Fable is Back Today: What do we need to know (and WHEN to actually use it?)

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Fable comes back online today. We've all heard the name for weeks, so here's a quick guide on what it is and (more importantly) when to actually use it, so we don't waste money.

First things first: What is Fable? (for anyone new to it).

Let's imagine Anthropic's AIs like a "family of brains". The regulars are Opus, Sonnet and Haiku. Fable is the new, smartest one, the first of a new generation (the Mythos family), able to do things no other model could. Basically, it's the strongest Claude we can get.

It disappeared for 3 weeks:

June 9: Fable launches, everyone's talking about it.
June 12: Amazon researchers find a trick that makes Fable point out software weaknesses (and once even write code to break in). The U.S. government blocks it, and since Anthropic can't check everyone's nationality fast enough, they switch it off for everybody.
Late June: they negotiate a deal with the government.
July 1 (today): Fable comes back on, worldwide.

(By the way: other AIs like Opus 4.8, GPT-5.5 and China's Kimi K2.7 could all do the same thing that the Amazon researchers found. So it wasn't some unique "super weapon". Just a simple jailbreak that worked in other models, and those other models were powerful enough to point out those weaknesses too.)

Now, the important part of this...WHEN do we use Fable instead of Opus? Is it really that powerful?

Let's use an analogy. Think of a race. Opus is a great sprinter. Fable is a marathon runner that checks its own work as it goes.

Fable's edge is long, hard jobs that run on their own. Anthropic's own words: "the longer and more complex the task, the larger Fable's lead."

So the best option to use Fable is when the task:

takes hours or days, not minutes
has many steps and we don't want to babysit, supervise or check each one
needs to hold a LOT at once (a big codebase, a pile of documents... up to 1,000,000 tokens)
should check its own work and keep going until it's done
is genuinely hard (senior-level reasoning, a big migration, deep research)

For quicker stuff: processes that are up to half an hour or one hour. Simple substeps and subagents. That's Opus territory.

For real simple stuff (short answers, small edits, everyday writing, basic questions): just use Sonnet or Haiku. Fable there is overkill and costs more.

Real examples of Fable jobs (where it beats Opus in a solid way):

Tp build a whole thing from one prompt and let it run. Real case scenarios: People are building full games or working apps in one go. Stripe fixed a 50-million-line codebase in a single day.
Deep research where it argues with itself. It spins up "sub-agents" that debate and challenge each other, so you get a solid report instead of a more "surface" answer.
Long jobs on the computer by itself: browse websites, cancel subscriptions, do sales outreach (find leads, verify emails, write personal messages), or edit raw video into a finished piece.
Read a mountain of documents at once (a 50-page spec, a stack of contracts, a whole knowledge base) and tell us what's done, half-done and missing.
Analyze your finances with a connector (categorize spending, flag subscriptions, draw the charts).
Act like a creative director with its own subagent marketing team: study a brand, write scripts, make image/video ads, and use its "eyes" to throw out the ones with typos.

For me, the quick rule of thumb:

You have a task, and:

If you'd hand it to a junior teammate for a full day -> Fable.
If you'd answer/solve it by yourself in 5/15/45 minutes -> Opus/Sonnet.

Wait, but...is this the same Fable as June?

Almost, with two changes:

Tighter safety locks. Right now the filter is a bit too strict, so some normal coding requests get quietly answered by Opus instead of Fable. Anthropic says they'll loosen it over the next weeks, so if some coding feels a bit weak these first days, that's why. (It can also be annoying for real security work, for the same reason.)

The price cliff:

Before (June 9): Fable was fully included in Pro/Max/Team/Enterprise, free June 9-22, then usage credits.
Now (July 1): included but capped at up to 50% of our weekly usage, free only July 1-7, then usage credits.
API price is the same: $10 per million input / $50 per million output (about 2x Opus).

So after July 7, if your plan doesn't have credits turned on, Fable stops being "included" and you pay per use. Something to plan for, especially for solo users and small teams.

A money tip: cached inputs (the repeated text you send back in, ex. reusing the same document) get 90% off.

And a smart pattern: let Fable run the big thinking and have it pass the small checks to cheaper models like Opus or Sonnet. You get Fable's brain while spending fewer of its expensive tokens.

Hope this helps!

And overall: Let's put Fable to work on the right jobs this week!!

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Fable is Back Today: What do we need to know (and WHEN to actually use it?)