Anthropic has introduced Claude Fable 5.2 and Claude Mythos 5.2, its latest AI models designed to tackle complex technical challenges involving coding, reasoning, scientific research and cybersecurity. The announcement comes as the company prepares for a potential blockbuster IPO, with recently circulated offering details briefly pointing to a possible $69.3 billion fundraising target.
The new models bring improvements in coding, vision and reasoning, with Anthropic claiming that they can generate responses up to 30% faster than their predecessors. The company has also reduced their standard API pricing while introducing an optional fast mode for users who need quicker output.
Interestingly, Fable and Mythos are based on the same underlying model but have different safety restrictions and availability. Here’s what the new Claude models offer.
Claude Fable 5.2 And Mythos 5.2: What’s New?
Introducing Claude Fable 5.2 and Claude Mythos 5.2, designed to tackle the most daunting technical challenges.
They’re capable collaborators on ambitious projects in many fields, and show improvements in areas like coding, reasoning, and vision. pic.twitter.com/jP0AutLxXb
— Claude (@claudeai) November 9, 2026Anthropic says the new models are designed for ambitious, open-ended technical work rather than everyday queries alone. They can handle complex software projects, research tasks, hardware design and advanced mathematical problems. During prerelease testing, Fable 5.2 helped engineers complete challenging software migrations, design three working electronic devices and formalise a proof of Fermat’s Last Theorem in just 30 hours using a team of AI agents. Some of the key improvements include:
Advanced agentic coding: Fable 5.2 can coordinate multiple AI agents to work on large software projects. In one experiment, more than 1,000 agents worked together for eight days to build a functioning operating system from an empty folder.
Improved reasoning and research: The model has demonstrated stronger performance in complex research and analytical tasks. Anthropic says Fable 5.2 also solved two previously open problems in theoretical physics related to black holes.
Better cybersecurity capabilities: Mythos 5.2 is Anthropic’s most capable model for cybersecurity engineering. It can identify, reproduce and help fix software vulnerabilities. On Anthropic’s internal evaluation, it found 10.2% more vulnerabilities than Opus 5.5 and 14.4% more than Mythos 5.1.
Hardware and robotics: Fable 5.2 designed three working electronic devices, including a voice-assistant hub, a USB speakerphone and a handheld virtual pet. It also showed improved performance in simulated robotics tasks.
Faster responses: Anthropic says both models generate outputs up to 30% faster than Fable 5.1 and Mythos 5.1, while offering improved communication and efficiency.
Fable 5.2 vs Mythos 5.2: What’s The Difference?
During pre-release testing, Claude Fable 5.2 and Claude Mythos 5.2 worked on ambitious projects in many different fields. Here are a few.
From a one-paragraph prompt, Fable 5.2 designed three working electronic devices, including this home voice assistant hub. https://t.co/efOYdhRr7K
— Claude (@claudeai) November 9, 2026Although both models share the same underlying technology, their safety restrictions and intended uses are different. Claude Fable 5.2 includes strong cybersecurity and biology safeguards, allowing Anthropic to make it available to a wider range of users. These safeguards block most high-risk cybersecurity and biological research requests.
Claude Mythos 5.2, meanwhile, is designed for advanced cybersecurity and biomedical research applications. It does not have the same safeguards as Fable and is therefore restricted to vetted organisations through Anthropic’s Cyber Verification and Life Sciences Verification programmes.
This means regular users and developers can access Fable 5.2, while organisations working on approved high-stakes research can apply for Mythos access.
Claude Fable 5.2 And Mythos 5.2 Pricing
Fable 5.2 is now available in the Claude Platform and Claude Code.
It’s up to 30% faster than Fable 5.1, and costs $8/$40 per 1M tokens, down from $10/$50. https://t.co/mHGJNRbIZS
— ClaudeDevs (@ClaudeDevs) November 9, 2026Anthropic has also reduced the standard pricing for both models. The API costs $8 per million input tokens and $40 per million output tokens. For users who need faster generation, the company offers an optional fast mode. It increases token generation speed by up to 2.5 times, but costs twice as much as standard usage.
| Pricing | Standard Mode | Fast Mode |
|---|---|---|
| Input Tokens | $8 per million | $16 per million |
| Output Tokens | $40 per million | $80 per million |
| Generation Speed | Standard | Up to 2.5x faster |
The pricing applies to both Fable 5.2 and Mythos 5.2. However, Mythos access and its fast mode remain restricted to eligible organisations.
Availability
Claude Fable 5.2 is available across Claude’s platforms, including Claude.ai and Claude Code. Developers can access it through the Claude Platform API using the model name claude-fable-5-2.
The model is also available through Amazon Web Services, Google Cloud and Microsoft Azure. Fast mode is supported on Claude Code, the Claude Platform and selected cloud offerings. Mythos 5.2 is not generally available. Cybersecurity professionals and life sciences researchers can apply through Anthropic’s respective verification programmes. Claude Enterprise customers can also access Mythos 5.2 through Claude Security.
Anthropic is additionally offering eligible paid subscribers extra Fable usage as part of the launch promotion, with the amount depending on subscription duration and plan.
Anthropic’s $69.3 Billion IPO Plans
The model launch comes at an important time for Anthropic as it prepares for a potential public listing. According to an exclusive Reuters report published on November 10, details of a proposed IPO were briefly circulated to investment bankers before being retracted. The initial filing indicated that Anthropic planned to sell approximately 866.7 million Class A shares at a price range of $70-$80 per share.
At the upper end of that range, the proposed offering could have raised approximately $69.3 billion. The proposed sale reportedly included 843.3 million shares from Anthropic and 23.3 million shares from existing shareholders.
However, Anthropic subsequently informed bankers that the pricing information was inaccurate and that it would circulate an updated filing. The company declined to comment, and Reuters said it could not establish which details were incorrect.
Therefore, the $69.3 billion figure should be treated as a preliminary, retracted IPO estimate rather than a confirmed fundraising target.
Claude Fable 5.2 And Mythos 5.2 Specifications
| Specifications | Claude Fable 5.2 | Claude Mythos 5.2 |
|---|---|---|
| Developer | Anthropic | Anthropic |
| Model Category | Advanced AI Model | Advanced AI Model |
| Underlying Model | Same | Same |
| Primary Focus | Coding, reasoning and research | Cybersecurity and advanced research |
| Output Speed | Up to 30% faster than 5.1 | Up to 30% faster than 5.1 |
| Input Pricing | $8 per million tokens | $8 per million tokens |
| Output Pricing | $40 per million tokens | $40 per million tokens |
| Fast Mode | Available | Restricted access |
| Fast Mode Speed | Up to 2.5x | Up to 2.5x |
| Fast Mode Input | $16 per million tokens | $16 per million tokens |
| Fast Mode Output | $80 per million tokens | $80 per million tokens |
| Cybersecurity Safeguards | Strong restrictions | Fewer restrictions; vetted access |
| Availability | General availability | Verification programmes |
Conclusion
With Claude Fable 5.2 and Mythos 5.2, Anthropic is pushing its AI capabilities further into complex software engineering, scientific research and cybersecurity. The ability to coordinate thousands of agents, tackle difficult mathematical problems and identify software vulnerabilities makes this a significant update.
The lower standard API pricing and faster generation are also important, particularly for developers and businesses using Claude for demanding workloads.
Meanwhile, Anthropic’s potential IPO adds another major development to the company’s story. Although the reported $69.3 billion offering figure was retracted, the proposed listing highlights the scale of investor interest surrounding the AI company.
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