diff --git a/Gemfile.lock b/Gemfile.lock
index eb8cd09c4..5c3b6877b 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -1,6 +1,6 @@
 GIT
   remote: https://github.com/basecamp/actiontext-lexical
-  revision: e6a47a42272d9e9250b47f6ea90caef8e8807c55
+  revision: d372bcc8ecc5e725086a68992387b86f80210605
   branch: prompts
   specs:
     actiontext-lexical (0.1.0)
diff --git a/app/models/concerns/mentions.rb b/app/models/concerns/mentions.rb
index 79ca110bd..86d017533 100644
--- a/app/models/concerns/mentions.rb
+++ b/app/models/concerns/mentions.rb
@@ -19,6 +19,10 @@ module Mentions
 
   private
     def scan_mentionees
+      mentionees_from_plain_text | mentionees_from_rich_text
+    end
+
+    def mentionees_from_plain_text
       scan_mentioned_handles.filter_map do |mention|
         mentionable_users.find { |user| user.mentionable_handles.include?(mention) }
       end
@@ -28,6 +32,14 @@ module Mentions
       mentionable_content.scan(/(?<!\w)@(\w+)/).flatten.uniq(&:downcase)
     end
 
+    def mentionees_from_rich_text
+      mentionees_from_attachments & mentionable_users
+    end
+
+    def mentionees_from_attachments
+      rich_text_associations.flat_map { send(it.name)&.body&.attachments&.collect { it.attachable } }.compact
+    end
+
     def mentionable_users
       collection.users
     end
diff --git a/test/models/concerns/mentions_test.rb b/test/models/concerns/mentions_test.rb
index f7454a322..006d77ec0 100644
--- a/test/models/concerns/mentions_test.rb
+++ b/test/models/concerns/mentions_test.rb
@@ -5,7 +5,7 @@ class MentionsTest < ActiveSupport::TestCase
     Current.session = sessions(:david)
   end
 
-  test "create mentions when creating messages" do
+  test "create mentions from plain text mentions" do
     assert_difference -> { Mention.count }, +1 do
       perform_enqueued_jobs only: Mention::CreateJob do
         collections(:writebook).cards.create title: "Cleanup", description: "Did you finish up with the cleanup, @david?"
@@ -13,6 +13,27 @@ class MentionsTest < ActiveSupport::TestCase
     end
   end
 
+  test "create mentions from rich text mentions" do
+    assert_difference -> { Mention.count }, +1 do
+      perform_enqueued_jobs only: Mention::CreateJob do
+        attachment = ActionText::Attachment.from_attachable(users(:david))
+        collections(:writebook).cards.create title: "Cleanup", description: "Did you finish up with the cleanup, #{attachment.to_html}?"
+      end
+    end
+  end
+
+  test "can't mention users that don't have access to the collection" do
+    collections(:writebook).update! all_access: false
+    collections(:writebook).accesses.revoke_from(users(:david))
+
+    assert_no_difference -> { Mention.count }, +1 do
+      perform_enqueued_jobs only: Mention::CreateJob do
+        attachment = ActionText::Attachment.from_attachable(users(:david))
+        collections(:writebook).cards.create title: "Cleanup", description: "Did you finish up with the cleanup, #{attachment.to_html}?"
+      end
+    end
+  end
+
   test "mentionees are added as watchers of the card" do
     perform_enqueued_jobs only: Mention::CreateJob do
       card = collections(:writebook).cards.create title: "Cleanup", description: "Did you finish up with the cleanup @kevin?"