fix: Convert literal \n strings to newlines in API channel messages

app/services/messages/markdown_renderer_service.rb

@@ -9,7 +9,8 @@ class Messages::MarkdownRendererService
     'Channel::Line' => :render_line,
     'Channel::TwitterProfile' => :render_plain_text,
     'Channel::Sms' => :render_plain_text,
-    'Channel::TwilioSms' => :render_plain_text
+    'Channel::TwilioSms' => :render_plain_text,
+    'Channel::Api' => :render_api_message
   }.freeze
 
   def initialize(content, channel_type, channel = nil)
@@ -56,6 +57,11 @@ class Messages::MarkdownRendererService
     restore_multiple_newlines(result)
   end
 
+  def render_api_message
+    # Convert literal \n strings to actual newlines for API channel messages
+    @content.gsub('\\n', "\n")
+  end
+
   def render_whatsapp
     # Strip whitespace from whitespace-only lines to normalize newlines
     normalized_content = @content.gsub(/^[ \t]+$/m, '')

spec/services/messages/markdown_renderer_service_spec.rb

@@ -493,6 +493,31 @@ RSpec.describe Messages::MarkdownRendererService, type: :service do
         result = described_class.new(content, channel_type).render
         expect(result).to eq("- Item 1\n- Item 2")
       end
+
+      it 'converts literal \\n strings to actual newlines' do
+        content = 'Hi \\ntext message \\nwith line \\nbreak'
+        result = described_class.new(content, channel_type).render
+        expect(result).to eq("Hi \ntext message \nwith line \nbreak")
+      end
+
+      it 'handles multiple literal \\n in sequence' do
+        content = 'Line 1\\n\\n\\nLine 2'
+        result = described_class.new(content, channel_type).render
+        expect(result).to eq("Line 1\n\n\nLine 2")
+      end
+
+      it 'preserves markdown formatting while converting \\n' do
+        content = '**bold**\\n_italic_\\n`code`'
+        result = described_class.new(content, channel_type).render
+        expect(result).to eq("**bold**\n_italic_\n`code`")
+      end
+
+      it 'handles real-world API payload with literal \\n strings' do
+        content = 'Hi \\ntext message \\nwith line \\nbreak'
+        result = described_class.new(content, channel_type).render
+        expect(result).to eq("Hi \ntext message \nwith line \nbreak")
+        expect(result).not_to include('\\n')
+      end
     end
 
     context 'when channel is Channel::TwitterProfile' do