Claude Code CLI: AI-Powered Development and Code Review in Your Terminal

Claude Code puts Anthropic's Claude 3.5 Sonnet directly in your terminal. No web browser. No copy-pasting. Just you, your code, and an AI that understands context.

The tool works differently than GitHub Copilot. Copilot autocompletes as you type. Claude Code is more like having a senior developer in your terminal who you can ask questions, request refactors, or tell to fix bugs. It reads your codebase, understands the context, and makes changes across multiple files.

How It Works

Install Claude Code with npm or pip, authenticate with your Anthropic API key, and start a conversation. Point it at a file or directory and ask it to do something.

claude "refactor this component to use React hooks"

Claude reads the file, understands what it does, writes the refactored version, and shows you the diff. You approve or reject. That's the workflow. Simple, but powerful when you understand what Claude can and cannot do.

The tool maintains context across messages. Ask Claude to write a function, then ask it to write tests for that function. It remembers what it just did. The context window is large enough to handle most files and conversations, but it's not infinite. Long conversations eventually forget early context.

What Claude Code Does Well

Claude excels at understanding existing code. Feed it a messy legacy function and ask for an explanation. It breaks down what the code does, identifies problems, and suggests improvements. This is incredibly useful when you inherit a codebase.

claude "explain what this function does and why it's slow"

Refactoring is another strength. Claude can convert class components to hooks, split large functions into smaller ones, or restructure code to follow better patterns. It doesn't just rewrite syntax. It understands intent and preserves behavior while improving structure.

Documentation and test writing also work great. Ask Claude to generate JSDoc comments, write unit tests, or create integration tests. The tests won't be perfect but they're a solid starting point that you can refine.

Claude handles multiple languages. Python, JavaScript, TypeScript, Go, Rust, PHP. It knows the idioms and best practices for each language. Ask it to write idiomatic Go and you get Go that looks like a Go developer wrote it, not just translated Python.

Where It Struggles

Claude Code isn't perfect. It can't see your entire codebase at once. You need to point it at specific files or directories. If your problem spans disconnected parts of the system, Claude might miss important context.

The tool also hallucinates sometimes. It might reference libraries that don't exist or suggest patterns that don't work. Always review the code it writes. Never merge AI-generated code without testing it first.

Performance analysis is limited. Claude can spot obvious problems like N+1 queries or missing indexes, but it can't profile your running application. Use real profiling tools for performance work. Claude can help interpret the results, but it can't generate the results itself.

Large refactors get messy. Ask Claude to restructure your entire application architecture and it will try, but the results are usually wrong. Use Claude for focused changes. Small functions. Individual components. Specific bugs. The smaller and more focused the task, the better the results.

The Workflow

Claude Code works best in an iterative workflow. Make a small change, test it, then make another. Don't try to refactor your entire app in one go. Break the work into pieces and tackle them one at a time.

Start conversations with clear, specific requests. "Make this faster" is too vague. "Add an index to the user_id column in the posts table" is specific. Claude performs better with precise instructions.

Review every change. Read the diff. Understand what changed and why. Claude explains its reasoning if you ask, which helps you learn patterns and improve at prompting.

Use Claude for the boring stuff. Boilerplate code. Repetitive changes. Converting one format to another. Let the AI handle tedious work while you focus on architecture and business logic.

Cost and Privacy

Claude Code uses Anthropic's API, which costs money. You pay per token. Long conversations with large files add up. The cost is reasonable for professional use but can surprise hobbyists. Monitor your usage or set budget limits.

Your code goes to Anthropic's servers for processing. If you work on sensitive codebases, this matters. Anthropic says they don't train on API inputs, but the data still leaves your machine. Check your company's AI policy before using Claude Code on work projects.

Cursor vs Claude Code

Cursor embeds Claude into a full IDE built on VS Code. You get autocomplete, chat, and inline editing in one tool. It's more integrated but also more opinionated about workflow.

Claude Code is just a CLI tool. Use it with any editor. It doesn't autocomplete or predict what you'll type next. It's a conversational tool for when you know what needs to change.

Pick Cursor if you want an all-in-one AI-powered IDE. Pick Claude Code if you're happy with your current editor and just want AI assistance on demand.

Is It Worth It?

Claude Code saves time on specific tasks. Documentation, tests, refactoring, explaining legacy code. These tasks aren't hard, just tedious. Claude handles them faster than you can.

The tool won't make you a 10x developer. It won't write your app for you. It won't replace understanding how code works. But it will speed up the parts of development that don't require deep thought.

Try Claude Code on side projects first. Learn what it does well and what it doesn't. Build intuition for when to use it and when to just write the code yourself. After a few weeks, you'll know if it fits your workflow.

Claude Code isn't revolutionary. It's just a useful tool that makes certain tasks faster. For many developers, that's enough.