Ensure backwards compatibility with Trix

app/helpers/content_filters/remove_solo_unfurled_link_text.rb

@@ -1,4 +1,7 @@
 class ContentFilters::RemoveSoloUnfurledLinkText < ActionText::Content::Filter
+  TWITTER_DOMAINS = %w[ x.com twitter.com ]
+  TWITTER_DOMAIN_MAPPING = { "x.com" => "twitter.com" }
+
   def applicable?
     normalize_tweet_url(solo_unfurled_url) == normalize_tweet_url(content.to_plain_text)
   end
@@ -12,9 +15,6 @@ class ContentFilters::RemoveSoloUnfurledLinkText < ActionText::Content::Filter
   end
 
   private
-    TWITTER_DOMAINS = %w[ x.com twitter.com ]
-    TWITTER_DOMAIN_MAPPING = { "x.com" => "twitter.com" }
-
     def solo_unfurled_url
       ActionText::Attachment::OpengraphEmbed.from_node(unfurled_links.first)&.href if unfurled_links.size == 1
     end

app/helpers/content_filters/sanitize_tags.rb

@@ -1,4 +1,8 @@
 class ContentFilters::SanitizeTags < ActionText::Content::Filter
+  ALLOWED_TAGS = %w[ a abbr acronym address b big blockquote br cite code dd del dfn div dl dt em h1 h2 h3 h4 h5 h6 hr i ins kbd li ol
+    p pre samp small span strong sub sup time tt ul var ] + ContentFilters::EDITOR_FORMATTING_TAGS +
+    [ ActionText::Attachment.tag_name, "figure", "figcaption" ]
+
   def applicable?
     true
   end
@@ -8,10 +12,6 @@ class ContentFilters::SanitizeTags < ActionText::Content::Filter
   end
 
   private
-    ALLOWED_TAGS = %w[ a abbr acronym address b big blockquote br cite code dd del dfn div dl dt em h1 h2 h3 h4 h5 h6 hr i ins kbd li ol
-      p pre samp small span strong sub sup time tt ul var ] + ContentFilters::EDITOR_FORMATTING_TAGS +
-      [ ActionText::Attachment.tag_name, "figure", "figcaption" ]
-
     def not_allowed_tags_css_selector
       ALLOWED_TAGS.map { |tag| ":not(#{tag})" }.join("")
     end

app/helpers/rich_text_helper.rb

@@ -1,4 +1,6 @@
 module RichTextHelper
+  LEGACY_EMBED_SELECTOR = "action-text-attachment[content-type='#{ActionText::Attachment::OpengraphEmbed::OPENGRAPH_EMBED_CONTENT_TYPE}'][href]"
+
   def rich_text_data_actions
     # submitByKeyboard runs in the capture phase so it can submit on Enter
     # before the editor turns the keystroke into a newline
@@ -9,4 +11,17 @@ module RichTextHelper
     tag.lexxy_prompt trigger: "@", name: "mention", src: autocompletable_users_path(room_id: room.id),
       "remote-filtering": true, "empty-results": "No matches"
   end
+
+  # Trix-era opengraph embeds carry their details as node attributes, which
+  # the editor doesn't round-trip. Rendering them into the content attribute
+  # lets the editor preserve them like any embed it created itself.
+  def editable_body(message)
+    fragment = ActionText::Fragment.wrap(message.body.body_before_type_cast)
+
+    transformed = fragment.replace(LEGACY_EMBED_SELECTOR) do |node|
+      node.tap { |n| n["content"] = render_action_text_attachment(ActionText::Attachment.from_node(n)) }
+    end
+
+    ActionText::RichText.new(body: transformed.to_html)
+  end
 end