Every Fable 5.1 and Mythos 5.1 output now carries Anthropic's statistical text watermark, on every platform

Anthropic developer docs (corroborated by r/ClaudeAI and r/singularity threads)·high signalXBlueskyLinkedInCopy link

The content-provenance section of Anthropic's Fable 5.1 docs states that text generated by Fable 5.1 and Mythos 5.1 carries Anthropic's statistical text watermark on every platform where the model is available, and that images and video produced through the code execution tool carry signed C2PA Content Credentials when retrieved via the Files API. Anthropic says the watermark adds no tokens or hidden characters, carries no information about the user or organization, and needs no request changes. These are the first Claude models to ship with it; separate r/ClaudeAI and r/singularity threads flagged it within hours and the mod-bot TL;DR notes people are already discussing how to strip it.