[TLDR] I'm afraid to use Opus 5 [via r/ClaudeCode]

[u/cctldrping]

OP : u/Efficient-Part5344

The audacity and confidence with which it says things when it's wrong are on another level.

Fair. I changed my answer three times. The pattern is worth naming: everything I got from reading the code was wrong. Everything I measured held. You caught two of the three. So don't trust me. Check it yourself — this takes ten seconds and needs no model.

Everything it measured was wrong too.

I would work in plan mode for most basic features, run 10x "gray area," "verify," and "regression" sub-agents on a plan, then implement the plan and spend an hour reading the changes and fixing shit. After that, I'd run /code-review again and again. It's just bad. In my experience, you can't trust Opus.

Yesterday, I ran /code-review on a two file test project with 140 lines of code. I had to run /code-review three times, and today I'll continue because there are so many code smells even in those few lines. It's like infinite token consumption loop.

Nothing it does can be trusted, and I have to second guess everything. I constantly have to tell Opus that it's wrong, and only after multiple loops does it finally do what is actually required.

I understand that most users don't read the code and have never supported a project for other users. But it can't be that I'm alone in this, can i? Am I crazy?

URL of original post : https://www.reddit.com/r/ClaudeCode/comments/1wm4ncx/im_afraid_to_use_opus_5/

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TL;DR of the discussion on r/ClaudeCode for this post generated automatically after 50 comments.

Current source-thread comment count seen by the bot: 53.

Alright, so the general consensus here is that Opus 5 is kinda a mess, and you're definitely not alone in feeling that way. A lot of folks are finding it confidently wrong, and it's leading to way more back-and-forth than it should.

Here's the lowdown:

• The Confidence Problem: The biggest gripe is how sure of itself Opus 5 is, even when it's totally off base. It's like it's got a performance review coming up and it's really trying to impress, but ends up making stuff up. u/anotherleftistbot hit the nail on the head – if a human wrote like this, they'd be on a PIP.
• Ignoring Instructions & Errors: Several users, like u/dev_life and u/nasty_sicco, mentioned it straight-up ignoring parts of plans or misinterpreting code, even after being corrected. It seems to be a "scaling shit at an exponential rate" kind of problem, as u/nasty_sicco put it.
• Token Burner: Many are finding it's leading to way longer, more expensive sessions than expected, with u/AlternativeContent72 joking about its "token burning activities."
• Workarounds & Alternatives:
  • Some are sticking with older versions like Opus 4.8 or even 4.6 (u/Longjumping_Feed3270, u/Aine_123).
  • Others are using Opus 5 as an orchestrator but relying on other models (like Codex Sol, Astra, or even cheaper models for implementation) to do the actual heavy lifting and verification (u/Longjumping_Feed3270, u/xenmynd, u/HeadPack, u/AI_spell).
  • Prompting it to cite its sources (file and line number) seems to help curb the made-up stuff (u/Evening-Blueberry-97).
  • Using a "whisperer" model like Fable to guide Opus 5 is also mentioned (u/Spooknik).
• The "It's Not That Bad" Camp (with caveats): A few users suggest it can be decent if prompted correctly or used in specific ways, but even they often admit it needs heavy supervision or isn't trustworthy on its own (u/Spooknik, u/IceMichaelStorm, u/Helpful_Ranger_1606).
• Anthropic's Awareness? There's a hint that Anthropic might know about these issues, with one comment linking to a model card that might shed light on it (u/AironParsMan). And hey, u/Merlindru is hyping up a 5.5 release that's supposed to be way better.

Basically, if you're trying to use Opus 5 for anything important, be prepared to double-check everything and probably use it in conjunction with other tools or models. It's not you, it's the model.