diff --git a/src/AsEventListener.php b/src/AsEventListener.php
new file mode 100644
index 0000000..a43eb4d
--- /dev/null
+++ b/src/AsEventListener.php
@@ -0,0 +1,29 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Phred\Beacon;
+
+use Attribute;
+
+/**
+ * AsEventListener Attribute
+ *
+ * Marks a class or method as an event listener for a specific event.
+ * Used by the ListenerDiscovery service to automatically register listeners.
+ */
+#[Attribute(Attribute::TARGET_CLASS | Attribute::TARGET_METHOD | Attribute::IS_REPEATABLE)]
+class AsEventListener
+{
+    /**
+     * @param string $event The fully qualified class name of the event to listen for.
+     * @param int $priority The priority (higher runs first).
+     * @param string|null $method The method name to call (if applied to a class). Defaults to __invoke.
+     */
+    public function __construct(
+        public string $event,
+        public int $priority = 0,
+        public ?string $method = null
+    ) {
+    }
+}
diff --git a/src/AsSubscriber.php b/src/AsSubscriber.php
new file mode 100644
index 0000000..b8cf88e
--- /dev/null
+++ b/src/AsSubscriber.php
@@ -0,0 +1,26 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Phred\Beacon;
+
+use Attribute;
+
+/**
+ * AsSubscriber Attribute
+ *
+ * Marks a class as an event subscriber.
+ * The class must implement SubscriberInterface to define its listeners.
+ * Used by the ListenerDiscovery service to automatically register subscribers.
+ */
+#[Attribute(Attribute::TARGET_CLASS)]
+class AsSubscriber
+{
+    /**
+     * @param int $priority Global priority for all listeners in this subscriber (if not overridden).
+     */
+    public function __construct(
+        public int $priority = 0
+    ) {
+    }
+}
diff --git a/src/ListenerDiscovery.php b/src/ListenerDiscovery.php
new file mode 100644
index 0000000..091032d
--- /dev/null
+++ b/src/ListenerDiscovery.php
@@ -0,0 +1,179 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Phred\Beacon;
+
+use ReflectionClass;
+use Psr\SimpleCache\CacheInterface;
+
+/**
+ * ListenerDiscovery
+ *
+ * Scans directories for classes using Beacon attributes (#[AsEventListener], #[AsSubscriber]).
+ * Supports PSR-16 caching to prevent redundant filesystem scans.
+ */
+class ListenerDiscovery
+{
+    /**
+     * @var string The cache key used for discovery results.
+     */
+    private const CACHE_KEY = 'phred.beacon.discovery';
+
+    /**
+     * @param array<string> $directories List of absolute paths to scan.
+     * @param CacheInterface|null $cache Optional PSR-16 cache.
+     */
+    public function __construct(
+        private readonly array $directories,
+        private readonly ?CacheInterface $cache = null
+    ) {
+    }
+
+    /**
+     * Discovers listeners and registers them to the provider.
+     *
+     * @param ListenerProvider $provider
+     * @return void
+     */
+    public function discover(ListenerProvider $provider): void
+    {
+        $map = $this->getDiscoveryMap();
+
+        foreach ($map['listeners'] as $item) {
+            $provider->addListener($item['event'], $item['listener'], $item['priority']);
+        }
+
+        foreach ($map['subscribers'] as $subscriber) {
+            $provider->addSubscriber($subscriber);
+        }
+    }
+
+    /**
+     * Gets the discovery map from cache or by scanning.
+     *
+     * @return array{listeners: array<int, array{event: string, listener: string|array{0: string, 1: string}, priority: int}>, subscribers: array<int, string>}
+     */
+    private function getDiscoveryMap(): array
+    {
+        if ($this->cache !== null && $this->cache->has(self::CACHE_KEY)) {
+            return $this->cache->get(self::CACHE_KEY);
+        }
+
+        $map = $this->scan();
+
+        if ($this->cache !== null) {
+            $this->cache->set(self::CACHE_KEY, $map);
+        }
+
+        return $map;
+    }
+
+    /**
+     * Scans the configured directories for attributes.
+     *
+     * @return array{listeners: array<int, array{event: string, listener: string|array{0: string, 1: string}, priority: int}>, subscribers: array<int, string>}
+     */
+    private function scan(): array
+    {
+        $map = ['listeners' => [], 'subscribers' => []];
+
+        foreach ($this->directories as $directory) {
+            $files = new \RecursiveIteratorIterator(new \RecursiveDirectoryIterator($directory));
+            
+            foreach ($files as $file) {
+                if (!$file->isFile() || $file->getExtension() !== 'php') {
+                    continue;
+                }
+
+                $className = $this->extractClassName($file->getPathname());
+                if ($className === null || !class_exists($className)) {
+                    continue;
+                }
+
+                $reflection = new ReflectionClass($className);
+
+                // Check for #[AsSubscriber]
+                $subAttributes = $reflection->getAttributes(AsSubscriber::class);
+                if (!empty($subAttributes)) {
+                    $map['subscribers'][] = $className;
+                }
+
+                // Check for #[AsEventListener] on class
+                $classAttributes = $reflection->getAttributes(AsEventListener::class);
+                foreach ($classAttributes as $attr) {
+                    /** @var AsEventListener $instance */
+                    $instance = $attr->newInstance();
+                    $map['listeners'][] = [
+                        'event' => $instance->event,
+                        'listener' => $instance->method ? [$className, $instance->method] : $className,
+                        'priority' => $instance->priority,
+                    ];
+                }
+
+                // Check for #[AsEventListener] on methods
+                foreach ($reflection->getMethods() as $method) {
+                    $methodAttributes = $method->getAttributes(AsEventListener::class);
+                    foreach ($methodAttributes as $attr) {
+                        /** @var AsEventListener $instance */
+                        $instance = $attr->newInstance();
+                        $map['listeners'][] = [
+                            'event' => $instance->event,
+                            'listener' => [$className, $method->getName()],
+                            'priority' => $instance->priority,
+                        ];
+                    }
+                }
+            }
+        }
+
+        return $map;
+    }
+
+    /**
+     * Extracts the fully qualified class name from a file.
+     * Basic implementation using token_get_all.
+     *
+     * @param string $file
+     * @return string|null
+     */
+    private function extractClassName(string $file): ?string
+    {
+        $content = file_get_contents($file);
+        $tokens = token_get_all($content);
+        $namespace = '';
+        $class = '';
+        $gettingNamespace = false;
+        $gettingClass = false;
+
+        foreach ($tokens as $index => $token) {
+            if (is_array($token)) {
+                if ($token[0] === T_NAMESPACE) {
+                    $gettingNamespace = true;
+                } elseif ($token[0] === T_CLASS) {
+                    $gettingClass = true;
+                }
+
+                if ($gettingNamespace) {
+                    if ($token[0] === T_NAME_QUALIFIED || $token[0] === T_STRING) {
+                        $namespace .= $token[1];
+                    }
+                }
+
+                if ($gettingClass) {
+                    if ($token[0] === T_STRING) {
+                        $class = $token[1];
+                        break;
+                    }
+                }
+            } else {
+                if ($token === ';' && $gettingNamespace) {
+                    $gettingNamespace = false;
+                }
+            }
+        }
+
+        $classFQCN = $namespace ? $namespace . '\\' . $class : $class;
+        return $classFQCN ?: null;
+    }
+}
diff --git a/tests/Integration/DiscoveryIntegrationTest.php b/tests/Integration/DiscoveryIntegrationTest.php
new file mode 100644
index 0000000..4060b6f
--- /dev/null
+++ b/tests/Integration/DiscoveryIntegrationTest.php
@@ -0,0 +1,133 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Phred\Beacon\Tests\Integration;
+
+use PHPUnit\Framework\TestCase;
+use Phred\Beacon\AsEventListener;
+use Phred\Beacon\AsSubscriber;
+use Phred\Beacon\EventDispatcher;
+use Phred\Beacon\ListenerDiscovery;
+use Phred\Beacon\ListenerProvider;
+use Phred\BeaconContracts\SubscriberInterface;
+use Psr\Container\ContainerInterface;
+
+class DiscoveryIntegrationTest extends TestCase
+{
+    private string $tempDir;
+
+    protected function setUp(): void
+    {
+        $this->tempDir = sys_get_temp_dir() . '/beacon_discovery_test_' . uniqid();
+        mkdir($this->tempDir);
+    }
+
+    protected function tearDown(): void
+    {
+        $this->removeDir($this->tempDir);
+    }
+
+    public function test_it_discovers_attributed_listeners(): void
+    {
+        $this->createTestClass('TestListener', <<<'PHP'
+namespace Phred\Discovery;
+use Phred\Beacon\AsEventListener;
+class TestListener {
+    #[AsEventListener(event: 'stdClass', priority: 10)]
+    public function onEvent($event): void { $event->called = true; }
+}
+PHP
+        );
+
+        $provider = new ListenerProvider();
+        $discovery = new ListenerDiscovery([$this->tempDir]);
+        $discovery->discover($provider);
+
+        $dispatcher = new EventDispatcher($provider);
+        $event = new \stdClass();
+        $event->called = false;
+
+        $dispatcher->dispatch($event);
+
+        $this->assertTrue($event->called);
+    }
+
+    public function test_it_discovers_subscribers(): void
+    {
+        $this->createTestClass('TestSubscriber', <<<'PHP'
+namespace Phred\Discovery;
+use Phred\Beacon\AsSubscriber;
+use Phred\BeaconContracts\SubscriberInterface;
+#[AsSubscriber]
+class TestSubscriber implements SubscriberInterface {
+    public static function getSubscribedEvents(): array {
+        return ['stdClass' => 'onEvent'];
+    }
+    public function onEvent($event): void { $event->sub_called = true; }
+}
+PHP
+        );
+
+        $provider = new ListenerProvider();
+        $discovery = new ListenerDiscovery([$this->tempDir]);
+        $discovery->discover($provider);
+
+        $dispatcher = new EventDispatcher($provider);
+        $event = new \stdClass();
+        $event->sub_called = false;
+
+        $dispatcher->dispatch($event);
+
+        $this->assertTrue($event->sub_called);
+    }
+
+    public function test_lazy_loading_via_container(): void
+    {
+        $this->createTestClass('LazyListener', <<<'PHP'
+namespace Phred\Discovery;
+use Phred\Beacon\AsEventListener;
+class LazyListener {
+    #[AsEventListener(event: 'stdClass')]
+    public function __invoke($event): void { $event->lazy_called = true; }
+}
+PHP
+        );
+
+        $container = $this->createMock(ContainerInterface::class);
+        $container->expects($this->once())
+            ->method('get')
+            ->with('Phred\Discovery\LazyListener')
+            ->willReturn(new class {
+                public function __invoke($event) { $event->lazy_called = true; }
+            });
+
+        $provider = new ListenerProvider($container);
+        $discovery = new ListenerDiscovery([$this->tempDir]);
+        $discovery->discover($provider);
+
+        $dispatcher = new EventDispatcher($provider);
+        $event = new \stdClass();
+        $event->lazy_called = false;
+
+        $dispatcher->dispatch($event);
+
+        $this->assertTrue($event->lazy_called);
+    }
+
+    private function createTestClass(string $name, string $content): void
+    {
+        file_put_contents($this->tempDir . '/' . $name . '.php', "<?php\n" . $content);
+        require_once $this->tempDir . '/' . $name . '.php';
+    }
+
+    private function removeDir(string $dir): void
+    {
+        $files = array_diff(scandir($dir), ['.', '..']);
+        foreach ($files as $file) {
+            $path = $dir . '/' . $file;
+            is_dir($path) ? $this->removeDir($path) : unlink($path);
+        }
+        rmdir($dir);
+    }
+}