Update page.tsx

src/app/(staff)/staff/clients/[id]/page.tsx

@@ -51,12 +51,18 @@ export default async function StaffCustomerDetailsPage({
   });
   if (!customer) notFound();
 
-  // "Belongs to this business" is via the appointment relation — see
+  // "Belongs to this business" mirrors the Clients list query exactly
-  // docs/phase-5-summary.md, same reasoning as the clients list query.
+  // (see (staff)/staff/clients/page.tsx) — either a real appointment here,
-  const belongsToBusiness = await prisma.appointment.findFirst({
+  // or a registered client with no appointment anywhere yet (added via
-    where: { customerId: id, businessId: context.businessId },
+  // /staff/clients/add, or self-registered but never booked). Without the
-    select: { id: true },
+  // second branch, a client visible in the list because of that same
-  });
+  // broadening would 404 the moment staff actually clicked into them —
+  // confirmed live, this exact gap.
+  const [appointmentsHereCount, totalAppointmentCount] = await Promise.all([
+    prisma.appointment.count({ where: { customerId: id, businessId: context.businessId } }),
+    prisma.appointment.count({ where: { customerId: id } }),
+  ]);
+  const belongsToBusiness = appointmentsHereCount > 0 || (!customer.isGuest && totalAppointmentCount === 0);
   if (!belongsToBusiness) notFound();
 
   const [upcoming, past, cancelled, notesRaw, loyalty] = await Promise.all([