diff --git a/src/tenants/tenants.service.ts b/src/tenants/tenants.service.ts
index 2bd6030..96cb197 100644
--- a/src/tenants/tenants.service.ts
+++ b/src/tenants/tenants.service.ts
@@ -69,16 +69,23 @@ export class TenantsService {
   }
 
   async create(dto: CreateTenantDto, userId?: string) {
-    const aliases = this.uniqueNormalizedHosts(dto.domains);
+    const slug = dto.slug.toLowerCase().trim();
+    const domain = this.normalizeDomain(dto.domain);
+    const aliases = this.uniqueNormalizedHosts(dto.domains).filter(
+      (host) => this.hostKey(host) !== this.hostKey(domain),
+    );
+
+    await this.assertSlugDomainAvailable({ slug, domain });
+
     try {
       const tenant = await this.prisma.$transaction(async (tx: any) => {
         const created = await tx.tenant.create({
           data: {
             product: dto.product,
-            slug: dto.slug.toLowerCase(),
+            slug,
             nameFa: dto.nameFa,
             nameEn: dto.nameEn,
-            domain: this.normalizeDomain(dto.domain),
+            domain,
             domains: aliases as unknown as Prisma.InputJsonValue,
             avatarUrl: dto.avatarUrl,
             primaryColor: dto.primaryColor,
@@ -140,8 +147,23 @@ export class TenantsService {
       throw new NotFoundException('نسخه یافت نشد');
     }
 
-    const nextAliases =
+    const nextDomain =
+      dto.domain !== undefined ? this.normalizeDomain(dto.domain) : before.domain;
+    const nextAliasesRaw =
       dto.domains !== undefined ? this.uniqueNormalizedHosts(dto.domains) : undefined;
+    const nextAliases =
+      nextAliasesRaw !== undefined
+        ? nextAliasesRaw.filter((host) => this.hostKey(host) !== this.hostKey(nextDomain))
+        : undefined;
+
+    if (dto.slug !== undefined || dto.domain !== undefined) {
+      await this.assertSlugDomainAvailable({
+        slug: dto.slug !== undefined ? dto.slug.toLowerCase().trim() : undefined,
+        domain: dto.domain !== undefined ? nextDomain : undefined,
+        excludeId: id,
+      });
+    }
+
     const aliasesChanged =
       nextAliases !== undefined &&
       JSON.stringify(this.uniqueNormalizedHosts(this.readDomains(before.domains))) !==
@@ -381,11 +403,52 @@ export class TenantsService {
     return `${Date.now()}`;
   }
 
+  private async assertSlugDomainAvailable(opts: {
+    slug?: string;
+    domain?: string;
+    excludeId?: string;
+  }) {
+    if (opts.slug) {
+      const bySlug = await this.prisma.tenant.findUnique({
+        where: { slug: opts.slug },
+        select: { id: true, nameFa: true, domain: true, slug: true },
+      });
+      if (bySlug && bySlug.id !== opts.excludeId) {
+        throw new ConflictException(
+          `slug «${opts.slug}» قبلاً برای نسخه «${bySlug.nameFa}» (${bySlug.domain}) ثبت شده است`,
+        );
+      }
+    }
+
+    if (opts.domain) {
+      const byDomain = await this.prisma.tenant.findUnique({
+        where: { domain: opts.domain },
+        select: { id: true, nameFa: true, domain: true, slug: true },
+      });
+      if (byDomain && byDomain.id !== opts.excludeId) {
+        throw new ConflictException(
+          `دامنه «${opts.domain}» قبلاً دامنهٔ اصلی نسخه «${byDomain.nameFa}» (slug: ${byDomain.slug}) است`,
+        );
+      }
+    }
+  }
+
   private handleUnique(error: unknown) {
     if (
       error instanceof Prisma.PrismaClientKnownRequestError &&
       error.code === 'P2002'
     ) {
+      const targets = Array.isArray(error.meta?.target)
+        ? (error.meta?.target as string[])
+        : [];
+      if (targets.includes('slug')) {
+        throw new ConflictException('slug تکراری است — این slug قبلاً برای نسخه دیگری ثبت شده');
+      }
+      if (targets.includes('domain')) {
+        throw new ConflictException(
+          'دامنه تکراری است — این دامنه قبلاً دامنهٔ اصلی نسخه دیگری است',
+        );
+      }
       throw new ConflictException('slug یا domain تکراری است');
     }
   }