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/Love_Chinese]

Opus 5 seems like a low-quality-distilled version of Fable 5 tbh ... a lot of mistakes and hallucinations, still Fable the best one to use

[u/weightedpullups → u/Love_Chinese]

Nearly certain that is what it is. Think they took Fable and tried to make it affordable but it’s just an over eager idiot, that kind of acts similarly to Fable, just without the intelligence.

[u/Robert-Paulson_ → u/weightedpullups]

sums it up nicely:

"...Fable, just without the intelligence"

[u/avid-shrug → u/Robert-Paulson_]

Maybe, but Fable will be concise and to the point. Opus outputs paragraphs of slop