diff --git a/tests/Doctrine/RepositoryClassMappingTest.php b/tests/Doctrine/RepositoryClassMappingTest.php
new file mode 100644
index 00000000..ae6f2d7b
--- /dev/null
+++ b/tests/Doctrine/RepositoryClassMappingTest.php
@@ -0,0 +1,44 @@
+<?php
+
+namespace App\Tests\Doctrine;
+
+use Doctrine\ORM\EntityManagerInterface;
+use Symfony\Bundle\FrameworkBundle\Test\KernelTestCase;
+
+/**
+ * Regression for the prod-only bug where entities without an explicit
+ * #[ORM\Entity(repositoryClass: ...)] fell back to Doctrine's default
+ * repository under opcache.preload, so custom finder methods threw
+ * BadMethodCallException (e.g. /oauth/userinfo 500).
+ *
+ * For every mapped entity that has a sibling <Entity>Repository class
+ * (App\<Domain>\Entity\X -> App\<Domain>\Repository\XRepository), assert
+ * getRepository() actually returns that custom class.
+ */
+class RepositoryClassMappingTest extends KernelTestCase
+{
+    public function testEntitiesWithCustomRepoDeclareIt(): void
+    {
+        self::bootKernel();
+        $em = static::getContainer()->get(EntityManagerInterface::class);
+
+        $offenders = [];
+        foreach ($em->getMetadataFactory()->getAllMetadata() as $meta) {
+            $entity = $meta->getName();
+            $repoFqcn = str_replace('\\Entity\\', '\\Repository\\', $entity) . 'Repository';
+            if (!class_exists($repoFqcn)) {
+                continue;
+            }
+            $actual = $em->getRepository($entity);
+            if (!$actual instanceof $repoFqcn) {
+                $offenders[] = sprintf('%s -> got %s, expected %s', $entity, $actual::class, $repoFqcn);
+            }
+        }
+
+        $this->assertSame(
+            [],
+            $offenders,
+            "Entities missing #[ORM\\Entity(repositoryClass: ...)]:\n" . implode("\n", $offenders),
+        );
+    }
+}