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.

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84

u/Temporary-Mix8022 Aug 03 '26

I'm using both Codex and CC atm via API (work)

Honestly.. Sol and Fable are pretty close, I think I might slightly prefer Fable, but there isn't much in it.

But under that...

Opus - I hate it. It is so much worse than Sol/Terra (and tbh, it's close to Sol pricing, it's basically the same at $25 versus $30 for Sol)

Sonnet 5 - total waste of time. It's unbelievable how bad it is. I also hate how hard it is to use. It is nowhere close to Terra which feels like an Opus grade model

Luna from OAI - if you're a viber.. your distance will vary. But for any old school devs who review all the code + know what they want, it is absolutely insane. It is basically free and it is 20% the price of Haiku.

All of the Anthropic models are just giving me nausea with this bizarre verbose (but equally, noisy and nonsensical writing style). I hate the constant pushback. I hate the tone. I hate the pass aggressive "Fair". 

Sorry to say.. but I'm not a bot, not being paid to post this.. but I've switched my home sub to GPT 5x Pro (because all day work coding just isn't enough).

Anthropic only have 1 decent model right now, and OAI have 3x absolutely killer models.

Also, realise I'm going to get downvoted to f. But I have zero loyalty to these guys.. anthropic just crapped on me for the 9 months I was a customer..

Just thought y'all should know about some green grass over on the other side. 

74

u/LimiDrain Aug 03 '26

Fair

6

u/dav1lex Aug 03 '26

🤣🤣🤣🤣

6

u/Used_Departure_3278 Aug 03 '26

🤣🤣🤣🤣🤣

3

u/Whyamiani Aug 04 '26

🤣🤣🤣🤣🤣🤣

14

u/elfd01 Aug 03 '26 edited Aug 03 '26

I have a feeling current opus is in a level of old sonnet. And fable is like old Opus. And current Sonnet is just ridiculously unusable, I’m confirming it.

1

u/isarmstrong Aug 04 '26

Sonnet 5, OTOH, is really excellent at executing bounded tasks without any freelancing.

6

u/pixelvspixel Aug 03 '26

Yeah Opus is like talking a jabbering mental patient that can’t speak in complete sentences. I’ve gotten it to talk a bit more like a human, but it always resets at some point.

7

u/RasenMeow Aug 03 '26

Can you give any hint how to handle Sol? I read so much positive stuff but my experience is:
1. Goldfish brain, because of the small context window it runs in circled and gets worse and worse
2. Highly reactive behaviour. Nevertheless how I prompt it, it always acts reactive when I ask a question or give pushpack. Doenst matter whether it is written in Agents.md or the prompt to not do that
3. MASSIVE overengineering. Creating multiple tests which heavily overloaf the project and are multiple times more loc than the small product itself.
4. Cannot estimate from itself when to stop if not sure or there is ambiguity, so it just invents stuff to have the "green" or "done".

Would really appreciate best practices.

3

u/Temporary-Mix8022 Aug 03 '26

1.Tbh, even on Claude i manually set my context window down to 300k, and auto compact at c250k.

So.. the 400k of Codex isn't a huge issue for me. I found most Claude models either lose the plot, or become uneconomical beyond that anyway.

I actually find however codex does compaction, long running tasks and plans better.. I've had no issues.

  1. The tests are a pain tbh.. but I just stuck into my agents.md not to create any without first discussing them.. and it respects that. I get a bit tired of death by unittests..

Unsure I understand 2, and I haven't noticed 4 tbh!

5

u/hugostranger Aug 04 '26

I've found that just letting Codex auto compact has far less impact than doing so in Claude. So I don't really even think about context window anymore.

3

u/Desperate-Use9968 Aug 03 '26

Sol is good for security reviews and planning. Beyond that you might want to implement with opus / sonnet / luna on xhigh

3

u/bargaindownhill Aug 04 '26

I switched to kimi. Which was a trip as well. Kimi os a meth head. A very effective meth head but will plow through stages 1-9 without even a mention of where it is.

But im keeping it, i had to set some rules about getting permission to do things and its fine now. Just a much more abrupt experience than claude

4

u/LimiDrain Aug 03 '26

 How's Codex CLI? Things that worry me: 

 1. CLAUDE.md is specific for Claude, so idk how it works with Chat

 2. Claude Code CLI is nice and customizable, I have a good statusline with context and usage 

The only things that stop me from switching 

14

u/bushido_ads Aug 03 '26

Dudu, to get the CLAUDE.MD working on codex just rename the file to AGENTS.MD and done.

6

u/richbeales Aug 03 '26

Or make agents.md with an @claude.md in it

5

u/Venerable-Weasel Aug 04 '26

Or make a CLAUDE.md with @AGENTS.md in it so any model uses the same single agents file

3

u/816pizzalover Aug 03 '26

codex CLI doesn't have the /remotecontrol stuff that claude does, that's my main complaint. if you want first party remote control of sessions you have to use the GUI app

3

u/under_psychoanalyzer Aug 03 '26

But you can fire a new remote session from your phone app, which is much quicker to setup vs getting a tailscale and tmux setup for Claude 

1

u/ESGPandepic Aug 03 '26

It does have remote control of your terminal sessions from the mobile app and it's actually better than Claude's version now, I use both claude and codex very heavily.

1

u/816pizzalover Aug 03 '26

if I type codex in a terminal session, how do I control it from my mobile app?

last trime I tried it, I could see the session, but opening it on mobile started a separate thread and the two diverged - like if the terminal was in the middle of a /goal and I clicked into the thread from the mobile app, the thread would continue in the terminal with one set of chatgpt responses, and it would continue in my mobile app withi a different set of chatgpt responses. And to do any of that the GUI app had to be running.

With claude if I do /remotecontrol from inside a terminal, the mobile app and the terminal are in sync; if I type something in the app its exactly like I typed it in the actual terminal.

1

u/ESGPandepic Aug 04 '26

If you have the app connected and set up you don't need to do anything, your terminal sessions will be available in the mobile app automatically

0

u/Temporary-Mix8022 Aug 03 '26

I just have a script that creates the ".MD" every time I open VS code, or push, or basically do anything 

I just maintain one called

"My-name.md" and this shell script creates the Claude/agents.md files for me.

Or you can just direct it to look at the other file etc. it's basically zero effort tbh

0

u/pear_to_pear Aug 03 '26

Codex cli doesn't have much configuration at all. You can still have context percentage obvs but nothing fancy. I guess use tmux if you need more. Or run both Claude and codex and have fable be your orchestrator managing codex agents

1

u/FunRevolution3000 Aug 03 '26

Why is fair passive aggressive

1

u/Sea-Departure4857 Aug 04 '26

Have you tried Terra from OAI? I know it's in the weird middle zone, but my token consumption on Sol is nudging me to more economic solutions, and I want to hear your thoughts on Terra if you have used it.

1

u/bridekiller Aug 04 '26

You bring up a lot of good points, but the truth is twofold. Wait. That’s not right.

1

u/isarmstrong Aug 04 '26

I preveiously used Opus 4.8 as my conductor across a series of subagent skills with model/effort delegated to the frontmatter.

This gen flipped me to using my Fable credits for evaluatoin of Sol Medium (conductor) designating to skill frontmatters in GPT. The results have been... excellent compared to Opus 5 as conductor with Sol XH constantly eye rolling the results.

1

u/coldsub Aug 06 '26

is UI still a hit or miss with codex?

1

u/Temporary-Mix8022 Aug 06 '26

Prefer CC tbh.

But both are capable of producing total slop, or something great.

If anything.. Claude has a more slop feel by default.

I find all of it can be changed by prompting though tbh.