Intermediate

Cursor

Cursor is a VS Code fork rebuilt around AI — Claude models are first-class citizens, not an add-on extension. Chat, inline completions, and Composer (multi-file agentic editing) are deeply integrated into the editor rather than bolted on.

Chat Panel: Questions About Your Codebase

The Cursor chat panel gives Claude access to your codebase context. Key features:

@ mentions: Reference specific files (@filename), symbols (@function), or the entire codebase (@codebase) to include them in context
Automatic context: Cursor includes the current file and visible code as implicit context — you don't need to paste code manually
Web search: @web lets Claude search the web for documentation or current information
Image input: Paste screenshots of error messages or UI mockups directly into the chat

Chat mode is for questions, explanations, and generating code snippets. For making actual changes to files, use Composer.

Composer: Multi-File Agentic Editing

Composer (Cmd/Ctrl+I) is Cursor's agentic mode. You describe a task; Claude plans and executes changes across multiple files:

Claude proposes a plan — which files to create, modify, or delete
Diffs are shown inline for each file before you accept them
You can accept all changes, accept individual files, or reject and refine the task
Composer can run terminal commands as part of the task (with your approval)

Best practices for Composer: give a clear, scoped task ("Add a dark mode toggle to the Settings component"); avoid very large tasks in one shot (splitting into phases works better than one massive prompt); review each file's diff before accepting.

Tab Autocomplete

Cursor's Tab key triggers AI-powered completions. Unlike Copilot-style completions, Cursor's completions are:

Context-aware across open files, not just the current file
Capable of multi-line completions — pressing Tab once can complete an entire function
Predictive — Cursor tries to anticipate your next edit based on recent changes (not just cursor position)

Cursor's tab completions use a smaller, faster model optimised for speed — not the full Claude model. The chat and Composer features use the selected Claude model.

Selecting Claude Models in Cursor

Cursor lets you select which model to use for Chat and Composer. As of 2025:

Claude Sonnet — default and recommended for most tasks; good balance of capability and speed
Claude Opus — more capable, slower; use for complex architecture, difficult debugging, or large refactors

Model selection is in Settings → Models. You can set different defaults for Chat and Composer separately. With your own Anthropic API key (Cursor can use BYOK — Bring Your Own Key), you can access the latest Claude models as soon as they are available.

Cursor Rules: Project-Level AI Instructions

.cursorrules is a file in your project root that provides persistent instructions to Claude for every interaction in that project. It is Cursor's equivalent of CLAUDE.md:

Project conventions: naming style, file organisation, patterns to follow
Technology stack: which libraries to use and avoid
Output preferences: comment style, TypeScript strictness, error handling patterns
Known constraints: files not to touch, production configs to leave alone

Example .cursorrules entry: "This is a Next.js 14 App Router project. Always use server components unless client interactivity is required. Use TypeScript strict mode. Never use any/unknown without a comment explaining why."

Checklist: Do You Understand This?

Chat panel: use @ mentions to include specific context (files, symbols, web) — Claude sees your current file automatically
Composer (Cmd/Ctrl+I): agentic multi-file editing — propose → review diff per file → accept/reject
Tab autocomplete: context-aware multi-line completions using a fast, smaller model
Model selection: Sonnet for most tasks, Opus for complex work — BYOK with Anthropic API for latest models
.cursorrules: persistent project instructions — put stack conventions, naming rules, and constraints here