Ensured the Page cache identifier is read in the same way and checking and saving the cache identifier

app/code/Magento/PageCache/Model/App/Request/Http/Identifier.php

@@ -0,0 +1,61 @@
+<?php
+declare(strict_types=1);
+
+namespace Magento\PageCache\Model\App\Request\Http;
+
+use Magento\Framework\App\ObjectManager;
+use Magento\Framework\App\PageCache\IdentifierInterface;
+use Magento\Framework\Serialize\Serializer\Json;
+
+class Identifier implements IdentifierInterface
+{
+    /**
+     * @var \Magento\Framework\App\Request\Http
+     */
+    protected $request;
+
+    /**
+     * @var \Magento\Framework\App\Http\Context
+     */
+    protected $context;
+
+    /**
+     * @var Json
+     */
+    private $serializer;
+
+    /**
+     * @param \Magento\Framework\App\Request\Http $request
+     * @param \Magento\Framework\App\Http\Context $context
+     * @param Json|null $serializer
+     */
+    public function __construct(
+        \Magento\Framework\App\Request\Http $request,
+        \Magento\Framework\App\Http\Context $context,
+        Json $serializer = null,
+        private IdentifierStoreReader $identifierStoreReader
+    ) {
+        $this->request = $request;
+        $this->context = $context;
+        $this->serializer = $serializer ?: ObjectManager::getInstance()->get(Json::class);
+    }
+
+    /**
+     * Return unique page identifier
+     *
+     * @return string
+     */
+    public function getValue()
+    {
+        $data = [
+            $this->request->isSecure(),
+            $this->request->getUriString(),
+            $this->request->get(\Magento\Framework\App\Response\Http::COOKIE_VARY_STRING)
+                ?: $this->context->getVaryString()
+        ];
+
+        $data = $this->identifierStoreReader->getPageTagsWithStoreCacheTags($data);
+
+        return sha1($this->serializer->serialize($data));
+    }
+}

app/code/Magento/PageCache/Model/App/Request/Http/IdentifierForSave.php

@@ -23,9 +23,10 @@ class IdentifierForSave implements IdentifierInterface
      * @param Json $serializer
      */
     public function __construct(
-        private Http $request,
-        private Context $context,
-        private Json $serializer
+        private Http                  $request,
+        private Context               $context,
+        private Json                  $serializer,
+        private IdentifierStoreReader $identifierStoreReader,
     ) {
     }
 
@@ -42,6 +43,8 @@ public function getValue()
             $this->context->getVaryString()
         ];
 
+        $data = $this->identifierStoreReader->getPageTagsWithStoreCacheTags($data);
+
         return sha1($this->serializer->serialize($data));
     }
 }

app/code/Magento/PageCache/Model/App/Request/Http/IdentifierStoreReader.php

@@ -0,0 +1,67 @@
+<?php
+declare(strict_types=1);
+
+namespace Magento\PageCache\Model\App\Request\Http;
+
+use Magento\Store\Model\StoreManager;
+
+class IdentifierStoreReader
+{
+    /**
+     * @var \Magento\Framework\View\DesignExceptions
+     */
+    private $designExceptions;
+
+    /**
+     * @var \Magento\Framework\App\RequestInterface
+     */
+    private $request;
+
+    /**
+     * @var \Magento\PageCache\Model\Config
+     */
+    private $config;
+
+    /**
+     * @param \Magento\Framework\View\DesignExceptions $designExceptions
+     * @param \Magento\Framework\App\RequestInterface $request
+     * @param \Magento\PageCache\Model\Config $config
+     */
+    public function __construct(
+        \Magento\Framework\View\DesignExceptions $designExceptions,
+        \Magento\Framework\App\RequestInterface $request,
+        \Magento\PageCache\Model\Config $config
+    ) {
+        $this->designExceptions = $designExceptions;
+        $this->request = $request;
+        $this->config = $config;
+    }
+
+    /**
+     * Adds a theme key to identifier for a built-in cache if user-agent theme rule is actual
+     *
+     * @param \Magento\Framework\App\PageCache\Identifier $identifier
+     * @param string $result
+     * @return array
+     * @SuppressWarnings(PHPMD.UnusedFormalParameter)
+     */
+    public function getPageTagsWithStoreCacheTags($data): ?array
+    {
+        if ($this->config->getType() === \Magento\PageCache\Model\Config::BUILT_IN && $this->config->isEnabled()) {
+            $ruleDesignException = $this->designExceptions->getThemeByRequest($this->request);
+            if ($ruleDesignException !== false) {
+                $data['DESIGN'] = $ruleDesignException;
+            }
+
+            if ($runType = $this->request->getServerValue(StoreManager::PARAM_RUN_TYPE)) {
+                $data[StoreManager::PARAM_RUN_TYPE] = $runType;
+            }
+
+            if ($runCode = $this->request->getServerValue(StoreManager::PARAM_RUN_CODE)) {
+                $data[StoreManager::PARAM_RUN_CODE] = $runCode;
+            }
+        }
+
+        return $data;
+    }
+}

app/code/Magento/PageCache/Test/Unit/Model/App/Request/Http/IdentifierForSaveTest.php

@@ -11,6 +11,7 @@
 use Magento\Framework\App\Request\Http as HttpRequest;
 use Magento\Framework\Serialize\Serializer\Json;
 use Magento\PageCache\Model\App\Request\Http\IdentifierForSave;
+use Magento\PageCache\Model\App\Request\Http\IdentifierStoreReader;
 use PHPUnit\Framework\MockObject\MockObject;
 use PHPUnit\Framework\TestCase;
 
@@ -40,6 +41,10 @@ class IdentifierForSaveTest extends TestCase
      * @var Json|MockObject
      */
     private mixed $serializerMock;
+    /**
+     * @var IdentifierStoreReader|MockObject
+     */
+    private $identifierStoreReader;
 
     /**
      * @inheritdoc
@@ -64,10 +69,16 @@ function ($value) {
                 }
             );
 
+        $this->identifierStoreReader = $this->getMockBuilder(IdentifierStoreReader::class)
+            ->onlyMethods(['getPageTagsWithStoreCacheTags'])
+            ->disableOriginalConstructor()
+            ->getMock();
+
         $this->model = new IdentifierForSave(
             $this->requestMock,
             $this->contextMock,
-            $this->serializerMock
+            $this->serializerMock,
+            $this->identifierStoreReader
         );
         parent::setUp();
     }
@@ -91,6 +102,12 @@ public function testGetValue(): void
             ->method('getVaryString')
             ->willReturn(self::VARY);
 
+        $this->identifierStoreReader->method('getPageTagsWithStoreCacheTags')->willReturnCallback(
+            function ($value) {
+                return $value;
+            }
+        );
+
         $this->assertEquals(
             sha1(
                 json_encode(

app/code/Magento/PageCache/Test/Unit/Model/App/Request/Http/IdentifierStoreReaderTest.php

@@ -0,0 +1,119 @@
+<?php
+declare(strict_types=1);
+
+namespace Magento\PageCache\Test\Unit\Model\App\Request\Http;
+
+use Magento\Framework\App\Request\Http;
+use Magento\Framework\App\RequestInterface;
+use Magento\Framework\TestFramework\Unit\Helper\ObjectManager;
+use Magento\Framework\View\DesignExceptions;
+use Magento\PageCache\Model\Config;
+use Magento\Store\Model\StoreManager;
+use PHPUnit\Framework\TestCase;
+
+class IdentifierStoreReaderTest extends TestCase
+{
+    /**
+     * @var DesignExceptions|\PHPUnit\Framework\MockObject\MockObject
+     */
+    private $designExceptionsMock;
+    /**
+     * @var RequestInterface|\PHPUnit\Framework\MockObject\MockObject
+     */
+    private \PHPUnit\Framework\MockObject\MockObject|RequestInterface $requestMock;
+    /**
+     * @var Config|\PHPUnit\Framework\MockObject\MockObject
+     */
+    private $configMock;
+    /**
+     * @var \Magento\PageCache\Model\App\Request\Http\IdentifierStoreReader
+     */
+    private $model;
+
+    protected function setUp(): void
+    {
+        $this->objectManager = new ObjectManager($this);
+
+        $this->designExceptionsMock = $this->createPartialMock(
+            DesignExceptions::class,
+            ['getThemeByRequest']
+        );
+
+        $this->requestMock = $this->createMock(Http::class);
+
+        $this->configMock = $this->getMockBuilder(Config::class)
+            ->onlyMethods(['getType', 'isEnabled'])
+            //->addMethods(['getType', 'isEnabled'])
+            ->disableOriginalConstructor()
+            ->getMockForAbstractClass();
+
+        $this->model = new \Magento\PageCache\Model\App\Request\Http\IdentifierStoreReader(
+            $this->designExceptionsMock,
+            $this->requestMock,
+            $this->configMock
+        );
+    }
+
+    public function testGetPageTagsWithStoreCacheTagsWhenVarnishCacheIsEnabled()
+    {
+        $this->configMock->expects($this->any())
+            ->method('getType')
+            ->willReturn(\Magento\PageCache\Model\Config::VARNISH);
+
+        $this->requestMock->expects($this->never())->method('getServerValue');
+
+        $data = ['anything'];
+        $this->model->getPageTagsWithStoreCacheTags($data);
+    }
+
+    public function testGetPageTagsWithStoreCacheTagsWhenFPCIsDisabled()
+    {
+        $this->configMock->expects($this->any())
+            ->method('isEnabled')
+            ->willReturn(false);
+
+        $this->requestMock->expects($this->never())->method('getServerValue');
+
+        $data = ['anything'];
+        $this->model->getPageTagsWithStoreCacheTags($data);
+    }
+
+    public function testGetPageTagsWithStoreCacheTagsWhenStoreDataAreInContext()
+    {
+        $this->configMock->expects($this->any())
+            ->method('isEnabled')
+            ->willReturn(true);
+
+        $this->configMock->expects($this->any())
+            ->method('getType')
+            ->willReturn(\Magento\PageCache\Model\Config::BUILT_IN);
+
+        $defaultRequestMock = clone $this->requestMock;
+        $defaultRequestMock->expects($this->any())
+            ->method('getServerValue')
+            ->willReturnCallback(
+                function ($param) {
+                    if ($param == StoreManager::PARAM_RUN_TYPE) {
+                        return 'store';
+                    }
+                    if ($param == StoreManager::PARAM_RUN_CODE) {
+                        return 'default';
+                    }
+                }
+            );
+
+        $data = ['anything'];
+
+        $this->model = new \Magento\PageCache\Model\App\Request\Http\IdentifierStoreReader(
+            $this->designExceptionsMock,
+            $defaultRequestMock,
+            $this->configMock
+        );
+        $newData = $this->model->getPageTagsWithStoreCacheTags($data);
+
+        $this->assertArrayHasKey(StoreManager::PARAM_RUN_TYPE, $newData);
+        $this->assertArrayHasKey(StoreManager::PARAM_RUN_CODE, $newData);
+        $this->assertEquals($newData[StoreManager::PARAM_RUN_TYPE], 'store');
+        $this->assertEquals($newData[StoreManager::PARAM_RUN_CODE], 'default');
+    }
+}