When to Plan vs Execute

The decision between Plan mode and Execute mode is not about preference. It is about the complexity of the task relative to the information Claude currently has. Simple, well-defined tasks — renaming a variable, adding a log statement, fixing a typo — do not need a plan. The specification is complete, the scope is obvious, and the execution path is clear. Switching to Plan mode for these tasks adds friction without adding value.

Complex tasks are a different calculus entirely. If Claude needs to understand architecture before acting, if there are multiple valid approaches, if the task spans more than three files, or if the consequences of a wrong approach require significant rollback — plan first. The cost of a five-minute planning conversation is trivial compared to the cost of a twenty-minute cleanup after Claude built the wrong thing confidently. The heuristic is: if you could not describe the complete solution in one sentence, you need a plan.

There is a third category that catches people: tasks that seem simple but are not. "Add a dark mode toggle" sounds like a one-liner. But it touches theme context, CSS variables, localStorage persistence, and every component that uses hardcoded colors. If you execute without planning, Claude will implement half the solution perfectly and miss the other half entirely. When in doubt, start in Plan mode. You can always switch to Execute after two minutes if the task turns out to be simple. You cannot undo an eager execution that went sideways.