It was likely a dealbreaker for Anthropic, since the export control excluded Anthropic’s own foreign employees from being able to access Mythos internally. Naturally, this makes model development hard.

Apparently, you won't be able to use Mythos OR Fable for coding. From their announcement...

> routine tasks like coding and debugging will fall back to Opus 4.8.

But it’s available in Claude Code. I’m hoping that’s a typo missing a word or two in the sentence.

Yeah I think it is after reading the linked blog post.

Where is that?

Presumably they reached a backdoor agreement.

You're suggesting a for-profit company both hobbled it's own product and is actively lying about doing so. The only way that's true is if the Trump admin has crawled all the way up Anthropic's ass. But by all accounts, this is just another 10% effort by Trump and friends.

Presumably there are different levels of safety. I assumed Fable was a nerfed Mythos, and not just via safety harnesses but actual model degredation.

I don't think this is the case just because of the 'fallback' method they described, where suspicious requests are routed to Opus 4.8. If the model was degraded for certain categories of knowledge, then they'd probably be fine letting the model answer to it. IMO, of course

"Fallback" is only for LLM-training related requests (ie, ones that would compete with Anthropic (!))

For cyber and bio related requests it just refuses.

When it was briefly available I had it fallback to Opus for security related tasks. It would only refuse if you explicitly told it not to fallback.

Anthropic claims the only difference is the draconian bans on cybersecurity and biology queries.

The Sol benchmarks show Fable has slightly lower performance compared to Mythos.

https://openai.com/index/previewing-gpt-5-6-sol/

I assume they did something to the model itself.

Either way, I do hope they lift those draconian bans. Using the model was a terrible experience because of the constant downgrades. I didn't manage to harden my own projects before Fable got banned.

The session reverts to opus if it trips a limiter. Is the benchmark detecting and correcting for that?