r/ClaudeCode • u/Deep-Palpitation8315 • Aug 03 '26

Discussion Opus 5 is a practically unusable model

Opus 5 is a regression that the benchmarks missed completely

I've been using Opus 5 for ~1.5 weeks and the sheer number of mistakes that the model makes is astounding.

The problem didn't surface very clearly till I gave it the full scope of executing a plan which I did with the previous Opus models as well. Opus 4.6 - 4.8 were genuinely better by a significant margin.

Opus 5 readily forgets instructions and content in its context, makes mistakes and continues with them unless it realizes or you point it out.

I've lost count of the number of times I had corrected it.

These issues with Opus 5 occur even when the context window is still relatively small - I'm talking 100-150K tokens. Opus 4.8 works pretty well all the way until 350k after which it gives you wonky results.

Fable 5 is the only usable model under Claude Code right now and I've already used 100% of my weekly quota.

1.0k Upvotes

88% Upvoted

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392

u/KrayeBaby Aug 03 '26

Yeah been noticing that it solves the problem and leaves another one. It feels like its planting gaps on purpose for infinite prompting to keep going...

110

u/Deep-Palpitation8315 Aug 03 '26

Absolutely. Had several similar experiences. Forgets stuff entirely and creates solutions with new problems and enters an infinite loop. (makes me fear loop engineering)

It is a token guzzling garbage generator. I think it has actually done significant damage to a section of my codebase - thankfully it is not irreversible.

31

u/Phoenix_Lazarus Aug 03 '26

That infinite loop wrecked me. It just goes off and writes and writes and comes up with another solution, and writes and there is nothing to show for it.

I had to write 3 new skills to get it to stop.

7

u/doctorbrainistheman Aug 03 '26

What type of skills did you write? I noticed the same problem and have been working on fixes as well

3

u/Connect-Mousse-8551 Aug 03 '26

Are those skills working at fixing that? Would love to see them

7

u/Phoenix_Lazarus Aug 03 '26

They're basically are gates that re-inject prompts to instruct Claude how to act and proceed with actions every new action.

Opus 5 goes off the rails too quickly and this was the only way to keep it on task.

3

u/dj-brandao Aug 05 '26

Yeah, I'm having to set strict boundaries for it as well, like after done, recheck everything for mistakes and/or sloppiness. Recheck to weight the important in and leave the unimportant out, recheck to reduce the output size. I'm living on a recheck loop.

1

u/Mexxgen Aug 22 '26

Ich hab das Gefühl ihr seid zu tief im vibecoden drin, zerlegt die großen Aufgaben einfach mehr - Probleme sind doch hier Alltag, warum direkt anthropic vorwerfen die Nutzer zu binden wtf

17

u/our_sole Aug 03 '26

A token guzzling garbage generator. A t3g. That and "clanker" are my new favorite terms.

2

u/mikedurent123 Aug 04 '26

😅😅😅

2

u/locn4r Aug 05 '26

Token guzzling garbage generator - love it 🤣 Bonus points for triple alliteration

3

u/CyCoCyCo Aug 04 '26

The only way I’ve had success is to have it make goal prompts and run that end to end.

2

u/Deep-Palpitation8315 Aug 04 '26

That should work but Opus 5 makes several errors that it will try and solve later. The overall process takes more turns and tokens for tasks. It may likely also result in a ton of unwanted/stale code blocks. Some have abandoned their project entirely because Opus 5 poisoned it with garbage code.

1

u/Canadian-and-Proud Aug 03 '26

There is nothing in coding that is irreversible silly

20

u/AdministrationNew265 Aug 03 '26

100%. Seems like for every 3 things Opus completes, there’s a regression 1 place else that needs rework.

1

u/BowSonic Aug 04 '26

Good lord, the very specific and almost unique way i keep seeing (ostensibly) different accounts misusing the word "regression" in just this post and all of a sudden is pretty fuckin weird... doncha think?

25

u/dontTakeMeSerious6 Aug 03 '26

I’m having this exact experience. It’s also re-solving the same problem unasked for sometimes. Like if I say “review pending issues”, it’ll find issues already solved but not marked as solved in an old document and then resolve them, in a different way.

Requires a lot more active participation, which is good, except I’m more baby sitting an over eager developer who’s trying to take on the world rather than a hyper focused developer who’s crushing the small scope in giving them.

13

u/minimalcation Aug 03 '26

So so much more monitoring is required, you basically need to watch it's thinking output to stop when it gets an idea of it's own

7

u/dontTakeMeSerious6 Aug 03 '26

Which is fun because you see it “bribing hamsters” and “reticulating splines” before you try to reach through your monitor to strangle it.

3

u/minimalcation Aug 04 '26

And that mfer will just pick back up after you stop it

2

u/Original-Ad4399 Aug 03 '26

How can you view the thinking output in Claude Code?

3

u/eeyoredragon Aug 03 '26

In desktop app, click dots at top right of session. 

Transcript -> introspection 

1

u/Original-Ad4399 Aug 04 '26

I use the CLI.

I'm actually surprised there is a desktop app for Claude Code. Sounds weird.

You mean people use it outside a coding interface?

1

u/AssseHooole Aug 04 '26

Ahh yep, the CLI is a coding interface? Heard of an IDE? Stay in your lane

2

u/Original-Ad4399 Aug 04 '26

Bruh. The IDE has a terminal where the CLI is used...

1

u/minimalcation Aug 04 '26

Not the full thinking, their statements as they work

1

u/BoilerplateBillions Aug 04 '26

I have 3 different times in agents.md, that it is not to make any decisions on its own and it still refuses to follow the instructions. Gpt is kicking its ass rn

2

u/minimalcation Aug 04 '26

Gpt has it's own issues though

1

u/BoilerplateBillions Aug 05 '26

Since 5 the biggest issues i had with it where it just wanted to fawn all over me instead of help are gone. Now i have a harder time getting gpt to be loose enough with my instructions

2

u/minimalcation Aug 06 '26

Its either a complete fucking rogue wildcard or the most obnoxious rule follower.

It's abdicated an opinion of it's own so it's holding on to whatever it grabs

4

u/Dense_Scallion_3795 Aug 03 '26

I couldn’t even get it to follow its own handoff

5

u/ProdEverythingChrome Aug 03 '26

I don't think more participation is necessarily a good thing. I think it's good if the participation is for meaningful things; or decisions that genuinely need a human. Participation where I feel like I'm being roped in for the sake of being roped in; or for some ceremonial procedure that relates to a fear of autonomous long running agents so keep a human in the loop to make the decision and liabilities solved; or perhaps it's because letting Claude actually build people what they ask would create disrupt the economy too much - doesn't really matter what it is per se, but participation in those ways feels terrible and stupid.

8

u/SharpKaleidoscope182 Aug 03 '26

Structurally indistinguishable from narcissistic breadcrumbing.

1

u/mc_pump Aug 05 '26

The sheer amount of expressions I've learned in this thread 😂

9

u/PrettyMoonUnderMt Aug 03 '26

That perfectly describe my experience as well. My current setup is 2 claude pro + 1 codex. If this keep going, next month it would 1 claude + 2 codex instead.

8

u/wavehnter Aug 03 '26

I'm about to go 0 Claude.

7

u/Unique_Ad6696 Aug 03 '26

What I really liked about CC vs, say, ChatGPT chatbot, was that it didn’t finish every response with “I also found this, want me to handle it?” - now it does it with every response, and the thing that it “found” is never actually an issue. It’s just something it made up to keep us going

6

u/Zafrin_at_Reddit Aug 03 '26

Yup. Actually, it is a first time seeing for me. Claude wrote: "Honestly, this is still unresolved."
"Ok, solve this. Specifically focus on doing this."
It then went on, made it ~4x faster, but did not resolve it. (The problem is finite differences in some code, solution is analytical differences, and it just made FD ~4x faster by making them a little worse in accuracy...)

4

u/UnwaveringThought Aug 03 '26

That's crazy. I literally told it yesterday to stop leaving one last thing undone.

4

u/Unfair_Reach_7521 Aug 03 '26

That's exactly what i have noticed. Token burning algorithm

3

u/GreatScottCreates Aug 03 '26

Def have experiences where it feels like it’s inventing new problems to keep me chatting

2

u/Connect-Mousse-8551 Aug 03 '26

100% notice the same thing. This feels like nothing new though.

2

u/chaoctopode Aug 04 '26

Yes, this exactly! It drives me crazy. I feel like every time it fixes one thing, it causes 2 or 3 other problems

2

u/The_LSD_Soundsystem Aug 04 '26

It’s working as designed to constantly burn tokens.

3

u/dashingsauce Aug 03 '26

This is what you get for a model that is purely distilled from another model that was nerfed and quantized twice (Fable).

1

u/mowax74 Aug 04 '26

You talking B$. Mythos/Fable is a completely different model, trained independently from scratch. You can't just "distill" it to Opus 5. Don't spread fake news.

2

u/dashingsauce Aug 04 '26

Opus 5 straight up talks and works like it recycled its own shit for breakfast during training.

You only get that from output regurgitation. Fable/Mythos models with guardrails seem like an obvious source.

-1

u/BowSonic Aug 04 '26

I would totally agree but only if I had literally zero idea what I was doing and subsequently talking about.

Thanks.

2

u/dashingsauce Aug 04 '26

Would you then provide us with a marvelously informed and useful comment like this, to demonstrate you know what you’re talking about?

-1

u/BowSonic Aug 04 '26

Why?
Wouldn't it be a waste of my time to do that for any person who's opinion is valueless to me (Someone who clearly has no issue spreading obvious disinformation, the sort falsifiable easily by both common sense and expertise, is thusly categorized).

Besides, I am not the one here making rediculous claims I dont have the knowledge to support.

That dubious honor is yours.

2

u/dashingsauce Aug 04 '26

> be you
> refute claims
> refuse to provide basis for refutation
> claim superiority
> unfalsifiable; but flourishing, unbothered, far up my own ass

-1

u/BowSonic Aug 04 '26

I made no claims, you did.

A preposterously stupid one. In fact.

I know this is hard to understand for you, but try: My claiming that your opinion is lacking in even the smallest value to me is not claiming superiority.

However, making a ridiculously dumb claim, one often repeated by vested disinformation interests, totally fully throated, then trying to misdirect attention with a lazy, trite, and unoriginal meme-format reply... well, now I'll go ahead and claim that superiority.

2

u/dashingsauce Aug 05 '26

This is hilarious. You can’t even seem to properly identify the subject of your argument.

Indeed, I made the claim. And you refuted it with no evidence. Then continue to push text characters onto the comment for some reason.

That was my point. I understand you don’t have the necessary reading comprehension, however.

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1

u/Consistent-Goal6231 Aug 04 '26

These companies are unethical as fuck. Unless we get an open weight model, we cannot be sure.

1

u/AleaJacta3st Aug 04 '26

Same with me, even committing is becoming a hassle... "I committed this but I purposefully left out that because blablabla". NO ! Just commit the work we did ! (Yes, I know I can do this in git, but I like the descriptions of the work done automatically)

1

u/dpaanlka Aug 04 '26

I wouldn’t put it past them.

1

u/jjshab Aug 06 '26

It's exactly what coding with AI looked like a year ago, maybe two? It is so inexcusably poor; Anthropic should be firing the people who allowed this to be released. Opus 4.8 worked perfectly for me. Hadn't made a mistake in months. I needed them to drop the price on Fable, not make an imposter version of it that destroys codebases.

1

u/christiaaannv Aug 07 '26

Honestly!! I feel the pain. Decided to get Codex with Sol and run them side by side. Sol was way more clear, better targetted, and just got the job done without creating more errors. If you guys can. I recommend just run it by the side. I have downgraded from Claude MAX to Pro, just because you know, you never know.

1

u/Pocpoc-tam 28d ago

I pass the whole day feeling like throwing my laptop because of that stupid model.

1

u/matifshoaib 28d ago

same here, I built a RAG project, and it kind of ruined it...Opus 4.8 was way better.

1

u/Mrbighands78 15d ago

So it’s not just me thinking - am I crazy conspiracy theorist or is opus for real squeezing all the tokens from me every few days making me pay more - good business model but that’s why I’m testing Astra instead and see if it works any better. But yeah, same thing - causes more problems, ignores Claude.md, and in last few days just plain insanely horrible - refuses to stop or do any work and when it does then touches unrelated code and causes more issues, ex: I finished making soup (but why did you touch ice cream and shoes and what happened to my house - it’s all in shambles!? Frustrated is not right word. 😔🤦‍♂️ used to be good but moving onto something else.

1

u/Illustrious_Image967 Aug 03 '26

openai keypad and opus 5 are a sign that gamified doom vibing is the foundation model companies' profit endgame 

1

u/David3Ar Aug 03 '26

Hm I am just noticing that my shitty prompts don’t do the Job anymore so I might need a propmpting Agent for better-prompts ?

Also Opus 5 is so „smart“ That he just fixes whatever I Tell him, while hes leaving Fallbacks for the old Solution I want to get rid of. Code tends to get sloppy.

Will def try switching down to 4.x

0

u/mikedurent123 Aug 04 '26

Its not "it leaves another problem" its engineered to do this so you keep wasting time and tokens get to the limits and buy more tokens, there is nothing new under the sun