Claude Code —
The AI Agent that writes code
from your terminal

What is Claude Code and why is it different?

Claude Code is an AI Coding Agent developed by Anthropic — the company behind Claude — and released to the general public in early 2025. Unlike tools like GitHub Copilot that offer line-by-line code completion, Claude Code acts as anautonomous Agent: it reads the code, understands the architecture, runs commands, and changes multiple files in full coordination.

In 2026 Claude Code became one of the most widely used development tools in the world. According to Anthropic's data, developers who use it report saving 40-70% of the time on Boilerplate, Debugging and Refactoring tasks. In a blind Benchmark conducted in 2026, developers preferred Claude Code's results in 67% of cases over competing tools.

What can Claude Code do?

• Read and understand your entire Codebase — including Config files, Tests and Docs
• Write, edit and delete files autonomously
• Run Terminal commands: npm test, git commit, docker build and more
• Open, read and close Pull Requests on GitHub/GitLab
• Connect external tools via MCP: Jira, Slack, Databases, APIs
• Plan a sequence of actions in Plan Mode before executing
• Work in parallel on multiple Tasks in separate windows

Installation and initial setup

As of April 2026, Anthropic offers two main installation methods: a CLI via the terminal and Desktop App dedicated to macOS and Windows. Both are free to download; usage requires a Claude Pro/Max subscription ($20/$100 per month) or an API Key from the Anthropic Console.

Method 1: Desktop App (recommended for beginners)

The Desktop App is the most convenient way to start. It includes a visual interface, project management, and support for working on multiple tasks in parallel.

Method 2: CLI (for experienced developers)

The CLI is suited to those who prefer working from the terminal, embedding in scripts, or integrating into a CI/CD Pipeline.

# macOS / Linux — no Node.js needed
curl -fsSL https://claude.ai/install.sh | sh

# after installation — first launch
claude

# Windows — via PowerShell
irm https://claude.ai/install.ps1 | iex

Authentication and account connection

On first launch you'll be asked to verify your identity. There are three authentication options:

• Claude Pro/Max — a monthly subscription ($20/$100), the simplest way for individual users
• Anthropic Console API Key — suited to teams and commercial development, pay-as-you-go pricing
• Amazon Bedrock / Google Vertex — for organizations that prefer a specific Cloud Provider

The key features of Claude Code

Plan Mode — plan before you execute

Plan Mode is one of the most important features of Claude Code. Instead of making changes immediately, Claude analyzes the problem, presents a detailed work plan, and waits for your approval before it starts working.

# activating Plan Mode from the CLI
claude --plan "Add a JWT authentication system to the Express API"

# within an existing conversation — type:
/plan Add a Redis Cache mechanism for all API calls

Plan Mode shows: a list of files that will change, the order of operations, an estimated time, and potential risks. Perfect for complex tasks you want to review before executing.

Agentic Context Window — understands the whole project

Claude Code doesn't work only with the open files — it scans the entire Repository, reads the README, understands the Dependencies, and discovers the architecture. This lets it make informed decisions that take into account the full context of the project.

Full Git Integration

Claude Code connects directly to Git and can perform all Version Control operations on your behalf:

• Creating new Branches by the task name
• Commits with descriptive, automatic Commit Messages
• Opening Pull Requests with a detailed Description
• Reading Comments on a PR and handling Requested Changes
• Squash, Rebase and Merge according to your settings

Multi-Session — parallel work

The Desktop App lets you open several "Sessions" in parallel — each with a separate Task. While one finishes Refactoring, the second writes Tests, and the third documents the API. Everything runs at the same time.

CLAUDE.md — the project memory

CLAUDE.md is a Markdown file placed at the project root, and Claude Code reads it every time a Session opens. This is the place to explain to the AI the "rules" of your project — the tech stack, preferred Conventions, run commands and more.

An example of a quality CLAUDE.md file

# Project: MyApp API

## Stack
- Node.js 22 + TypeScript 5.4
- Fastify (not Express!) for HTTP
- PostgreSQL + Drizzle ORM
- Redis for caching (TTL: 300s default)

## Conventions
- Always use async/await, never .then()
- Error handling: throw custom AppError class (src/errors.ts)
- Tests: Vitest, run `npm test` before any commit
- Branch naming: feature/TICKET-description

## Run Commands
- Dev: `npm run dev` (port 3000)
- Build: `npm run build`
- DB migrate: `npm run db:migrate`
- Lint: `npm run lint` — must pass before PR

## Important Files
- src/config/index.ts — all env variables
- src/middleware/ — auth, rate-limit, logging
- Never edit generated files in src/generated/

CLAUDE.md for large projects

In projects with a Monorepo or multiple sub-modules, you can create additional CLAUDE.md files inside specific folders. Claude Code reads all of them and creates a Hierarchy of instructions — the general one is written in the Root, the specific one in the relevant folder.

Comparison to other tools

The market is full of AI Coding tools. Here's an honest comparison between Claude Code and the most popular tools in 2026:

Use cases — what Claude Code does best

1. Large-scale Refactoring

You have 50 files using an old Callback Pattern and need to move to async/await? Claude Code will plan the change, do it file by file, run the Tests after each change, and fix Regressions that appear along the way.

# an example of an effective Refactoring prompt
"Refactor the callbacks in the src/services/ folder to use async/await.
Run the Tests after each file. If a Test fails — fix it before continuing.
Create a separate Branch: refactor/async-await"

2. Automatic Test writing

Claude Code can analyze existing code and write full Coverage: Unit Tests, Integration Tests and Edge Cases you might not have thought of. It understands your Testing Framework (Vitest, Jest, Pytest) and will write Tests that fit the project.

3. Complex Debugging

Give Claude Code access to the Logs, the Stack Trace and the relevant code. It will identify the Root Cause, explain what went wrong, and suggest 2-3 fix options with the Trade-offs of each.

4. Creating a new Feature from scratch

"Add a Notification system to our API — Email via Resend, Push via Firebase, and a Webhook. Each type needs a separate Queue in Redis. Add a simple Admin Panel to manage the Templates." Claude Code will build the whole system, write Tests, and open a PR with full documentation.

5. Code Review and Security Audit

Let Claude Code scan a PR before Merge. It will identify: potential SQL Injection, exposed Secrets, missing Input Validation, N+1 Queries in the database, and Performance Issues — all with an explanation and a suggested fix.

6. Documentation

Claude Code will read the code and write: a detailed README, JSDoc/TSDoc for every Function and Class, an OpenAPI Spec for the REST API, and an organized CHANGELOG from the Git History. Tedious for developers, but essential for the project.

Advanced tips

Connect tools via MCP

MCP (Model Context Protocol) lets you connect Claude Code to external tools. With MCP you can give Claude Code direct access to:

• Jira / Linear — read Tasks, update status, open new Tickets
• Slack / Teams — send automatic updates to the team channel
• PostgreSQL / MySQL — run Queries to check data
• Sentry / Datadog — read Errors and Alerts from Production
• Figma — read Design Tokens and generate matching CSS

# adding an MCP Server to Claude Code (in the ~/.claude/config.json file)
{
  "mcpServers": {
    "jira": {
      "command": "npx",
      "args": ["-y", "@atlassian/mcp-jira"],
      "env": {
        "JIRA_URL": "https://your-company.atlassian.net",
        "JIRA_API_TOKEN": "your-token"
      }
    }
  }
}

Useful Slash Commands

Within a conversation with Claude Code, there are built-in Commands that speed up the work:

Effective Prompting for Claude Code

Claude Code responds well to prompts that include: what the problem is (not what the solution is), success criteria (how we'll know it worked), andconstraints (what must not be touched).

Custom Instructions — defining a personality

You can define "Custom Instructions" in Claude Code's settings that apply to all conversations. For example: "always write code with TypeScript Strict Mode", "always add full Error Handling", "always add Logging in Production Code". This eliminates the need to repeat these instructions in every prompt.

Conclusions — when is it worth adopting Claude Code?

Claude Code is especially suited toexisting projects with a Codebase and Tests — that's where its Agentic abilities come into full expression. For brand-new projects, consider combining it with tools like Lovable.dev or Bolt.new for the scaffolding stage, and then moving to Claude Code for the development stage.

If you're a developer who writes code by hand only — Claude Code will change the way you work. If you already use Cursor or Windsurf — Claude Code is an addition that complements them, not replaces them: Cursor/Windsurf for active editing, Claude Code for long, autonomous tasks.

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