diff --git a/app/services/whatsapp/providers/base_service.rb b/app/services/whatsapp/providers/base_service.rb
index 9fd1f6267..4f8a6e489 100644
--- a/app/services/whatsapp/providers/base_service.rb
+++ b/app/services/whatsapp/providers/base_service.rb
@@ -54,6 +54,20 @@ class Whatsapp::Providers::BaseService
     message.save!
   end
 
+  # WhatsApp coexistence / username migration: a contact may become addressable only by a Business-Scoped
+  # User ID (BSUID, e.g. "BR.123..."), with no phone number available. The Cloud API requires a BSUID to be
+  # passed in the `recipient` field (with recipient_type: individual), NOT in `to`. Passing a BSUID in `to`
+  # returns HTTP 200 with a message id but the message is silently dropped: the "CC." prefix is stripped and
+  # the remainder is treated as a phone number (wa_id), which never resolves. Phone numbers keep using `to`.
+  # See: https://developers.facebook.com/documentation/business-messaging/whatsapp/business-scoped-user-ids/
+  def recipient_params(identifier)
+    if identifier.to_s.match?(RegexHelper::WHATSAPP_BSUID_REGEX)
+      { recipient_type: 'individual', recipient: identifier }
+    else
+      { to: identifier }
+    end
+  end
+
   def create_buttons(items)
     buttons = []
     items.each do |item|
diff --git a/app/services/whatsapp/providers/whatsapp_cloud_service.rb b/app/services/whatsapp/providers/whatsapp_cloud_service.rb
index d65c6cc62..09270a588 100644
--- a/app/services/whatsapp/providers/whatsapp_cloud_service.rb
+++ b/app/services/whatsapp/providers/whatsapp_cloud_service.rb
@@ -17,7 +17,8 @@ class Whatsapp::Providers::WhatsappCloudService < Whatsapp::Providers::BaseServi
     request_body = {
       messaging_product: 'whatsapp',
       recipient_type: 'individual', # Only individual messages supported (not group messages)
-      to: phone_number,
+      # BSUID -> `recipient`; phone number -> `to` (see recipient_params in the base provider).
+      **recipient_params(phone_number),
       type: 'template',
       template: template_body
     }
@@ -128,7 +129,7 @@ class Whatsapp::Providers::WhatsappCloudService < Whatsapp::Providers::BaseServi
       body: {
         messaging_product: 'whatsapp',
         context: whatsapp_reply_context(message),
-        to: phone_number,
+        **recipient_params(phone_number),
         text: { body: message.outgoing_content },
         type: 'text'
       }.to_json
@@ -148,7 +149,7 @@ class Whatsapp::Providers::WhatsappCloudService < Whatsapp::Providers::BaseServi
       body: {
         :messaging_product => 'whatsapp',
         :context => whatsapp_reply_context(message),
-        'to' => phone_number,
+        **recipient_params(phone_number),
         'type' => type,
         type.to_s => type_content
       }.to_json
@@ -243,7 +244,7 @@ class Whatsapp::Providers::WhatsappCloudService < Whatsapp::Providers::BaseServi
       headers: api_headers,
       body: {
         messaging_product: 'whatsapp',
-        to: phone_number,
+        **recipient_params(phone_number),
         interactive: payload,
         type: 'interactive'
       }.to_json
diff --git a/spec/services/whatsapp/providers/whatsapp_cloud_service_spec.rb b/spec/services/whatsapp/providers/whatsapp_cloud_service_spec.rb
index a94ba2e44..c409c9a69 100644
--- a/spec/services/whatsapp/providers/whatsapp_cloud_service_spec.rb
+++ b/spec/services/whatsapp/providers/whatsapp_cloud_service_spec.rb
@@ -227,6 +227,59 @@ describe Whatsapp::Providers::WhatsappCloudService do
     end
   end
 
+  describe 'when the recipient is a Business-Scoped User ID (BSUID)' do
+    # Meta requires a BSUID to be sent in the `recipient` field (with recipient_type: individual), not `to`.
+    let(:bsuid) { 'BR.13491208655302741918' }
+
+    it 'sends a text message via the recipient field instead of to' do
+      stub_request(:post, 'https://graph.facebook.com/v13.0/123456789/messages')
+        .with(
+          body: {
+            messaging_product: 'whatsapp',
+            context: nil,
+            recipient_type: 'individual',
+            recipient: bsuid,
+            text: { body: message.content },
+            type: 'text'
+          }.to_json
+        )
+        .to_return(status: 200, body: whatsapp_response.to_json, headers: response_headers)
+
+      expect(service.send_message(bsuid, message)).to eq 'message_id'
+    end
+
+    it 'sends a template via the recipient field instead of to' do
+      template_info = { name: 'test_template', namespace: 'test_namespace', lang_code: 'en_US', parameters: [] }
+      stub_request(:post, 'https://graph.facebook.com/v13.0/123456789/messages')
+        .with(body: hash_including({ messaging_product: 'whatsapp', recipient_type: 'individual', recipient: bsuid, type: 'template' }))
+        .to_return(status: 200, body: whatsapp_response.to_json, headers: response_headers)
+
+      expect(service.send_template(bsuid, template_info, message)).to eq 'message_id'
+    end
+
+    it 'sends an interactive message via the recipient field instead of to' do
+      interactive_message = create(:message, message_type: :outgoing, content: 'test', inbox: whatsapp_channel.inbox,
+                                             content_type: 'input_select',
+                                             content_attributes: { items: [{ title: 'Burito', value: 'Burito' }] })
+      stub_request(:post, 'https://graph.facebook.com/v13.0/123456789/messages')
+        .with(body: hash_including({ messaging_product: 'whatsapp', recipient_type: 'individual', recipient: bsuid, type: 'interactive' }))
+        .to_return(status: 200, body: whatsapp_response.to_json, headers: response_headers)
+
+      expect(service.send_message(bsuid, interactive_message)).to eq 'message_id'
+    end
+
+    it 'sends an attachment via the recipient field instead of to' do
+      attachment = message.attachments.new(account_id: message.account_id, file_type: :image)
+      attachment.file.attach(io: Rails.root.join('spec/assets/avatar.png').open, filename: 'avatar.png', content_type: 'image/png')
+
+      stub_request(:post, 'https://graph.facebook.com/v24.0/123456789/messages')
+        .with(body: hash_including({ messaging_product: 'whatsapp', recipient_type: 'individual', recipient: bsuid, type: 'image' }))
+        .to_return(status: 200, body: whatsapp_response.to_json, headers: response_headers)
+
+      expect(service.send_message(bsuid, message)).to eq 'message_id'
+    end
+  end
+
   describe '#sync_templates' do
     context 'when called' do
       it 'updated the message templates' do