diff --git a/migrations/Version20260519175142.php b/migrations/Version20260519175142.php
new file mode 100644
index 0000000..6f89e01
--- /dev/null
+++ b/migrations/Version20260519175142.php
@@ -0,0 +1,38 @@
+<?php
+
+declare(strict_types=1);
+
+namespace DoctrineMigrations;
+
+use Doctrine\DBAL\Schema\Schema;
+use Doctrine\Migrations\AbstractMigration;
+use Doctrine\Migrations\Exception\MigrationException;
+
+final class Version20260519175142 extends AbstractMigration
+{
+    public function getDescription(): string
+    {
+        return 'Attach existing projects to Standard workflow (NOT NULL, RESTRICT)';
+    }
+
+    public function up(Schema $schema): void
+    {
+        $standardId = $this->connection->fetchOne("SELECT id FROM workflow WHERE name = 'Standard'");
+        if (!$standardId) {
+            throw new MigrationException('Workflow Standard introuvable.');
+        }
+
+        $this->addSql('ALTER TABLE project ADD COLUMN workflow_id INT DEFAULT NULL');
+        $this->addSql("UPDATE project SET workflow_id = {$standardId}");
+        $this->addSql('ALTER TABLE project ALTER COLUMN workflow_id SET NOT NULL');
+        $this->addSql('ALTER TABLE project ADD CONSTRAINT FK_project_workflow FOREIGN KEY (workflow_id) REFERENCES workflow (id) ON DELETE RESTRICT NOT DEFERRABLE');
+        $this->addSql('CREATE INDEX IDX_project_workflow ON project (workflow_id)');
+    }
+
+    public function down(Schema $schema): void
+    {
+        $this->addSql('ALTER TABLE project DROP CONSTRAINT FK_project_workflow');
+        $this->addSql('DROP INDEX IDX_project_workflow');
+        $this->addSql('ALTER TABLE project DROP COLUMN workflow_id');
+    }
+}