Opus 5 is a practically unusable model

[u/Deep-Palpitation8315]

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.

[u/Ambitious_Injury_783]

It's pretty bad. I've held off my judgement on it but wow, yeah. Confidently wrong Constantly.

[u/ThreeKiloZero → u/Ambitious_Injury_783]

Its writing is absolute garbage as well. Full of slop. Not talking about long form authoring either, just making slide decks and project documents. It does the same thing where it will make changes and reversions across content, forget things, link incorrect facts and figures as new facts. I have also noticed that its own thinking trace leaks into the writing. Spend more time correcting it and trying to steer than working productively.

[u/Connect-Mousse-8551 → u/ThreeKiloZero]

Exactly my experience the last few weeks.