What is Claude Fable 5.1?

Claude Fable 5.1 is an advanced general-purpose AI model from Anthropic focused on coding, scientific research, knowledge work, business processes, and long-horizon agentic reasoning. It is the generally available counterpart to Claude Mythos 5.1, which uses the same underlying model but is offered with different safeguards for vetted cybersecurity and life sciences users. Compared with Claude Fable 5, Fable 5.1 shows stronger performance across agentic coding, research, computer use, multidisciplinary reasoning, business workflow automation, and other complex benchmarks. The model is designed to remain effective during long-running tasks that involve planning, tool use, repeated verification, code modification, research, and multi-step decision making. In software engineering scenarios, it can investigate difficult bugs, trace problems across large codebases, perform code review, and work through complex implementation tasks with less supervision. Anthropic also positions Fable 5.1 as a stronger research model, with demonstrated capabilities in scientific analysis, computational modeling, and other technically demanding workflows. Improvements to cache-read pricing reduce the cost of reusing previously processed context, making the model more economical for workflows that involve long conversations, large codebases, or repeated tool calls. Fable 5.1 introduces updated enterprise privacy and security options, including Enterprise Frontier Safeguards and zero-data-retention access for eligible customers during the rollout period. Its cybersecurity protections are designed to permit more benign defensive security work, including vulnerability discovery, while continuing to restrict higher-risk activities such as exploit development and certain penetration-testing tasks. The model is available through Claude.ai, Claude Code, Claude Cowork, the Claude API, Amazon Web Services, Google Cloud, and Microsoft Azure under the claude-fable-5-1 model identifier for API users.

Pricing

Price Starts At:
$10 per 1M tokens (input)
Price Overview:
$10 per million input tokens and $50 per million output tokens

Integrations

Offers API?:
Yes, Claude Fable 5.1 provides an API
All Claude Fable 5.1 Integrations

Screenshots and Video

Claude Fable 5.1 Screenshot 1
Claude Fable 5.1 Screenshot 1

Company Facts

Company Name:
Anthropic
Date Founded:
2021
Company Location:
United States
Company Website:
claude.ai

Product Details

Deployment
SaaS
Training Options
Documentation Hub
Support
Web-Based Support

Product Details

Target Company Sizes
Individual
1-10
11-50
51-200
201-500
501-1000
1001-5000
5001-10000
10001+
Target Organization Types
Mid Size Business
Small Business
Enterprise
Freelance
Nonprofit
Government
Startup
Supported Languages
English

Claude Fable 5.1 Categories and Features

Multimodal Models

Large Language Models

Foundation Models

AI Vision Models

AI Reasoning Models

AI Models

AI Coding Models

Claude Fable 5.1 Customer Reviews

Write a Review
  • Reviewer Name: A Verified Reviewer
    Position: Developer
    Has used product for: Less than 6 months
    Uses the product: Daily
    Org Size (# of Employees): 100 - 499
    Feature Set
    Ease Of Use
    Cost
    Would you Recommend to Others?
    1 2 3 4 5 6 7 8 9 10

    Fable 5.1 is WILD!

    Date: Sep 01 2026
    Summary

    Overall, Claude Fable 5.1 is the strongest model for long-context, high-effort, agentic work. It is not the everyday cheap option, but when the task is big, complicated, and important, this is exactly the kind of model I would want available.

    Positive

    This feels like the model you reach for when the work is genuinely difficult. Not every task needs Fable, but for complex coding, long-horizon agents, deep research, and big messy knowledge-work projects, Fable 5.1 looks built for the hard stuff. The 1M-token context window is a huge advantage. For developers and AI power users, that means you can work across large repos, long docs, research sets, transcripts, spreadsheets, and project history without constantly chopping everything into pieces. I also like that Anthropic specifically calls out document, spreadsheet, and slide work. That makes it feel useful beyond coding alone — more like a high-end model for serious professional workflows.

    Negative

    The downside is price and complexity. Anthropic says most workloads should start with Claude Opus 5, and Fable 5.1 is better reserved for demanding reasoning or cases where Opus 5 still falls short.

    Read More...
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