diff --git a/src/Hub/Controller/SubscribeController.php b/src/Hub/Controller/SubscribeController.php
index 6f606c7..1cffadb 100644
--- a/src/Hub/Controller/SubscribeController.php
+++ b/src/Hub/Controller/SubscribeController.php
@@ -8,6 +8,7 @@
 use Freddie\Hub\HubControllerInterface;
 use Freddie\Hub\HubInterface;
 use Freddie\Message\Update;
+use Freddie\Subscription\Subscriber;
 use Lcobucci\JWT\UnencryptedToken;
 use Psr\Http\Message\ResponseInterface;
 use Psr\Http\Message\ServerRequestInterface;
@@ -57,6 +58,8 @@ public function __invoke(
         $allowedTopics = $this->extractAllowedTopics($request);
         $lastEventId = extract_last_event_id($request);
 
+        $subscriber = new Subscriber($subscribedTopics);
+
         if (null !== $lastEventId) {
             async(
                 function () use ($lastEventId, $stream, $subscribedTopics, $allowedTopics) {
@@ -68,15 +71,16 @@ function () use ($lastEventId, $stream, $subscribedTopics, $allowedTopics) {
         }
 
         async(
-            function () use ($stream, $subscribedTopics, $allowedTopics) {
+            function () use ($stream, $subscribedTopics, $allowedTopics, $subscriber) {
                 $callback = fn(Update $update) => $this->sendUpdate(
                     $update,
                     $stream,
                     $subscribedTopics,
                     $allowedTopics
                 );
-                $this->hub->subscribe($callback);
-                $stream->on('close', fn() => $this->hub->unsubscribe($callback));
+                $subscriber->setCallback($callback);
+                $this->hub->subscribe($subscriber);
+                $stream->on('close', fn() => $this->hub->unsubscribe($subscriber));
             }
         )();
 
diff --git a/src/Hub/Hub.php b/src/Hub/Hub.php
index b23c9f7..0cadef0 100644
--- a/src/Hub/Hub.php
+++ b/src/Hub/Hub.php
@@ -9,6 +9,7 @@
 use Freddie\Hub\Transport\PHP\PHPTransport;
 use Freddie\Hub\Transport\TransportInterface;
 use Freddie\Message\Update;
+use Freddie\Subscription\Subscriber;
 use Generator;
 use InvalidArgumentException;
 use React\EventLoop\Loop;
@@ -75,14 +76,14 @@ public function publish(Update $update): PromiseInterface
             });
     }
 
-    public function subscribe(callable $callback): void
+    public function subscribe(Subscriber $subscriber): void
     {
-        $this->transport->subscribe($callback);
+        $this->transport->subscribe($subscriber);
     }
 
-    public function unsubscribe(callable $callback): void
+    public function unsubscribe(Subscriber $subscriber): void
     {
-        $this->transport->unsubscribe($callback);
+        $this->transport->unsubscribe($subscriber);
     }
 
     public function reconciliate(string $lastEventID): Generator
diff --git a/src/Hub/HubInterface.php b/src/Hub/HubInterface.php
index ac68b82..154974d 100644
--- a/src/Hub/HubInterface.php
+++ b/src/Hub/HubInterface.php
@@ -5,6 +5,7 @@
 namespace Freddie\Hub;
 
 use Freddie\Message\Update;
+use Freddie\Subscription\Subscriber;
 use Generator;
 use React\Promise\PromiseInterface;
 
@@ -17,9 +18,9 @@ public function getOption(string $name): mixed;
      */
     public function publish(Update $update): PromiseInterface;
 
-    public function subscribe(callable $callback): void;
+    public function subscribe(Subscriber $subscriber): void;
 
-    public function unsubscribe(callable $callback): void;
+    public function unsubscribe(Subscriber $subscriber): void;
 
     /**
      * @param string $lastEventID
diff --git a/src/Message/Message.php b/src/Message/Message.php
index 7ee6938..8030436 100644
--- a/src/Message/Message.php
+++ b/src/Message/Message.php
@@ -4,6 +4,8 @@
 
 namespace Freddie\Message;
 
+use Symfony\Component\Uid\Ulid;
+
 use function explode;
 use function str_contains;
 
@@ -18,6 +20,7 @@ public function __construct(
         public ?string $event = null,
         public ?int $retry = null,
     ) {
+        $this->id ??= (string) new Ulid();
     }
 
     public function __toString(): string
diff --git a/src/Message/Update.php b/src/Message/Update.php
index 2397575..cf724ae 100644
--- a/src/Message/Update.php
+++ b/src/Message/Update.php
@@ -7,16 +7,23 @@
 use Freddie\Helper\TopicHelper;
 
 use function Freddie\topic;
+use function is_string;
 
 final class Update
 {
+    /**
+     * @var string[]
+     */
+    public array $topics;
+
     /**
      * @param string[] $topics
      */
     public function __construct(
-        public array $topics,
+        array|string $topics,
         public Message $message,
     ) {
+        $this->topics = is_string($topics) ? [$topics] : $topics;
     }
 
     /**
diff --git a/src/Subscription/Subscriber.php b/src/Subscription/Subscriber.php
new file mode 100644
index 0000000..ff78f6a
--- /dev/null
+++ b/src/Subscription/Subscriber.php
@@ -0,0 +1,50 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Freddie\Subscription;
+
+use Symfony\Component\Uid\Ulid;
+
+use function array_map;
+
+final class Subscriber
+{
+    /**
+     * @var Subscription[]
+     */
+    public readonly array $subscriptions;
+
+    /**
+     * @var callable
+     */
+    private $callback;
+
+    /**
+     * @param string[] $topics
+     */
+    public function __construct(
+        public readonly array $topics,
+        public readonly mixed $payload = null,
+        public readonly Ulid $id = new Ulid(),
+        public bool $active = true,
+    ) {
+        $this->subscriptions = array_map(
+            fn(string $topic) => new Subscription($this, $topic),
+            $this->topics,
+        );
+    }
+
+    public function setCallback(callable $callback): void
+    {
+        $this->callback = $callback;
+    }
+
+    /**
+     * @param mixed ...$args
+     */
+    public function __invoke(...$args): void
+    {
+        ($this->callback)(...$args);
+    }
+}
diff --git a/src/Subscription/Subscription.php b/src/Subscription/Subscription.php
new file mode 100644
index 0000000..508a227
--- /dev/null
+++ b/src/Subscription/Subscription.php
@@ -0,0 +1,14 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Freddie\Subscription;
+
+final class Subscription
+{
+    public function __construct(
+        public readonly Subscriber $subscriber,
+        public readonly string $topic,
+    ) {
+    }
+}
diff --git a/tests/Unit/Hub/HubTest.php b/tests/Unit/Hub/HubTest.php
index fedfe8f..5fa7d89 100644
--- a/tests/Unit/Hub/HubTest.php
+++ b/tests/Unit/Hub/HubTest.php
@@ -8,6 +8,7 @@
 use Freddie\Hub\Transport\TransportInterface;
 use Freddie\Message\Message;
 use Freddie\Message\Update;
+use Freddie\Subscription\Subscriber;
 use Generator;
 use InvalidArgumentException;
 use React\Promise\PromiseInterface;
@@ -48,19 +49,21 @@ public function reconciliate(string $lastEventID): Generator
     $hub = new Hub(transport: $transport);
     $update = new Update(['foo'], new Message(Ulid::generate()));
     $subscribeFn = fn () => 'bar';
+    $subscriber = new Subscriber(['foo']);
+    $subscriber->setCallback($subscribeFn);
     $lastEventId = Ulid::generate();
 
     // When
     $hub->publish($update);
-    $hub->subscribe($subscribeFn);
+    $hub->subscribe($subscriber);
     iterator_to_array($hub->reconciliate($lastEventId));
-    $hub->unsubscribe($subscribeFn);
+    $hub->unsubscribe($subscriber);
 
     // Then
     expect($transport->called['publish'])->toBe([$update]);
-    expect($transport->called['subscribe'])->toBe([$subscribeFn]);
+    expect($transport->called['subscribe'])->toBe([$subscriber]);
     expect($transport->called['reconciliate'])->toBe([$lastEventId]);
-    expect($transport->called['unsubscribe'])->toBe([$subscribeFn]);
+    expect($transport->called['unsubscribe'])->toBe([$subscriber]);
 });
 
 it('complains when requesting an unrecognized option', function () {
diff --git a/tests/Unit/Message/MessageTest.php b/tests/Unit/Message/MessageTest.php
index 21c2e82..39908cd 100644
--- a/tests/Unit/Message/MessageTest.php
+++ b/tests/Unit/Message/MessageTest.php
@@ -5,6 +5,7 @@
 namespace Freddie\Tests\Unit\Message;
 
 use Freddie\Message\Message;
+use Symfony\Component\Uid\Ulid;
 
 it('stringifies messages', function (Message $message, string $expected) {
     expect((string) $message)->toBe($expected);
@@ -34,3 +35,9 @@
         "id:1\nevent:message\ndata:foo\ndata:bar\n\n",
     ];
 });
+
+it('has a default id', function () {
+    $message = new Message();
+    expect($message->id)->not()->toBeNull();
+    expect(Ulid::isValid($message->id))->toBeTrue();
+});
diff --git a/tests/Unit/Message/UpdateTest.php b/tests/Unit/Message/UpdateTest.php
index 54f4b0a..6b02c3b 100644
--- a/tests/Unit/Message/UpdateTest.php
+++ b/tests/Unit/Message/UpdateTest.php
@@ -103,3 +103,8 @@
         'expected' => true, // Private update allowed on all
     ];
 });
+
+it('accepts a single topic', function () {
+    $update = new Update('/foo', new Message());
+    expect($update->topics)->toBe(['/foo']);
+});