Claude Mythos

Evidence (7)

• 4Simon Willison·8/9/2026framework_update
  Claude Opus 5 system prompt explains export-control handling

  This item quotes part of the Claude Opus 5 system prompt, which instructs the model to answer accurately about the temporary suspension and later restoration of access to Claude Fable 5 and Claude Mythos 5 due to U.S. export controls. It also says the model should avoid speculation, point users to Anthropic’s statement, and check for newer information when possible.

• 7Simon Willison·7/28/2026research
  Claude finds new weaknesses in HAWK and reduced-round AES

  Anthropic says Claude Mythos Preview autonomously discovered improved attacks against two cryptographic targets: the post-quantum digital signature scheme HAWK and a reduced-round version of AES. The findings do not affect deployed production systems, but they show AI models can help uncover mathematical flaws in cryptographic algorithms, not just implementation bugs.

• 6Hacker News·6/27/2026research
  Post-Mythos Cybersecurity and the Limits of AI Vulnerability Hunting

  The article argues that Anthropic’s Claude Mythos Preview has been framed as a major cybersecurity breakthrough, but that its results are better understood as an incremental improvement over earlier models. It notes that benchmark wins and old-vulnerability findings may be impressive, yet they do not necessarily reflect realistic enterprise environments or fundamentally new attack capability. The main practical impact may be the ability of well-funded organizations to scale exhaustive vulnerability searches at higher cost.

• 8InfoQ·6/26/2026security
  Anthropic and 19 groups launch Akrites open-source security body

  The Linux Foundation has launched Akrites, a coordinated open-source security body backed by about 20 organizations including Anthropic, Google, Microsoft, AWS, OpenAI, and others. The initiative creates a shared incident response process to consolidate vulnerability findings, reduce duplicate reports, and help upstream fixes before disclosures.

• 9Anthropic News·6/9/2026model_release
  Anthropic launches Claude Fable 5 and Claude Mythos 5

  Anthropic introduced Claude Fable 5 as a safe-for-general-use model and Claude Mythos 5 as a restricted-access variant for cyberdefenders and infrastructure providers. The company says both models deliver state-of-the-art performance across software engineering, knowledge work, vision, and scientific research, while adding safeguards and lower pricing than prior offerings.

• 8Anthropic News·6/2/2026security
  Anthropic expands Project Glasswing to 150 more organizations

  Anthropic is expanding Project Glasswing, a security program that gives trusted organizations access to Claude Mythos Preview for scanning codebases for vulnerabilities. The new cohort includes about 150 organizations across more than 15 countries, with a focus on critical infrastructure sectors such as power, water, healthcare, communications, and hardware. The company also said it is releasing Claude Security and sharing internal tools with trusted security teams to help detect and fix vulnerabilities faster.

• 8Anthropic News·4/16/2026model_release
  Anthropic releases Claude Opus 4.7

  Anthropic has generally released Claude Opus 4.7, a new model that improves on Opus 4.6 in advanced software engineering, instruction following, long-running tasks, and image understanding. The launch also includes cyber safeguards that block prohibited or high-risk cybersecurity requests, while keeping pricing unchanged across Claude products and partner platforms.