Claude Fable 5

Claude Fable 5

Anthropic
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About

Claude Fable 5 is an advanced AI model from Anthropic designed to assist with software engineering, research, knowledge work, vision tasks, and complex reasoning. Built on the Mythos-class architecture, it delivers significantly improved performance across coding, analysis, and long-context workflows. The model can handle extended autonomous tasks while maintaining focus and consistency over large amounts of information. Claude Fable 5 integrates advanced reasoning, multimodal understanding, and memory capabilities to support professional and enterprise use cases. Anthropic has implemented specialized safeguards that automatically route certain high-risk cybersecurity, biology, chemistry, and model distillation requests to a different model. Claude Fable 5 helps organizations and professionals accelerate complex work while maintaining strong safety and governance controls.

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 Fable 5 is designed for software engineers, researchers, enterprise organizations, data analysts, scientists, product teams, developers, business professionals, knowledge workers, and organizations seeking advanced AI for coding, research, automation, analysis, and enterprise productivity

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
support 5.0 / 5

Reviews/Ratings

Overall 5.0 / 5
ease 5.0 / 5

Pros & Cons from Real Users

Pros

  • Claude Fable 5 is the most capable coding model I've used for complex software development. It understands large codebases remarkably well and can maintain context across long implementation sessions without losing track of requirements. The model excels at architecture discussions, debugging difficult issues, and generating production-quality code. Its reasoning feels more deliberate than many competing models, making it especially valuable for backend development, refactoring, and technical design work. I was particularly impressed by its ability to handle multi-step engineering tasks. Instead of solving problems one prompt at a time, it often anticipates edge cases and implementation details before I ask.

Cons

  • The safety guardrails can occasionally get in the way of legitimate security-related development work. Certain cybersecurity topics may be redirected to a less capable model, which can interrupt advanced technical workflows. Pricing is also higher than previous Claude models, which may be a consideration for teams with heavy API usage. Like any AI coding assistant, it still requires careful review of generated code before deployment, especially for critical production systems.

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: 2021
United States
claude.ai

Company Information

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

Alternatives

Alternatives

Laguna XS 2.1

Laguna XS 2.1

Poolside

Categories

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

Categories

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

Integrations

Anything Supported
Bash Supported
Brokk Supported
Dart Supported
Databricks Supported
Devin Desktop Supported
Factory Droid Supported
GitHub Copilot CLI Supported
JetBrains Junie Supported
Nebius Not Supported
OpenRouter Not Supported
Pi Agent Supported
ReSharper Supported
Rider Supported
Rust Supported
SQL Supported
StackAI Supported
TypeScript Supported
Vellum Supported
Viktor Supported

Integrations

Anything Not Supported
Bash Not Supported
Brokk Not Supported
Dart Not Supported
Databricks Not Supported
Devin Desktop Not Supported
Factory Droid Not Supported
GitHub Copilot CLI Not Supported
JetBrains Junie Not Supported
Nebius Supported
OpenRouter Supported
Pi Agent Not Supported
ReSharper Not Supported
Rider Not Supported
Rust Not Supported
SQL Not Supported
StackAI Not Supported
TypeScript Not Supported
Vellum Not Supported
Viktor Not Supported
Claim Claude Fable 5 and update features and information
Claim Claude Fable 5 and update features and information
Claim Muse Spark Open and update features and information
Claim Muse Spark Open and update features and information