Plan mode
Also called planning mode, /plan
A coding agent setting where it reads the code and writes out what it means to change, for you to approve before it edits.
Ask a coding agent for a change and it usually starts editing at once, making choices as it goes: which files matter, which pattern to follow, whether to change every caller or add a wrapper. Plan mode makes it stop after the reading and say what it intends to do. A wrong assumption caught there costs a sentence to correct; caught in the diff, it costs a revert.
It's worth it when you're unsure of the approach, the change spans several files, or you don't know the code. For a fix you could describe in one sentence, the plan is mostly reading what you already knew.
For example
Before moving sign-in to a new session library, a developer switches to plan mode, sees the agent means to rewrite every caller, and asks for a wrapper instead.
Put it to use
Where you'll meet plan mode in ChatGPT, Gemini and Claude, how to use it there, and the mix-up most people make.
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