diff --git a/src/BusProNet/DataProcessor/BookingDataProcessor.php b/src/BusProNet/DataProcessor/BookingDataProcessor.php
index c7e20cd..2686e34 100644
--- a/src/BusProNet/DataProcessor/BookingDataProcessor.php
+++ b/src/BusProNet/DataProcessor/BookingDataProcessor.php
@@ -8,6 +8,7 @@ use App\BusProNet\Constants;
 use App\BusProNet\Model\Booking;
 use App\BusProNet\Model\Travel;
 use App\BusProNet\Utility\DirectionMapper;
+use App\BusProNet\XmlLoader\AgencyLoader;
 use App\Form\Model\BankAccountDto;
 use App\Form\Model\BookingDto;
 use App\Form\Model\ParticipantDto;
@@ -42,11 +43,12 @@ class BookingDataProcessor
      *
      * IMPORTANT: Address handling for edit mode
      * - ParticipantDto::fromPersonalData() clones address objects to prevent shared references
-     * - First participant's address is NOT auto-populated from applicant
-     * - Template uses placeholders to show applicant's address as hints
-     * - This prevents address data from being inadvertently modified during form binding
+     * - For normal bookings, participant[0]'s missing address/dimensions are filled from the
+     *   applicant (same person in normal bookings, but BPN may omit fields in <teilnehmer>)
+     * - For internal agency bookings, this copy is skipped: the applicant is a customer, not
+     *   the first participant, so copying applicant data into participant[0] would be incorrect
      */
-    public function createBookingDtoFromBooking(Booking $booking, Travel $travel): BookingDto
+    public function createBookingDtoFromBooking(Booking $booking, Travel $travel, bool $isInternalAgencyBooking = false): BookingDto
     {
         $dto = new BookingDto($travel, $booking->hotelId);
 
@@ -68,11 +70,12 @@ class BookingDataProcessor
             $participantData = ParticipantDto::fromPersonalData($participant);
             $participantData->index = $index;
 
-            // First participant (applicant): copy data from applicant if participant data is empty
-            // BPN API may return full data only in <anmelder> but minimal/empty data in <teilnehmer id="1">
-            if (0 === $index) {
+            // For normal bookings, applicant === participant[0]: copy address and body dimensions
+            // from applicant when BPN returns full data only in <anmelder> and minimal data in
+            // <teilnehmer id="1">. Skipped for internal agency bookings where the applicant is
+            // a customer (a different entity from the first traveler).
+            if (0 === $index && false === $isInternalAgencyBooking) {
                 // Copy address if first participant has no street (indicating empty/incomplete address)
-                // This allows applicant and first participant to be different people with different addresses
                 $isEmpty = null === $participantData->address
                     || null === $participantData->address->street
                     || '' === trim($participantData->address->street);
diff --git a/src/Service/BookingEditDataLoader.php b/src/Service/BookingEditDataLoader.php
index 01b1544..0a7ad73 100644
--- a/src/Service/BookingEditDataLoader.php
+++ b/src/Service/BookingEditDataLoader.php
@@ -138,13 +138,21 @@ class BookingEditDataLoader
         $this->travelDataService->patchAvailabilities($travelData, $availabilities);
         $this->travelDataService->patchMutability($travelData, $mutableData);
 
-        $formData = $this->bookingDataProcessor->createBookingDtoFromBooking($bookingData, $travelData);
-
-        // Set agency code for internal agency detection (used by field state conditions)
-        $formData->agencyCode = null !== $bookingData->agencyId
+        // Resolve agency code before building the DTO so the internal-agency flag can be
+        // passed to createBookingDtoFromBooking, preventing applicant data from being
+        // copied into participant[0] for agency bookings where they are different people.
+        $agencyCode = null !== $bookingData->agencyId
             ? $this->agencyLoader->loadById($bookingData->agencyId)?->code
             : null;
 
+        $formData = $this->bookingDataProcessor->createBookingDtoFromBooking(
+            $bookingData,
+            $travelData,
+            AgencyLoader::INTERNAL_AGENCY_CODE === $agencyCode,
+        );
+
+        $formData->agencyCode = $agencyCode;
+
         // Set original fingerprint BEFORE applying draft, so dirty detection
         // compares against the original API data (not the draft-modified data)
         $formData->originalFingerprint = $this->fingerprintService->generateFingerprint($formData, true);
diff --git a/src/Service/BookingEditSubmitGuard.php b/src/Service/BookingEditSubmitGuard.php
index f092a45..89db821 100644
--- a/src/Service/BookingEditSubmitGuard.php
+++ b/src/Service/BookingEditSubmitGuard.php
@@ -34,7 +34,7 @@ class BookingEditSubmitGuard
      */
     public function reconcileImmutableCategories(BookingDto $workingDto, Booking $freshBooking): bool
     {
-        $baselineDto = $this->bookingDataProcessor->createBookingDtoFromBooking($freshBooking, $workingDto->travel);
+        $baselineDto = $this->bookingDataProcessor->createBookingDtoFromBooking($freshBooking, $workingDto->travel, $workingDto->isInternalAgencyBooking());
         // Booking-level D-4 cutoff used as submit-time safety net for rentals.
         $serviceCutoffReachedCondition = new TravelStartCutoffReachedCondition(
             TravelStartCutoffReachedCondition::DEFAULT_DAYS_BEFORE_START