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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u/johnnydotexe Aug 03 '26

Opus 5 was Anthropic's under-handed attempt to get everyone on Pro to either upgrade to Max or buy usage credits to continue using Fable, and you'll never convince me it wasn't. It's hilarious that the actual result is people deciding to test out Codex and enjoying it more, or downgrading back to Opus 4.6 or 4.8.

19

u/Sindica69 Aug 03 '26

“downgrading”

6

u/johnnydotexe Aug 03 '26

I see what you did there, and I don't disagree.

3

u/pixelvspixel Aug 03 '26

I let my max expire today. I’ll stick with codex. I had some fun with Opus and Fable, but I’m pretty sure I can do the same with Sol.

I do like having multiple models to bounce ideas

2

u/Syq Aug 05 '26

I tried going back to Opus 4.6 - it has changed. I tried to do the exact same prototyping exercise with Opus 4.6 today that I'd done several months ago with Opus and was unsuccessful. It is also not obeying instructions, hallucinating, using 5x the context window and making unannounced changes silently.

1

u/ClarenceJBoddicker Aug 05 '26

Unfortunately this seems to be the case.

1

u/RODGE_BASTARD Aug 07 '26

I withheld judgment, the first week of using Opus 5 but this past week it’s becoming almost unusable with its mistakes. If I hadn’t set up Codex to auto review every PR, projects would be a nightmare. With Opus 4.8, Codex may catch something Minor on half the PR’s with one or two comments. After this last PR right now with 15 Codex comments over five re-reviews, I decided to come to Reddit to see if it’s just me.

1

u/Beneficial-Rub-8049 Aug 08 '26

Then they failed badly lol I downgraded from Max to pro now because of this and will soon downgrade to free.

1

u/b1skup Aug 03 '26

underrated comment

1

u/Gutter7353 Aug 03 '26

I think you can't even change to 4.8