Finally we got a Mythos class model

Anthropic just dropped Claude Fable 5

And I have been playing with it

I think Fable 5 is not just an upgrade to Opus 4.8

It is a completely different tier

Anthropic calls it Mythos-class, which basically means it sits above everything they have ever released publicly

Complex, long tasks where Opus 4.8 would struggle or take many turns, Fable 5 just handles. Cleanly

Sometimes mid-session, it silently switches to Opus 4.8 to respond

Not a bug. That is intentional

Fable 5 is so capable in areas like cybersecurity that Anthropic added safety classifiers on top

When your query touches certain sensitive topics, it automatically hands the response to Opus 4.8 instead

So Opus 4.8 is not retired

It is literally the safety net behind the most powerful model they have ever shipped

In practice though, over 95% of sessions never trigger that switch at all

For most of what builders actually do, you are getting Fable 5 the whole time

I am still testing it on my own projects but early impressions are genuinely different from anything before

Have you tried it yet? What are you planning to test it on first?

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