[MODEL] Opus 4.8 very bad, like cursor(auto) 1 year ago

Open 💬 0 comments Opened Jun 20, 2026 by ariran5

Preflight Checklist

  • [x] I have searched existing issues for similar behavior reports
  • [x] This report does NOT contain sensitive information (API keys, passwords, etc.)

Type of Behavior Issue

Claude ignored my instructions or configuration

What You Asked Claude to Do

after the release of fable 5, I feel a strong degradation of opus 4.8. It shows poor results in agent-based task execution scenarios, does not do enough research before execution, and as a result, it does low-quality work that needs to be improved a lot with it.

I asked opus to make beautiful designs for me in html file format, he didn't make them beautiful, and when we were done with 40 options that I didn't like, I switched to Haiku and only he returned to the problem of clarifying the details and was able to figure out what needed to be done differently. Opus has become very bad for me

What Claude Actually Did

Use opus

Expected Behavior

Good work

Files Affected

Permission Mode

Accept Edits was ON (auto-accepting changes)

Can You Reproduce This?

Yes, every time with the same prompt

Steps to Reproduce

_No response_

Claude Model

Opus

Relevant Conversation

Impact

Critical - Data loss or corrupted project

Claude Code Version

Version 2.1.183

Platform

Anthropic API

Additional Context

_No response_

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