Most of the time I see someone complain that AI coding assistants "don't actually save time," the assistant isn't the problem. The prompt is. I've been keeping a running list of the prompt failure modes that turn a 30-second Cursor / Claude Code / Copilot Chat interaction into a 20-minute back-and-forth. Eight have come up often enough to be worth writing down. None of them are about model choice. All of them are fixable in the prompt itself. If you read this and recognise three or four of your own habits in here, you'll get more time back than from upgrading to a bigger model. 1. "Please debug this" with no failure mode The canonical bad prompt. You paste 200 lines of code, type "please debug this," and the assistant hallucinates a problem because you didn't tell it which problem to look for. A function with no obvious bug has infinite possible bugs. The model picks one that sounds plausible and you spend the next ten minutes arguing about a non-issue. Fix: name the failure mode before pasting code.…