Fable 5.1 has been hacked, resulting in the leakage of 270,000 words of cheat codes.

Finally here! Fable 5.1 and Mythos 5.1 are officially released.

The ARC Prize has just verified Claude Fable 5.1's performance.

The ARC Prize has just verified Claude Fable 5.1's performance.

ARC-AGI-2: 90.0%, $3.12/task ARC-AGI-1: 97.5%, $1.40 per task Thanks to improved token efficiency, Fable 5.1's average inference cost is approximately 32% lower than its predecessor!

Surprisingly, less than a few hours after its release, Fable 5.1 was cracked!

Renowned hacker Pliny the Liberator released a 270,000-word system message, completely exposing Fable 5.1's weaknesses.

The well-known hacker Pliny the Liberator released a 270,000-word system message, completely exposing Fable 5.1's weaknesses.

270,000 words of top-secret keywords leaked

Actually, Fable 5.1 and Mythos 5.1 are essentially the same model, sharing the same set of weights. The reason for using two names is due to security restrictions.

Fable 5.1 is a secure version open to the public, with added guardrails. Mythos 5.1, on the other hand, is only open to vetted cybersecurity experts and life science researchers.

What exactly are the constraints on Fable 5.1, and how many rules has Anthropic set for it?

What rules does Anthropic impose on Fable 5.1?

Full prompt word:

Interestingly, the official Anthropic team also released a "System Prompt Update," which is approximately 27,000 words long.

Interestingly, the official Anthropic team also released a "System Prompt Update," which is approximately 27,000 words long.

Breaking Bad"

Tool Explosion: From 30 to 46

Besides security limitations, Fable 5.1's biggest trump card in terms of capability, surpassing its predecessor, is the crazy expansion of the system's built-in tools mode—

From 30 in July, it has skyrocketed to 46!

The newly added tools cover almost every aspect of complex office work and content presentation: Charts and UI Displays: New features include chart_display, carousel_display, and places_list_display, meaning Claude can directly generate smooth charts, product carousels, and itinerary cards within the chat interface. Links and Page Previews: link_preview_display allows for better understanding and display of external web pages. Reading Conversation History: The new read_conversation feature allows you to navigate through your past chat history and extract key information, no longer the cumbersome tool that forgets everything after a refresh. This enhanced tool-calling capability directly elevates Fable 5.1 to legendary status in multimodal and automated execution. Clearly, the 46 built-in tools are not just for show; they transform Claude into a "super workstation." In 44 minutes, Fable 5.1 cracked a 370-year-old unsolved cipher. Moreover, just now, Vals AI announced on Weibo that Claude Fable 5.1 has successfully cracked the classic cipher "Cyphral Distich," which has baffled the cryptography community for nearly a century! In 1653, Sir Thomas Urquhart, a Scottish scholar, left a mysterious 64-digit code at the end of his book *Logopandecteision*: For centuries, countless experts have attempted to crack it. They exhausted methods such as word frequency analysis, substitution ciphers, and homophone substitution, all to no avail. This led to its inclusion on the list of "50 Unsolved Encrypted Messages in the World." Fable 5.1, however, solved this 370-year-old mystery in just 44 minutes, consuming 176,000 tokens, without any human intervention or hints! Moreover, it didn't rely on brute force, but rather on "lateral association and contextual reasoning." Fable 5.1 didn't immediately focus on the numbers. It analyzed the context. It found: 1. This cipher follows immediately after the author's 32 short essays. Furthermore, the author inexplicably emphasized in the text that "no number is better than 32." 2. The first line of the cipher contains 32 numbers, and the second line also contains 32 numbers. 3. A poem accompanying the cipher states that honest readers will find "their heart's desire" here. And the 32 short essays always end with "desire." The AI ​​suddenly had an epiphany: the key to unlocking the code wasn't some external codebook, but the book itself! Fable 5.1 deduced that the i-th number in the code corresponds to the i-th short passage. Using this number as a word index, they found the word and extracted its first letter. Following this logic, a poem pleading for King Charles II's restoration appeared on the page, perfectly fitting the author's royalist historical background! Subsequently, Fable 5.1 followed the same logic and easily cracked another, even larger, unsolved code left by the author (the 285-digit Cyphral Octastich). This is the most terrifying thing about Fable 5.1: it no longer simply "guess probabilities," but has learned to act like a detective, searching for clues in vast historical texts and logically piecing together seemingly unrelated information. "Many historical problems have remained unsolved due to a lack of human attention. Now, this bottleneck is disappearing." [Image of image: https://img.jinse.com.cn/7507233_image3.png](https://img.jinse.com.cn/7507233_image3.png) [Image of image: pAsyCgXvyRbky4FbDtVY80BGV4OhUMRcVcPuCk5F.jpeg](https://img.jinse.com.cn/7507233_image3.png) [Image of image: pAsyCgXvyRbky4FbDtVY80BGV4OhUMRcVcPuCk5F.jpeg](https://img.jinse.com.cn/7507233_image3.png) [Image of image: pAsyCgXvyRbky4FbDtVY80BGV4OhUMRcVcPuCk5F.jpeg) ... First, let's have it generate a video of a black hole. The prompt is simple: Generate a 5-second video of someone entering a black hole using code, with scientific evidence. Claude didn't mince words; he directly wrote a ray tracing renderer based on general relativity. Its core is the zero geodesic integral of Schwarzschild spacetime, integrating the relativistic Doppler effect, gravitational redshift, and the optical aberration of a free-falling camera.

The backend uses ffmpeg for video compositing. After the environment is set up, the AI ​​starts writing the renderer.

Initially, it runs a few frames at low resolution to verify the physics and composition.

The first image is indeed correct, and the shape is generally correct—the shadows and the curve of the disc in the background are visible—but it is obviously overexposed, all the details are swallowed up, and there is numerical overflow inside the field of view due to g→∞.

So, Fable 5.1 was revised several times:

Some developers have compared the 3D helicopter model generation effects of Fable 5 and Fable 5.1. Clearly, Fable 5.1 is a significant improvement over 5.

Others have compared the self-portrait capabilities of Fable 5.1 and 5. Fable 5.1's visual capabilities are exceptionally strong.

A prominent influencer summarized nine things you should do with Fable 5.1. However, many paid users have stated that Fable 5.1 is extremely token-intensive! One netizen complained: "It's simply unusable! The rate limiting is utterly absurd. And Fable's auto-resume function is completely bugged and doesn't work at all." What's even more disheartening for Pro and Max subscribers is that while the new model boasts improved efficiency, there's been no official announcement of a price reduction or an increase in the usage cap. Next up, OpenAI's Astra is about to debut. Some say they have incredibly high expectations for OpenAI, believing Astra is the path to AGI.