Anthropic Fable 5/Mythos 5

Fable 5/Mythos 5 are out now! How does it do? Do you like it? What’s good and what’s not is here! Not everyone is praising it, especially when it downgrades to Opus 4.8 in between the promptings and the use of user prompts.

Read more details here.

— Mythos 5 has also been released, but for restricted use and restricted availability, and will be deployed through a special process.

— The underlying model of Mythos 5 and Fable 5 is the same.

— Context size: Millions of tokens.

— It showed better results in drug discovery, molecular biology and coding.

— Anthropic Fable 5’s/ Mythos 5’s capabilities are superior to any other Anthropic release ever. So, this is a critical moment for Anthropic and the world itself.

****Still at times Opus 4.8 takes over. But all that to stop wrong use, however it can stop a crucial biological work too, say drug discovery for some severe disease?

— However, not everyone is taking this well, as Anthropic is blocking some biology and other prompts from being completed with Mythos 5/Fable 5.

— The company says sensitive topics would instead be answered by Opus 4.8, and this switching between Fable 5 and Opus 4.8 would be seamless, as it sounds. However, not everyone is happy with the switch between Fable 5 and Opus 4.8.

— Fable 5 is like Mythos, released some weeks earlier; Mythos has well-known cybersecurity issues, and Fable has the power of Mythos, but at the same time it has constraints put in place when a risky mode is engaged with Fable. These include judging the prompt for its safety and what it can access from the deep model.

— Anthropic says it has outpaced many complex tasks that other models can’t even come close to and has broken previous benchmarks as well. Tasks tested include software engineering, vision, research, etc.

— It is more expensive than Opus 4.8 and GPT 5.5.

— The testing shows better results of Fable 5/Mythos 5 than other models in coding, biology, and other areas that were presented with Agentic Coding improving radically.

— Fable has been tested for hundreds of hours for its accuracy; still, if something happens, they say they would look into it through certain measures.

— Fable 5 offers far more advanced vision solutions, such as coding from screenshots and even playing Pokémon FireRed with efficiency using game screenshots, no maps, and no extra state information as against prior Claude models.

— The company affirms the use of safeguards well enough to avoid being exploited.

— As per the internet, Anthropic Fable 5 requires a user’s data to be kept on its servers for 1 month to years, depending on the prompt and any violations that may occur during processing. This may be why Microsoft has limited its use of Fable among its employees.

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