sounds like Anthropic’s watermarking is MUCH more interesting than hiding invisible Unicode, as most people assumed.
the watermark is baked into the token selection itself!
at a high level:
normal Claude:
context → probability cloud + random sampling → token
watermarked Claude:
context → probability cloud + key/context-derived sampling → token
Anthropic confirmed they’re using a version of Google DeepMind’s SynthID-Text.
instead of pushing Claude toward some special set of words, the watermark changes the source of randomness used to choose between words Claude already considers plausible.
do that once and there’s basically nothing to see.
do it across hundreds or thousands of tokens and those choices accumulate into a statistical signature that someone with the key can recognize.
so the watermark isn’t attached to Claude’s output.
the output IS the watermark.
that’s why copy/pasting doesn’t remove anything. you copied the carrier signal itself. 🧬