diff --git a/api/src/State/Processor/BookRemoveProcessor.php b/api/src/State/Processor/BookRemoveProcessor.php
index de79ac002..7b33351b7 100644
--- a/api/src/State/Processor/BookRemoveProcessor.php
+++ b/api/src/State/Processor/BookRemoveProcessor.php
@@ -28,7 +28,7 @@ public function __construct(
     /**
      * @param Book $data
      */
-    public function process(mixed $data, Operation $operation, array $uriVariables = [], array $context = []): Book
+    public function process(mixed $data, Operation $operation, array $uriVariables = [], array $context = []): void
     {
         $object = clone $data;
 
@@ -48,11 +48,9 @@ public function process(mixed $data, Operation $operation, array $uriVariables =
                 $uriVariables,
                 $context + [
                     'item_uri_template' => $uriTemplate,
-                    'data' => json_encode(['@id' => $iri]),
+                    MercureProcessor::DATA => json_encode(['@id' => $iri]),
                 ]
             );
         }
-
-        return $data;
     }
 }
diff --git a/api/src/State/Processor/MercureProcessor.php b/api/src/State/Processor/MercureProcessor.php
index 20690a6ae..baa693c73 100644
--- a/api/src/State/Processor/MercureProcessor.php
+++ b/api/src/State/Processor/MercureProcessor.php
@@ -19,6 +19,8 @@
 
 final readonly class MercureProcessor implements ProcessorInterface
 {
+    public const DATA = 'mercure_data';
+
     public function __construct(
         private SerializerInterface $serializer,
         private HubRegistry $hubRegistry,
@@ -42,8 +44,8 @@ public function process(mixed $data, Operation $operation, array $uriVariables =
         if (!isset($context['topics'])) {
             $context['topics'] = [$this->iriConverter->getIriFromResource($data, UrlGeneratorInterface::ABS_URL, $operation)];
         }
-        if (!isset($context['data'])) {
-            $context['data'] = $this->serializer->serialize(
+        if (!isset($context[self::DATA])) {
+            $context[self::DATA] = $this->serializer->serialize(
                 $data,
                 key($this->formats),
                 ($operation->getNormalizationContext() ?? []) + (isset($context['item_uri_template']) ? [
@@ -54,7 +56,7 @@ public function process(mixed $data, Operation $operation, array $uriVariables =
 
         $this->hubRegistry->getHub()->publish(new Update(
             topics: $context['topics'],
-            data: $context['data']
+            data: $context[self::DATA]
         ));
 
         return $data;
diff --git a/api/src/State/Processor/ReviewRemoveProcessor.php b/api/src/State/Processor/ReviewRemoveProcessor.php
index 05efb2ce9..4f8401938 100644
--- a/api/src/State/Processor/ReviewRemoveProcessor.php
+++ b/api/src/State/Processor/ReviewRemoveProcessor.php
@@ -28,7 +28,7 @@ public function __construct(
     /**
      * @param Review $data
      */
-    public function process(mixed $data, Operation $operation, array $uriVariables = [], array $context = []): Review
+    public function process(mixed $data, Operation $operation, array $uriVariables = [], array $context = []): void
     {
         $object = clone $data;
 
@@ -48,11 +48,9 @@ public function process(mixed $data, Operation $operation, array $uriVariables =
                 $uriVariables,
                 $context + [
                     'item_uri_template' => $uriTemplate,
-                    'data' => json_encode(['@id' => $iri]),
+                    MercureProcessor::DATA => json_encode(['@id' => $iri]),
                 ]
             );
         }
-
-        return $data;
     }
 }
diff --git a/api/tests/State/Processor/BookRemoveProcessorTest.php b/api/tests/State/Processor/BookRemoveProcessorTest.php
index 8eea20cb4..f0217c6e2 100644
--- a/api/tests/State/Processor/BookRemoveProcessorTest.php
+++ b/api/tests/State/Processor/BookRemoveProcessorTest.php
@@ -14,6 +14,7 @@
 use ApiPlatform\State\ProcessorInterface;
 use App\Entity\Book;
 use App\State\Processor\BookRemoveProcessor;
+use App\State\Processor\MercureProcessor;
 use PHPUnit\Framework\MockObject\MockObject;
 use PHPUnit\Framework\TestCase;
 
@@ -87,7 +88,7 @@ public function testItRemovesBookAndSendMercureUpdates(): void
                     [],
                     [
                         'item_uri_template' => '/admin/books/{id}{._format}',
-                        'data' => json_encode(['@id' => '/admin/books/9aff4b91-31cf-4e91-94b0-1d52bbe23fe6']),
+                        MercureProcessor::DATA => json_encode(['@id' => '/admin/books/9aff4b91-31cf-4e91-94b0-1d52bbe23fe6']),
                     ],
                 ],
                 [
@@ -96,7 +97,7 @@ public function testItRemovesBookAndSendMercureUpdates(): void
                     [],
                     [
                         'item_uri_template' => '/books/{id}{._format}',
-                        'data' => json_encode(['@id' => '/books/9aff4b91-31cf-4e91-94b0-1d52bbe23fe6']),
+                        MercureProcessor::DATA => json_encode(['@id' => '/books/9aff4b91-31cf-4e91-94b0-1d52bbe23fe6']),
                     ],
                 ],
             );
diff --git a/api/tests/State/Processor/MercureProcessorTest.php b/api/tests/State/Processor/MercureProcessorTest.php
index 6192d096a..8b48947ba 100644
--- a/api/tests/State/Processor/MercureProcessorTest.php
+++ b/api/tests/State/Processor/MercureProcessorTest.php
@@ -104,7 +104,7 @@ public function testItSendsAMercureUpdateWithContextOptions(): void
         $this->processor->process($this->objectMock, $this->operationMock, [], [
             'item_uri_template' => '/admin/books/{id}{._format}',
             'topics' => ['/admin/books/9aff4b91-31cf-4e91-94b0-1d52bbe23fe6'],
-            'data' => json_encode(['bar' => 'baz']),
+            MercureProcessor::DATA => json_encode(['bar' => 'baz']),
         ]);
     }
 }
diff --git a/api/tests/State/Processor/ReviewRemoveProcessorTest.php b/api/tests/State/Processor/ReviewRemoveProcessorTest.php
index e1f434e70..12dc38928 100644
--- a/api/tests/State/Processor/ReviewRemoveProcessorTest.php
+++ b/api/tests/State/Processor/ReviewRemoveProcessorTest.php
@@ -13,6 +13,7 @@
 use ApiPlatform\Metadata\Resource\ResourceMetadataCollection;
 use ApiPlatform\State\ProcessorInterface;
 use App\Entity\Review;
+use App\State\Processor\MercureProcessor;
 use App\State\Processor\ReviewRemoveProcessor;
 use PHPUnit\Framework\MockObject\MockObject;
 use PHPUnit\Framework\TestCase;
@@ -87,7 +88,7 @@ public function testItRemovesBookAndSendMercureUpdates(): void
                     [],
                     [
                         'item_uri_template' => '/admin/reviews/{id}{._format}',
-                        'data' => json_encode(['@id' => '/admin/reviews/9aff4b91-31cf-4e91-94b0-1d52bbe23fe6']),
+                        MercureProcessor::DATA => json_encode(['@id' => '/admin/reviews/9aff4b91-31cf-4e91-94b0-1d52bbe23fe6']),
                     ],
                 ],
                 [
@@ -96,7 +97,7 @@ public function testItRemovesBookAndSendMercureUpdates(): void
                     [],
                     [
                         'item_uri_template' => '/books/{bookId}/reviews/{id}{._format}',
-                        'data' => json_encode(['@id' => '/books/8ad70d36-abaf-4c9b-aeaa-7ec63e6ca6f3/reviews/9aff4b91-31cf-4e91-94b0-1d52bbe23fe6']),
+                        MercureProcessor::DATA => json_encode(['@id' => '/books/8ad70d36-abaf-4c9b-aeaa-7ec63e6ca6f3/reviews/9aff4b91-31cf-4e91-94b0-1d52bbe23fe6']),
                     ],
                 ],
             );