June 16, 2026
NEWSLETTER: Latest in AI, TikTok, Cybersecurity and “Anthropic’s Fable 5 and Mythos 5: From Launch…
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Nitin Garg
6 min read
Anthropic's Fable 5 and Mythos 5: From Launch to Shut down in Just Days
Trump Administration Announces AI Policy (June 2):
The Trump administration signed an executive order taking a more hands-off approach to AI cybersecurity regulation.
2(d) Within 30 days of the date of this order, the Secretary of the Treasury, in consultation with the National Cyber Director, the Secretary of War, through the Director of the National Security Agency (NSA), and the Secretary of Homeland Security, through the Director of CISA, shall form an AI cybersecurity clearinghouse, in voluntary collaboration with the AI industry and operators of critical infrastructure, that coordinates and deconflicts scanning for software vulnerabilities, discovers and validates such vulnerabilities, and coordinates and prioritizes remediation and distribution of vulnerability patches.
3(b) design a voluntary framework with AI developers through which developers would be able to:
(i) engage the Federal Government to determine whether model(s) under development meet the designation of "covered frontier model";
(ii) provide the Federal Government with access to covered frontier models, subject to appropriate confidentiality, cybersecurity, insider-risk, and intellectual-property protection, use, and nondisclosure requirements, for a period of up to 30 days before they plan to release such models to other trusted partners; and
(iii) collaborate with the Federal Government to select trusted partners that will have early access to covered frontier models to promote secure innovation and strengthen the cybersecurity of critical infrastructure.
3(c) Nothing in this section shall be construed to authorize the creation of a mandatory governmental licensing, preclearance, or permitting requirement for the development, publication, release, or distribution of new AI models, including frontier models.
Anthropic Releases a Series of Cybersecurity Announcements (June 2 — June 12):
1. Project Glasswing (June 2):
- Anthropic expanded Project Glasswing, its cybersecurity initiative powered by the restricted Claude Mythos Preview model.
- Growing access from roughly 50 initial partners to adding approximately 150 new organizations across more than 15 countries.
- The program now includes critical infrastructure providers in sectors such as power, water, healthcare, communications, and hardware, with partners collectively uncovering over 10,000 high- and critical-severity vulnerabilities.
- Anthropic says the initiative is helping prepare defenders for a future where Mythos-class AI cyber capabilities become widely available, while also accelerating vulnerability discovery, patching, penetration testing, and software security at global scale.
2. Cyber Threat Report (June 3):
- Anthropic analyzed 832 malicious accounts banned between March 2025 and March 2026 and found that cybercriminals are increasingly using AI for more advanced post-compromise activities such as malware development, account discovery, lateral movement, and privilege escalation. The company reported that the share of medium- and high-risk attackers using AI rose from 33% to 56% in just six months, while warning that AI is enabling less-skilled actors to conduct sophisticated attacks. Anthropic also argued that existing frameworks like MITRE ATT&CK no longer fully capture emerging AI-powered cyberattack techniques, particularly autonomous AI agents capable of executing multi-stage attacks with minimal human involvement. Which mean:
o Earlier attackers used AI for phishing emails, malware code generation & social engineering.
o Now, attackers can use AI for account discovery
- Finding admin accounts
- Finding privileged users
o Lateral movement
- Moving from one server to another
- Expanding control inside networks
o Privilege escalation
- Gaining administrator access
o Autonomous decision-making
- Choosing next attack steps
o AI is helping average attackers perform activities that previously required expert-level skills.
o Now even a low-skill attacker can now — gain access, ask AI what to do next, use AI-generated scripts & use AI-generated attack chains.
o Anthropic think — The real threat is not AI answering questions
- The real threat is AI agents that can now execute commands, make decisions, chain attack steps together, adapt to defenses & continue operating autonomously.
o Anthropic think — existing frameworks like MITRE ATT&CK track attacker techniques, but they don't fully describe autonomous AI-driven attacks e.g. AI decision-making, autonomous attack chains, multi-agent attacks….
o And that is the reason Anthropic is investing in project Glasswing.
o AI is reducing the skill barrier for advanced cyber operations.
3. Fable 5 / Mythos 5 Released Public Version (June 9):
- Anthropic released the public version of its Claude Mythos model as "Claude Fable 5" on June 9, bringing advanced cybersecurity capabilities to wider access, alongside "Claude Mythos 5" for trusted-access users.
- Anthropic launched Claude Fable 5, a "Mythos-class" model made safe for general use, with capabilities exceeding any previously released Claude model — state-of-the-art on nearly all benchmarks, with the biggest gains on long, complex tasks. In early testing, Stripe reported Fable 5 compressed months of engineering into days, completing a codebase-wide migration on a 50-million-line Ruby codebase in one day versus two months for a full team. Because of the risk profile, Fable 5 ships with new safety classifiers that automatically reroute certain cybersecurity, biology/chemistry, and distillation-related queries to Claude Opus 4.8 instead.
- Alongside it, Anthropic launched Claude Mythos 5 for a small group of cyber defenders and infrastructure providers — the same underlying model as Fable 5 but with safeguards lifted in some areas, deployed initially via Project Glasswing with the US government as an upgrade to Claude Mythos Preview, with the strongest cybersecurity capabilities of any model in the world.
- On the science side, using Mythos 5, Anthropic's internal protein design experts accelerated parts of the drug design process roughly 10x, with the model matching or beating skilled human operators on choosing binding sites and running design tools autonomously. Mythos 5 also conducted novel genomics research over a week of largely autonomous work, training a custom model on single-cell data from 138 species that outperformed a recent Science-published model despite being 100x smaller.
4. Fable 5 / Mythos 5 Suspended (June 12):
- Anthropic released Fable 5 (public) and Mythos 5 (restricted cyber/research version) on June 9 2026 and just three days later on June 12 2026, The US government issued an export control directive ordering Anthropic to suspend all access to Claude Fable 5 and Mythos 5 for any foreign national, including foreign Anthropic employees, citing national security concerns, which forced Anthropic to disable both models for all customers; access to other Anthropic models is unaffected.
Why Government ordered Anthropic to suspend Fable 5 and Mythos 5:
- Recent reporting suggests that researchers (reportedly including Amazon researchers, according to reports citing the Wall Street Journal) used prompts that got Fable 5 to identify some software vulnerabilities.
- Amazon security researchers reportedly tested Fable 5 and found a prompting technique that caused the model to reveal information useful for vulnerability discovery.
- Those findings were reportedly communicated through Amazon leadership and eventually reached senior U.S. officials and the White House.
- The U.S. government then issued the export-control directive restricting Fable 5 and Mythos 5 access.
- After this Anthropic publish its statement arguing:
o The reported issue was a narrow, non-universal jailbreak
o It exposed only simple, already known vulnerabilities
o Similar capability exists in other frontier models
We looked at what they're talking about, and it's nothing serious — just some minor, already-known bugs that basically any AI model could find, jailbreak or not. Other AI models like GPT-5.5 can do this too. We think this is an overreaction, and if every government did this every time someone found a small flaw, no company could ever release a new AI model.
Anthropic said : We are complying with the government's legal directive and are removing access to Fable 5 and Mythos 5 for all users. However, we disagree that the finding of a narrow potential jailbreak should be cause for recalling a commercial model deployed to hundreds of millions of people. If this standard was applied across the industry, we believe it would essentially halt all new model deployments for all frontier model providers.
We apologize for this disruption to our customers. We believe this is a misunderstanding and are working to restore access as soon as possible.
This controversy also comes after a disagreement between Anthropic and the Trump administration. Anthropic reportedly refused to allow its AI models to be used in fully autonomous weapons that could operate without human control. Because of this, the Pentagon reportedly viewed Anthropic as too risky for certain government uses and placed restrictions on its use. Now, with the new export controls on Fable 5 and Mythos 5, the government is effectively saying these models are also too sensitive or powerful to be freely available to foreign users.
https://x.com/PeteHegseth/status/2065897156226015690
This highlights the growing tension between promoting AI innovation and managing the risks posed by increasingly powerful frontier AI systems.
From Project Glasswing to Government Suspension: How Anthropic's most powerful AI models became the center of a national security debate in just 10 days.