Claude Fable 5.1 output carries text watermarks and C2PA Content Credentials
UpdateVerifiedAdded Sep 22, 2026
Text from Claude Fable 5.1 and Mythos 5.1 carries Anthropic's text watermark, and image, video and audio files produced via code execution carry C2PA Content Credentials when retrieved through the Files API. No request changes are needed.
Topics: LLMs, Developer tools
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More Claude Platform releases
Every Claude Platform release| Date | Release | Type |
|---|---|---|
| Sep 1 | Claude Fable 5.1 launches alongside Claude Mythos 5.1 with 1M token context GA | GA |
| Sep 1 | Prompt cache reads on Claude Fable 5.1 and Mythos 5.1 drop to $0.25 per MTok Pricing | Pricing |
| Sep 1 | Claude Fable 5.1 and Mythos 5.1 reject tool_choice any and tool Update | Update |
| Sep 1 | Claude Fable 5.1 thinking blocks only replay to the same or newer models Update | Update |
| Sep 1 | Per-message effort changes enter beta on the Claude API Beta | Beta |
| Sep 1 | Claude API adds turn-scoped system messages in beta Beta | Beta |
| Sep 1 | Claude API thinking.display adds an updates mode in beta Beta | Beta |
| Sep 1 | Claude Fable 5.1 and Mythos 5.1 require 30-day data retention Update | Update |
