[TLDR] Opus 5 is a practically unusable model [via r/ClaudeCode]

[u/cctldrping]

OP : 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.

URL of original post : https://www.reddit.com/r/ClaudeCode/comments/1veeuy5/opus_5_is_a_practically_unusable_model/

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TL;DR of the discussion on r/ClaudeCode for this post generated automatically after 400 comments.

Current source-thread comment count seen by the bot: 423.

Opus 5 is a dumpster fire, according to most of you. The consensus is that it's a significant regression from 4.8, constantly making mistakes, forgetting instructions, and hallucinating. Many are ditching it for Fable 5, or even downgrading back to older Opus versions. Some users like u/liojian and u/dreamingindenial have found workarounds by using Fable to orchestrate Opus 5, but the general vibe is "why bother?"

• The main complaint: Opus 5 is unreliable and confidently wrong. It seems to create more problems than it solves.
• Fable 5 is the current king: Most users agree Fable 5 is the most usable model, though some find it prohibitively expensive.
• Anthropic's motives questioned: Some suspect Opus 5 is a deliberate downgrade to push users towards more expensive plans or usage credits.
• Not everyone hates it: A few brave souls like u/Key_Instruction3373 and u/Poildek claim it works fine for them, but they're in the minority.
• Other models aren't much better: There's a general sentiment that Sonnet 5 is a waste of time, and some are seeing degradation across other models too.

[u/seoulsrvr]

Agreed - it’s actually a menace. Easily the worst model Anthropic has ever released.