Anthropic published the official Opus 5 prompting guide, and most of it is subtraction — it tells you to delete three lines you've put in every serious prompt for two years, including the check-your-work line everyone ends with. The whole thing is four blocks in the prompt, one line deleted, and one rule for reviews. No API, no code — just the regular Claude app. - The build rules. Hand over one complete brief up front (not step-by-step — that was for older models that drifted). Fence it: write what NOT to build or invent, and let it decide the cosmetics. Use two separate caps — one on the thing it builds (e.g. 5 sections), one on the chat reply. And delete "double-check and fix mistakes" — Opus 5 already reviews itself as it builds, so that line just reruns a check it already did and burns your limits. - The review rule I had backwards. When you hand it something finished, "only flag serious issues" doesn't tell it how hard to look — it tells it how much to say, and you never see the long list. Ask for "every issue, big or small, I'll decide what matters" and filter yourself after. Same page: conservative gave me 3 issues; "list everything" surfaced a long list the first run never mentioned. - The head-to-head. Same job, two prompts. The rule-built one finished fast with a 2-line reply and exactly the 5 sections I asked for. The old roleplay + step-by-step + be-thorough + check-twice prompt ran 10+ minutes and built more than I asked. Same model — the old prompt was just written for a model that needed the help. My take: they killed the ritual half — the lines you bolt on to make it "try harder." What survived and got more important is the boring half: clear instructions, real context, why it matters, an example when you need a format. If you can brief a person, you can prompt this model. Caveat: it's one week and one page, so test it on your own work before rewriting every saved prompt. 📎 Full guide PDF pinned below — all five rules, the finished prompt, and the old-vs-new head-to-head.