Nextjs API auth.api.getSession session.user.role undefined

 // one of the API Check authentication
    const session = await auth.api.getSession({
      headers: request.headers,
    });

    if (!session?.user) {
      return NextResponse.json({ error: "Unauthorized" }, { status: 401 });
    }
    console.log("session", session);
    const userRole = session.user.role; <---- aways undefined
    if (userRole !== "admin") {
      return NextResponse.json({ error: "Forbidden" }, { status: 403 });
    }

//console.log
session {
  session: {
    ...
    userId: 'admin',
    impersonatedBy: undefined,
    id: 'B3E53U7JbzzuY2r1baDBV89imYnMjRMS'
  },
  user: {
    name: 'Admin User',
    email: 'admin@admin.com',
    emailVerified: true,
    image: 'https://images.unsplash.com/photo-1472099645785-5658abf4ff4e?w=400',
    createdAt: 2025-07-05T19:45:02.505Z,
    updatedAt: 2025-07-05T19:45:02.505Z,
    role: undefined,
    banned: undefined,
    banReason: undefined,
    banExpires: undefined,
    id: 'admin'
  }
}


//Auth Config
export const auth = betterAuth({
  database: prismaAdapter(prisma, {
    provider: "postgresql",
  }),
  plugins: [
    nextCookies(),
    apiKey({
      enableMetadata: true,
    }),
    openAPI(),
    admin({
      ac, // Access control system
      roles: {
        user: user,
        admin: adminRole,
      },
      defaultRole: "user", // Default role for new registrations
      adminRoles: ["admin"], // Only admin role has full admin privileges
      defaultBanReason: "Violation of platform terms and conditions",
      impersonationSessionDuration: 60 * 60 * 2, // 2 hours for admin impersonation
      bannedUserMessage:
        "Your account has been suspended. Please contact support for assistance.",
    }),
  ],
  },
  emailAndPassword: {
    enabled: true,
  }
});