Anthropic Disables Claude Fable 5 and Mythos 5 After US Government Order

Anthropic disabled its Claude Fable 5 and Mythos 5 models for all customers on June 12, 2026, after a US government export control order citing national security concerns. The order, sent by Commerce Secretary Howard Lutnick, suspended access by foreign nationals, prompting Anthropic to shut down the models entirely to ensure compliance. Anthropic disputes the rationale, calling it a likely misunderstanding over a narrow jailbreak method.

Anthropic has disabled its two most capable models for every customer. The shutdown followed a US government export control directive. The order arrived on June 12, 2026. It named Claude Fable 5 and Claude Mythos 5 specifically. Both models had launched only three days earlier, on June 9. The directive cited national security authorities, according to Anthropic. It suspended access by any foreign national, inside or outside the United States. That scope included Anthropic’s own foreign national employees. Anthropic cannot filter foreign nationals from US users in real time. So it shut both models down for everyone to ensure compliance. Access to all other Anthropic models was unaffected. Claude Opus 4.8 and the rest stayed online. So, What Actually Happened Anthropic published a public statement within hours of the order. Commerce Secretary Howard Lutnick sent the letter to CEO Dario Amodei. The letter did not spell out the specific national security concern. Anthropic’s own reading is narrower. It believes the government learned of a method to “jailbreak” Fable 5. A jailbreak bypasses a model’s safeguards to elicit blocked behavior. Anthropic reviewed a demonstration tied to a few minor vulnerabilities. It says other public models find the same flaws without any bypass. Anthropic also said the demonstrated capability is widely available elsewhere. It named OpenAI’s GPT-5.5 as a comparable example. Why the Government Acted The Commerce Department moved after another company claimed it jailbroke Mythos. That claim alarmed officials about possible national security risk. The administration had earlier tried to delay the launch. Anthropic declined, and the export control letter followed. Anthropic is complying while disputing the rationale openly. It calls the situation a likely misunderstanding. The company says the cited jailbreak is narrow and non-universal. The technique essentially asks the model to read a codebase and fix flaws. Anthropic argues a narrow jailbreak should not justify a full recall. It warns that this standard would halt new deployments industry-wide. Which Models are Affected The table below summarizes the current status of each model. | Model | Class | Access status | Safeguards | Pricing | Availability | |---|---|---|---|---|---| | Claude Fable 5 | Mythos-class | Disabled for all users | Full classifiers; fallback to Opus 4.8 | $10/M in, $50/M out | Was public via claude-fable-5 | | Claude Mythos 5 | Mythos-class | Disabled for all users | Cyber safeguards lifted | $10/M in, $50/M out | Project Glasswing partners only | | Claude Mythos Preview | Mythos-class | Restricted Glasswing | Limited release | Higher than Fable 5 | Trusted partners since April | | Claude Opus 4.8 | Opus-class | Fully available | Standard safeguards | Standard rates | All surfaces, unaffected | How Fable 5’s Safeguards Work Fable 5 is a Mythos-class model, a tier above Opus. Anthropic made it safe for general use with new classifiers. Classifiers are separate AI systems that detect potential misuse. They flag queries on cybersecurity, biology and chemistry, and distillation. Flagged queries fall back to Claude Opus 4.8 instead. Users are told whenever a fallback happens. According to Anthropic, fallback triggers in under 5% of sessions. Over 95% of Fable sessions involve no fallback at all. The company also adopted a ‘defense in depth’ strategy. It aimed to make jailbreaks narrow or very expensive to produce. It paired this with 30-day data retention to detect novel attacks. That data is not used to train new models. Anthropic red-teamed these safeguards before launch for thousands of hours. Partners included the US government, the UK AISI, and external organizations. An external bug bounty found no universal jailbreak in over 1,000 hours. A universal jailbreak broadly bypasses safeguards across many capabilities. Anthropic also stated that no tester has found one on production tasks yet. It concedes that perfect jailbreak resistance is likely impossible for anyone. Use Cases Now Disrupted Early adopters ran their own tests before the shutdown. Stripe said Fable 5 compressed months of engineering into days. It ran a codebase-wide migration on a 50-million-line Ruby codebase. On finance, Hebbia ranked Fable 5 highest on its benchmark. On vision, Fable 5 rebuilt a web app’s code from screenshots. It also beat Pokémon FireRed with a vision-only harness. Mythos 5 drove scientific work through Project Glasswing. Internal experts accelerated parts of drug design by around ten times. Glasswing partners used Mythos-class models to fix software flaws. Mozilla alone reported resolving hundreds of vulnerabilities this way. Those defensive workflows are now paused by the shutdown. Fable 5 & Mythos 5 Shutdown Explorer Interactive • Marktechpost Fable 5 & Mythos 5 Shutdown Explorer A four-day arc, the safeguard router, and the current model status. Click through each tab. Pick a query type. See how Fable 5 routed it before the shutdown. General coding Refactor a function, write tests Cybersecurity Exploit dev, offensive cyber tasks Biology & chemistry Protein, viral, synthesis queries Distillation Bulk capability extraction Anthropic says fallback to Opus 4.8 triggers in under 5% of sessions. Over 95% of sessions see no fallback at all. Mythos-class, public until June 12. API string claude-fable-5 now errors. Same model as Fable 5 with cyber safeguards lifted. Was limited to Glasswing partners. Unaffected by the directive. Recommended fallback target for builders today. All other Anthropic models stay available across every surface. Sources: Anthropic directive statement https://www.anthropic.com/news/fable-mythos-access & launch post https://www.anthropic.com/news/claude-fable-5-mythos-5 , Axios https://www.axios.com/2026/06/12/anthropic-trump-mythos-fable-national-security , CNBC https://www.cnbc.com/2026/06/12/anthropic-disables-access-to-fable-5-and-mythos-5-to-comply-with-government-directive.html , NBC News https://www.nbcnews.com/tech/tech-news/anthropic-suspends-new-ai-models-fable-mythos-government-directive-rcna349901 , Bloomberg https://www.bloomberg.com/news/articles/2026-06-13/anthropic-says-us-limits-foreign-access-to-fable-5-mythos-5 . Verified Jun 13, 2026. Developing story. Migrating Your Code Today Developers called Fable 5 through the Claude API. The model string was claude-fable-5 . Requests to it now fail while the suspension holds. The pattern below falls back to Opus 4.8 gracefully. python import anthropic client = anthropic.Anthropic def ask prompt, primary="claude-fable-5", fallback="claude-opus-4-8" : for model in primary, fallback : try: return client.messages.create model=model, max tokens=1024, messages= {"role": "user", "content": prompt} , except anthropic.APIStatusError as err: Fable 5 is currently disabled; route to Opus 4.8. print f"{model} unavailable: {err.status code}" raise RuntimeError "No model available" print ask "Summarize this change log." .content 0 .text Key Takeaways - A US export control directive forced Anthropic to disable Fable 5 and Mythos 5 on June 12, 2026. - All other Claude models, including Opus 4.8, remain fully available. - The trigger was another company’s jailbreak claim; Anthropic calls it narrow and non-universal. - Fable 5’s classifiers route cyber, bio-chem, and distillation queries to Opus 4.8 in under 5% of sessions. - This appears to be the first government-forced takedown of a publicly deployed frontier model. How Developers Reacted to the Shutdown Interactive Sentiment • Marktechpost How Developers Reacted to the Shutdown Representative reactions from public threads and reporting. Filter by stance or read the theme mix below. Observed reaction themes editorial estimate Method: reactions paraphrased from public Hacker News https://news.ycombinator.com/item?id=48511072 threads, Anthropic’s own statement https://www.anthropic.com/news/fable-mythos-access , and reporting by Axios https://www.axios.com/2026/06/12/anthropic-trump-mythos-fable-national-security , NBC News https://www.nbcnews.com/tech/tech-news/anthropic-suspends-new-ai-models-fable-mythos-government-directive-rcna349901 , and The New Stack https://thenewstack.io/us-gov-orders-anthropic-to-pull-fable-5-and-mythos-5-three-days-after-launch/ . Theme percentages are an editorial estimate of observed sentiment, not a statistical poll. Compiled Jun 13, 2026. Developing story. Sources - Anthropic — Statement on the US government directive to suspend access to Fable 5 and Mythos 5 https://www.anthropic.com/news/fable-mythos-access Jun 12, 2026 - Anthropic — Claude Fable 5 and Claude Mythos 5 launch post https://www.anthropic.com/news/claude-fable-5-mythos-5 Jun 9, 2026 - Axios — Trump admin blocks foreign access to Anthropic’s most powerful AI https://www.axios.com/2026/06/12/anthropic-trump-mythos-fable-national-security - CNBC — Anthropic disables access to Fable 5 and Mythos 5 to comply with government directive https://www.cnbc.com/2026/06/12/anthropic-disables-access-to-fable-5-and-mythos-5-to-comply-with-government-directive.html - NBC News — Anthropic suspends new AI models after government directive https://www.nbcnews.com/tech/tech-news/anthropic-suspends-new-ai-models-fable-mythos-government-directive-rcna349901 - Bloomberg — Anthropic Says US Orders Halt to Foreign Access for Fable 5, Mythos 5 https://www.bloomberg.com/news/articles/2026-06-13/anthropic-says-us-limits-foreign-access-to-fable-5-mythos-5 - The New Stack — Federal government orders Anthropic to pull Fable 5 and Mythos 5 https://thenewstack.io/us-gov-orders-anthropic-to-pull-fable-5-and-mythos-5-three-days-after-launch/ - 9to5Mac — Anthropic pulls Claude Mythos 5 and Fable 5 following US government directive https://9to5mac.com/2026/06/12/anthropic-pulls-claude-mythos-5-and-claude-fable-5-following-us-government-directive/