Anthropic Opens Up Its Most Powerful AI Model Yet — But Only for a Limited Time

Anthropic is giving regular users a taste of its most advanced AI system, called Mythos, through a new model named Fable. Starting today, Claude subscribers can try Fable 5 for free until June 22, without burning through their usage credits.

Mythos first debuted in April through Project Glasswing, a program that gave select partners like Apple and NVIDIA early access to help them protect their software from AI-powered cyberattacks. That project even pushed the White House to reconsider its AI regulations. Now, after promising last week to release a version with strong safety features, Anthropic is delivering on that pledge.

Fable 5, the company says, outperforms every public model they've ever released — including their previous top-tier Opus 4.8, as well as GPT-5.5 from OpenAI and Gemini 3.1 Pro from Google. It shines in software engineering, drug design, and document analysis, but also makes big strides in areas where Anthropic's earlier models struggled, particularly vision.

Remember when Anthropic streamed Claude failing at Pokémon Red last year? That model needed a special overlay just to understand the game's pixel graphics, and it lost track of where it was between frames. Fable, by contrast, can beat Pokémon FireRed using only its vision — no tricks needed. It can also grab exact numbers from complex scientific charts and rebuild a web app's source code from screenshots alone.

To keep things safe, Fable automatically routes certain sensitive requests through the less capable Opus 4.8. Anthropic admits these safeguards are conservative — they might flag harmless prompts about 5 percent of the time — but the company says it's working to reduce those false positives.

On Tuesday, Anthropic also released Mythos 5, which runs on the same core technology but with fewer restrictions. It's available first through Project Glasswing, with wider access planned later. After June 22, Fable 5 will cost $10 per million input tokens and $50 per million output tokens, though Anthropic hopes to eventually fold it back into standard subscription plans.