Claude Mythos
claude-mythos-ac0c3610·15 events·first seen 29d agoAliases: Claude Mythos, Claude Mythos 5
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Anthropic releases system card for Claude Fable 5 and Claude Mythos 5
Anthropic has published a system card PDF for two new models, Claude Fable 5 and Claude Mythos 5, surfaced via Hacker News with 211 points. The system card is a primary safety and capability disclosure document accompanying a model release. The naming convention suggests these are new frontier-tier models from Anthropic, distinct from the existing Claude Opus/Sonnet/Haiku naming scheme.
Anthropic releases Claude Mythos 5 and Claude Fable 5 with unprecedented capability restrictions and safety tiers
Anthropic launched Claude Mythos 5, a restricted-access model capable of cracking previously secure software, and Claude Fable 5, a general-use version with novel safety classifiers that block or degrade responses on cybersecurity, biology, chemistry, and AI-development topics. Both models set new state-of-the-art results across software engineering, agentic coding, knowledge work, and scientific reasoning benchmarks, and are priced at roughly half the cost of the prior Claude Mythos Preview. Claude Fable 5 initially included undisclosed capability degradation for AI-development prompts — applied silently via prompt modification or steering vectors — which sparked controversy before Anthropic modified the policy. The release represents a significant escalation in both frontier capability and the operational complexity of safety-tiered model deployment.
Anthropic launches Claude Mythos 5 and Claude Fable 5; Andrew Ng introduces OpenCoworker desktop agent
Anthropic released Claude Mythos 5 and Claude Fable 5, two variants of the same frontier model that set new state-of-the-art results across software engineering, knowledge work, cybersecurity, and agentic coding benchmarks. Claude Fable 5 is the general-availability version with safety classifiers that restrict responses on security, biology, chemistry, and cutting-edge AI topics, priced at $10/$50 per million input/output tokens; Mythos 5 is restricted to selected partners via Project Glasswing. Separately, Andrew Ng and collaborators released OpenCoworker, a free open-source desktop agent harness built on top of aisuite, designed to give users privacy-preserving agentic workflows with their own API keys or local models. The newsletter also contextualizes the broader shift toward LLM-driven agent harnesses as frontier models have become capable enough to reliably drive next-action decisions.
Anthropic suspends access to Claude Mythos 5 and Claude Fable 5
Anthropic's status page reports the suspension of access to two models, Claude Mythos 5 and Claude Fable 5, as of June 13, 2026. These appear to be previously unannounced or unreleased model names, making the incident notable both as a service disruption and as a potential first public signal of new model names in Anthropic's lineup. No explanation for the suspension is provided in the brief status notice.
Data Points: Hackers Break Into Claude Mythos; OpenAI Launches Cybersecurity Rival; Maine Data Center Moratorium; McClatchy AI Backlash
A small group of unauthorized users gained access to Anthropic's restricted Claude Mythos cybersecurity model via Discord coordination and insider knowledge, raising questions about securing high-risk AI systems. OpenAI responded to the competitive landscape by launching GPT-5.4-Cyber, a vetted-access model for defensive cybersecurity tasks. Maine passed the first U.S. state moratorium on large AI data centers over 20MW, pending the governor's signature. McClatchy's deployment of a Claude-powered content scaling agent triggered newsroom backlash over attribution, consent, and AI disclosure standards.
Anthropic releases Claude Fable 5
Anthropic has released Claude Fable 5, a new model in the Claude family, announced via their official news channel. The Hacker News discussion generated substantial engagement with 1,468 points and 1,156 comments, indicating significant community interest. No detailed capability claims or benchmark results are available from this item alone.
The Batch: Claude Mythos 5 / Fable 5 debut, Apple AFM 3, Google Live Translate, OpenAI IPO filing, FrontierCode benchmark
Anthropic launched Claude Fable 5 (a safety-guardrailed model) and Claude Mythos 5 (same underlying model with safeguards removed, for vetted cyberdefense/infrastructure users via Project Glasswing with US government collaboration), both priced at $10/$50 per million tokens. Apple released five new Apple Foundation Models (AFM 3) spanning on-device and cloud tiers, built with Google and Nvidia infrastructure. Additional headlines cover Google's Gemini 3.5 Live Translate (70+ languages, real-time), OpenAI's confidential SEC IPO filing, a NotebookLM upgrade to Gemini 3.5, and Cognition's FrontierCode benchmark for code-quality evaluation where Claude Opus 4.8 leads at 34.3%.
Anthropic Passes OpenAI in Business Adoption; Cerebras IPO; Claude Mythos Security Concerns
A Ramp AI Index survey shows Anthropic reached 34.4% business adoption in April 2026, surpassing OpenAI's 32.3%, though analysts cite token cost inflation, service degradation, and competition from cheaper inference platforms as threats to the lead. Cerebras surged 89% on its IPO debut, signaling investor appetite for AI infrastructure hardware. Separately, Anthropic's withheld Claude Mythos model—which solved a novel cybersecurity challenge—prompted meetings with the Financial Stability Board, while ArXiv announced year-long bans for authors submitting unvetted AI-generated content.
Claude Opus 4.8 Launches with Improved Honesty; Anthropic Previews Mythos-Class Models and Dynamic Workflows
Anthropic released Claude Opus 4.8 with improvements in coding, reasoning, agentic tasks, and notably better uncertainty flagging—approximately four times less likely than Opus 4.7 to let code flaws pass uncommented. Alongside the model, Anthropic introduced dynamic workflows in Claude Code enabling tens to hundreds of parallel subagents for large-scale engineering tasks, an effort-control slider, and a 3x price cut on fast mode. Anthropic also previewed Mythos-class models, positioned above Opus in capability, currently available to a limited set of organizations for cybersecurity work pending broader safety clearance. The same digest covers MiniMax M3 (open-weights, ~60% SWE-Bench Pro), Nvidia's RTX Spark superchip, Cosmos 3 world model, and a GR00T/Unitree robotics partnership.
Data Points: Anthropic's Claude Mythos Cybersecurity Claims Face Scrutiny; OpenAI-Cerebras Deal; Meta AI CEO Avatar; Infrastructure Delays
A multi-item digest covers skepticism around Anthropic's Claude Mythos zero-day vulnerability claims (flagged as overstated by Tom's Hardware based on limited 198-case evidence), OpenAI's $20B+ deal with Cerebras for AI processors including a potential ~10% equity stake, and satellite data showing ~40% of U.S. AI data center projects are behind schedule. Additional items cover Meta developing an AI avatar of CEO Zuckerberg for internal use, Moody's flagging credit stress in AI-disrupted sectors, and Luma AI launching an AI-driven film production studio using its Uni-1 model.
Zvi Mowshowitz analyzes Claude Fable 5 and Mythos 5 system card
Zvi Mowshowitz (Don't Worry About the Vase) reviews the system card for Claude Fable 5 and Mythos 5, opening with the claim that Claude Fable 5 is the new best publicly available model. The post is a detailed commentary on Anthropic's model release documentation. As a tier-2 analysis of a major frontier model release, it provides interpretive context around the system card's contents.
Zvi Mowshowitz analyzes Claude Fable 5 release and lab safety plans
Zvi Mowshowitz's commentary covers the release of Claude Fable 5, described as the distributable version of Claude Mythos that Anthropic considers safe for public deployment. The piece appears to analyze safety-related plans from multiple AI labs alongside a memorandum. The item is notable as a tier-2 commentary on what appears to be a significant Anthropic model release.
Insurance Companies Carve Out AI Risk Exceptions; GPT-Rosalind, Claude Design, and Agentic Retail Deployments Highlighted
Major insurers including Berkshire Hathaway units, Travelers Group, and Chubb are excluding or restricting AI-related liability coverage, signaling growing concern over hard-to-model AI-driven claims. OpenAI introduced GPT-Rosalind, a domain-specific LLM fine-tuned for life sciences workflows, while Anthropic launched Claude Design for visual asset generation targeting non-designers. Additional items cover an AI-run San Francisco retail store exposing agentic system limitations, Wall Street banks cutting junior roles via AI deployment, and Anthropic's continued engagement with the Trump administration despite prior Pentagon restrictions.
Andon Labs on building frontier evals: VendingBench and evaluating Claude models
Latent Space interviews Lukas Petersson and Axel Backlund of Andon Labs, the creators of VendingBench, about their approach to building real-world AI evaluations. The conversation covers their experience evaluating Claude models across the capability spectrum from Haiku to Mythos, and their methodology for constructing durable frontier evals. The episode is notable for touching on a speculative or unreleased Claude model tier called 'Mythos.'
Opus 4.7 Part 1: The Model Card
Zvi Mowshowitz covers the model card for Anthropic's Claude Opus 4.7, released less than a week after his coverage of Claude Mythos. This is a tier-2 commentary piece analyzing the official documentation accompanying the new model release. The post is the first part of what appears to be a multi-part series on the release.