Autotitle conversations whose reply is wrapped in a markdown json fence

app/jobs/autotitle_conversation_job.rb

@@ -50,7 +50,7 @@ def usable_topic(response)
       return nil
     end
 
-    document = JSON.parse(response)
+    document = JSON.parse(unfenced(response))
     topic = document.is_a?(Hash) ? document["topic"] : nil
 
     if topic.is_a?(String) && topic.present?
@@ -64,6 +64,12 @@ def usable_topic(response)
     nil
   end
 
+  def unfenced(text)
+    return text unless text.is_a?(String)
+
+    text[/```(?:json)?\s*(.*?)\s*```/m, 1] || text
+  end
+
   def system_message
     <<~END
       You extract a 2-4 word topic from text. I will give the text of a chat. You reply with the topic of this chat,

test/jobs/autotitle_conversation_job_test.rb

@@ -35,6 +35,17 @@ class AutotitleConversationJobTest < ActiveJob::TestCase
     assert_equal "Claude Summary", conversation.reload.title
   end
 
+  test "a topic wrapped in a markdown json fence is still used" do
+    conversation = conversations(:hello_claude)
+    conversation.update!(title: nil)
+
+    TestClient::Anthropic.stub :text, "```json\n{ \"topic\": \"Vermont's capital\" }\n```" do
+      AutotitleConversationJob.perform_now(conversation.id)
+    end
+
+    assert_equal "Vermont's capital", conversation.reload.title, "The fence should be stripped before parsing the JSON"
+  end
+
   test "gemini conversations are titled through the same intent path" do
     conversation = conversations(:gemini_conversation)
     conversation.update!(title: nil)