diff --git a/src/Module/Core/Domain/Entity/Role.php b/src/Module/Core/Domain/Entity/Role.php
index f5a2a31..14d20cd 100644
--- a/src/Module/Core/Domain/Entity/Role.php
+++ b/src/Module/Core/Domain/Entity/Role.php
@@ -13,6 +13,7 @@ use ApiPlatform\Metadata\GetCollection;
 use ApiPlatform\Metadata\Patch;
 use ApiPlatform\Metadata\Post;
 use App\Module\Core\Domain\Exception\SystemRoleDeletionException;
+use App\Module\Core\Infrastructure\ApiPlatform\State\Processor\RoleProcessor;
 use App\Module\Core\Infrastructure\Doctrine\DoctrineRoleRepository;
 use Doctrine\Common\Collections\ArrayCollection;
 use Doctrine\Common\Collections\Collection;
@@ -47,16 +48,19 @@ use Symfony\Component\Validator\Constraints as Assert;
             denormalizationContext: ['groups' => ['role:write']],
             // TODO ticket #345 : remplacer par is_granted('core.roles.manage')
             security: "is_granted('ROLE_ADMIN')",
+            processor: RoleProcessor::class,
         ),
         new Patch(
             normalizationContext: ['groups' => ['role:read']],
             denormalizationContext: ['groups' => ['role:write']],
             // TODO ticket #345 : remplacer par is_granted('core.roles.manage')
             security: "is_granted('ROLE_ADMIN')",
+            processor: RoleProcessor::class,
         ),
         new Delete(
             // TODO ticket #345 : remplacer par is_granted('core.roles.manage')
             security: "is_granted('ROLE_ADMIN')",
+            processor: RoleProcessor::class,
         ),
     ],
     normalizationContext: ['groups' => ['role:read']],
@@ -159,6 +163,19 @@ class Role
         return $this->permissions;
     }
 
+    /**
+     * Setter expose uniquement a la denormalisation API Platform pour
+     * permettre au RoleProcessor de detecter une tentative de modification
+     * du code (garde "code immuable"). Le code reste en pratique fige apres
+     * creation : le processor refuse toute modification via 400.
+     */
+    public function setCode(string $code): static
+    {
+        $this->code = $code;
+
+        return $this;
+    }
+
     /**
      * Met a jour le libelle affichable du role. Le code reste immuable pour
      * garantir la stabilite des references cote fixtures et migrations.
diff --git a/src/Module/Core/Infrastructure/ApiPlatform/State/Processor/RoleProcessor.php b/src/Module/Core/Infrastructure/ApiPlatform/State/Processor/RoleProcessor.php
new file mode 100644
index 0000000..70a8ba3
--- /dev/null
+++ b/src/Module/Core/Infrastructure/ApiPlatform/State/Processor/RoleProcessor.php
@@ -0,0 +1,78 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Module\Core\Infrastructure\ApiPlatform\State\Processor;
+
+use ApiPlatform\Metadata\DeleteOperationInterface;
+use ApiPlatform\Metadata\Operation;
+use ApiPlatform\State\ProcessorInterface;
+use App\Module\Core\Domain\Entity\Role;
+use App\Module\Core\Domain\Exception\SystemRoleDeletionException;
+use Doctrine\ORM\EntityManagerInterface;
+use Symfony\Component\DependencyInjection\Attribute\Autowire;
+use Symfony\Component\HttpKernel\Exception\AccessDeniedHttpException;
+use Symfony\Component\HttpKernel\Exception\BadRequestHttpException;
+
+/**
+ * Processor applicatif pour l'entite Role.
+ *
+ * Choix d'implementation : une seule classe qui recoit en dependances les deux
+ * processors Doctrine decores (Persist et Remove) et branche l'un ou l'autre
+ * selon le type d'operation. Ce choix reste plus lisible que deux classes
+ * jumelees et reflete la symetrie des gardes metier (immuabilite du `code`
+ * cote ecriture, protection des roles systeme cote suppression).
+ *
+ * Gardes metier :
+ *  - DELETE : delegue a Role::ensureDeletable() et traduit la
+ *    SystemRoleDeletionException en AccessDeniedHttpException (403).
+ *  - POST/PATCH : refuse toute modification du `code` (champ immuable apres
+ *    creation), regle uniforme pour les roles systeme ET custom.
+ *
+ * @implements ProcessorInterface<Role, null|Role>
+ */
+final class RoleProcessor implements ProcessorInterface
+{
+    public function __construct(
+        #[Autowire(service: 'api_platform.doctrine.orm.state.persist_processor')]
+        private readonly ProcessorInterface $persistProcessor,
+        #[Autowire(service: 'api_platform.doctrine.orm.state.remove_processor')]
+        private readonly ProcessorInterface $removeProcessor,
+        private readonly EntityManagerInterface $entityManager,
+    ) {}
+
+    public function process(mixed $data, Operation $operation, array $uriVariables = [], array $context = []): mixed
+    {
+        if (!$data instanceof Role) {
+            // Securite : si le provider n'a pas fourni un Role, on delegue
+            // quand meme au processor approprie pour ne pas etouffer
+            // silencieusement un bug de configuration.
+            return $operation instanceof DeleteOperationInterface
+                ? $this->removeProcessor->process($data, $operation, $uriVariables, $context)
+                : $this->persistProcessor->process($data, $operation, $uriVariables, $context);
+        }
+
+        if ($operation instanceof DeleteOperationInterface) {
+            try {
+                $data->ensureDeletable();
+            } catch (SystemRoleDeletionException $e) {
+                // Traduction HTTP : le domaine reste pur, l'API renvoie 403.
+                throw new AccessDeniedHttpException($e->getMessage(), $e);
+            }
+
+            return $this->removeProcessor->process($data, $operation, $uriVariables, $context);
+        }
+
+        // Ecriture (POST/PATCH) : verifier l'immuabilite du `code`.
+        // L'UnitOfWork n'expose un etat d'origine que pour les entites deja
+        // managees (PATCH). Pour un POST (entite nouvelle), `getOriginalEntityData`
+        // retourne un tableau vide : aucune comparaison necessaire.
+        $originalData = $this->entityManager->getUnitOfWork()->getOriginalEntityData($data);
+
+        if (isset($originalData['code']) && $originalData['code'] !== $data->getCode()) {
+            throw new BadRequestHttpException("Le code d'un role est immuable apres creation.");
+        }
+
+        return $this->persistProcessor->process($data, $operation, $uriVariables, $context);
+    }
+}
diff --git a/tests/Module/Core/Api/RoleApiTest.php b/tests/Module/Core/Api/RoleApiTest.php
index a0b0fa4..e204652 100644
--- a/tests/Module/Core/Api/RoleApiTest.php
+++ b/tests/Module/Core/Api/RoleApiTest.php
@@ -245,6 +245,77 @@ final class RoleApiTest extends ApiTestCase
         self::assertNull($em->getRepository(Role::class)->find($id));
     }
 
+    public function testDeleteSystemRoleReturns403(): void
+    {
+        $role = $this->getEm()->getRepository(Role::class)->findOneBy(['code' => SystemRoles::ADMIN_CODE]);
+        self::assertNotNull($role);
+
+        $client = $this->authenticatedClient('admin', 'admin');
+        $client->request('DELETE', '/api/roles/'.$role->getId());
+
+        self::assertResponseStatusCodeSame(403);
+
+        // Le role systeme doit toujours exister.
+        $em = $this->getEm();
+        $em->clear();
+        self::assertNotNull($em->getRepository(Role::class)->findOneBy(['code' => SystemRoles::ADMIN_CODE]));
+    }
+
+    public function testPatchSystemRoleLabelReturns200(): void
+    {
+        $em   = $this->getEm();
+        $role = $em->getRepository(Role::class)->findOneBy(['code' => SystemRoles::ADMIN_CODE]);
+        self::assertNotNull($role);
+        $originalLabel = $role->getLabel();
+        $roleId        = $role->getId();
+
+        $client = $this->authenticatedClient('admin', 'admin');
+
+        try {
+            $response = $client->request('PATCH', '/api/roles/'.$roleId, [
+                'headers' => ['Content-Type' => 'application/merge-patch+json'],
+                'json'    => ['label' => 'Administrateur (modifie test)'],
+            ]);
+
+            self::assertResponseIsSuccessful();
+            $data = $response->toArray();
+            self::assertSame('Administrateur (modifie test)', $data['label']);
+            self::assertSame(SystemRoles::ADMIN_CODE, $data['code']);
+            self::assertTrue($data['isSystem']);
+        } finally {
+            // Restauration defensive du label original pour ne pas polluer
+            // les tests suivants (les fixtures systeme sont partagees).
+            $em = $this->getEm();
+
+            /** @var null|Role $reloaded */
+            $reloaded = $em->getRepository(Role::class)->findOneBy(['code' => SystemRoles::ADMIN_CODE]);
+            if (null !== $reloaded && $reloaded->getLabel() !== $originalLabel) {
+                $reloaded->setLabel($originalLabel);
+                $em->flush();
+            }
+        }
+    }
+
+    public function testPatchRoleCodeChangeReturns400(): void
+    {
+        $role = $this->getEm()->getRepository(Role::class)->findOneBy(['code' => 'test_editor']);
+        self::assertNotNull($role);
+
+        $client = $this->authenticatedClient('admin', 'admin');
+        $client->request('PATCH', '/api/roles/'.$role->getId(), [
+            'headers' => ['Content-Type' => 'application/merge-patch+json'],
+            'json'    => ['code' => 'test_editor_renamed'],
+        ]);
+
+        self::assertResponseStatusCodeSame(400);
+
+        // Verification cote base : le code d'origine n'a pas bouge.
+        $em = $this->getEm();
+        $em->clear();
+        self::assertNotNull($em->getRepository(Role::class)->findOneBy(['code' => 'test_editor']));
+        self::assertNull($em->getRepository(Role::class)->findOneBy(['code' => 'test_editor_renamed']));
+    }
+
     public function testUnauthenticatedGetCollectionReturns401(): void
     {
         $client = self::createClient();
diff --git a/tests/Module/Core/Infrastructure/ApiPlatform/State/Processor/RoleProcessorTest.php b/tests/Module/Core/Infrastructure/ApiPlatform/State/Processor/RoleProcessorTest.php
new file mode 100644
index 0000000..dc890b9
--- /dev/null
+++ b/tests/Module/Core/Infrastructure/ApiPlatform/State/Processor/RoleProcessorTest.php
@@ -0,0 +1,212 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Tests\Module\Core\Infrastructure\ApiPlatform\State\Processor;
+
+use ApiPlatform\Metadata\Delete;
+use ApiPlatform\Metadata\Patch;
+use ApiPlatform\Metadata\Post;
+use ApiPlatform\State\ProcessorInterface;
+use App\Module\Core\Domain\Entity\Role;
+use App\Module\Core\Infrastructure\ApiPlatform\State\Processor\RoleProcessor;
+use Doctrine\ORM\EntityManagerInterface;
+use Doctrine\ORM\UnitOfWork;
+use PHPUnit\Framework\Attributes\AllowMockObjectsWithoutExpectations;
+use PHPUnit\Framework\MockObject\MockObject;
+use PHPUnit\Framework\TestCase;
+use ReflectionClass;
+use Symfony\Component\HttpKernel\Exception\AccessDeniedHttpException;
+use Symfony\Component\HttpKernel\Exception\BadRequestHttpException;
+
+/**
+ * Tests unitaires du RoleProcessor : couvre les gardes metier
+ * (immuabilite du code, refus de suppression des roles systeme) et la
+ * delegation aux processors Doctrine decores.
+ *
+ * @internal
+ */
+#[AllowMockObjectsWithoutExpectations]
+final class RoleProcessorTest extends TestCase
+{
+    private MockObject&ProcessorInterface $persistProcessor;
+    private MockObject&ProcessorInterface $removeProcessor;
+    private EntityManagerInterface&MockObject $entityManager;
+    private MockObject&UnitOfWork $unitOfWork;
+    private RoleProcessor $processor;
+
+    protected function setUp(): void
+    {
+        $this->persistProcessor = $this->createMock(ProcessorInterface::class);
+        $this->removeProcessor  = $this->createMock(ProcessorInterface::class);
+        $this->entityManager    = $this->createMock(EntityManagerInterface::class);
+        $this->unitOfWork       = $this->createMock(UnitOfWork::class);
+
+        $this->entityManager->method('getUnitOfWork')->willReturn($this->unitOfWork);
+
+        $this->processor = new RoleProcessor(
+            $this->persistProcessor,
+            $this->removeProcessor,
+            $this->entityManager,
+        );
+    }
+
+    public function testDeleteCustomRoleDelegatesToRemoveProcessor(): void
+    {
+        $role = new Role('editor', 'Editor', false);
+
+        $this->removeProcessor
+            ->expects(self::once())
+            ->method('process')
+            ->with($role)
+            ->willReturn(null)
+        ;
+
+        $this->persistProcessor->expects(self::never())->method('process');
+
+        $result = $this->processor->process($role, new Delete());
+
+        self::assertNull($result);
+    }
+
+    public function testDeleteSystemRoleThrowsAccessDeniedHttpException(): void
+    {
+        $role = new Role('admin', 'Admin', true);
+
+        $this->removeProcessor->expects(self::never())->method('process');
+        $this->persistProcessor->expects(self::never())->method('process');
+
+        $this->expectException(AccessDeniedHttpException::class);
+
+        $this->processor->process($role, new Delete());
+    }
+
+    public function testPostCreatesCustomRoleDelegatesToPersistProcessor(): void
+    {
+        $role = new Role('editor', 'Editor', false);
+
+        // Entite nouvelle : l'UnitOfWork n'a pas d'etat d'origine.
+        $this->unitOfWork
+            ->expects(self::once())
+            ->method('getOriginalEntityData')
+            ->with($role)
+            ->willReturn([])
+        ;
+
+        $this->persistProcessor
+            ->expects(self::once())
+            ->method('process')
+            ->with($role)
+            ->willReturn($role)
+        ;
+
+        $this->removeProcessor->expects(self::never())->method('process');
+
+        $result = $this->processor->process($role, new Post());
+
+        self::assertSame($role, $result);
+    }
+
+    public function testPatchWithChangedCodeThrowsBadRequestHttpException(): void
+    {
+        // L'entite arrive avec le nouveau code deja applique par le denormalizer.
+        $role = new Role('editor_renamed', 'Editor', false);
+        $this->setRoleId($role, 42);
+
+        $this->unitOfWork
+            ->expects(self::once())
+            ->method('getOriginalEntityData')
+            ->with($role)
+            ->willReturn([
+                'id'       => 42,
+                'code'     => 'editor',
+                'label'    => 'Editor',
+                'isSystem' => false,
+            ])
+        ;
+
+        $this->persistProcessor->expects(self::never())->method('process');
+        $this->removeProcessor->expects(self::never())->method('process');
+
+        $this->expectException(BadRequestHttpException::class);
+        $this->expectExceptionMessage("Le code d'un role est immuable apres creation.");
+
+        $this->processor->process($role, new Patch());
+    }
+
+    public function testPatchWithUnchangedCodeDelegatesToPersistProcessor(): void
+    {
+        $role = new Role('editor', 'Editor modifie', false, 'desc');
+        $this->setRoleId($role, 42);
+
+        $this->unitOfWork
+            ->expects(self::once())
+            ->method('getOriginalEntityData')
+            ->with($role)
+            ->willReturn([
+                'id'       => 42,
+                'code'     => 'editor',
+                'label'    => 'Editor',
+                'isSystem' => false,
+            ])
+        ;
+
+        $this->persistProcessor
+            ->expects(self::once())
+            ->method('process')
+            ->with($role)
+            ->willReturn($role)
+        ;
+
+        $this->removeProcessor->expects(self::never())->method('process');
+
+        $result = $this->processor->process($role, new Patch());
+
+        self::assertSame($role, $result);
+    }
+
+    public function testPatchSystemRoleLabelDelegatesToPersistProcessor(): void
+    {
+        // Regle uniforme : un role systeme peut voir son label modifie tant
+        // que son code reste inchange. Seul le DELETE est bloque.
+        $role = new Role('admin', 'Administrateur', true);
+        $this->setRoleId($role, 1);
+
+        $this->unitOfWork
+            ->expects(self::once())
+            ->method('getOriginalEntityData')
+            ->with($role)
+            ->willReturn([
+                'id'       => 1,
+                'code'     => 'admin',
+                'label'    => 'Admin',
+                'isSystem' => true,
+            ])
+        ;
+
+        $this->persistProcessor
+            ->expects(self::once())
+            ->method('process')
+            ->with($role)
+            ->willReturn($role)
+        ;
+
+        $this->removeProcessor->expects(self::never())->method('process');
+
+        $result = $this->processor->process($role, new Patch());
+
+        self::assertSame($role, $result);
+    }
+
+    /**
+     * Positionne l'id d'un Role via reflection pour simuler une entite deja
+     * persistee (les mocks d'UnitOfWork n'alimentent pas l'id tout seul).
+     */
+    private function setRoleId(Role $role, int $id): void
+    {
+        $refl = new ReflectionClass($role);
+        $prop = $refl->getProperty('id');
+        $prop->setAccessible(true);
+        $prop->setValue($role, $id);
+    }
+}