diff --git a/config/services.yaml b/config/services.yaml
index d5e698e..282f9e3 100644
--- a/config/services.yaml
+++ b/config/services.yaml
@@ -56,7 +56,7 @@ when@test:
             autoconfigure: true
             public: true
 
-        # App\Service\ModelTypeSyncService:
-        #     autowire: true
-        #     autoconfigure: true
-        #     public: true
+        App\Service\ModelTypeSyncService:
+            autowire: true
+            autoconfigure: true
+            public: true
diff --git a/src/Controller/ModelTypeSyncController.php b/src/Controller/ModelTypeSyncController.php
new file mode 100644
index 0000000..17db51c
--- /dev/null
+++ b/src/Controller/ModelTypeSyncController.php
@@ -0,0 +1,74 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Controller;
+
+use App\DTO\SyncConfirmation;
+use App\Repository\ModelTypeRepository;
+use App\Service\ModelTypeSyncService;
+use Doctrine\ORM\EntityManagerInterface;
+use Symfony\Bundle\FrameworkBundle\Controller\AbstractController;
+use Symfony\Component\HttpFoundation\JsonResponse;
+use Symfony\Component\HttpFoundation\Request;
+use Symfony\Component\HttpFoundation\Response;
+use Symfony\Component\Routing\Attribute\Route;
+
+#[Route('/api/model_types/{id}')]
+final class ModelTypeSyncController extends AbstractController
+{
+    public function __construct(
+        private readonly ModelTypeRepository $modelTypes,
+        private readonly ModelTypeSyncService $syncService,
+        private readonly EntityManagerInterface $em,
+    ) {}
+
+    #[Route('/sync-preview', name: 'api_model_type_sync_preview', methods: ['POST'])]
+    public function preview(string $id, Request $request): JsonResponse
+    {
+        $this->denyAccessUnlessGranted('ROLE_GESTIONNAIRE');
+
+        $modelType = $this->modelTypes->find($id);
+
+        if (!$modelType) {
+            return new JsonResponse(
+                ['message' => 'Catégorie introuvable.'],
+                Response::HTTP_NOT_FOUND,
+            );
+        }
+
+        $body      = json_decode($request->getContent(), true);
+        $structure = $body['structure'] ?? [];
+
+        $result = $this->syncService->preview($modelType, $structure);
+
+        return new JsonResponse($result);
+    }
+
+    #[Route('/sync', name: 'api_model_type_sync', methods: ['POST'])]
+    public function sync(string $id, Request $request): JsonResponse
+    {
+        $this->denyAccessUnlessGranted('ROLE_GESTIONNAIRE');
+
+        $modelType = $this->modelTypes->find($id);
+
+        if (!$modelType) {
+            return new JsonResponse(
+                ['message' => 'Catégorie introuvable.'],
+                Response::HTTP_NOT_FOUND,
+            );
+        }
+
+        $body         = json_decode($request->getContent(), true);
+        $confirmation = new SyncConfirmation(
+            confirmDeletions: $body['confirmDeletions'] ?? false,
+            confirmTypeChanges: $body['confirmTypeChanges'] ?? false,
+        );
+
+        $result = $this->em->wrapInTransaction(function () use ($modelType, $confirmation) {
+            return $this->syncService->execute($modelType, $confirmation);
+        });
+
+        return new JsonResponse($result);
+    }
+}
diff --git a/src/Service/ModelTypeSyncService.php b/src/Service/ModelTypeSyncService.php
new file mode 100644
index 0000000..3d57c67
--- /dev/null
+++ b/src/Service/ModelTypeSyncService.php
@@ -0,0 +1,44 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Service;
+
+use App\DTO\SyncConfirmation;
+use App\DTO\SyncExecutionResult;
+use App\DTO\SyncPreviewResult;
+use App\Entity\ModelType;
+use App\Service\Sync\SyncStrategyInterface;
+use LogicException;
+use Symfony\Component\DependencyInjection\Attribute\AutowireIterator;
+
+class ModelTypeSyncService
+{
+    /** @param iterable<SyncStrategyInterface> $strategies */
+    public function __construct(
+        #[AutowireIterator('app.sync_strategy')]
+        private readonly iterable $strategies,
+    ) {}
+
+    public function preview(ModelType $modelType, array $newStructure): SyncPreviewResult
+    {
+        foreach ($this->strategies as $strategy) {
+            if ($strategy->supports($modelType)) {
+                return $strategy->preview($modelType, $newStructure);
+            }
+        }
+
+        throw new LogicException('No sync strategy found for category: '.$modelType->getCategory()->value);
+    }
+
+    public function execute(ModelType $modelType, SyncConfirmation $confirmation): SyncExecutionResult
+    {
+        foreach ($this->strategies as $strategy) {
+            if ($strategy->supports($modelType)) {
+                return $strategy->execute($modelType, $confirmation);
+            }
+        }
+
+        throw new LogicException('No sync strategy found for category: '.$modelType->getCategory()->value);
+    }
+}
diff --git a/tests/Api/Controller/ModelTypeSyncControllerTest.php b/tests/Api/Controller/ModelTypeSyncControllerTest.php
new file mode 100644
index 0000000..33a37b0
--- /dev/null
+++ b/tests/Api/Controller/ModelTypeSyncControllerTest.php
@@ -0,0 +1,267 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Tests\Api\Controller;
+
+use App\Entity\SkeletonPieceRequirement;
+use App\Entity\SkeletonProductRequirement;
+use App\Enum\ModelCategory;
+use App\Tests\AbstractApiTestCase;
+
+/**
+ * @internal
+ */
+class ModelTypeSyncControllerTest extends AbstractApiTestCase
+{
+    // ── sync-preview ────────────────────────────────────────────────
+
+    public function testPreviewReturnsNoImpactWhenNoItems(): void
+    {
+        $mt = $this->createModelType('Comp Cat', 'CC-001', ModelCategory::COMPONENT);
+
+        $client = $this->createGestionnaireClient();
+        $client->request('POST', '/api/model_types/'.$mt->getId().'/sync-preview', [
+            'json' => [
+                'structure' => [
+                    'pieces'        => [],
+                    'products'      => [],
+                    'subcomponents' => [],
+                    'customFields'  => [],
+                ],
+            ],
+        ]);
+
+        $this->assertResponseIsSuccessful();
+        $data = json_decode($client->getResponse()->getContent(), true);
+        $this->assertSame(0, $data['itemCount']);
+        $this->assertSame($mt->getId(), $data['modelTypeId']);
+    }
+
+    public function testPreviewDetectsNewSlots(): void
+    {
+        $mt        = $this->createModelType('Comp Cat', 'CC-001', ModelCategory::COMPONENT);
+        $pieceType = $this->createModelType('Piece Type', 'PT-001', ModelCategory::PIECE);
+        $this->createComposant('C1', $mt);
+
+        $client = $this->createGestionnaireClient();
+        $client->request('POST', '/api/model_types/'.$mt->getId().'/sync-preview', [
+            'json' => [
+                'structure' => [
+                    'pieces'        => [['typePieceId' => $pieceType->getId(), 'position' => 0]],
+                    'products'      => [],
+                    'subcomponents' => [],
+                    'customFields'  => [],
+                ],
+            ],
+        ]);
+
+        $this->assertResponseIsSuccessful();
+        $data = json_decode($client->getResponse()->getContent(), true);
+        $this->assertSame(1, $data['itemCount']);
+        $this->assertSame(1, $data['additions']['pieceSlots']);
+    }
+
+    public function testPreview403ForViewer(): void
+    {
+        $mt = $this->createModelType('Comp Cat', 'CC-001', ModelCategory::COMPONENT);
+
+        $client = $this->createViewerClient();
+        $client->request('POST', '/api/model_types/'.$mt->getId().'/sync-preview', [
+            'json' => ['structure' => []],
+        ]);
+
+        $this->assertResponseStatusCodeSame(403);
+    }
+
+    public function testPreview401ForUnauthenticated(): void
+    {
+        $mt = $this->createModelType('Comp Cat', 'CC-001', ModelCategory::COMPONENT);
+
+        $client = $this->createUnauthenticatedClient();
+        $client->request('POST', '/api/model_types/'.$mt->getId().'/sync-preview', [
+            'json' => ['structure' => []],
+        ]);
+
+        $this->assertResponseStatusCodeSame(401);
+    }
+
+    public function testPreview404ForUnknownModelType(): void
+    {
+        $client = $this->createGestionnaireClient();
+        $client->request('POST', '/api/model_types/nonexistent-id/sync-preview', [
+            'json' => ['structure' => []],
+        ]);
+
+        $this->assertResponseStatusCodeSame(404);
+    }
+
+    // ── sync ────────────────────────────────────────────────────────
+
+    public function testSyncAddsSlots(): void
+    {
+        $mt        = $this->createModelType('Comp Cat', 'CC-001', ModelCategory::COMPONENT);
+        $pieceType = $this->createModelType('Piece Type', 'PT-001', ModelCategory::PIECE);
+        $this->createComposant('C1', $mt);
+
+        // Add a skeleton requirement (simulates a PATCH that already happened)
+        $em  = $this->getEntityManager();
+        $req = new SkeletonPieceRequirement();
+        $req->setModelType($mt);
+        $req->setTypePiece($pieceType);
+        $req->setPosition(0);
+        $em->persist($req);
+        $em->flush();
+
+        $client = $this->createGestionnaireClient();
+        $client->request('POST', '/api/model_types/'.$mt->getId().'/sync', [
+            'json' => [
+                'confirmDeletions'   => false,
+                'confirmTypeChanges' => false,
+            ],
+        ]);
+
+        $this->assertResponseIsSuccessful();
+        $data = json_decode($client->getResponse()->getContent(), true);
+        $this->assertSame(1, $data['itemsUpdated']);
+        $this->assertSame(1, $data['additions']['pieceSlots']);
+    }
+
+    public function testSyncDeletesSlotsWithConfirmation(): void
+    {
+        $mt        = $this->createModelType('Comp Cat', 'CC-001', ModelCategory::COMPONENT);
+        $pieceType = $this->createModelType('Piece Type', 'PT-001', ModelCategory::PIECE);
+        $composant = $this->createComposant('C1', $mt);
+        $this->createComposantPieceSlot($composant, $pieceType, null, 1, 0);
+
+        // No skeleton requirements → slot is orphaned
+        $client = $this->createGestionnaireClient();
+        $client->request('POST', '/api/model_types/'.$mt->getId().'/sync', [
+            'json' => [
+                'confirmDeletions'   => true,
+                'confirmTypeChanges' => false,
+            ],
+        ]);
+
+        $this->assertResponseIsSuccessful();
+        $data = json_decode($client->getResponse()->getContent(), true);
+        $this->assertSame(1, $data['deletions']['pieceSlots']);
+    }
+
+    public function testSyncSkipsDeletionsWithoutConfirmation(): void
+    {
+        $mt        = $this->createModelType('Comp Cat', 'CC-001', ModelCategory::COMPONENT);
+        $pieceType = $this->createModelType('Piece Type', 'PT-001', ModelCategory::PIECE);
+        $composant = $this->createComposant('C1', $mt);
+        $this->createComposantPieceSlot($composant, $pieceType, null, 1, 0);
+
+        $client = $this->createGestionnaireClient();
+        $client->request('POST', '/api/model_types/'.$mt->getId().'/sync', [
+            'json' => [
+                'confirmDeletions'   => false,
+                'confirmTypeChanges' => false,
+            ],
+        ]);
+
+        $this->assertResponseIsSuccessful();
+        $data = json_decode($client->getResponse()->getContent(), true);
+        $this->assertSame(0, $data['deletions']['pieceSlots']);
+    }
+
+    public function testSync403ForViewer(): void
+    {
+        $mt = $this->createModelType('Comp Cat', 'CC-001', ModelCategory::COMPONENT);
+
+        $client = $this->createViewerClient();
+        $client->request('POST', '/api/model_types/'.$mt->getId().'/sync', [
+            'json' => ['confirmDeletions' => false, 'confirmTypeChanges' => false],
+        ]);
+
+        $this->assertResponseStatusCodeSame(403);
+    }
+
+    public function testSync404ForUnknownModelType(): void
+    {
+        $client = $this->createGestionnaireClient();
+        $client->request('POST', '/api/model_types/nonexistent-id/sync', [
+            'json' => ['confirmDeletions' => false, 'confirmTypeChanges' => false],
+        ]);
+
+        $this->assertResponseStatusCodeSame(404);
+    }
+
+    public function testSyncIsIdempotent(): void
+    {
+        $mt        = $this->createModelType('Comp Cat', 'CC-001', ModelCategory::COMPONENT);
+        $pieceType = $this->createModelType('Piece Type', 'PT-001', ModelCategory::PIECE);
+        $this->createComposant('C1', $mt);
+
+        $em  = $this->getEntityManager();
+        $req = new SkeletonPieceRequirement();
+        $req->setModelType($mt);
+        $req->setTypePiece($pieceType);
+        $req->setPosition(0);
+        $em->persist($req);
+        $em->flush();
+
+        $client = $this->createGestionnaireClient();
+
+        // First sync
+        $client->request('POST', '/api/model_types/'.$mt->getId().'/sync', [
+            'json' => ['confirmDeletions' => false, 'confirmTypeChanges' => false],
+        ]);
+        $this->assertResponseIsSuccessful();
+        $data1 = json_decode($client->getResponse()->getContent(), true);
+        $this->assertSame(1, $data1['itemsUpdated']);
+
+        // Second sync — idempotent, no changes
+        $client->request('POST', '/api/model_types/'.$mt->getId().'/sync', [
+            'json' => ['confirmDeletions' => false, 'confirmTypeChanges' => false],
+        ]);
+        $this->assertResponseIsSuccessful();
+        $data2 = json_decode($client->getResponse()->getContent(), true);
+        $this->assertSame(0, $data2['itemsUpdated']);
+    }
+
+    public function testSyncWorksForPieceCategory(): void
+    {
+        $mt          = $this->createModelType('Piece Cat', 'PC-001', ModelCategory::PIECE);
+        $productType = $this->createModelType('Prod Type', 'PD-001', ModelCategory::PRODUCT);
+        $this->createPiece('P1', 'P1-REF', $mt);
+
+        $em  = $this->getEntityManager();
+        $req = new SkeletonProductRequirement();
+        $req->setModelType($mt);
+        $req->setTypeProduct($productType);
+        $req->setPosition(0);
+        $em->persist($req);
+        $em->flush();
+
+        $client = $this->createGestionnaireClient();
+        $client->request('POST', '/api/model_types/'.$mt->getId().'/sync', [
+            'json' => ['confirmDeletions' => false, 'confirmTypeChanges' => false],
+        ]);
+
+        $this->assertResponseIsSuccessful();
+        $data = json_decode($client->getResponse()->getContent(), true);
+        $this->assertSame(1, $data['itemsUpdated']);
+        $this->assertSame(1, $data['additions']['productSlots']);
+    }
+
+    public function testSyncWorksForProductCategory(): void
+    {
+        $mt = $this->createModelType('Prod Cat', 'PD-001', ModelCategory::PRODUCT);
+        $this->createProduct('PR1', 'PR1-REF', $mt);
+        $this->createCustomField('CF1', 'text', typeProduct: $mt, orderIndex: 0);
+
+        $client = $this->createGestionnaireClient();
+        $client->request('POST', '/api/model_types/'.$mt->getId().'/sync', [
+            'json' => ['confirmDeletions' => false, 'confirmTypeChanges' => false],
+        ]);
+
+        $this->assertResponseIsSuccessful();
+        $data = json_decode($client->getResponse()->getContent(), true);
+        $this->assertSame(1, $data['itemsUpdated']);
+        $this->assertSame(1, $data['additions']['customFieldValues']);
+    }
+}