Claude Fable 5.1 and Mythos 5.1: access, safeguards and deployment limits

Anthropic temporarily suspended both models after US export controls took effect on June 12, 2026, then restored access after those controls were lifted. Fable 5 returned to global users on July 1.

Anthropic now presents Mythos 5.1 as the vetted-access version of the September 2026 release, while Fable 5.1 is broadly available. Anthropic describes the two as the same underlying model with different safeguards and access paths.

Fable 5.1 is the broadly available version for coding and knowledge work. Mythos 5.1 uses a trusted-access program for vetted organizations because Anthropic applies stricter safeguards to higher-risk capabilities.

Anthropic says Fable 5.1 and Mythos 5.1 use the same underlying model. Fable 5.1 is generally available, while Mythos 5.1 is limited to trusted access programs with safeguards designed for cybersecurity and life-sciences work.

Anthropic's September announcement separates access by safeguard level. Fable 5.1 is generally available. Mythos 5.1 is available through trusted access programs for vetted organizations.

Deployment review should record which model and access path are in use, which organization-level permissions apply and which safeguards are active. Anthropic's public announcement does not describe every customer configuration.

Anthropic documents the earlier June suspension and July restoration for Fable 5 and Mythos 5. Its September 1 release now makes Fable 5.1 and Mythos 5.1 the current versions, with separate access paths.

Those records support a factual comparison of access rules and controls. They do not establish how every customer deployment is configured or how the models perform outside the published evaluations.