Which AI tools generate hidden unicode? I just pasted a random response from Gemini and ChatGPT to it and they did not have any. Supposedly Anthropic now has w

Which AI tools generate hidden unicode? I just pasted a random response from Gemini and ChatGPT to it and they did not have any. Supposedly Anthropic now has watermarking, but as I undestand it, it's not done by inserting hidden unicode characters.