I spent a long time thinking the brief was the problem, and rewrote mine maybe twenty times before noticing the wandering was the agent filling in whatever I hadn't decided. Asking for the check before the goal is what narrows the goal, because you have to decide what counts as done before you can describe what you want. The spec lives in the repo and the agent goes back to it as it works, javadoc or markdown, the location matters less than the habit.