diff --git a/config/services.yaml b/config/services.yaml
index 9647068..d5e698e 100644
--- a/config/services.yaml
+++ b/config/services.yaml
@@ -45,3 +45,18 @@ when@test:
             autowire: true
             autoconfigure: true
             public: true
+
+        App\Service\Sync\ComposantSyncStrategy:
+            autowire: true
+            autoconfigure: true
+            public: true
+
+        App\Service\Sync\PieceSyncStrategy:
+            autowire: true
+            autoconfigure: true
+            public: true
+
+        # App\Service\ModelTypeSyncService:
+        #     autowire: true
+        #     autoconfigure: true
+        #     public: true
diff --git a/src/Service/Sync/PieceSyncStrategy.php b/src/Service/Sync/PieceSyncStrategy.php
new file mode 100644
index 0000000..32618eb
--- /dev/null
+++ b/src/Service/Sync/PieceSyncStrategy.php
@@ -0,0 +1,238 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Service\Sync;
+
+use App\DTO\SyncConfirmation;
+use App\DTO\SyncExecutionResult;
+use App\DTO\SyncPreviewResult;
+use App\Entity\CustomField;
+use App\Entity\CustomFieldValue;
+use App\Entity\ModelType;
+use App\Entity\Piece;
+use App\Entity\PieceProductSlot;
+use App\Entity\SkeletonProductRequirement;
+use App\Enum\ModelCategory;
+use Doctrine\ORM\EntityManagerInterface;
+use Symfony\Component\DependencyInjection\Attribute\AutoconfigureTag;
+
+#[AutoconfigureTag('app.sync_strategy')]
+class PieceSyncStrategy implements SyncStrategyInterface
+{
+    public function __construct(
+        private readonly EntityManagerInterface $em,
+    ) {}
+
+    public function supports(ModelType $modelType): bool
+    {
+        return ModelCategory::PIECE === $modelType->getCategory();
+    }
+
+    public function preview(ModelType $modelType, array $newStructure): SyncPreviewResult
+    {
+        $pieces = $this->em->getRepository(Piece::class)->findBy(['typePiece' => $modelType]);
+
+        $proposedProducts     = $newStructure['products'] ?? [];
+        $proposedCustomFields = $newStructure['customFields'] ?? [];
+
+        $addedProductSlots   = 0;
+        $deletedProductSlots = 0;
+        $addedCfValues       = 0;
+        $deletedCfValues     = 0;
+
+        // Map proposed products by (typeProductId, position) keys
+        $proposedProductKeys = [];
+        foreach ($proposedProducts as $pp) {
+            $proposedProductKeys[$pp['typeProductId'].'|'.$pp['position']] = true;
+        }
+
+        // Map proposed custom fields by orderIndex
+        $proposedCfByOrder = [];
+        foreach ($proposedCustomFields as $pcf) {
+            $proposedCfByOrder[$pcf['orderIndex']] = $pcf;
+        }
+
+        // Get existing custom fields for this model type
+        $existingFields = $this->em->getRepository(CustomField::class)->findBy(
+            ['typePiece' => $modelType],
+            ['orderIndex' => 'ASC']
+        );
+        $existingCfByOrder = [];
+        foreach ($existingFields as $field) {
+            $existingCfByOrder[$field->getOrderIndex()] = $field;
+        }
+
+        // Count custom field additions/deletions (definition-level, affects all pieces)
+        $cfAdded   = 0;
+        $cfDeleted = 0;
+        foreach ($proposedCfByOrder as $orderIndex => $pcf) {
+            if (!isset($existingCfByOrder[$orderIndex])) {
+                ++$cfAdded;
+            }
+        }
+        foreach ($existingCfByOrder as $orderIndex => $ef) {
+            if (!isset($proposedCfByOrder[$orderIndex])) {
+                ++$cfDeleted;
+            }
+        }
+
+        foreach ($pieces as $piece) {
+            // Product slots
+            $productSlots        = $this->em->getRepository(PieceProductSlot::class)->findBy(['piece' => $piece]);
+            $existingProductKeys = [];
+            foreach ($productSlots as $slot) {
+                $key                       = ($slot->getTypeProduct()?->getId() ?? '').'|'.$slot->getPosition();
+                $existingProductKeys[$key] = true;
+            }
+            foreach ($proposedProductKeys as $key => $_) {
+                if (!isset($existingProductKeys[$key])) {
+                    ++$addedProductSlots;
+                }
+            }
+            foreach ($existingProductKeys as $key => $_) {
+                if (!isset($proposedProductKeys[$key])) {
+                    ++$deletedProductSlots;
+                }
+            }
+
+            // Custom field values
+            $addedCfValues += $cfAdded;
+            $deletedCfValues += $cfDeleted;
+        }
+
+        $itemCount = count($pieces);
+
+        return new SyncPreviewResult(
+            modelTypeId: $modelType->getId(),
+            category: 'piece',
+            itemCount: $itemCount,
+            additions: [
+                'productSlots'      => $addedProductSlots,
+                'customFieldValues' => $addedCfValues,
+            ],
+            deletions: [
+                'productSlots'      => $deletedProductSlots,
+                'customFieldValues' => $deletedCfValues,
+            ],
+        );
+    }
+
+    public function execute(ModelType $modelType, SyncConfirmation $confirmation): SyncExecutionResult
+    {
+        $pieces = $this->em->getRepository(Piece::class)->findBy(['typePiece' => $modelType]);
+
+        // Load skeleton requirements
+        $productReqs  = $this->em->getRepository(SkeletonProductRequirement::class)->findBy(['modelType' => $modelType]);
+        $customFields = $this->em->getRepository(CustomField::class)->findBy(
+            ['typePiece' => $modelType],
+            ['orderIndex' => 'ASC']
+        );
+
+        // Map requirements by (typeProductId, position)
+        $productReqKeys = [];
+        foreach ($productReqs as $req) {
+            $productReqKeys[$req->getTypeProduct()->getId().'|'.$req->getPosition()] = $req;
+        }
+
+        $addedProductSlots   = 0;
+        $deletedProductSlots = 0;
+        $addedCfValues       = 0;
+        $deletedCfValues     = 0;
+        $itemsUpdated        = 0;
+
+        foreach ($pieces as $piece) {
+            $changed = false;
+
+            // --- Product slots ---
+            $productSlotEntities  = $this->em->getRepository(PieceProductSlot::class)->findBy(['piece' => $piece]);
+            $existingProductSlots = [];
+            foreach ($productSlotEntities as $slot) {
+                $key                        = ($slot->getTypeProduct()?->getId() ?? '').'|'.$slot->getPosition();
+                $existingProductSlots[$key] = $slot;
+            }
+
+            // Add missing product slots
+            foreach ($productReqKeys as $key => $req) {
+                if (!isset($existingProductSlots[$key])) {
+                    $slot = new PieceProductSlot();
+                    $slot->setPiece($piece);
+                    $slot->setTypeProduct($req->getTypeProduct());
+                    $slot->setPosition($req->getPosition());
+                    if (null !== $req->getFamilyCode()) {
+                        $slot->setFamilyCode($req->getFamilyCode());
+                    }
+                    $this->em->persist($slot);
+                    ++$addedProductSlots;
+                    $changed = true;
+                }
+            }
+
+            // Delete orphaned product slots
+            if ($confirmation->confirmDeletions) {
+                foreach ($existingProductSlots as $key => $slot) {
+                    if (!isset($productReqKeys[$key])) {
+                        $piece->removeProductSlot($slot);
+                        $this->em->remove($slot);
+                        ++$deletedProductSlots;
+                        $changed = true;
+                    }
+                }
+            }
+
+            // --- Custom field values ---
+            $existingValues = $this->em->getRepository(CustomFieldValue::class)->findBy([
+                'piece' => $piece,
+            ]);
+
+            $existingByFieldId = [];
+            foreach ($existingValues as $cfv) {
+                $existingByFieldId[$cfv->getCustomField()->getId()] = $cfv;
+            }
+
+            // Add missing custom field values
+            foreach ($customFields as $cf) {
+                if (!isset($existingByFieldId[$cf->getId()])) {
+                    $cfv = new CustomFieldValue();
+                    $cfv->setCustomField($cf);
+                    $cfv->setPiece($piece);
+                    $cfv->setValue('');
+                    $this->em->persist($cfv);
+                    ++$addedCfValues;
+                    $changed = true;
+                }
+            }
+
+            // Delete orphaned custom field values
+            if ($confirmation->confirmDeletions) {
+                $fieldIds = array_map(fn (CustomField $cf) => $cf->getId(), $customFields);
+                foreach ($existingValues as $cfv) {
+                    if (!in_array($cfv->getCustomField()->getId(), $fieldIds, true)) {
+                        $this->em->remove($cfv);
+                        ++$deletedCfValues;
+                        $changed = true;
+                    }
+                }
+            }
+
+            if ($changed) {
+                $piece->incrementVersion();
+                ++$itemsUpdated;
+            }
+        }
+
+        $this->em->flush();
+
+        return new SyncExecutionResult(
+            itemsUpdated: $itemsUpdated,
+            additions: [
+                'productSlots'      => $addedProductSlots,
+                'customFieldValues' => $addedCfValues,
+            ],
+            deletions: [
+                'productSlots'      => $deletedProductSlots,
+                'customFieldValues' => $deletedCfValues,
+            ],
+        );
+    }
+}
diff --git a/tests/Api/Service/PieceSyncStrategyTest.php b/tests/Api/Service/PieceSyncStrategyTest.php
new file mode 100644
index 0000000..22ae5ee
--- /dev/null
+++ b/tests/Api/Service/PieceSyncStrategyTest.php
@@ -0,0 +1,103 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Tests\Api\Service;
+
+use App\DTO\SyncConfirmation;
+use App\Entity\SkeletonProductRequirement;
+use App\Enum\ModelCategory;
+use App\Service\Sync\PieceSyncStrategy;
+use App\Tests\AbstractApiTestCase;
+
+/**
+ * @internal
+ */
+class PieceSyncStrategyTest extends AbstractApiTestCase
+{
+    private PieceSyncStrategy $strategy;
+
+    protected function setUp(): void
+    {
+        parent::setUp();
+        $this->strategy = static::getContainer()->get(PieceSyncStrategy::class);
+    }
+
+    public function testSupportsPieceCategory(): void
+    {
+        $mt = $this->createModelType('Piece Cat', 'PC-001', ModelCategory::PIECE);
+        $this->assertTrue($this->strategy->supports($mt));
+    }
+
+    public function testPreviewDetectsNewProductSlot(): void
+    {
+        $mt          = $this->createModelType('Piece Cat', 'PC-001', ModelCategory::PIECE);
+        $productType = $this->createModelType('Product Type', 'PT-001', ModelCategory::PRODUCT);
+        $this->createPiece('P1', 'P1-REF', $mt);
+
+        $result = $this->strategy->preview($mt, [
+            'products'     => [['typeProductId' => $productType->getId(), 'position' => 0]],
+            'customFields' => [],
+        ]);
+
+        $this->assertSame(1, $result->itemCount);
+        $this->assertSame(1, $result->additions['productSlots']);
+    }
+
+    public function testExecuteAddsProductSlots(): void
+    {
+        $mt          = $this->createModelType('Piece Cat', 'PC-001', ModelCategory::PIECE);
+        $productType = $this->createModelType('Product Type', 'PT-001', ModelCategory::PRODUCT);
+        $piece       = $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();
+
+        $result = $this->strategy->execute($mt, new SyncConfirmation());
+
+        $this->assertSame(1, $result->itemsUpdated);
+        $this->assertSame(1, $result->additions['productSlots']);
+
+        $em->refresh($piece);
+        $this->assertSame(2, $piece->getVersion());
+        $this->assertCount(1, $piece->getProductSlots());
+    }
+
+    public function testExecuteDeletesWithConfirmation(): void
+    {
+        $mt          = $this->createModelType('Piece Cat', 'PC-001', ModelCategory::PIECE);
+        $productType = $this->createModelType('Product Type', 'PT-001', ModelCategory::PRODUCT);
+        $piece       = $this->createPiece('P1', 'P1-REF', $mt);
+        $this->createPieceProductSlot($piece, $productType, null, null, 0);
+
+        $result = $this->strategy->execute($mt, new SyncConfirmation(confirmDeletions: true));
+        $this->assertSame(1, $result->deletions['productSlots']);
+    }
+
+    public function testExecuteIsIdempotent(): void
+    {
+        $mt          = $this->createModelType('Piece Cat', 'PC-001', ModelCategory::PIECE);
+        $productType = $this->createModelType('Product Type', 'PT-001', ModelCategory::PRODUCT);
+        $piece       = $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();
+
+        $result1 = $this->strategy->execute($mt, new SyncConfirmation());
+        $this->assertSame(1, $result1->additions['productSlots']);
+
+        $em->refresh($piece);
+        $result2 = $this->strategy->execute($mt, new SyncConfirmation());
+        $this->assertSame(0, $result2->itemsUpdated);
+    }
+}