This scheme has a fatal flaw, the same secret key is used for watermarking and detection. This means you need to trust that Anthropic: * Shows the real result

This scheme has a fatal flaw, the same secret key is used for watermarking and detection. This means you need to trust that Anthropic: * Shows the real result from their detector instead of manipulating them, you have no way to verify * Has good enough security to prevent a key leak * Rotates keys to reduce the impact of a leak (once a key is leaked anyone can rewrite text to look more/less claude generated and it becomes useless) * Will not secretly give watermark-less access to governments or high profile corporate users * Will not use multiple secret keys to track individual users. This one might be less realistic because embedding ~32 bits of signal would probably affect quality a lot more than 1 bit. And don't forget that the detection API will work as an oracle. If it detects your content you can send it to a different model and try again until it comes back clean.