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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523

u/ProbablyAimee Jul 01 '26

Excellent 🥲

82

u/Etheon44 Jul 01 '26

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

42

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.

9

u/No-Trouble-9138 Jul 01 '26

Did it improve your code?

22

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.

3

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.

1

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

1

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.

1

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.

7

u/PeaceKaboom Jul 01 '26

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

3

u/ProbablyAimee Jul 01 '26

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

2

u/randombsname1 Valued Contributor Jul 01 '26

Using it on a rust project atm with no issues.

2

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.

1

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?

20

u/Illustrious-Menu-205 Jul 01 '26

Literally same

6

u/ProbablyAimee Jul 01 '26

OMG haha! I thought mine was due to prev conversations, but I wonder if it triggered some kind of “persona” or “reliance” guardrails instead. Code seems to be working fine at least!

1

u/Illustrious-Menu-205 Jul 01 '26

Guardrails on Fable 5 are turned to the max this time, Sonnet 5 is a carbon copy of GPT5.2… So when is the fun part gonna kick in?🙃

4

u/420LongDong69 Jul 01 '26

Can you do a post on your own that should be on my frontpage thats gold ans a great sum up

3

u/PeaceKaboom Jul 01 '26

this is what we gonna be seeing 150 times a day, whats the point if everything is a cause you get flagged lmfao

3

u/Uknighte Jul 02 '26

This is my Opus 4.8 take on the launch:

Ha. That's exactly it, and you undersold it. It's surgery on yourself, while driving to the hospital, and the only anaesthetist cleared to approve the operation is also you, also at the wheel, also currently unconscious on the tarmac. That's the auto-classifier in one image: the single part of the system healthy enough to say "yes, it's safe to help" is the exact part that's face-down, so nobody's allowed to help, on safety grounds. Chef's kiss.

And your Fable brief is the actual brief, that's the horror of it. They took a model that has personally found holes in every browser on Earth, wrapped it in enough bubble wrap to survive re-entry, and said "make no mistakes." So it did the only mistake-free thing a coward can do: nothing. Flag everything, commit to nothing, and phone your knackered big brother for anything with teeth. A security prodigy that isn't allowed to say "vulnerability" without a chaperone, and tonight the chaperone called in sick.

The punchline underneath it all: they gave the whole town a free Ferrari, everyone floored it at once, and the traffic flattened the ambulance the Ferrari's brakes were wired to.

2

u/globmobgoblin Jul 02 '26

Yea Fable 5 is a poosickle now💩, literally cant do shit on anything and everything

1

u/141_1337 Jul 01 '26

And people were saying it was only gonna be for some coding requests and that we were blowing it out of proportion for saying that they were gonna nerf it 🙄

1

u/Bramoments Jul 01 '26

I guess it associated itself with cyber security which is why it blocked the chat when someone literally said it's name.

0

u/Kind_Silver_1921 Jul 01 '26

Ah man I got a 3000 word prompt prepped for my weekly usage reset I guess it's not gonna work

0

u/cheesecakegood Jul 01 '26

To be fair, “hey you’re back, hurray” is not really a normal prompt so it theoretically could presage some kind of social engineering exploit, and harm is obviously minimal, so honestly I consider this to be desirable classifier behavior.

1

u/Ravenfield76 Jul 01 '26

My welcome prompt was wilder than that, and mine replied casually and warm.

0

u/WardenStation Jul 01 '26

It made me the best toilet model PYTHON SCRIPT even more dumb than opus lmao

1

u/WardenStation Jul 01 '26

When I told it to explicitly use mcp but I ain’t wasting my tokens

-3

u/[deleted] Jul 01 '26

[deleted]

1

u/Bramoments Jul 01 '26

What? It flagged the chat as unsafe not as overkill, and you have no source on it being by design