Comment by tancop

The only one who decides if something gets flagged is Anthropic. There is no way to verify it independently because you need the same secret key used to create the watermark. I don't know about you but I always have a hard time trusting corporations to tell the truth.

Every watermark scheme is like that on some level. If you make it public (not even open source or downloadable, API access is enough) your enemies will use it as a detection oracle and spam small changes to a document until it passes the detector every time. If you keep it private and only give trusted organizations access then there is no way to prove to the public that you're not getting paid to flag specific content as AI and discredit the author.

But the biggest problem here is the way it can hurt output quality. Most LLMs (probably including Fable) are autoregressive so a couple tokens worth of "mistakes" caused by watermarking can derail the whole reasoning chain. That means you have to try again and spend more credits or silently get a worse answer than what you would get without the scheme. It's not a real problem in diffusion based image models where quality loss stays local.