Not exactly bulletproof, is it?

A successful detection result would indicate that Claude may have processed content. It would not prove that Claude was the original author, because users can submit human-created text, research, images, or files to Claude for summarizing, editing, translation, or proofreading.

Likewise, the absence of a watermark should not be treated as proof that a human wrote content. Older Claude models may not yet support marking, short text may contain too little material for reliable detection, and heavily edited output may lose its signal.