TestingCatalog reported on November 1 that a hidden label on Anthropic's Mythos webpage named version 5.5. It embedded public posts describing the supposed change, including a post by Chetaslua about hidden headings and image descriptions. Those posts are evidence of a claim, not proof that a new model is available.

What we could check now

On November 3 we fetched Anthropic's current Mythos page directly. It describes Mythos 5.1 and trusted access for vetted organizations; our saved page did not contain a Mythos 5.5 label. The current Fable page likewise describes Fable 5.1 availability. This check cannot reconstruct an earlier page or establish whether a reported label was briefly present.

Direct access to the original Chubby post returned 403 during our review. TestingCatalog reproduces related posts, but we did not authenticate their screenshots or independently capture the alleged earlier webpage. Reposts of the same image do not supply independent confirmation.

A label is not a launch

Neither a reported webpage string nor an impressive output identifies the model behind a response. Claims of Fable 5.5 routing, a joint release, launch timing, specifications, access and prices remain unconfirmed. We have not assigned the rumored versions existing Fable or Mythos prices or benchmark scores.

Our 35/100 rumor score is a coarse assessment of sourcing limitations, not a probability of release. Watch for an official announcement and documentation for the exact variant before making deployment decisions. The image is newly generated conceptual artwork, not a leaked screenshot.