What's New

Anthropic shipped Claude Fable 5 today (June 9, 2026) — in their own words, the most capable model they've made generally available. And in Ayeto you can assign it to any assistant right now, with no waiting and no migration.

Fable 5 belongs to Anthropic's new "Mythos" class, which sits above their existing Opus models. Put simply: it's the strongest thing from Anthropic you can currently run in production.

Why It Matters

Fable 5 targets work that earlier models couldn't sustain — long, multi-step, asynchronous tasks. Anthropic says the model can work autonomously for days at a time: planning across stages, delegating to sub-agents, and checking its own output.

A few concrete points from Anthropic's announcement:

Software engineering. According to Anthropic, Stripe used Fable 5 to run a codebase-wide migration across a 50-million-line Ruby codebase in a single day — work that would have taken a team over two months by hand.
Vision. Fable 5 is the new state of the art for vision tasks — reading numbers from charts, tables and PDFs, and rebuilding a web app's source from screenshots alone.
Knowledge work. Top scores on finance and analytics benchmarks for senior-level reasoning, with strong document-based reasoning.

This fits Ayeto well: an assistant equipped with tools now gets a model that can carry longer, more complex jobs with minimal supervision.

What You Should Know

Fable 5 is frontier-grade performance, and that comes with a couple of things worth keeping in mind:

Pricing. Anthropic lists it at $10 per million input tokens and $50 per million output tokens (with a 90% prompt-caching discount). It's a premium model — in Ayeto that shows up in credits, so keep a cheaper model for routine work and bring in Fable 5 where it earns its keep.
Safety fallback. Anthropic launched Fable 5 with safeguards: queries related to cybersecurity, biology and chemistry are automatically handled by Claude Opus 4.8 instead. Per Anthropic, this triggers in fewer than 5% of sessions, and the user is always informed when it happens.

How to Switch It On in Ayeto

The Ayeto principle stays the same — no vendor lock-in. You assign Fable 5 just like any other model:

Open the assistant you want to upgrade.
In model settings, select Claude Fable 5.
Save and test it on a real task.

And if you're not sure a premium model is worth it, use Model Comparison to put Fable 5 next to Opus or Sonnet on your own prompt — you'll see the difference in output, time and credits side by side.

Source for the model details: Anthropic's official announcement.

Try Fable 5 today — assign it to your most demanding assistant and let us know how it did.