diff --git a/src/main/kotlin/com/android/trisolarisserver/controller/BookingFlow.kt b/src/main/kotlin/com/android/trisolarisserver/controller/BookingFlow.kt
index f1ec6d6..dbdf994 100644
--- a/src/main/kotlin/com/android/trisolarisserver/controller/BookingFlow.kt
+++ b/src/main/kotlin/com/android/trisolarisserver/controller/BookingFlow.kt
@@ -7,16 +7,20 @@ import com.android.trisolarisserver.controller.dto.BookingCheckInRequest
 import com.android.trisolarisserver.controller.dto.BookingCheckOutRequest
 import com.android.trisolarisserver.controller.dto.BookingCreateRequest
 import com.android.trisolarisserver.controller.dto.BookingCreateResponse
+import com.android.trisolarisserver.controller.dto.BookingLinkGuestRequest
 import com.android.trisolarisserver.controller.dto.BookingNoShowRequest
 import com.android.trisolarisserver.controller.dto.RoomStayPreAssignRequest
 import com.android.trisolarisserver.db.repo.BookingRepo
+import com.android.trisolarisserver.db.repo.GuestDocumentRepo
 import com.android.trisolarisserver.db.repo.GuestRepo
+import com.android.trisolarisserver.db.repo.GuestRatingRepo
 import com.android.trisolarisserver.models.booking.BookingStatus
 import com.android.trisolarisserver.models.booking.TransportMode
 import com.android.trisolarisserver.models.room.RoomStay
 import com.android.trisolarisserver.models.room.RateSource
 import com.android.trisolarisserver.models.property.Role
 import com.android.trisolarisserver.repo.AppUserRepo
+import com.android.trisolarisserver.repo.GuestVehicleRepo
 import com.android.trisolarisserver.repo.PropertyRepo
 import com.android.trisolarisserver.repo.RoomRepo
 import com.android.trisolarisserver.repo.RoomStayRepo
@@ -44,7 +48,10 @@ class BookingFlow(
     private val roomStayRepo: RoomStayRepo,
     private val appUserRepo: AppUserRepo,
     private val propertyRepo: PropertyRepo,
-    private val roomBoardEvents: RoomBoardEvents
+    private val roomBoardEvents: RoomBoardEvents,
+    private val guestVehicleRepo: GuestVehicleRepo,
+    private val guestRatingRepo: GuestRatingRepo,
+    private val guestDocumentRepo: GuestDocumentRepo
 ) {
 
     @PostMapping
@@ -111,6 +118,32 @@ class BookingFlow(
         )
     }
 
+    @PostMapping("/{bookingId}/link-guest")
+    @ResponseStatus(HttpStatus.NO_CONTENT)
+    @Transactional
+    fun linkGuest(
+        @PathVariable propertyId: UUID,
+        @PathVariable bookingId: UUID,
+        @AuthenticationPrincipal principal: MyPrincipal?,
+        @RequestBody request: BookingLinkGuestRequest
+    ) {
+        requireMember(propertyAccess, propertyId, principal)
+        val booking = requireBooking(propertyId, bookingId)
+        val guest = guestRepo.findById(request.guestId).orElseThrow {
+            ResponseStatusException(HttpStatus.NOT_FOUND, "Guest not found")
+        }
+        if (guest.property.id != propertyId) {
+            throw ResponseStatusException(HttpStatus.BAD_REQUEST, "Guest not in property")
+        }
+        val previous = booking.primaryGuest
+        booking.primaryGuest = guest
+        booking.updatedAt = OffsetDateTime.now()
+        bookingRepo.save(booking)
+        if (previous != null && previous.id != guest.id && isPlaceholderGuest(previous) && isSafeToDelete(previous)) {
+            guestRepo.delete(previous)
+        }
+    }
+
     @PostMapping("/{bookingId}/check-in")
     @ResponseStatus(HttpStatus.CREATED)
     @Transactional
@@ -345,4 +378,21 @@ class BookingFlow(
         return allowed.contains(mode)
     }
 
+    private fun isPlaceholderGuest(guest: com.android.trisolarisserver.models.booking.Guest): Boolean {
+        return guest.phoneE164.isNullOrBlank() &&
+            guest.name.isNullOrBlank() &&
+            guest.nationality.isNullOrBlank() &&
+            guest.addressText.isNullOrBlank() &&
+            guest.signaturePath.isNullOrBlank()
+    }
+
+    private fun isSafeToDelete(guest: com.android.trisolarisserver.models.booking.Guest): Boolean {
+        val id = guest.id ?: return false
+        if (bookingRepo.countByPrimaryGuestId(id) > 0) return false
+        if (guestVehicleRepo.existsByGuestId(id)) return false
+        if (guestDocumentRepo.existsByGuestId(id)) return false
+        if (guestRatingRepo.existsByGuestId(id)) return false
+        return true
+    }
+
 }
diff --git a/src/main/kotlin/com/android/trisolarisserver/controller/dto/BookingDtos.kt b/src/main/kotlin/com/android/trisolarisserver/controller/dto/BookingDtos.kt
index a2ccce9..c06cdf1 100644
--- a/src/main/kotlin/com/android/trisolarisserver/controller/dto/BookingDtos.kt
+++ b/src/main/kotlin/com/android/trisolarisserver/controller/dto/BookingDtos.kt
@@ -32,6 +32,10 @@ data class BookingCreateResponse(
     val expectedCheckOutAt: String?
 )
 
+data class BookingLinkGuestRequest(
+    val guestId: UUID
+)
+
 data class BookingCheckOutRequest(
     val checkOutAt: String? = null,
     val notes: String? = null