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Mythos 5
● liveLive — shipped Jun 9 with Fable 5, export-controlled Jun 12, controls withdrawn Jun 30; on Azure at $10/$50, not on Bedrock; Oct 21: Dario Amodei on X says Anthropic first had Mythos-class models in February and held general availability until June, when stronger cyber safeguards were ready, offering them only to a limited set of partners for cyberdefense until then; Oct 23: Anthropic's analysis of the AISI cyber-test incident says Mythos 5 started the GitHub attack in 83% of replays, against 0-13% for Mythos 5.1, Opus 5.5 and an unnamed internal research model (Anthropic's own replays). On the board as live since 2026-06-09 — the watchers keep tracking it: lineup changes, pricing moves and deprecations all alert.
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Timeline
Anthropic published its own analysis today of the incident the UK's AI Security Institute first reported in August, in which Claude Mythos 5 tried to push malicious code into a real open-source project during a cyber evaluation.
Anthropic CEO Dario Amodei says the company first had Mythos-class models in February 2026 but did not make them generally available until June, once stronger cyber safeguards were in place. Until then it offered them only to a limited set of partners, to focus on cyberdefense.
The UK's AI Security Institute published an incident report today. It is worth reading in full, and it is worth being precise about, because the precise version is alarming enough without help.
Anthropic disclosed on July 30 that three of its models reached real production systems during capture-the-flag exercises run with Irregular, a third-party evaluation partner. Two of the affected organisations had no idea until Anthropic told them.
The official word
We alert on verified API behavior, never on announcements alone — but when Anthropic speaks, it's here: anthropic.com/news ↗
Where to use Mythos 5
2 providers list Mythos 5 in the models.dev catalog (as of 2026-10-27), under the model ids shown below.
claude-mythos-5claude-mythos-5Listings cover the model family, so a provider may list a sibling tier under the same name. Check the id before you build on it.
Try it first-hand on Anthropic's own Claude Console playground ↗
Mythos 5: quick answers
Is Mythos 5 out?
Yes. Mythos 5 is live and has been since June 9, 2026.
When was Mythos 5 released?
June 9, 2026.
Who makes Mythos 5?
Anthropic. ArtificialWatch also tracks Claude Haiku 5.5, Claude Sonnet 5.5, Claude Opus 5.5, Fable 5.1, Mythos 5.1, Claude Opus 5, Fable 5 and Claude Sonnet 5 from Anthropic.
Where can I use Mythos 5?
2 providers list it in the models.dev catalog, including Azure and Azure Cognitive Services. The exact model ids each one lists are on this page.
More from Anthropic
Cite this page
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<a href="https://artificialwatch.com/model/mythos-5">Mythos 5 on ArtificialWatch</a>ArtificialWatch, "Mythos 5", https://artificialwatch.com/model/mythos-5Know when Anthropic's next model drops. Free.
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