Claude Mythos 5

Claude Mythos 5

Anthropic
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About

Claude Mythos 5 is Anthropic’s most advanced restricted-access AI model, designed for trusted cyberdefenders, infrastructure providers, and select research organizations. It uses the same underlying model as Claude Fable 5 but provides lifted safeguards in approved areas for specialized high-trust use cases. The model delivers exceptional capabilities in cybersecurity, software engineering, scientific research, long-context reasoning, vision, and autonomous task execution. Anthropic initially deployed Claude Mythos 5 through Project Glasswing in collaboration with the U.S. government to help protect critical software and infrastructure. The model also shows strong potential in life sciences, including protein design, molecular biology hypothesis generation, and genomics research. Claude Mythos 5 is built for organizations that need frontier AI capabilities under controlled, trusted-access conditions.

About

Muse Spark Open is an open-weight, natively multimodal language model for developers and organizations building AI applications, coding systems, and agentic workflows. The released model has 816 billion total parameters, 42 billion active parameters, and a 1-million-token context window. Teams can download the model weights, run inference through supported engines such as vLLM, SGLang, TensorRT-LLM, Hugging Face Transformers, Apple MLX, llama.cpp, or Unsloth, and customize the model using PyTorch. It supports long-context reasoning, software engineering, coding, tool use, and multimodal inputs. Deployment options include cloud inference through listed API providers or self-hosting on compatible GPU systems; Meta documents a desktop setup using two Apple M5 Ultra Mac Studio computers. The model is released under the Muse Model License with limited commercial terms.

Platforms Supported

Windows Not Supported
Mac Not Supported
Linux Not Supported
Cloud Supported
On-Premises Not Supported
iPhone Not Supported
iPad Not Supported
Android Not Supported
Chromebook Not Supported

Platforms Supported

Windows Supported
Mac Supported
Linux Supported
Cloud Supported
On-Premises Supported
iPhone Not Supported
iPad Not Supported
Android Not Supported
Chromebook Not Supported

Audience

Claude Mythos 5 is designed for cyberdefense teams, critical infrastructure providers, government partners, biomedical researchers, life sciences organizations, advanced AI research teams, and trusted enterprises that need restricted access to frontier AI capabilities

Audience

AI developers, machine learning engineers, software engineers, AI researchers, enterprise development teams, and organizations seeking customizable open-weight multimodal models for local inference, autonomous agents, complex coding, and long-context AI applications

Support

Phone Support Not Supported
24/7 Live Support Not Supported
Online Supported

Support

Phone Support Not Supported
24/7 Live Support Not Supported
Online Not Supported

API

Offers API Supported

API

Offers API Not Supported

Screenshots and Videos

Screenshots and Videos

Pricing

$10 per 1 million (input)
$10 per million input tokens and $50 per million output tokens
Free Version Not Supported
Free Trial Not Supported

Pricing

$0
Model weights are available at no charge under the Muse Model License, which has limited commercial-use terms. Hosted inference providers set their own usage prices.
Free Version Supported
Free Trial Not Supported

Reviews/Ratings

Overall 5.0 / 5
ease 5.0 / 5
features 5.0 / 5
design 5.0 / 5

Reviews/Ratings

Overall 5.0 / 5
ease 5.0 / 5

Pros & Cons from Real Users

Pros

  • As a cybersecurity professional, Claude Mythos 5 is the most capable AI system I've seen for vulnerability research, threat analysis, and security engineering. It can identify attack paths, analyze complex codebases, and reason through security problems at a level that feels significantly beyond previous-generation models. What stands out most is its ability to connect seemingly unrelated findings into a coherent security assessment. Whether reviewing application code, examining infrastructure risks, or analyzing exploit chains, Mythos 5 consistently provides insights that would normally require multiple senior analysts working together. The model appears particularly strong at vulnerability discovery and defensive security workflows. Its capabilities were significant enough that Anthropic initially restricted access to a small group of trusted organizations before expanding availability through its Project Glasswing program.

Cons

  • The biggest downside is accessibility. Most security professionals cannot simply sign up and use Mythos 5. Access remains limited to approved organizations, which makes it difficult for independent researchers and smaller security teams to evaluate its full potential. The model's power also comes with operational constraints. Organizations using it must navigate additional security controls, monitoring requirements, and deployment restrictions that are not typically associated with mainstream AI tools. There is also a learning curve. Mythos 5 is not a replacement for security expertise—it amplifies expertise. Teams without strong cybersecurity fundamentals may struggle to get the same value from it as experienced practitioners.

Pros & Cons from Real Users

Pros

  • Meta finally opened up a genuinely frontier-level Muse model. The 1M-token context window and 42B active parameters make it strong enough for large repos, long agent sessions, multimodal work, and complex coding without feeling like a stripped-down open model. The local deployment story is also a huge deal. Being able to run something this capable on two M5 Ultra Mac Studios is impressive, especially for teams that want more control over data, infrastructure, and customization. I also like how much of the stack is open around it. Muse Spark Open works with MLX, vLLM, SGLang, TensorRT-LLM, Transformers, llama.cpp, and Unsloth, and Meta is making the weights available through Hugging Face, SageMaker, Google Cloud Model Garden, and Microsoft Foundry.

Cons

  • Even though it is technically desktop-capable, needing two M5 Ultra Mac Studios for the full local experience is still a serious setup, so most developers will probably use hosted inference instead.

Training

Documentation Supported
Webinars Not Supported
Live Online Not Supported
In Person Not Supported

Training

Documentation Supported
Webinars Not Supported
Live Online Not Supported
In Person Not Supported

Company Information

Anthropic
Founded: 2023
United States
claude.ai

Company Information

Meta
Founded: 2004
United States
research.meta.ai/blog/muse-spark-open

Alternatives

Alternatives

Claude Fable 5

Claude Fable 5

Anthropic
Inkling

Inkling

Thinking Machines Lab

Categories

AI Coding Models Supported
AI Models Supported
AI Vision Models Supported
Foundation Models Supported

Categories

AI Coding Models Supported
AI Models Supported
AI Receptionists Supported
Foundation Models Supported
Multimodal Models Supported

Integrations

Baseten Not Supported
Brokk Supported
CSS Supported
Claude Supported
Claude Max Supported
Claude Pro Supported
Dart Supported
Factory Droid Supported
Kotlin Supported
OpenClaw Supported
OpenCode Supported
OpenRouter Not Supported
Oxen.ai Supported
Perplexity Pro Supported
Qwen Code Supported
ReSharper Supported
Scalestack Supported
Skymel Supported
Trinity-Large-Thinking Supported
Versuno Supported

Integrations

Baseten Supported
Brokk Not Supported
CSS Not Supported
Claude Not Supported
Claude Max Not Supported
Claude Pro Not Supported
Dart Not Supported
Factory Droid Not Supported
Kotlin Not Supported
OpenClaw Not Supported
OpenCode Not Supported
OpenRouter Supported
Oxen.ai Not Supported
Perplexity Pro Not Supported
Qwen Code Not Supported
ReSharper Not Supported
Scalestack Not Supported
Skymel Not Supported
Trinity-Large-Thinking Not Supported
Versuno Not Supported
Claim Claude Mythos 5 and update features and information
Claim Claude Mythos 5 and update features and information
Claim Muse Spark Open and update features and information
Claim Muse Spark Open and update features and information