The Claude web UI popped a modal up a few days ago advertising their new model to me. It was full of HTML tags that were escaped or otherwise not rendered so that the text was literally

  <b>Included in your plan limits until Jun 22</b> <br><br>Fable takes 2x the usage of Opus.
  <b> Switch models when a message is flagged</b><k <br> When safety measures flag a message, automatically switch to a different model to keep chatting. When off, your chat will pause instead. <a href="https://support.claude.com/en/articles/153636
  target="_blank" rel="noopener noreferrer" > Learn more</a>

...and this was presumably generated with the flagship model from the world's most prestigious LLM company.