The Power of Composer for Multi-File and Feature Development

In this lesson, we will master Cursor’s tools for complex, multi-file back-end development. By the end, we will have built the authentication module for the “NoteIt” application and understand the distinct roles of the chat modes and the Composer interface.

In our previous lesson, we accomplished a major feat: we crafted the entire professional frontend for our NoteIt application through a series of precise prompts. When we used a single prompt to generate all of our UI pages across multiple files, we were implicitly witnessing the power of Cursor’s core multi-file editing engine.

We intentionally kept our focus on the art of prompting, learning what to ask for. Now, we shift our focus to the tools that execute these complex requests. This lesson is a deep dive into how Cursor handles complex changes. It clarifies the roles of its chat modes and the powerful Composer interface.

Understanding Cursor’s editing workflows

To use Cursor effectively, we need to understand the two main ways we can ask it to edit our code, and the behavioral modes that control how it responds.

Two primary ways to request an edit

There are two ways to request an edit, the in-line targeted edits, and multi-file composer edits.

• In-line edit (Cmd+K): This is our tool for surgical, targeted changes. We select a specific block of code within a single file and give the AI a direct command (e.g., “refactor this,” “add comments”).

• The chat panel (Cmd+L or Cmd+I): This is our command center for everything else, from simple questions to complex, project-wide features that span multiple files. The behavior of the AI within the chat is governed by the chat mode.

Understanding the chat modes

The chat mode we select dictates how the AI generates and applies changes.

• Ask mode: This mode is for learning, planning, and asking questions. When we ask it to make a change, it will first generate a diff and then ask for our permission to apply it. We must explicitly click a button to accept the diff before the changes are staged for final review.

• Agent mode: This mode is for complex ...