Is Claude Mythos 5.1 out yet?

What is Claude Mythos 5.1?

Claude Mythos 5.1 is a rumored, unannounced Anthropic model that would be the direct successor to Claude Mythos 5, the high-capability deployment released on July 1, 2026, after Anthropic split Claude into separate Fable and Mythos lines. According to a reported internal-portal note (June 22) and AI observer Andrew Curran, Anthropic finished training the successor roughly nine days after a US export-control suspension, and it could ship as Mythos 5.1 or Mythos 6 — or remain internal to accelerate self-improvement work. Anthropic has not confirmed any of this, so the model's existence and naming remain speculative.

Rumors from late June 2026 say training on the Mythos 5 successor is already complete, so expectations center on a more capable follow-up to Mythos 5, whose cybersecurity capabilities observers like Ethan Mollick described as living up to the hype. With the US having lifted restrictions on Anthropic's most powerful models in July 2026, some watchers expect a public release under the Mythos 5.1 or Mythos 6 name, though it may instead stay internal; no timing has been confirmed.

AI-assisted summary of the news and rumors tracked on this page, updated Jul 8, 2026- sources under News, leaks & rumors.

When is Claude Mythos 5.1 coming out?

Claude Mythos 5.1 is not out yet. Readers guessing here settle on an average of Aug 15, 2026, drawn from 3 guesses. OutYet.ai rechecks Anthropic's official release surfaces every minute and flips this page the moment access goes live. Last checked Aug 15, 2026.