Plan before you edit: Plan mode

🎯Goal. Make Claude research and propose a plan you approve before it changes a single file.

1. 1Press Shift+Tab to cycle permission modes until the status bar shows plan mode (default → acceptEdits → plan), or start with claude --permission-mode plan. In plan mode Claude reads files and runs read-only commands but does not edit your source.
2. 2Describe a bigger change — "Split my single-file RNA-seq script into modules and add tests". Claude explores the repo and writes a step-by-step plan instead of editing.
3. 3When the plan is ready Claude asks how to proceed: approve and let it edit, approve and review each edit, or keep planning with feedback. Press Shift+Tab again to leave plan mode without approving.

✓You'll see. A written, step-by-step plan you can read and correct before any code changes — no surprise edits.

💳Cost. Plan mode prevents expensive re-work: Claude proposes the approach up front, so you catch a wrong direction before it writes (and re-writes) files.

💡Takeaway. For anything non-trivial, plan first — Shift+Tab into plan mode, approve the approach, then let Claude implement it.