What I think is more alarming is that Claude's advice for prompting Opus 5 says that Opus will verify its own work [1]:

> Claude Opus 5 verifies its own work without being told to. If your prompt contains explicit verification instructions ("include a final verification step for any non-trivial task," "use a subagent to verify"), remove them: instructions like these cause over-verification on Claude Opus 5, and removing them reduces wasted tokens with no loss in quality.

My own experience over the past ~20 hours hasn't been great either, with Opus producing sloppy mockups (e.g. buttons overflowing past cards) without doing any of the purported verification.

[1] https://platform.claude.com/docs/en/build-with-claude/prompt...