Claude Opus 5 Quality Complaints Mount

A thread asking 'Why does Opus 5 feel worse to work with?' surfaced real frustration from active users. Complaints included degraded code output quality compared to 4.5, slower completion times, and outputs that are hard to parse or act on. One commenter shared an example where the model returned fragmented, nearly incoherent instructions. Another noted that for non-English speakers (specifically Italian), the model 'approximates' words in ways that introduce errors.

This is notable because Anthropic has positioned Opus as its premium, high-reasoning tier. If the flagship is regressing in perceived quality while competitors are shipping at lower price points, that's a real retention problem. The complaints aren't about a niche use case either: they're about everyday coding and writing tasks.

The counterpoint is that model quality perception is subjective and prompt-sensitive. But when multiple commenters with different use cases and languages converge on the same 'it got worse' conclusion, that's not just vibes.