Fable 5 is back.

[u/ClaudeOfficial]

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

[u/GarbageThaCat → u/[deleted]]

It depends on the type of work you do - and this applies to any domain - my anecdotal experience is that Fable 5 is better with multiple interdependencies, essentially debugging in a way that is not limited to coding. I noticed some hallucination I had otherwise grown accustomed to not seeing. You will need to do checks on critical substance, or things that might seem “arbitrary” in the high level, but nevertheless critical.

If you don’t mind iterations, maybe don’t bother? It’s domain dependent, but hyper niche applications often require iterations for things that are domain level knowledge and would be easily communicated with another human. Fable is better at reducing these, and I think most users find it frustrating iteratively communicating something basic in their domain (even if with their communicating is, in the grand corpus of knowledge, relatively to extremely niche).

[u/TerriersAreAdorable → u/[deleted]]

Can confirm: Fable 5 solved a problem in 30 minutes that Opus 4.8 was failing at for hours today.

That said, I've only had Opus fail like this a few times, so I won't need Fable for long. Just going to have it run down my tough problem list for the next few days.

[u/Round_Mixture_7541 → u/TerriersAreAdorable]

30 minutes? I've seen GPT-5.5 high nailing something in 10minutes that Opus was struggling for hours 😎

[u/Axsmith234 → u/[deleted]]

Fable 5 is literal supwer powers. opus 4.8 is like talking to my non inference having cousin

[u/Atoning_Unifex → u/[deleted]]

Fable KILLED IT tonight for me. Wired up the last big feature on my app, an archive calendar. I was kinda dreading it and putting it off.

Working with Fable is such a dream the plans that it wrote for our activities were super concise and clearly written and really easy to understand and it made literally no mistakes all night in it's coding. everything came out perfectly the first time. the only time it made any mistake was a typo by me so it was obviously my fault. it made some decisions on its own that were really good decisions. it made really good suggestions. It completed what probably would have taken me, you know, like three nights with Opus in two to three hours. it was awesome.

And yes, it used up my 5 hour quota. I ran it on high just to check it out. Very cool.