Plan Mode, and the One-Sentence Rule for Skipping It

You ask for a feature. It starts editing immediately, and solves the wrong problem in the wrong place.

Plan mode separates exploration from implementation. First: read this directory and understand how sessions work. Then: I want to add X: what changes, and what's the plan? Approve it, then let it build.

In my own use, reviewing a plan runs about thirty seconds. Unwinding a wrong diff has cost me thirty minutes or more.

And the counter-rule, which matters just as much: if you can describe the diff in one sentence, skip the plan. Rename a variable, add a log line: planning that is pure ceremony.