# Mythos 5

> **TL;DR.** Claude Mythos 5 is Anthropic's restricted frontier model — the unrestricted sibling of [Claude Fable 5](https://www.

- **Category:** AI / Frontier Models / AI Safety
- **Stage:** nascent
- **Age:** 5 days
- **Origin date:** 2026-06-09
- **First detected:** 2026-06-13
- **Canonical URL:** https://earlyterms.com/term/mythos-5
- **Sources:** 8 primary URLs

## Definition

Claude Mythos 5 is Anthropic's restricted frontier model — the unrestricted sibling of [Claude Fable 5](https://www.anthropic.com/news/claude-fable-5-mythos-5) — offering the full Mythos-class capability set including offensive cybersecurity research, autonomous genomics work, and drug design without the safety fallbacks that constrain the public release.

Launched June 9, 2026 alongside Fable 5, Mythos 5 is accessible only through Project Glasswing: a US government-adjacent program serving vetted critical infrastructure operators, cyberdefenders, and select biology researchers. Both models cost $10/$50 per million tokens — but on June 12, a US Commerce Department export control order suspended global access to both after Anthropic received the directive at 5:21 PM ET.

## Analogy

Think of it as the unreleased master tape: same recording as the commercial release, but with none of the tracks muted.

## Why it's emerging now

On June 12, the US Commerce Department ordered Anthropic to suspend all access to Fable 5 and Mythos 5 globally — including for foreign national employees — citing a jailbreak technique. Anthropic complied immediately while publicly disputing the order as technically ungrounded, calling the jailbreak 'narrow and non-universal' and noting identical capabilities exist in OpenAI's GPT-5.5.

## Related terms

- *related:* Claude Fable 5
- *parent:* Claude Mythos
- *parent:* Claude Mythos Preview
- *parent:* Mythos-class
- *competitor:* Claude Opus 4.8
- *competitor:* GPT-5.5
- *related:* Project Glasswing
- *related:* AI Safety
- *related:* AI export controls
- *related:* jailbreak
- *parent:* frontier model
- *related:* killswitch

## Sources

1. [Anthropic — Claude Fable 5 and Mythos 5 launch announcement (Jun 9, 2026)](https://www.anthropic.com/news/claude-fable-5-mythos-5)
2. [Anthropic — Statement on US government directive to suspend access (Jun 12, 2026)](https://www.anthropic.com/news/fable-mythos-access)
3. [Anthropic — Project Glasswing: securing critical software for the AI era](https://www.anthropic.com/glasswing)
4. [Fortune — Anthropic releases its first Mythos-class model to the public (Jun 9, 2026)](https://fortune.com/2026/06/09/anthropic-releases-its-first-mythos-model-to-the-public/)
5. [Fortune — Anthropic disables Fable and Mythos following US export ban (Jun 13, 2026)](https://fortune.com/2026/06/13/anthropic-disables-fable-mythos-export-controls-national-security-threat/)
6. [TechCrunch — Anthropic's Claude Fable 5 is a version of Mythos the public can access (Jun 9, 2026)](https://techcrunch.com/2026/06/09/anthropics-claude-fable-5-is-a-version-of-mythos-the-public-can-access-today/)
7. [Cybersecurity Dive — Anthropic shares Mythos with 150 more organizations (Jun 2, 2026)](https://www.cybersecuritydive.com/news/ai-anthropic-claude-mythos-project-glasswing-expand/821714/)
8. [Vidoc Security — We reproduced Anthropic's Mythos findings with public models (Apr 17, 2026)](https://blog.vidocsecurity.com/blog/we-reproduced-anthropics-mythos-findings-with-public-models)

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