What is Claude Mythos? And how to see it in action with Claude Fable 5 (opens in new tab)

On April 7, 2026, Claude Mythos Preview was officially announced, but it was apparently too dangerous to release. According to Anthropic, Claude Mythos represented a unique cybersecurity threat (they claimed that "the fallout—for economies, public safety, and national security—could be severe.") Instead of releasing Mythos to the general public, they spun up Project Glasswing, a cybersecurity initiative that also involved some big-name companies. The idea was that they'd be able to deploy Mythos