Claude Fable 5 and Claude Mythos 5 Review

The Anthropic team released their latest AI models, Mythos 5 and Fable 5, on June 9, 2026. The Mythos 5 and Fable 5 models demonstrate advanced capabilities, high benchmark performance, and excellent handling of complex and longer tasks. If you're curious about the capabilities and offerings of the Claude Fable 5 and Claude Mythos 5 models released by Anthropic, we've got you covered! 

In this article, we will examine the Claude Mythos 5 and Fable 5 models and discover what they offer.

TL; DR

Anthropic released Claude Fable 5 and Mythos 5 on June 9, 2026. Both models share the same architecture and performance, with Fable 5 adding extra safeguards for cyber and bio-related requests. They lead benchmarks in agentic coding (SWE-bench Pro: 80.3%, FrontierCode diamond: 29.3%) and outperform GPT-5.5, Gemini 3.1 Pro, and Claude Opus 4.8 across most tests. Fable 5 excels at large-scale engineering (e.g., migrating 50-million-line codebases in days versus months), token-efficient coding, document reasoning, vision tasks (screenshot-to-code, precise data extraction), and long-context memory. API pricing is $10 per million input tokens, $50 per million output tokens, with cache write options at $12.5 and $20. Mythos 5 remains in limited trusted access; Fable 5 is available via paid Claude plans, Claude Code, and API. Neither is GDPR/EU AI Act compliant by default, but TextCortex offers Fable 5 as an EU-hosted, compliant API and AI agent, alongside 18 other LLMs through a single integration.

What are Claude Fable 5 and Mythos 5?

Claude Fable 5 and Mythos 5 are large language models developed by Anthropic and released on June 9, 2026. These models demonstrate exceptional performance in software engineering, knowledge work, vision, scientific research, and many other areas. Furthermore, their advanced features include their ability to maintain stable performance even with complex and long tasks.

What’s the Difference Between Claude Fable 5 and Mythos 5?

Fable 5 and Mythos 5 are essentially the same models in terms of performance and architecture. The only difference is that the Claude Fable 5 model comes with extra safeguards that reroute cyber and bio-related requests.

How to Access Claude Fable 5 and Mythos 5?

The Claude Mythos 5 model is not fully accessible yet; the Anthropic team will make it fully available through a broader trusted access program. Until then, we have limited access to the Claude Mythos 5 model. On the other hand, you can access the Claude Fable 5 model through the Claude AI web app. The only requirement to access the Claude Fable 5 model is to have one of the paid Claude plans. You can also access the Fable 5 model through Claude Code. Another way to access the Claude Fable 5 model is to use it as the Claude API.

If you want to access the Claude Fable 5 model as EU-hosted and GDPR compliant and integrate it into your enterprise workflow, TextCortex is the solution for you. With TextCortex, you can access frontier AI models, including Claude Fable 5, via a single API as EU-hosted, GDPR and EU AI Act compliant.

Claude Fable 5 Pricing

If you want to access Claude Fable 5 through Anthropic AI, you'll need to subscribe to one of the paid plans, starting at $20 per month.

If you plan to use the Claude Fable 5 or Mythos 5 models as an API, you will need to pay the following pricing:

• 10 por cada millón de tokens introducidos
• 50 por cada millón de tokens emitidos
• $12.5 per million 5m cache writes tokens
• $20 per million 1h cache writes tokens

The API pricing for the model is half the price of the preview version.

Claude Fable 5 and Mythos 5 Performance & Features

If you're curious about the performance and innovations offered by the Claude Fable 5 and Mythos 5 models, keep reading!

Claude Fable 5 and Mythos 5 Benchmark Performance

The Claude Fable 5 and Mythos 5 models outperform their competitors, such as the GPT-5.5 and Gemini 3.1 Pro, as well as the latest Anthropic model, the Claude Opus 4.8, in all benchmarks. The Claude Fable 5 and Mythos 5 models lead the SWE-bench Pro and FrontierCode (diamond) benchmarks, designed for agentic coding, with scores of 80.3% and 29.3%, respectively. However, the Claude Fable 5 and Mythos 5 models do not lead in the OSWorld-Verified benchmark, designed solely for computer use, and the Humanity’s Last Exam benchmark, designed for reasoning. In these benchmarks, the models have scores of 85.0% and 64.5%, respectively, with the Claude Mythos Preview model holding the lead by a slight margin.

Claude Fable 5 Coding and Software Engineering Performance

The Claude Fable 5 model offers higher performance in coding, agentic coding, and reasoning compared to both its competing large language models and the Claude Opus 4.8 model. According to Anthropic’s article, the Claude Fable 5 model completed a codebase-wide migration of a 50-million-line Ruby codebase in a few days, a task that would have taken the entire team more than two months. Furthermore, the Claude Fable 5 model demonstrated more token-efficient (and therefore cost-efficient) performance on coding tasks than previous Claude models. According to FrontierCode’s cost vs. accuracy evaluation, Claude Fable 5 scores highest among frontier models, even at medium effort.

Knowledge Work & Vision

Two areas where the Claude Fable 5 and Mythos 5 models excel are knowledge work and vision. The Claude Fable 5 model demonstrates high performance in document-based reasoning, chart and table interpretation, and problem-solving using documents. Furthermore, the Fable 5 model possesses vision capabilities that allow it to complete tasks such as precise number extraction from detailed documentation and rebuilding a web app's source code from a screenshot.

Memory and Long Context

The Claude Fable 5 model is adept at focusing on the tasks given in long-term tasks using millions of tokens and enhancing output using its own notes. In other words, the Claude Fable 5 model can remember the given instructions and complete long-context tasks accurately and successfully. If you are looking for an LLM to help you perform long-term tasks or tasks requiring strong memory, Claude Fable 5 could be the solution for you.

Claude Fable 5 Safeguards

Claude Fable 5 offers strong performance and will be used by enterprises and organizations in critical and high-risk tasks. Therefore, the Anthropic team has enhanced the safeguards of the Claude Fable 5 model. This sometimes causes irrelevant user input to trigger the safeguards. However, the Claude Fable 5 model is not inherently GDPR and EU AI Act compliant. To use the model as GDPR-compliant, you need to configure your deployment method or obtain it from a provider that offers it as GDPR-compliant.

TextCortex AI: Access Claude Fable 5 as GDPR-Compliant

TextCortex is a leading knowledge management, workflow automation, and EU-hosted frontier model provider that aims to help organizations and enterprises to leverage the full benefits of AI. TextCortex offers a wide range of large language models, including Claude Fable 5, as a GDPR-compliant and EU-hosted API. In addition to the API, you can use state-of-the-art large language models via TextCortex to automate your enterprise workflow and enhance your knowledge work.

Access Claude Fable 5 via TextCortex

With TextCortex, you can access the Claude Fable 5 model both as an AI agent and as an API. To use the Claude Fable 5 model as an AI agent with TextCortex:

• Dirígete a la aplicación web TextCortex
• Hit the “Create new agent” button
• Select the default LLM as Fable 5

and that’s really all. Afterwards, you can optimize your AI agent for the tasks you need, and even make it modular and suitable for multitasking through skills.

It is possible to access the Claude Fable 5 model API via TextCortex, which is EU-hosted and GDPR-compliant. If you have an organization serving the European region, you can use the TextCortex API instead of configuring the Fable 5 model from scratch. What’s more, thanks to the TextCortex API, you can simultaneously access 19 different large language models, including Claude Fable 5.

Preguntas frecuentes

Is Fable 5 available in the Claude Code?

Yes, Claude is available in the Claude Code as of the release of Fable 5.

Is Claude Fable 5 free?

No, the Claude Fable 5 model, both as an API and as the Claude AI chatbot, is not free.

Is Claude Fable 5 Mythos?

Yes, Claude Fable 5 and Claude Mythos 5 are identical models sharing the same architecture and features. The only difference between the two models is that Fable 5 comes with extra safeguards.