diff --git a/app/models/concerns/smooch_capi.rb b/app/models/concerns/smooch_capi.rb
index 291dc03433..2f51ed9a01 100644
--- a/app/models/concerns/smooch_capi.rb
+++ b/app/models/concerns/smooch_capi.rb
@@ -39,7 +39,9 @@ def capi_api_get_user_data(uid, payload)
     end
 
     def get_capi_uid(value)
-      "#{value.dig('metadata', 'display_phone_number')}:#{value.dig('contacts', 0, 'wa_id')}"
+      # Get WhatsApp phone and fallback to WhatsApp BSUID
+      user_id = value.dig('contacts', 0, 'wa_id') || value.dig('contacts', 0, 'user_id')
+      "#{value.dig('metadata', 'display_phone_number')}:#{user_id}"
     end
 
     def get_capi_message_text(message)
@@ -69,7 +71,8 @@ def store_capi_media(media_id, mime_type)
     def handle_capi_system_message(message)
       if message.dig('system', 'type') == 'user_changed_number'
         old_uid = "#{self.config['capi_phone_number']}:#{message['from']}"
-        new_uid = "#{self.config['capi_phone_number']}:#{message['system']['wa_id']}"
+        user_id = message['system']['wa_id'] || message['system']['user_id']
+        new_uid = "#{self.config['capi_phone_number']}:#{user_id}"
         TiplineSubscription.where(uid: old_uid).find_each do |subscription|
           subscription.uid = new_uid
           subscription.save!
diff --git a/test/models/concerns/smooch_capi_test.rb b/test/models/concerns/smooch_capi_test.rb
index 2a9f9d3277..89fc2eb193 100644
--- a/test/models/concerns/smooch_capi_test.rb
+++ b/test/models/concerns/smooch_capi_test.rb
@@ -164,6 +164,16 @@ def teardown
     assert_equal 'message:appUser', preprocessed_message[:trigger]
   end
 
+  test 'should preprocess incoming text and fallback to user_id' do
+    payload = JSON.parse(@incoming_text_message_payload.clone)
+    payload['entry'][0]['changes'][0]['value']['contacts'][0]['wa_id'] = nil
+    payload['entry'][0]['changes'][0]['value']['contacts'][0]['user_id'] = 'id:654321'
+    preprocessed_message = Bot::Smooch.preprocess_message(payload.to_json)
+    # Verify _id and authId include user_id when wa_id is nil
+    assert_equal "123456:id:654321", preprocessed_message.dig('appUser', '_id')
+    assert_equal "123456:id:654321", preprocessed_message.dig('messages', 0, 'authorId')
+  end
+
   test 'should preprocess message delivery event' do
     preprocessed_message = Bot::Smooch.preprocess_message(@message_delivery_payload)
     assert_equal @uid, preprocessed_message.dig('appUser', '_id')