fix: preserve email signature separator with empty line

app/services/messages/markdown_renderer_service.rb

@@ -42,7 +42,7 @@ class Messages::MarkdownRendererService
 
   def render_html
     markdown_renderer = BaseMarkdownRenderer.new
-    doc = CommonMarker.render_doc(@content, :DEFAULT, [:strikethrough])
+    doc = CommonMarker.render_doc(MarkdownSetextEscape.call(@content), :DEFAULT, [:strikethrough])
     markdown_renderer.render(doc)
   end
 

lib/chatwoot_markdown_renderer.rb

@@ -5,7 +5,7 @@ class ChatwootMarkdownRenderer
 
   def render_message(hardbreaks: false)
     markdown_renderer = BaseMarkdownRenderer.new(options: hardbreaks ? [:HARDBREAKS] : :DEFAULT)
-    doc = CommonMarker.render_doc(@content, :DEFAULT, [:strikethrough, :autolink])
+    doc = CommonMarker.render_doc(MarkdownSetextEscape.call(@content), :DEFAULT, [:strikethrough, :autolink])
     html = markdown_renderer.render(doc)
     render_as_html_safe(html)
   end

lib/markdown_setext_escape.rb

@@ -0,0 +1,15 @@
+# cmark parses a dashes/equals line sitting directly under a hard-break
+# backslash ("\" + newline) as a setext heading underline: the dashes vanish
+# into markup and the stray "\" renders as heading text. The reply editor
+# serializes an empty line above the "--" signature delimiter exactly that
+# way. Escaping the underline keeps it literal text (matching the dashboard,
+# which disables setext parsing), while intentional setext headings — no
+# trailing backslash — stay untouched. Stored content can be CRLF, so both
+# line endings are handled.
+module MarkdownSetextEscape
+  UNDERLINE_AFTER_HARD_BREAK = /\\\r?\n(?=(?:-+|=+)[ \t]*\r?(?:\n|\z))/
+
+  def self.call(content)
+    content.gsub(UNDERLINE_AFTER_HARD_BREAK) { |hard_break| "#{hard_break}\\" }
+  end
+end

spec/lib/chatwoot_markdown_renderer_spec.rb

@@ -84,6 +84,14 @@ RSpec.describe ChatwootMarkdownRenderer do
         expect(renderer.render_message.to_s).to eq("<p>Visit <a href=\"https://example.com\">https://example.com</a> for details</p>\n")
       end
     end
+
+    context 'with an empty line above the signature delimiter' do
+      let(:markdown_content) { "Answer\n\n\\\n--\n\nRegards" }
+
+      it 'keeps the delimiter and the empty line instead of rendering a setext heading' do
+        expect(rendered_message.to_s).to eq("<p>Answer</p>\n<p><br />\n--</p>\n<p>Regards</p>\n")
+      end
+    end
   end
 
   describe '#render_markdown_to_plain_text' do

spec/lib/markdown_setext_escape_spec.rb

@@ -0,0 +1,48 @@
+require 'rails_helper'
+
+RSpec.describe MarkdownSetextEscape do
+  describe '.call' do
+    it 'escapes the delimiter when an empty line sits directly above it' do
+      content = "Answer\n\n\\\n--\n\nRegards"
+      expect(described_class.call(content)).to eq("Answer\n\n\\\n\\--\n\nRegards")
+    end
+
+    it 'handles CRLF line endings' do
+      content = "Answer\r\n\r\n\\\r\n--\r\n\r\nRegards"
+      expect(described_class.call(content)).to eq("Answer\r\n\r\n\\\r\n\\--\r\n\r\nRegards")
+    end
+
+    it 'escapes equals underlines the same way' do
+      expect(described_class.call("Answer\n\n\\\n==\n\nRegards")).to eq("Answer\n\n\\\n\\==\n\nRegards")
+    end
+
+    it 'escapes only the underline when several empty lines precede the delimiter' do
+      content = "Answer\n\n\\\n\\\n--\n\nRegards"
+      expect(described_class.call(content)).to eq("Answer\n\n\\\n\\\n\\--\n\nRegards")
+    end
+
+    it 'escapes a delimiter at the end of the content' do
+      expect(described_class.call("Answer\n\n\\\n--")).to eq("Answer\n\n\\\n\\--")
+    end
+
+    it 'leaves a plain delimiter without a preceding empty line untouched' do
+      content = "Answer\n\n--\n\nRegards"
+      expect(described_class.call(content)).to eq(content)
+    end
+
+    it 'leaves hard breaks followed by regular text untouched' do
+      content = "Thanks \\\nSivin | Chatwoot"
+      expect(described_class.call(content)).to eq(content)
+    end
+
+    it 'leaves intentional setext headings untouched' do
+      content = "Title\n---\n\nBody"
+      expect(described_class.call(content)).to eq(content)
+    end
+
+    it 'leaves thematic breaks untouched' do
+      content = "para\n\n---\n\npara2"
+      expect(described_class.call(content)).to eq(content)
+    end
+  end
+end

spec/services/messages/markdown_renderer_service_spec.rb

@@ -362,6 +362,13 @@ RSpec.describe Messages::MarkdownRendererService, type: :service do
         result = described_class.new(content, channel_type).render
         expect(result).to include('<del>strikethrough text</del>')
       end
+
+      it 'keeps the signature delimiter when an empty line sits above it' do
+        content = "Answer\n\n\\\n--\n\nRegards"
+        result = described_class.new(content, channel_type).render
+        expect(result).to include("<p><br />\n--</p>")
+        expect(result).not_to include('<h2>')
+      end
     end
 
     context 'when channel is Channel::WebWidget' do