diff --git a/src/Form/Service/ParticipantFieldOptionsProvider.php b/src/Form/Service/ParticipantFieldOptionsProvider.php
index 4bfad1c..4a7cee0 100644
--- a/src/Form/Service/ParticipantFieldOptionsProvider.php
+++ b/src/Form/Service/ParticipantFieldOptionsProvider.php
@@ -10,11 +10,13 @@ use App\BusProNet\Model\Pickup;
 use App\BusProNet\Model\Service;
 use App\BusProNet\Utility\DirectionMapper;
 use App\Form\Model\BookingDto;
+use App\Form\Model\RoomSelectionDto;
 use App\Form\Service\Abstract\AbstractFieldOptionsProvider;
 use App\Form\Service\Factory\ParticipantRoomChoiceLoaderFactory;
 use App\Service\BookingPriceCalculatorService;
 use App\Service\InsuranceService;
 use App\Service\ServiceAvailabilityCalculator;
+use App\Validator\Constraints\RoomSelection;
 
 /**
  * Provides dynamic field options for participant form fields.
@@ -119,35 +121,35 @@ class ParticipantFieldOptionsProvider extends AbstractFieldOptionsProvider
         // Room assignment field provider (available for both create and edit workflows)
         $this->fieldOptionProviders['assignedRoomId'] = function (BookingDto $bookingDto, int $participantIndex, array $options = []) {
             $choiceLoader = null;
-            $disabled = false;
+            $singleChoice = false;
 
             if (BookingDto::MODE_CREATE === $bookingDto->getMode()) {
-                // Create context: use selected rooms from step 1
-                $choiceLoader = $this->roomChoiceLoaderFactory->createForCreate(
-                    $bookingDto->getSelectedRooms()
+                // Create context: use selected rooms from step 1, filtered by participant age
+                $filteredRooms = $this->filterRoomsByParticipantAge(
+                    $bookingDto->getSelectedRooms(),
+                    $bookingDto,
+                    $participantIndex
                 );
-                // Disable when only one room type selected (auto-assigned)
-                $disabled = 1 === count($bookingDto->getSelectedRooms());
+                $choiceLoader = $this->roomChoiceLoaderFactory->createForCreate($filteredRooms);
+                $singleChoice = 1 === count($filteredRooms);
             } elseif (BookingDto::MODE_EDIT === $bookingDto->getMode()) {
                 // Edit context: use already-booked rooms from booking
                 $choiceLoader = $this->roomChoiceLoaderFactory->createForEdit(
                     $bookingDto->booking->rooms
                 );
-                // Disable when only one room in booking (no reassignment needed)
-                $disabled = 1 === count($bookingDto->booking->rooms);
+                $singleChoice = 1 === count($bookingDto->booking->rooms);
             }
 
             return [
                 'label' => 'Zimmer',
-                'placeholder' => 'Nicht zugeordnet',
+                // No placeholder when only one room available - the only option is pre-selected
+                'placeholder' => $singleChoice ? false : 'Nicht zugeordnet',
                 // Use factory to create context-aware choice loader that:
                 // - Shows only available rooms for this participant
                 // - Excludes rooms already assigned to other participants
                 // - Respects room capacity and booking constraints
+                // - Filters Baby rooms for participants over 2 years old
                 'choice_loader' => $choiceLoader,
-                // Make field read-only when only one room type is available
-                // Room is auto-assigned or cannot be changed, no user choice needed
-                'disabled' => $disabled,
             ];
         };
 
@@ -540,6 +542,54 @@ class ParticipantFieldOptionsProvider extends AbstractFieldOptionsProvider
         // ];
     }
 
+    /**
+     * Filters room selections by participant age constraints.
+     *
+     * Baby rooms (code 'Baby') are only available for participants aged 2 years or younger.
+     * Other room types are available for all participants regardless of age.
+     *
+     * @param RoomSelectionDto[] $roomSelections   Array of room selections from Step 1
+     * @param BookingDto         $bookingDto       The booking DTO containing participant and travel data
+     * @param int                $participantIndex Index of the participant to evaluate
+     *
+     * @return RoomSelectionDto[] Filtered array of room selections available for this participant
+     */
+    private function filterRoomsByParticipantAge(array $roomSelections, BookingDto $bookingDto, int $participantIndex): array
+    {
+        $participant = $bookingDto->getParticipant($participantIndex);
+
+        // If no participant or no date of birth, return all rooms (field visibility handles this case)
+        if (null === $participant || null === $participant->dateOfBirth) {
+            return $roomSelections;
+        }
+
+        // Calculate participant's age at travel start date
+        $age = $participant->getAge($bookingDto->travel->dateFrom);
+        if (null === $age) {
+            return $roomSelections;
+        }
+
+        // Get available rooms from travel data to look up room codes
+        $availableRooms = $bookingDto->travel->getAvailableRooms();
+
+        return array_filter($roomSelections, function (RoomSelectionDto $roomSelection) use ($availableRooms, $age) {
+            $room = $availableRooms[$roomSelection->roomId] ?? null;
+
+            // Exclude rooms not found in travel data to avoid validation issues
+            if (null === $room) {
+                return false;
+            }
+
+            // Baby rooms only available for participants 2 years or younger
+            if (RoomSelection::BABY_ROOM_CODE === $room->code) {
+                return $age <= 2;
+            }
+
+            // All other rooms available for all ages
+            return true;
+        });
+    }
+
     /**
      * Filters rental services by selected skipass duration.
      *