diff --git a/src/Module/Core/Domain/Security/AdminHeadcountGuard.php b/src/Module/Core/Domain/Security/AdminHeadcountGuard.php
index 779f819..8978398 100644
--- a/src/Module/Core/Domain/Security/AdminHeadcountGuard.php
+++ b/src/Module/Core/Domain/Security/AdminHeadcountGuard.php
@@ -17,7 +17,7 @@ use App\Module\Core\Domain\Repository\UserRepositoryInterface;
  * Il compte les admins restants et leve LastAdminProtectionException si
  * le seuil minimum (1) serait franchi.
  */
-final class AdminHeadcountGuard
+final class AdminHeadcountGuard implements AdminHeadcountGuardInterface
 {
     public function __construct(private readonly UserRepositoryInterface $userRepository) {}
 
diff --git a/src/Module/Core/Domain/Security/AdminHeadcountGuardInterface.php b/src/Module/Core/Domain/Security/AdminHeadcountGuardInterface.php
new file mode 100644
index 0000000..b45be17
--- /dev/null
+++ b/src/Module/Core/Domain/Security/AdminHeadcountGuardInterface.php
@@ -0,0 +1,31 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Module\Core\Domain\Security;
+
+use App\Module\Core\Domain\Entity\User;
+use App\Module\Core\Domain\Exception\LastAdminProtectionException;
+
+/**
+ * Contrat du gardien de l'invariant "au moins un admin sur l'instance".
+ *
+ * Separer l'interface de l'implementation permet de tester unitairement
+ * les processors qui dependent de ce garde sans instancier le repository.
+ */
+interface AdminHeadcountGuardInterface
+{
+    /**
+     * Verifie qu'il restera au moins un admin apres la demote de $user.
+     *
+     * @throws LastAdminProtectionException si le seuil minimum serait franchi
+     */
+    public function ensureAtLeastOneAdminRemainsAfterDemotion(User $user): void;
+
+    /**
+     * Verifie qu'il restera au moins un admin apres la suppression de $user.
+     *
+     * @throws LastAdminProtectionException si le seuil minimum serait franchi
+     */
+    public function ensureAtLeastOneAdminRemainsAfterDeletion(User $user): void;
+}
diff --git a/src/Module/Core/Infrastructure/ApiPlatform/State/Processor/UserProcessor.php b/src/Module/Core/Infrastructure/ApiPlatform/State/Processor/UserProcessor.php
new file mode 100644
index 0000000..3bd1e89
--- /dev/null
+++ b/src/Module/Core/Infrastructure/ApiPlatform/State/Processor/UserProcessor.php
@@ -0,0 +1,62 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Module\Core\Infrastructure\ApiPlatform\State\Processor;
+
+use ApiPlatform\Metadata\Operation;
+use ApiPlatform\State\ProcessorInterface;
+use App\Module\Core\Domain\Entity\User;
+use App\Module\Core\Domain\Exception\LastAdminProtectionException;
+use App\Module\Core\Domain\Security\AdminHeadcountGuardInterface;
+use LogicException;
+use Symfony\Component\DependencyInjection\Attribute\Autowire;
+use Symfony\Component\HttpKernel\Exception\BadRequestHttpException;
+
+/**
+ * Processor dedie a l'operation `DELETE /api/users/{id}`.
+ *
+ * Delegue la suppression au RemoveProcessor Doctrine decore apres avoir
+ * applique la garde "dernier admin global" : si l'utilisateur cible est
+ * le seul admin restant sur l'instance, la suppression est refusee pour
+ * preserver l'invariant "au moins un administrateur reste toujours".
+ *
+ * La garde est portee par AdminHeadcountGuard (domaine), partagee avec
+ * UserRbacProcessor qui gere le meme invariant sur le chemin PATCH /rbac.
+ *
+ * @implements ProcessorInterface<User, User>
+ */
+final class UserProcessor implements ProcessorInterface
+{
+    public function __construct(
+        #[Autowire(service: 'api_platform.doctrine.orm.state.remove_processor')]
+        private readonly ProcessorInterface $removeProcessor,
+        private readonly AdminHeadcountGuardInterface $adminHeadcountGuard,
+    ) {}
+
+    public function process(mixed $data, Operation $operation, array $uriVariables = [], array $context = []): mixed
+    {
+        if (!$data instanceof User) {
+            // Ce processor est wire exclusivement sur l'operation Delete de User.
+            // Si on arrive ici avec un autre type, c'est une misconfiguration.
+            throw new LogicException(sprintf(
+                'UserProcessor attend une instance de %s, %s recu.',
+                User::class,
+                get_debug_type($data),
+            ));
+        }
+
+        // Garde dernier admin global : on ne verifie que si on supprime
+        // effectivement un admin. La suppression d'un user standard n'a
+        // aucun impact sur le compteur d'administrateurs.
+        if ($data->isAdmin()) {
+            try {
+                $this->adminHeadcountGuard->ensureAtLeastOneAdminRemainsAfterDeletion($data);
+            } catch (LastAdminProtectionException $exception) {
+                throw new BadRequestHttpException($exception->getMessage(), $exception);
+            }
+        }
+
+        return $this->removeProcessor->process($data, $operation, $uriVariables, $context);
+    }
+}
diff --git a/tests/Module/Core/Infrastructure/ApiPlatform/State/Processor/UserProcessorTest.php b/tests/Module/Core/Infrastructure/ApiPlatform/State/Processor/UserProcessorTest.php
new file mode 100644
index 0000000..6836e4e
--- /dev/null
+++ b/tests/Module/Core/Infrastructure/ApiPlatform/State/Processor/UserProcessorTest.php
@@ -0,0 +1,130 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Tests\Module\Core\Infrastructure\ApiPlatform\State\Processor;
+
+use ApiPlatform\Metadata\Delete;
+use ApiPlatform\State\ProcessorInterface;
+use App\Module\Core\Domain\Entity\User;
+use App\Module\Core\Domain\Exception\LastAdminProtectionException;
+use App\Module\Core\Domain\Security\AdminHeadcountGuardInterface;
+use App\Module\Core\Infrastructure\ApiPlatform\State\Processor\UserProcessor;
+use LogicException;
+use PHPUnit\Framework\Attributes\AllowMockObjectsWithoutExpectations;
+use PHPUnit\Framework\MockObject\MockObject;
+use PHPUnit\Framework\TestCase;
+use stdClass;
+use Symfony\Component\HttpKernel\Exception\BadRequestHttpException;
+
+/**
+ * Tests unitaires du UserProcessor : couvre la garde "dernier admin global"
+ * et la delegation au RemoveProcessor Doctrine decore pour l'operation DELETE.
+ *
+ * @internal
+ */
+#[AllowMockObjectsWithoutExpectations]
+final class UserProcessorTest extends TestCase
+{
+    private MockObject&ProcessorInterface $removeProcessor;
+    private AdminHeadcountGuardInterface&MockObject $adminHeadcountGuard;
+    private UserProcessor $processor;
+
+    protected function setUp(): void
+    {
+        $this->removeProcessor     = $this->createMock(ProcessorInterface::class);
+        $this->adminHeadcountGuard = $this->createMock(AdminHeadcountGuardInterface::class);
+
+        $this->processor = new UserProcessor(
+            $this->removeProcessor,
+            $this->adminHeadcountGuard,
+        );
+    }
+
+    public function testDelegatesWhenUserIsNotAdmin(): void
+    {
+        $user = new User();
+        $user->setUsername('alice');
+        $user->setIsAdmin(false);
+
+        // La garde ne doit jamais etre appellee pour un non-admin.
+        $this->adminHeadcountGuard
+            ->expects($this->never())
+            ->method('ensureAtLeastOneAdminRemainsAfterDeletion')
+        ;
+
+        $this->removeProcessor
+            ->expects($this->once())
+            ->method('process')
+            ->with($user)
+            ->willReturn(null)
+        ;
+
+        $result = $this->processor->process($user, new Delete());
+
+        self::assertNull($result);
+    }
+
+    public function testDelegatesWhenAdminButNotLast(): void
+    {
+        $user = new User();
+        $user->setUsername('admin');
+        $user->setIsAdmin(true);
+
+        // La garde est appelee et ne leve pas d'exception (il reste d'autres admins).
+        $this->adminHeadcountGuard
+            ->expects($this->once())
+            ->method('ensureAtLeastOneAdminRemainsAfterDeletion')
+            ->with($user)
+        ;
+
+        $this->removeProcessor
+            ->expects($this->once())
+            ->method('process')
+            ->with($user)
+            ->willReturn(null)
+        ;
+
+        $this->processor->process($user, new Delete());
+    }
+
+    public function testBlocksWhenDeletingLastAdmin(): void
+    {
+        $user = new User();
+        $user->setUsername('admin');
+        $user->setIsAdmin(true);
+
+        $exceptionMessage = 'Impossible : au moins un administrateur doit rester sur l\'instance.';
+
+        $this->adminHeadcountGuard
+            ->expects($this->once())
+            ->method('ensureAtLeastOneAdminRemainsAfterDeletion')
+            ->with($user)
+            ->willThrowException(new LastAdminProtectionException($exceptionMessage))
+        ;
+
+        // La suppression ne doit pas etre executee si la garde echoue.
+        $this->removeProcessor
+            ->expects($this->never())
+            ->method('process')
+        ;
+
+        $this->expectException(BadRequestHttpException::class);
+        $this->expectExceptionMessage($exceptionMessage);
+
+        $this->processor->process($user, new Delete());
+    }
+
+    public function testFailFastOnInvalidDataType(): void
+    {
+        // Garde-fou contre une misconfiguration : ce processor est wire
+        // exclusivement sur l'operation Delete de User.
+        $this->adminHeadcountGuard->expects($this->never())->method('ensureAtLeastOneAdminRemainsAfterDeletion');
+        $this->removeProcessor->expects($this->never())->method('process');
+
+        $this->expectException(LogicException::class);
+        $this->expectExceptionMessage('UserProcessor attend une instance de');
+
+        $this->processor->process(new stdClass(), new Delete());
+    }
+}