Plan First, Then Execute
Why planning mode prevents most agent disasters, how to review a plan, and how to break large features into agent-sized steps.
The worst agent sessions follow the same script. You ask for a feature, the agent starts editing immediately, and twenty minutes later you're looking at changes across thirty files built on an assumption you'd have rejected in one sentence, if anyone had asked. Now you either untangle it or throw it all away.
Almost all of that pain is avoidable with one habit: make the agent plan before it codes, and review the plan before you approve it. A plan is cheap to change; code is expensive to unwind. In this lesson you'll learn how to get a good plan from any coding agent, a fast way to review one, how to break big features into agent-sized steps, and when it's fine to skip planning altogether.
Why planning prevents most agent disasters
Three things make planning disproportionately valuable with agents.
Misunderstandings surface early. When an agent writes a plan, it has to commit to an interpretation of your task in plain English. You can read that in a minute and catch "wait, I meant the admin dashboard, not the customer one" before a single file changes.
First ideas create momentum. Once an agent has written code along one approach, it tends to keep building on it, patching problems rather than stepping back. Choosing the approach during planning, when nothing exists yet, avoids sunk-cost spirals.
Big decisions become visible. Adding a dependency, changing a database schema, rewriting a shared component: these are the choices you most want a say in, and in a plan they're spelled out instead of buried in a diff.
The cost curve is stark. Fixing a wrong assumption in a plan means editing a sentence. Fixing it after implementation means reviewing, reverting, and re-running the whole task.