Plan Mode in Claude Code

Plan mode is one of the most important features in Claude Code, and it's the practical starting point for spec-driven development. When you enter plan mode using Shift+Tab, Claude switches into a restricted state where it can read your codebase, search files, deploy subagents to analyze your architecture, fetch web content, read and write tasks, and ask you clarifying questions — but it cannot create, edit, or delete any files, run modifying commands, or install packages. The goal is to come away with a highly detailed markdown plan before any building begins.

This lesson walks through a live demo of starting a brand new project — a financial agency dashboard — entirely from plan mode. You'll see how to enter plan mode, what Claude can and can't do while in it, and how the process naturally leads into the clarifying questions and task management workflows covered in the next lessons.

What's covered:

• How to enter plan mode: Shift+Tab cycling, the --permission-mode plan CLI flag, and setting it as default in settings.json
• What Claude can do in plan mode: read files, search, subagents, web fetch, todos, and ask questions
• What Claude cannot do: edit, create, or delete files, run modifying commands, or install packages
• Live demo starting a new project from an empty folder with a raw CSV dataset
• How Claude automatically enters plan mode for complex prompts in longer sessions
• Why plan mode matters more in existing codebases where Claude explores architecture before asking questions