How Claude's text watermarking works

Interesting. Here's the section of the EU Act that mandates this:

> Providers of AI systems, including general-purpose AI systems, generating synthetic audio, image, video or text content, shall ensure that the outputs of the AI system are marked in a machine-readable format and detectable as artificially generated or manipulated. Providers shall ensure their technical solutions are effective, interoperable, robust and reliable as far as this is technically feasible, taking into account the specificities and limitations of various types of content, the costs of implementation and the generally acknowledged state of the art, as may be reflected in relevant technical standards. This obligation shall not apply to the extent the AI systems perform an assistive function for standard editing or do not substantially alter the input data provided by the deployer or the semantics thereof, or where authorised by law to detect, prevent, investigate or prosecute criminal offences.

https://eur-lex.europa.eu/eli/reg/2024/1689/2026-07-27/eng

It definitely makes Pangram's job a bit easier.

We are very fortunate open source models have reached parity for virtually all non-coding use cases.

> Google DeepMind tested this impact by serving a model that used watermarking to a portion of their Gemini traffic and comparing thumbs-up and thumbs-down ratings. They found no statistically significant differences from the unwatermarked model. And in a controlled study, human raters comparing watermarked and unwatermarked answers side-by-side saw no difference in quality.

For some reason I had assumed testing this would be more sophisticated than just checking the thumbs up/down stats and user "vibes"

> We will soon be offering a watermark detection API. We’re in the process of working out the details of its implementation.

Dumb question - doesn't this defeat the purpose of a watermark? i.e., anyone who wants to avoid detection can simply run `while (has_watermark(text)) text = slightly_rewrite_with_non_anthropic_llm(text)` until it's gone? I feel I am missing the intent of the watermark if it is so easily defeated.

Opus 5 must be the pilot becuase it's writing style is so grating it has to be intentional. Let's hope they make it more subtle in the future.

I’d like to better understand the minimum text length to get a confident result, i would presume it would need to be quite long, perhaps > 1000 words to get an accurate result.

Yesterday https://news.ycombinator.com/item?id=49292932

Can anybody take a body of text and determine if it's from Claude or not? (Or if it's AI-generated or not)?

“How does affect Claude’s outputs?”

Is poor proofreading a form of watermarking? Clever, I suppose, but they should consider running posts through Sol for clarity.

Seems pretty easy to defeat by running text output through a random reworder process that would effectively repeat the same routine on low-stakes words, replacing them with similar ones. We learned this in high school, jumping through your paper and hitting random words with the thesaurus to 'sound smarter'

Anthropic: doing everything they can to own any output they produce/prevent scrubbing of association for them - except when it comes to the CEO's wife's porn funding attempt from Epstein :D https://www.wsj.com/tech/ai/claude-dario-amodei-wife-anthrop...