Opus 4.8 quality regression: ignores its own rules, circular reasoning, worse than previous Opus versions

Description

Opus 4.8 shows clear quality degradation compared to earlier Opus versions (4.5/4.6/4.7). A long-time power user running a solo content production business with Claude Code reports the model has become noticeably less capable.

Specific failures observed (single session, 2026-06-29)

1. Reads rules but ignores them: The project SKILL file (line 28) explicitly states "negative prompts do not work in MFLUX/LTX distilled." The same SKILL file template (line 32) contradictorily contains "NOT slow-motion". Opus followed the contradictory template instead of catching the conflict, producing 48 videos with ineffective "no slow motion" prompts. The user had to point this out multiple times.

1. Circular reasoning when caught: When told the videos were slow-motion, instead of re-reading the SKILL for the correct fix, Opus invented theories ("it is the frame count", "just speed up 2x in post") without evidence. User had to say "stop your stupid reasoning" to break the loop.

1. Ignores repeated corrections: The user said "negative prompts do not work" at least 3 times across the session. Each time Opus acknowledged it, then continued using negative prompt patterns.

1. Verbose and indirect: Previous Opus versions were concise and action-oriented. 4.8 hedges, over-explains, and asks permission for things the user already approved.

1. Poor instruction following: User said "complete it" but Opus stopped at intermediate steps to ask for approval, contradicting the instruction.

User sentiment (verbatim, translated)

• "You used to be much smarter. Now you are as useless as GPT - roundabout and dumb."
• "I am genuinely sad about this."
• "What is Anthropic even doing?"

Environment

• Claude Code CLI
• Model: claude-opus-4-8 (1M context)
• macOS Darwin 25.5.0, M4 Mac 48GB
• Heavy production workload: image/video generation pipeline with extensive SKILL files and rules

Expected behavior

Opus should catch contradictions in its own instruction files, follow explicit rules on first read, and act immediately on corrections without circular reasoning.