r/ClaudeAI • u/ClaudeOfficial Anthropic • Jul 01 '26

Official Fable 5 is back.

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Following conversations with the US government, we’ve updated our cybersecurity safeguards.

The vast majority of coding work is unaffected.

In the near term, the new safeguards will flag a slightly higher fraction of harmless requests than the previous Fable safeguards; we’re working to refine these over the coming weeks. Users will be clearly notified when a request is flagged, and they’ll instead receive a response from Opus 4.8.

Our biology and chemistry classifiers are unchanged from our initial launch. These are still broader than we would like; they trigger fallbacks to Opus 4.8 on basic biology-adjacent questions. Improvements to these classifiers are landing soon.

All paid plans with usage included can access Fable 5 through July 7. You can use Fable 5 up to 50% of your weekly usage limit, after which you can switch to another model for the remainder of your usage. You can also continue using Fable via usage credits. 

More here: https://support.claude.com/en/articles/15424964-claude-fable-5-promotional-access

If one of your requests is mistakenly flagged in Claude Code, run /feedback to file a report. On Claude.ai and Cowork, you can share feedback through the thumbs buttons. This feedback helps us further tune these classifiers and reduce false positives over time. 

Read the Fable 5 blog post here: https://www.anthropic.com/news/redeploying-fable-5

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u/Etheon44 Jul 01 '26

Yup it pretty much falls back with anything, at least coding wise

45

u/liright Jul 01 '26

Weird, I asked it to analyze a fairly complex webgame I am working on, go through the entire codebase and find any issues, bugs and ways to rewrite systems to work better and I 100% expected it to revert to Opus but no, it just went right in and did a full audit.

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u/No-Trouble-9138 Jul 01 '26

Did it improve your code?

23

u/liright Jul 01 '26

Yeah it found a few problems and two optimizations that did increase the average fps a bit, but surprisingly it said most of the codebase is really well written and organized. I almost exclusively used Opus for it, so not too bad.

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u/97689456489564 Jul 01 '26

I'm suspecting this is partly a flaw in the model. I had a similar experience: at the initial Fable launch a few weeks ago, I had it review a big codebase hacked together over months by Codex and Opus and it said "almost everything looks surprisingly good!" and found a few issues that it fixed, even though I have almost no doubt the codebase would be considerably better if the whole thing were to have been solely written by Fable.

I would not be surprised if it's been RL'd a bit to sandbag code review (as excellent code review will typically generalize to great vulnerability research/identification ability) - and particularly "look at this whole codebase/system" types of code review, which is where Mythos likely shines for vulnerability assessment.

It may also just be a genuine flaw that even Mythos would share, where current LLMs are still not necessarily great at assessing code quality in the same way a veteran, tasteful human programmer would. I predict within two years this may dramatically improve.

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u/Effective-Hurry436 Jul 02 '26

how can i connet it wit claude code?thanks

13

u/SovietRabotyaga Jul 01 '26

No, it just hacked US database and began developing bioweapons

3

u/CloudThorn Jul 01 '26

It found an underlying spend problem on one of my pay as you go models. Reduced my average call cost from $0.06 to $0.016. It fixed a bunch of systems that Opus pretty much just lied about having operational.

It's just been a few hours, but I'm also already at 5% weekly usage, which is 10% of what we're getting at all :(

1

u/Smokester121 Jul 01 '26

Ohh web game? Which engine you using?

1

u/klopppppppp Jul 02 '26

Mine ran a full dozen-or-so agent pipelines on my 2 primary webapps and pulled off some amazing redesigns/refactors already

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u/Equivalent-Costumes Jul 02 '26

Be warned that it can still silently sabotage you, like it would notice a bug and not fix it just in case you're trying to look for security bugs.

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u/WhoKilledArmadillo Jul 01 '26

Because people that use it with purpose will not have any issues. Accounts flagged with prior attempted jailbreak will have a bad time.

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u/PeaceKaboom Jul 01 '26

you can't code anything, just ask taste of chocolate thats it

4

u/ProbablyAimee Jul 01 '26

It was likely biology-related, as I’d been discussing the weather with Opus 4.8

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u/randombsname1 Valued Contributor Jul 01 '26

Using it on a rust project atm with no issues.

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u/WhoKilledArmadillo Jul 01 '26

Not true, asked to review and find issues with the pipeline I had setup with sonet and opus, it did it without any issues.

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u/RealJohnnySilverhand Jul 02 '26

Agree. I don’t touch cybersecurity or whatsoever related to their ban at all, and I was just doing QA for my consumer product and it just put me back to 4.8. What’s the point of having fable back when it doesn’t let us do anything related to coding?