diff --git a/lib/auth.ts b/lib/auth.ts
index 5a2cec7..c5d50ee 100644
--- a/lib/auth.ts
+++ b/lib/auth.ts
@@ -1,9 +1,24 @@
-import NextAuth from 'next-auth'
+import NextAuth, { DefaultSession } from 'next-auth'
 import { PrismaAdapter } from '@auth/prisma-adapter'
 import Credentials from 'next-auth/providers/credentials'
 import bcrypt from 'bcryptjs'
 import { prisma } from '@/lib/db'
 
+// NextAuth type augmentation — session.user.role için
+declare module 'next-auth' {
+  interface Session {
+    user: {
+      role?: string
+    } & DefaultSession['user']
+  }
+}
+
+declare module 'next-auth/jwt' {
+  interface JWT {
+    role?: string
+  }
+}
+
 export const { handlers, auth, signIn, signOut } = NextAuth({
   adapter: PrismaAdapter(prisma),
   providers: [
@@ -31,7 +46,7 @@ export const { handlers, auth, signIn, signOut } = NextAuth({
     },
     session({ session, token }) {
       if (token && session.user) {
-        session.user.role = token.role as string
+        session.user.role = token.role
       }
       return session
     },