Simple explanation
Welcome to Day 17. On Day 3 you used Plan Mode to plan a single change before making it. Today you use Plan Mode the way experienced builders use it — to map out an entire project before touching anything. The difference between small Plan Mode and big Plan Mode Small Plan Mode: "I want to add a button — let me plan this first." Result: Claude Code plans one change. You approve. It builds. Big Plan Mode: "I want to add a complete new section to my site over the next week — let me map the whole thing before I start." Result: Claude Code maps every file that needs changing, every new file that needs creating, every potential conflict, and every step in order. You review the entire picture. You adjust anything that looks wrong. Then you build one step at a time — with the whole map in front of you. Big Plan Mode eliminates the most expensive mistake in building: starting something complex without understanding all the pieces involved. How to use Plan Mode for a big build Turn on Plan Mode: press Shift + Tab twice. Then write a complete project brief — not a single task prompt. Describe the whole thing: "I want to add a complete resources section to my site. This includes: a new resources page at /resources, six resource cards with icons, a navigation update, a simple email capture form connected to my existing subscription system, and a thank you state after submission. Plan every file that needs to be created or changed. Show me the steps in order. Do not build anything yet." Claude Code produces a complete map. Every file. Every step. Every dependency. Read it carefully — this is where you catch problems before they cost you hours.
What to do
What to look for in a big plan: Files you did not expect — if Claude Code plans to change a file you did not think was involved, ask why before approving. Steps in the wrong order — sometimes Claude Code plans to build something that depends on something else it has not built yet. Reorder if needed. Missing pieces — read the plan and ask "what happens if a user does X?" If the plan does not cover it — add it before building. Scope creep — if the plan includes things you did not ask for, remove them now. Easier than removing them after they are built. Today's practical task 1. Think about the next big thing you want to add to your site. 2. Turn on Plan Mode (Shift + Tab twice). 3. Write a full project brief — not a task prompt — describing the complete feature. 4. Read the plan Claude Code produces. 5. Identify at least one thing in the plan you want to change before building. 6. Adjust the plan. 7. Save the approved plan as a note — this becomes your building roadmap for the next session. 8. Do not build anything today. Planning is the entire task. The saved plan is valuable beyond today. When you start next session, paste it back in with: "Here is the approved plan from our last session. Continue from step [X]." Claude Code picks up exactly where it left off.
Copy-paste prompt
I am planning a complete new feature — do not build anything yet. Here is what I want: [describe your full feature in plain English]. Plan every file that needs to be created or changed, every step in order, every dependency between steps, and any potential conflicts or risks. Show me the complete plan before doing anything.
Course note
Key takeaway
Big Plan Mode takes a complete project brief and maps every file, every step, and every dependency before touching anything. Read the plan. Adjust it. Only then build. Starting with a map is always faster than stopping to find your way mid-build.