diff --git a/Tests/IntegrationTests/TestDistribution/DistributionPackages/Neos.TestNodeTypes/Classes/Application/RemoveAdditionalSettings/Controller/RemoveAdditionalSettingsController.php b/Tests/IntegrationTests/TestDistribution/DistributionPackages/Neos.TestNodeTypes/Classes/Application/RemoveAdditionalSettings/Controller/RemoveAdditionalSettingsController.php
index badea48a01..db3ddac910 100644
--- a/Tests/IntegrationTests/TestDistribution/DistributionPackages/Neos.TestNodeTypes/Classes/Application/RemoveAdditionalSettings/Controller/RemoveAdditionalSettingsController.php
+++ b/Tests/IntegrationTests/TestDistribution/DistributionPackages/Neos.TestNodeTypes/Classes/Application/RemoveAdditionalSettings/Controller/RemoveAdditionalSettingsController.php
@@ -14,12 +14,13 @@
 
 namespace Neos\TestNodeTypes\Application\RemoveAdditionalSettings\Controller;
 
+use GuzzleHttp\Psr7\Response;
 use Neos\Flow\Annotations as Flow;
 use Neos\Flow\Mvc\ActionRequest;
-use Neos\Flow\Mvc\ActionResponse;
 use Neos\Flow\Mvc\Controller\ControllerInterface;
 use Neos\TestNodeTypes\Application\RemoveAdditionalSettings\RemoveAdditionalSettingsCommand;
 use Neos\TestNodeTypes\Application\RemoveAdditionalSettings\RemoveAdditionalSettingsCommandHandler;
+use Psr\Http\Message\ResponseInterface;
 
 #[Flow\Scope("singleton")]
 final class RemoveAdditionalSettingsController implements ControllerInterface
@@ -27,46 +28,33 @@ final class RemoveAdditionalSettingsController implements ControllerInterface
     #[Flow\Inject]
     protected RemoveAdditionalSettingsCommandHandler $commandHandler;
 
-    public function processRequest(ActionRequest $request, ActionResponse $response)
+    public function processRequest(ActionRequest $request): ResponseInterface
     {
-        $request->setDispatched(true);
-        $response->setContentType('application/json');
-
         try {
             $command = RemoveAdditionalSettingsCommand::fromArray($request->getArguments());
             $this->commandHandler->handle($command);
-
-            $response->setStatusCode(200);
-            $response->setContent(
-                json_encode(
-                    ['success' => true],
-                    JSON_THROW_ON_ERROR
-                )
-            );
+            return new Response(status: 200, headers: ['Content-Type' => 'application/json'], body: json_encode(
+                ['success' => true],
+                JSON_THROW_ON_ERROR
+            ));
         } catch (\InvalidArgumentException $e) {
-            $response->setStatusCode(400);
-            $response->setContent(
-                json_encode(
-                    ['error' => [
-                        'type' => $e::class,
-                        'code' => $e->getCode(),
-                        'message' => $e->getMessage(),
-                    ]],
-                    JSON_THROW_ON_ERROR
-                )
-            );
+            return new Response(status: 400, headers: ['Content-Type' => 'application/json'], body: json_encode(
+                ['error' => [
+                    'type' => $e::class,
+                    'code' => $e->getCode(),
+                    'message' => $e->getMessage(),
+                ]],
+                JSON_THROW_ON_ERROR
+            ));
         } catch (\Exception $e) {
-            $response->setStatusCode(500);
-            $response->setContent(
-                json_encode(
-                    ['error' => [
-                        'type' => $e::class,
-                        'code' => $e->getCode(),
-                        'message' => $e->getMessage(),
-                    ]],
-                    JSON_THROW_ON_ERROR
-                )
-            );
+            return new Response(status: 500, headers: ['Content-Type' => 'application/json'], body:                 json_encode(
+                ['error' => [
+                    'type' => $e::class,
+                    'code' => $e->getCode(),
+                    'message' => $e->getMessage(),
+                ]],
+                JSON_THROW_ON_ERROR
+            ));
         }
     }
 }
diff --git a/Tests/IntegrationTests/TestDistribution/DistributionPackages/Neos.TestNodeTypes/Classes/Application/WriteAdditionalSettings/Controller/WriteAdditionalSettingsController.php b/Tests/IntegrationTests/TestDistribution/DistributionPackages/Neos.TestNodeTypes/Classes/Application/WriteAdditionalSettings/Controller/WriteAdditionalSettingsController.php
index cfbed1e39a..e2944f2ce0 100644
--- a/Tests/IntegrationTests/TestDistribution/DistributionPackages/Neos.TestNodeTypes/Classes/Application/WriteAdditionalSettings/Controller/WriteAdditionalSettingsController.php
+++ b/Tests/IntegrationTests/TestDistribution/DistributionPackages/Neos.TestNodeTypes/Classes/Application/WriteAdditionalSettings/Controller/WriteAdditionalSettingsController.php
@@ -14,12 +14,13 @@
 
 namespace Neos\TestNodeTypes\Application\WriteAdditionalSettings\Controller;
 
+use GuzzleHttp\Psr7\Response;
 use Neos\Flow\Annotations as Flow;
 use Neos\Flow\Mvc\ActionRequest;
-use Neos\Flow\Mvc\ActionResponse;
 use Neos\Flow\Mvc\Controller\ControllerInterface;
 use Neos\TestNodeTypes\Application\WriteAdditionalSettings\WriteAdditionalSettingsCommand;
 use Neos\TestNodeTypes\Application\WriteAdditionalSettings\WriteAdditionalSettingsCommandHandler;
+use Psr\Http\Message\ResponseInterface;
 
 #[Flow\Scope("singleton")]
 final class WriteAdditionalSettingsController implements ControllerInterface
@@ -27,46 +28,33 @@ final class WriteAdditionalSettingsController implements ControllerInterface
     #[Flow\Inject]
     protected WriteAdditionalSettingsCommandHandler $commandHandler;
 
-    public function processRequest(ActionRequest $request, ActionResponse $response)
+    public function processRequest(ActionRequest $request): ResponseInterface
     {
-        $request->setDispatched(true);
-        $response->setContentType('application/json');
-
         try {
             $command = WriteAdditionalSettingsCommand::fromArray($request->getArguments());
             $this->commandHandler->handle($command);
-
-            $response->setStatusCode(200);
-            $response->setContent(
-                json_encode(
-                    ['success' => true],
-                    JSON_THROW_ON_ERROR
-                )
-            );
+            return new Response(status: 200, headers: ['Content-Type' => 'application/json'], body: json_encode(
+                ['success' => true],
+                JSON_THROW_ON_ERROR
+            ));
         } catch (\InvalidArgumentException $e) {
-            $response->setStatusCode(400);
-            $response->setContent(
-                json_encode(
-                    ['error' => [
-                        'type' => $e::class,
-                        'code' => $e->getCode(),
-                        'message' => $e->getMessage(),
-                    ]],
-                    JSON_THROW_ON_ERROR
-                )
-            );
+            return new Response(status: 400, headers: ['Content-Type' => 'application/json'], body: json_encode(
+                ['error' => [
+                    'type' => $e::class,
+                    'code' => $e->getCode(),
+                    'message' => $e->getMessage(),
+                ]],
+                JSON_THROW_ON_ERROR
+            ));
         } catch (\Exception $e) {
-            $response->setStatusCode(500);
-            $response->setContent(
-                json_encode(
-                    ['error' => [
-                        'type' => $e::class,
-                        'code' => $e->getCode(),
-                        'message' => $e->getMessage(),
-                    ]],
-                    JSON_THROW_ON_ERROR
-                )
-            );
+            return new Response(status: 500, headers: ['Content-Type' => 'application/json'], body: json_encode(
+                ['error' => [
+                    'type' => $e::class,
+                    'code' => $e->getCode(),
+                    'message' => $e->getMessage(),
+                ]],
+                JSON_THROW_ON_ERROR
+            ));
         }
     }
 }
diff --git a/packages/neos-ui-guest-frame/src/initializeGuestFrame.js b/packages/neos-ui-guest-frame/src/initializeGuestFrame.js
index 07b9b84df5..c4250deff5 100644
--- a/packages/neos-ui-guest-frame/src/initializeGuestFrame.js
+++ b/packages/neos-ui-guest-frame/src/initializeGuestFrame.js
@@ -60,9 +60,6 @@ export default ({globalRegistry, store}) => function * initializeGuestFrame() {
         return;
     }
 
-    // Load legacy node data scripts from guest frame - remove with Neos 9.0
-    const legacyNodeData = guestFrameWindow['@Neos.Neos.Ui:Nodes'] || {};
-
     // Load all nodedata for nodes in the guest frame and filter duplicates
     const {q} = yield backend.get();
     const nodeContextPathsInGuestFrame = findAllNodesInGuestFrame().map(node => node.getAttribute('data-__neos-node-contextpath'));
@@ -83,7 +80,6 @@ export default ({globalRegistry, store}) => function * initializeGuestFrame() {
 
     const nodes = Object.assign(
         {},
-        legacyNodeData, // Merge legacy node data from the guest frame - remove with Neos 9.0
         fullyLoadedNodesFromContent,
         {
             [documentInformation.metaData.documentNode]: documentInformation.metaData.documentNodeSerialization
@@ -93,9 +89,6 @@ export default ({globalRegistry, store}) => function * initializeGuestFrame() {
     // Merge new nodes into the store
     yield put(actions.CR.Nodes.merge(nodes));
 
-    // Remove the legacy inline scripts after initialization - remove with Neos 9.0
-    Array.prototype.forEach.call(guestFrameWindow.document.querySelectorAll('script[data-neos-nodedata]'), element => element.parentElement.removeChild(element));
-
     const state = store.getState();
 
     // Set the current document node to the one that is rendered in the guest frame which might be different from the one that is currently selected in the page tree