diff --git a/src/main/kotlin/com/android/trisolarisserver/controller/Guests.kt b/src/main/kotlin/com/android/trisolarisserver/controller/Guests.kt
index 933c109..974e41b 100644
--- a/src/main/kotlin/com/android/trisolarisserver/controller/Guests.kt
+++ b/src/main/kotlin/com/android/trisolarisserver/controller/Guests.kt
@@ -44,6 +44,15 @@ class Guests(
         if (phone.isBlank()) {
             throw ResponseStatusException(HttpStatus.BAD_REQUEST, "phoneE164 required")
         }
+        val booking = bookingRepo.findById(request.bookingId).orElseThrow {
+            ResponseStatusException(HttpStatus.NOT_FOUND, "Booking not found")
+        }
+        if (booking.property.id != property.id) {
+            throw ResponseStatusException(HttpStatus.BAD_REQUEST, "Booking not in property")
+        }
+        if (booking.primaryGuest != null) {
+            throw ResponseStatusException(HttpStatus.CONFLICT, "Booking already linked to guest")
+        }
         val existing = guestRepo.findByPropertyIdAndPhoneE164(propertyId, phone)
         if (existing != null) {
             throw ResponseStatusException(HttpStatus.CONFLICT, "Guest already exists")
@@ -58,8 +67,11 @@ class Guests(
             addressText = request.addressText?.trim()?.ifBlank { null },
             updatedAt = now
         )
-        guestRepo.save(guest)
-        return setOf(guest).toResponse(guestVehicleRepo, guestRatingRepo).first()
+        val saved = guestRepo.save(guest)
+        booking.primaryGuest = saved
+        booking.updatedAt = now
+        bookingRepo.save(booking)
+        return setOf(saved).toResponse(guestVehicleRepo, guestRatingRepo).first()
     }
 
     @GetMapping("/search")
diff --git a/src/main/kotlin/com/android/trisolarisserver/controller/dto/OrgPropertyDtos.kt b/src/main/kotlin/com/android/trisolarisserver/controller/dto/OrgPropertyDtos.kt
index 2807a5d..953286f 100644
--- a/src/main/kotlin/com/android/trisolarisserver/controller/dto/OrgPropertyDtos.kt
+++ b/src/main/kotlin/com/android/trisolarisserver/controller/dto/OrgPropertyDtos.kt
@@ -51,6 +51,7 @@ data class GuestResponse(
 
 data class GuestCreateRequest(
     val phoneE164: String,
+    val bookingId: UUID,
     val name: String? = null,
     val nationality: String? = null,
     val addressText: String? = null