OperatingSystem $os,
-        Environment $env,
-        callable $map,
+        private \Closure $build,
+        private Container $locate,
+        private OperatingSystem $os,
+        private Environment $env,
+        private \Closure $map,
     ) {
-        $this->build = $build;
-        $this->locate = $locate;
-        $this->os = $os;
-        $this->env = $env;
-        $this->map = $map;
     }
 
     #[\Override]
diff --git a/src/Environment.php b/src/Environment.php
index c14e2b4..318f7b0 100644
--- a/src/Environment.php
+++ b/src/Environment.php
@@ -15,15 +15,11 @@
  */
 final class Environment
 {
-    /** @var Map<string, string> */
-    private Map $variables;
-
     /**
      * @param Map<string, string> $variables
      */
-    private function __construct(Map $variables)
+    private function __construct(private Map $variables)
     {
-        $this->variables = $variables;
     }
 
     /**
diff --git a/src/Http/Router.php b/src/Http/Router.php
index f3dab7b..09b17f9 100644
--- a/src/Http/Router.php
+++ b/src/Http/Router.php
@@ -23,19 +23,14 @@
  */
 final class Router implements RequestHandler
 {
-    /** @var Sequence<Route|Under> */
-    private Sequence $routes;
-    /** @var Maybe<\Closure(ServerRequest): Response> */
-    private Maybe $notFound;
-
     /**
      * @param Sequence<Route|Under> $routes
      * @param Maybe<\Closure(ServerRequest): Response> $notFound
      */
-    public function __construct(Sequence $routes, Maybe $notFound)
-    {
-        $this->routes = $routes;
-        $this->notFound = $notFound;
+    public function __construct(
+        private Sequence $routes,
+        private Maybe $notFound,
+    ) {
     }
 
     #[\Override]
diff --git a/src/Http/Routes.php b/src/Http/Routes.php
index e7c6653..1bfe116 100644
--- a/src/Http/Routes.php
+++ b/src/Http/Routes.php
@@ -14,15 +14,11 @@
  */
 final class Routes
 {
-    /** @var Sequence<Route|Under> */
-    private Sequence $routes;
-
     /**
      * @param Sequence<Route|Under> $routes
      */
-    private function __construct(Sequence $routes)
+    private function __construct(private Sequence $routes)
     {
-        $this->routes = $routes;
     }
 
     /**
diff --git a/src/Http/Service.php b/src/Http/Service.php
index ab4de0a..0a326c1 100644
--- a/src/Http/Service.php
+++ b/src/Http/Service.php
@@ -15,13 +15,10 @@
 
 final class Service
 {
-    private Container $container;
-    private Ref $service;
-
-    private function __construct(Container $container, Ref $service)
-    {
-        $this->container = $container;
-        $this->service = $service;
+    private function __construct(
+        private Container $container,
+        private Ref $service,
+    ) {
     }
 
     public function __invoke(ServerRequest $request, Variables $variables): Response
diff --git a/src/Http/To.php b/src/Http/To.php
index a281eb4..2bd9c03 100644
--- a/src/Http/To.php
+++ b/src/Http/To.php
@@ -17,11 +17,8 @@
 
 final class To
 {
-    private Service $service;
-
-    private function __construct(Service $service)
+    private function __construct(private Service $service)
     {
-        $this->service = $service;
     }
 
     public function __invoke(
diff --git a/src/Middleware/Optional.php b/src/Middleware/Optional.php
index 8e42f10..257209c 100644
--- a/src/Middleware/Optional.php
+++ b/src/Middleware/Optional.php
@@ -10,19 +10,14 @@
 
 final class Optional implements Middleware
 {
-    /** @var class-string<Middleware> */
-    private string $middleware;
-    /** @var callable(): Middleware */
-    private $factory;
-
     /**
      * @param class-string<Middleware> $middleware
-     * @param callable(): Middleware $factory
+     * @param \Closure(): Middleware $factory
      */
-    private function __construct(string $middleware, callable $factory)
-    {
-        $this->middleware = $middleware;
-        $this->factory = $factory;
+    private function __construct(
+        private string $middleware,
+        private \Closure $factory,
+    ) {
     }
 
     #[\Override]
@@ -45,7 +40,7 @@ public static function of(string $middleware, ?callable $factory = null): self
     {
         return new self(
             $middleware,
-            $factory ?? static fn() => new $middleware,
+            \Closure::fromCallable($factory ?? static fn() => new $middleware),
         );
     }
 }