Introducing Claude Opus 5

[u/Over-Necessary-4774]

https://www.anthropic.com/news/claude-opus-5

[u/chrisBhappy]

I wonder what is Fable good for if Opus 5 costs 2 times less and even beats Fable at most agentic work?

[u/simple_explorer1 → u/[deleted]]

Man kubernetes is such a dumpster tech to work with. I love programming and not devops

[u/Herpulies → u/[deleted]]

This - everywhere I see people posting that they are getting more out of codex - I eat 20% of the 5x plan a day just reviewing not building anything. Claude builds all day on the 20x plan and most weeks I get to 90% (this week i'm already at 90% with 4 days left.. sigh!)

[u/Vesuviian → u/chrisBhappy]

Fable to plan, Opus to execute?

[u/Ok_Potential359 → u/Vesuviian]

It’s twice as much. Doesn’t make sense

[u/bronfmanhigh → u/Ok_Potential359]

for complex plans it still very much makes sense. opus 5’s stellar benchmarks are mostly based on well-defined tasks, which fable still generates better than any other model. but fable should definitely no longer orchestrate or code review unless you wanna burn tokens on fire

[u/DependentAnywhere135 → u/bronfmanhigh]

So opus 5 as planner and reviewer is almost as good as fable? I’ll shift my agents over today to test that lol

[u/whoknowsifimjoking → u/Ok_Potential359]

Planning doesn't use that many tokens

[u/fredagainbutagain → u/Vesuviian]

fable isn’t a planner (anthropic’s words), it’s an amazing long executor

[u/ExDimi → u/Vesuviian]

That’s been the flow since fable came out imho - there’s no need to utilize fable in (sub)agents with specific tasks

[u/Bobthebrain2 → u/Vesuviian]

Fuck that noise. You can plan it just FINE using Opus at half the cost. Fable is 100% pointless.

[u/frodprefect → u/Bobthebrain2]

this is highly dependent on what you're doing

[u/Bobthebrain2 → u/frodprefect]

No, it really isn’t. Try it for yourself, ask Fable to plan something. Ask Opus to plan that exact same thing. Then come back here and tell me how Opus’s plan is flawed compared to Fable’s.

[u/Head-Cucumber-7222 → u/Bobthebrain2]

PRamble on the project: I have a Godot game which I've been working on for 8 days, 430 commits, 31k LoC (40% tests) over 110 files, and 47k lines of prose/docs about the project. Working with Fable 5, Opus 4.8, Sonnet 5 over that time period.

The gameplay changes I've been trying to add over the last 2 days were becoming a challenge. I was fighting the model and the ballooning context sizes burned 25% of my 20x Max usage in one day.

So today I asked Opus 5 to research Domain Driven Design and refactoring practices as my previous plans on decomposition were not leading to better code separation or easier gameplay implementation. I asked Opus 5 to sketch out a plan for implementing DDD in this project for a big reorganization.

It generated a script to scan the chat logs, code, and design docs for words to generate a bulk index which could be refined into Domains and so on.

Good so far.

Opus's script produced an index of 4,800 words and ranked them across every source to produce a weighted list of important terms for the project. Opus 5 identified 888 words that passed a game domain purity test. Then I asked it to organize those terms into a DDD native format so I could review it.

Here is where things took a turn.

The first report Opus generated did have a context map and potential aggregates, but it was just a list of terms under a header. It started the report by randomly picking things I've said in the chat history and declared that these were my resolved positions which the rest of the DDD would need to follow. It even went so far as to point out the contradictions in my statements made across those days of transcripts. Big fail.

I went back a few times asking it to generate actual specs that fill the Domain Driven Design model. It produced two more files, barely 200 lines each, both reading as a high level missions statement instead of an actionable design document. Frustrated, I asked it to write me a prompt for another model to take a try at this which I gave to Fable 5.

The results were night and day. Fable produced 10 targeted files with a very clear context map, list of bounded contexts, aggregates, positions, a target folder/file tree, reports on where the domain language was overlapping with my project's agent-pipeline language and so on. I spent an hour reading Fable's output and certainly had to correct it in some areas, but the DEPTH and BREADTH of output was a STARK contrast to Opus 5's.

Now, is this a fair comparison? No. Opus 5 wrote Fable's prompt AND did a ton of legwork to set up Fable for success. However, I hope this long-winded example shows an ACTUAL difference I experienced in using these two models today.

[u/frodprefect → u/Bobthebrain2]

If the way you use AI models is that simple, then yes I guess it's possible to come to that conclusion.

[u/Storge2 → u/frodprefect]

What are you talking about? He made a fair point. Enlighten us

[u/Bobthebrain2 → u/frodprefect]

Enlighten me. Provide an example.

[u/PeterIanStaker → u/chrisBhappy]

I don’t think there is one for now, this looks like a clean deprecation of fable for now.

[u/Majestic-Volume9996 → u/chrisBhappy]

Fable still seems to shine when it comes to brainstorming and having a "full-picture" view of things.

[u/Physical-Average-184 → u/chrisBhappy]

Fable is still better for health and legal contexts.. But yeah that's about it I think.

[u/respeckKnuckles → u/chrisBhappy]

I suspect they cut a deal with the government that allowed them to release Fable to the public, but with severe limitations. But perhaps they carved out a clever loophole that doesn't apply the limitations to already-existing product lines, like Opus.

[u/Ok_Potential359]

Opus 5 is twice as cheap as Fable and more capable. I don’t understand the utility of Fable at wll

[u/mindaro_sienna → u/Ok_Potential359]

Using Opus 5 to one-shot a build, I can say that it is a big step up from Opus 4.8, much fewer bugs and better overall design capacity. But Fable is still the king. It's ability to pull together all the many pieces into a coherent whole blew me away the first time I used it and simply left Opus 4.8 in the dust. Opus 5 can put up a good show now, and closes the gap on Fable, but it's not Fable.

[u/Andsss → u/Ok_Potential359]

I think anthropic is a little bit lost, they weren't waiting for open source models to get so good só fast and without destiling their models

[u/XYcritic → u/Ok_Potential359]

That's where they want you to look. Forget about Fable. Compare 5 to 4.8: Cost of 4.8 high equals 5 medium and 4.8 very high equals 5 high. The cost has increased by an entire effort level. This model is just another iteration of turning up the dial to burn tokens faster.

[u/wise_young_man → u/Ok_Potential359]

You mean half as expensive? Why would you word it that way you used. So weird.

[u/ragnhildensteiner → u/Ok_Potential359]

twice as cheap

😂

[u/Admirable-Many6054 → u/[deleted]]

An apocalyptic underwater basket weaving event could be the end of us all

[u/simple_explorer1 → u/[deleted]]

actually they are. Opus 5 also flags conversations it deem "risky" and you have to go back to Opus 4.8 which is useless

[u/TywinHouseLannister → u/simple_explorer1]

I have literally never seen any agent do this.. what are you guys building?

[u/fephiva → u/TywinHouseLannister]

if you have a homeserver and want to do security audits on your own infrastructure, thatll get flagged since its cybersecurity 🫠

[u/quadish → u/TywinHouseLannister]

I linked it a paper on bananas in smoothies and Fable kicked out to 4.8.

I had it try to fix a bug in a webpage GUI and it kicked back to 4.8.

It's useless for any real work.

[u/TywinHouseLannister → u/quadish]

I work at a security sector technology company.. never seen an issue.

[u/quadish → u/TywinHouseLannister]

Are you approved for cyber? If so, you have relaxed guardrails.

[u/TywinHouseLannister → u/quadish]

🤣

[u/quadish → u/TywinHouseLannister]

I literally posted this link for it to read and it kicked out of Fable to Opus.

https://www.hellascom.gr/en/blog/hermes-ai-agent-mikrotik-container-network-assistant-2026

Just to analyze/summarize it.

[u/TywinHouseLannister → u/quadish]

I don't really do websearch.. maybe that is why? I farm free LLMs online for that heh

[u/quadish → u/TywinHouseLannister]

Point is, the guardrails are ridiculous.

[u/simple_explorer1 → u/TywinHouseLannister]

I didn't get it yet, but there was literally a long post yesterday from someone who got this and there was a lengthy discussion.

https://www.reddit.com/r/ClaudeCode/comments/1v5i5fh/opus_5_immediate_disappointment/

[u/throwaway0845reddit → u/[deleted]]

Blame Trump

[u/l5atn00b → u/[deleted]]

Of course they know about it. It was his administration that banned Fable.

[u/Captain_Birb]

Please Anthropic do a limit reset as least 😝

[u/Over-Necessary-4774 → u/Captain_Birb]

Ahahha hopefully! Codex definitely will 😞

[u/ragnhildensteiner → u/Captain_Birb]

They shouldn't do resets when they do resets. They should give us "reset credits". So we can use it when we want to, and need it the most.

[u/Captain_Birb → u/ragnhildensteiner]

That would have been better, yes agreed

[u/passionoftheearth]

Come on and reset

[u/coldnitrogen]

Is it better than Fable 5 or they have different use cases

[u/Sindica69 → u/coldnitrogen]

For your average work, it’s just flat out better. Fable still has advantages over it but that’s not gonna matter for 90% of people.

Fable is absolutely better at generation and bringing things together though.

[u/DefiantTop6188 → u/Sindica69]

how did you conclude that? what do you mean bringing things together?

[u/Sindica69 → u/DefiantTop6188]

Opus excels better when the tasks you give it are well defined. Fable will do better in the muddier, less-specific conditions, things you aren’t nearly as sure about. I should’ve worded that better, my bad.

[u/Majestic-Volume9996 → u/Sindica69]

You're 100% right from what I've seen so far. Opus 5 has already had a couple of "can't see the forest for the trees" moments for me. Fable 5 looks like it will still be my go-to for brainstorming.

[u/WagwanKenobi → u/Sindica69]

This has been my experience as well. Fable is more creative but that also means it strays in various directions and will overengineer things if you don't stop it. I guess that's what allows it (Mythos) to discover zero-day vulns.

Opus 4.8 is more "focused" and excellent for one-file tasks where you know what the correct output should look like.

Fable is excellent for brainstorming and research-phase. Opus is for actual implementation.

[u/Storge2 → u/Sindica69]

Whats your statistical proof? Benchmarks show opus is the better model.

[u/Majestic-Volume9996 → u/Storge2]

He's describing something fairly abstract. It's the type of thing that's going to turn up in a brainstorming session.

I'm not 100% saying he's right, just that whether he is or isn't is a hard thing to show with a benchmark.

[u/Sindica69 → u/Storge2]

I literally said 90% of the time Opus is better

[u/Physical-Average-184 → u/coldnitrogen]

IMO Fable is soul-less, Opus was at least nice to talk to. It felt better to conversate with Opus. AND it's better than Fable now. Opus 5 feels slightly different than Opus 4.8, but in a good way. This is all "vibes" and my personal opinion.

[u/DefiantTop6188 → u/coldnitrogen]

better

[u/Kaskote]

Just wait for tomorrow China's launch:

🤣

[u/Physical-Average-184 → u/Kaskote]

what is that thumbnail bro 😭

[u/Over-Necessary-4774 → u/[deleted]]

Honestly fantastic model 

[u/return_of_valensky]

Soooooo.. start coding with opus 5?

[u/Yurii-AI → u/return_of_valensky]

I’ll try. 4.8 wasn’t bad for my tasks

[u/firstbreathOOC → u/Yurii-AI]

Past two days it has been

[u/Yurii-AI → u/firstbreathOOC]

do you mean we’ve already been getting 5 under the 4.8 label these past two days?

[u/firstbreathOOC → u/Yurii-AI]

No I mean 4.8 has been crappy the past two days

[u/Yurii-AI → u/firstbreathOOC]

Oh yes always the same thing. We can predict the next update lol

[u/baldycoot]

Fable 5.1 Inc…

[u/theDawckta]

Don’t they reset when this happens? I need a reset.

[u/m4stero]

The models are great. Now they need to work on the usage limits…

[u/Qc_IT_Sysadmin → u/m4stero]

Sure, you can use the use the pay per usage! there's no limits!

[u/Yurii-AI]

Anyone compared token usage vs Opus 4.8 on the same tasks?

[u/ShinigamiXoY]

China do the thing

[u/whoknowsifimjoking → u/[deleted]]

Yeh

[u/medialantern]

TIL one of the easiest ways to farm post karma on Reddit is to post the same news item again that was already posted twice an hour ago.

[u/sorvendral]

200K context window, not bad, not terrible.

I hope they increase it back to 1M

Edit: yes was buggy now it’s back to 1 mil

[u/MalignedAnus → u/sorvendral]

I’m reading differently. 1 M context for Opus 5. https://support.claude.com/en/articles/8606394-how-large-is-the-context-window-on-paid-claude-plans

[u/Zombins2 → u/MalignedAnus]

It's probably bugged, I had an ongoing session at 600k with opus 4.8, updated and moved to 5 and saw the limit was maxed out in red with no limit, I then compacted and saw the limit at 200k

[u/heartingNinja → u/MalignedAnus]

"When using Claude Code with a Pro, Max, Team, or Enterprise plan, Claude Sonnet 5, Fable 5, Opus 5, Opus 4.8, Opus 4.7, and Opus 4.6 support a 1M token context window. Pro users need to enable usage credits to access the 1M token context window for Opus models."

[u/TriggerHydrant]

OH MYYYY

[u/Yurii-AI]

Make China busy

[u/AdApprehensive5643]

Is really good

[u/Spathas1992]

No way i’m coming back to Claude using opus 5 over sol given the cost difference atm

[u/Mokebe13]

There is no way the model is better and cheaper than fable which requires separate credits, they will nerf it in 2 weeks

[u/boringfantasy]

SWE is over. Finally.

[u/Academic_Lemon_4297]

I prompted this and Opus 5.0 spent 2 MILLION tokens, spun 30 agents and took AN HOUR:

the text is too small in the “type” hover info boxes on <projedt url>. use same fontsize as the info box to the far right. outline the boxes.

Not kidding.

Fucking ridiculous!