fix: resolve named middleware lazily so registration order does not drop it

src/Router.php

@@ -668,20 +668,14 @@ protected static function mapHandler(
 
         if (is_array($handler)) {
             if (is_string($handler['middleware'] ?? null)) {
-                $parsedOptions['middleware'] = (class_exists($handler['middleware'])) ? function () use ($handler) {
-                    (new $handler['middleware']())->call();
-                } : static::$namedMiddleware[$handler['middleware']] ?? null;
+                $parsedOptions['middleware'] = static::resolveMiddleware($handler['middleware']);
             }
 
             if (is_array($handler['middleware'] ?? null)) {
                 $parsedOptions['middleware'] = [];
 
                 foreach ($handler['middleware'] as $middleware) {
-                    if (is_string($middleware)) {
-                        $parsedOptions['middleware'][] = static::$namedMiddleware[$middleware] ?? null;
-                    } else {
-                        $parsedOptions['middleware'][] = $middleware;
-                    }
+                    $parsedOptions['middleware'][] = static::resolveMiddleware($middleware);
                 }
             }
 
@@ -805,6 +799,42 @@ public static function use($middleware)
         }
     }
 
+    /**
+     * Turn a middleware reference into something invokable.
+     *
+     * Class names are wrapped so the class is instantiated and called
+     * at request time. Named middleware is resolved lazily, so it does
+     * not matter whether registerMiddleware() runs before or after the
+     * routes that use it. A name that is still unknown when the request
+     * hits the route throws instead of silently letting the route run.
+     *
+     * @param callable|string $middleware A callable, a class name or a registered middleware name
+     *
+     * @return callable
+     */
+    protected static function resolveMiddleware($middleware): callable
+    {
+        if (!is_string($middleware)) {
+            return $middleware;
+        }
+
+        if (class_exists($middleware)) {
+            return function () use ($middleware) {
+                (new $middleware())->call();
+            };
+        }
+
+        return function (...$params) use ($middleware) {
+            if (!isset(static::$namedMiddleware[$middleware])) {
+                throw new \RuntimeException(
+                    "Middleware named '$middleware' not found. Register it with registerMiddleware() before the request is handled."
+                );
+            }
+
+            return static::$namedMiddleware[$middleware](...$params);
+        };
+    }
+
     /**
      * Register a middleware in your Leaf application by name
      *

tests/middleware.test.php

@@ -163,3 +163,56 @@ class StaticTestClassMid
     expect($ran['global'])->toBeTrue()
         ->and($ran['group'])->toBeTrue();
 });
+
+test('named middleware registered after the routes still runs', function () {
+    \Leaf\Router::reset();
+    app()->setBasePath('/');
+    $_SERVER['REQUEST_METHOD'] = 'GET';
+    $_SERVER['REQUEST_URI'] = '/late/42';
+
+    $ran = ['string' => false, 'array' => false, 'group' => false];
+
+    app()->get('/late/{id}', ['middleware' => 'late.string', function () {}]);
+    app()->get('/late-array/{id}', ['middleware' => ['late.array'], function () {}]);
+    app()->group('/late-group', ['middleware' => 'late.group', function () {
+        app()->get('/{id}', function () {});
+    }]);
+
+    // registered AFTER the routes above were declared
+    app()->registerMiddleware('late.string', function () use (&$ran) {
+        $ran['string'] = true;
+    });
+    app()->registerMiddleware('late.array', function () use (&$ran) {
+        $ran['array'] = true;
+    });
+    app()->registerMiddleware('late.group', function () use (&$ran) {
+        $ran['group'] = true;
+    });
+
+    app()->run();
+    expect($ran['string'])->toBeTrue();
+
+    $_SERVER['REQUEST_URI'] = '/late-array/42';
+    app()->run();
+    expect($ran['array'])->toBeTrue();
+
+    $_SERVER['REQUEST_URI'] = '/late-group/42';
+    app()->run();
+    expect($ran['group'])->toBeTrue();
+});
+
+test('a route using an unregistered named middleware fails closed', function () {
+    \Leaf\Router::reset();
+    app()->setBasePath('/');
+    $_SERVER['REQUEST_METHOD'] = 'GET';
+    $_SERVER['REQUEST_URI'] = '/never';
+
+    $handlerRan = false;
+
+    app()->get('/never', ['middleware' => 'never.registered', function () use (&$handlerRan) {
+        $handlerRan = true;
+    }]);
+
+    expect(fn () => app()->run())->toThrow(RuntimeException::class, 'never.registered');
+    expect($handlerRan)->toBeFalse();
+});