Those hidden markers will be very hard to hide in code review in an IDE which highlights invisible Unicode code points. For code, adding watermarks is likely to cause bugs. For text, Chinese models are as good - so just switching to them solves the issue.
I think, Anthropic doesn’t want to perform economic seppuku.

They want to check and control what the output is used for, IE who train on their output… The big US scum-corps are just tightening their ps*cho control regime (although most of us escapes them via Chinese open models)…

This should be legally mandatory by use in countries.

I think this is honestly one of those 100% vs >80% issues. I get that it’s very possible — maybe even easy — to subvert this, but we have had several SITTING POLITICIANS read a fucking AI prompt in the middle of their “big speech” and nobody bats an eye. If they add a measure to outputs that works automatically for 100% of outputs without the people reading it knowing, there’s no chance that it won’t allow you to determine whether or not many outputs are AI.