Claude Code: Complete Guide to Anthropic's AI Coding CLI (2026)

Claude Code: Complete Guide to Anthropic's AI Coding CLI (2026)

Claude Code is Anthropic's official command-line interface for AI-assisted software development. Unlike browser-based AI chat tools, Claude Code operates directly in your terminal, reading and writing files, running commands, and navigating your codebase with full context awareness.

This guide covers everything from installation to advanced workflows, making it the definitive resource for getting the most out of Claude Code in 2026.

What Is Claude Code?

Claude Code is a CLI tool that gives Claude direct access to your development environment. When you run it in a project directory, it can:

• Read and understand your entire codebase
• Edit files across multiple directories
• Run shell commands (builds, tests, git operations)
• Search code and navigate file structures
• Create commits and pull requests
• Debug errors by reading logs and stack traces

It is different from AI coding tools like GitHub Copilot or Cursor in that it operates entirely in the terminal as an agent, taking multi-step actions to complete tasks rather than just providing inline suggestions.

Installation and Setup

Requirements

Requirement	Minimum
Node.js	18+
Operating System	macOS, Linux, or Windows (via WSL)
Anthropic API key	Or Claude Pro/Max subscription

Install

npm install -g @anthropic-ai/claude-code

Verify Installation

claude --version

Authentication

On first launch, Claude Code will prompt you to authenticate. You have two options:

Option 1: Anthropic API Key

export ANTHROPIC_API_KEY="sk-ant-your-key-here"
claude

Option 2: Claude Pro/Max Subscription

Launch Claude Code and follow the browser-based OAuth flow:

claude
# Follow the authentication prompts

Claude Pro subscribers get limited Claude Code usage. Claude Max ($100/month or $200/month) subscribers get significantly higher limits.

Subscription Comparison

Plan	Claude Code Access	Monthly Limit
Free	No	N/A
Pro ($20/month)	Limited	Low usage cap
Max ($100/month)	Yes	High usage cap
Max ($200/month)	Yes	Very high usage cap
API (pay-per-use)	Yes	Based on spending
Team/Enterprise	Yes	Based on plan

Basic Usage

Interactive Mode

Launch Claude Code in your project directory:

cd your-project
claude

You enter an interactive session where you can type natural language instructions. Claude Code reads your project structure and responds with understanding of your codebase.

One-Shot Mode

Send a single prompt without entering interactive mode:

claude "explain what this project does"

Print Mode

Get a response without any interactive session or tool use:

claude -p "what does the main function in src/index.ts do?"

Pipe Input

Feed content into Claude Code via stdin:

cat error.log | claude "explain this error and suggest a fix"
git diff | claude "review these changes"
npm test 2>&1 | claude "fix the failing tests"

Resume a Conversation

# Resume the most recent conversation
claude --resume

# Continue the last conversation
claude --continue

Key CLI Flags

Flag	Short	Description
--version	-v	Print version
--help	-h	Show help
--resume	-r	Resume most recent conversation
--continue	-c	Continue last conversation
--print	-p	Print mode (no interactive session)
--model	-m	Specify model (e.g., claude-sonnet-4-20250514)
--max-turns		Limit agentic turns
--system-prompt		Custom system prompt
--allowedTools		Restrict available tools
--output-format		Output format: text, json, stream-json
--dangerously-skip-permissions		Auto-approve all tool use

Slash Commands

Inside an interactive session, use slash commands for quick actions:

Command	Description
/help	Show available commands
/compact	Compress conversation to save context
/clear	Clear conversation history
/cost	Show token usage and estimated cost
/model	Switch the model mid-conversation
/permissions	View and manage tool permissions
/config	View current configuration
/bug	Report a bug to Anthropic
/quit	Exit Claude Code

Configuration

Project-Level Configuration

Create a CLAUDE.md file in your project root to give Claude Code persistent context:

# CLAUDE.md

## Project Overview
This is a Next.js 15 application using the App Router, TypeScript, and Tailwind CSS.

## Tech Stack
- Next.js 15 (App Router)
- TypeScript (strict mode)
- Tailwind CSS + shadcn/ui
- Prisma ORM with PostgreSQL
- NextAuth.js for authentication

## Conventions
- Use server components by default
- Place API routes in app/api/
- Use Zod for all input validation
- Write tests with Vitest

## Important Notes
- Never modify the database schema without creating a migration
- Always run `npm run typecheck` before committing
- The env variables are in .env.local (do not read or modify this file)

Claude Code reads this file automatically at the start of every conversation.

Settings File

Create .claude/settings.json for tool permissions and behavior:

{
  "allowedTools": [
    "Read",
    "Write",
    "Glob",
    "Grep",
    "Bash(npm run *)",
    "Bash(npx *)",
    "Bash(git *)"
  ],
  "ignorePatterns": [
    "node_modules",
    "dist",
    ".next"
  ]
}

User-Level Configuration

For settings that apply across all projects, create ~/.claude/settings.json or ~/.claude.md.

Common Workflows

1. Implement a Feature

Add a rate limiting middleware to the API. Use Redis for the token bucket.
It should limit to 100 requests per minute per API key.
Add tests.

Claude Code will read your existing middleware, understand the project structure, create the implementation, and write tests.

2. Fix a Bug

# Pipe the error directly
npm test 2>&1 | claude "fix these failing tests"

Or describe the bug:

Users are reporting that the password reset email is not being sent.
Debug the issue and fix it.

3. Code Review

git diff main...feature-branch | claude "review this code for bugs, security issues, and style problems"

4. Refactoring

Refactor the user service to use the repository pattern.
Move database queries out of the route handlers and into a UserRepository class.
Update all imports and tests.

5. Documentation

Add JSDoc comments to all exported functions in the src/utils/ directory.

6. Git Operations

Create a new branch called feature/rate-limiting, commit the current changes
with a descriptive message, and push to origin.

7. Debugging with Logs

cat server.log | claude "find the root cause of the 500 errors happening after 3pm"

Advanced Usage

Custom System Prompts

Override the default behavior for specific tasks:

claude --system-prompt "You are a security auditor. Review all code for vulnerabilities." \
  "audit the authentication module"

Scripting and Automation

Use Claude Code in CI/CD pipelines or scripts:

# Generate a changelog from recent commits
git log --oneline v1.0..HEAD | claude -p --output-format json \
  "Generate a changelog grouped by category (features, fixes, other)"

# Auto-fix lint errors
npx eslint src/ --format json 2>&1 | claude "fix all these lint errors"

Multi-Model Workflows

Switch models for different tasks:

# Use a faster model for simple tasks
claude -m claude-haiku-4-20250514 "rename the variable 'x' to 'userCount' in src/stats.ts"

# Use the most capable model for complex tasks
claude -m claude-opus-4-20250514 "redesign the database schema to support multi-tenancy"

Limit Tool Access

For sensitive operations, restrict what Claude Code can do:

# Read-only mode
claude --allowedTools "Read,Glob,Grep" "explain the authentication flow"

# No bash access
claude --allowedTools "Read,Write,Glob,Grep" "refactor the utils"

Tips for Better Results

Tip	Example
Be specific about files	"Edit src/auth/login.ts" not "fix the login"
Give context on what you tried	"I tried X but got error Y"
Break large tasks into steps	One feature per conversation
Use /compact for long sessions	Prevents context window issues
Include error messages	Paste the full stack trace
Specify the "why"	"Add caching to reduce API calls" not just "add caching"
Use CLAUDE.md for project context	Saves repeating setup every time

Cost Management

Monitoring Usage

/cost

This shows tokens used and estimated cost for the current session.

Reducing Costs

1. Use /compact regularly to compress long conversations.
2. Use print mode (-p) for quick questions that do not need tool use.
3. Limit tools when you only need code reading, not editing.
4. Use Haiku for simple tasks like renaming or formatting.
5. Break tasks into focused sessions instead of one long conversation.

Troubleshooting

Issue	Solution
"API key not found"	Set ANTHROPIC_API_KEY environment variable
Slow responses	Check internet connection; try /compact
Context window errors	Start a new conversation
Permission denied	Check .claude/settings.json allowedTools
Claude Code stuck in a loop	Press Escape, then give clearer instructions
"Rate limit exceeded"	Wait a few minutes or upgrade your plan
Cannot read certain files	Check .gitignore and ignorePatterns

Wrapping Up

Claude Code is the most capable AI coding assistant available in the terminal. It works best when you give it clear instructions, maintain project context through CLAUDE.md, and break complex tasks into focused sessions. Whether you are building new features, debugging production issues, or refactoring legacy code, Claude Code can handle the heavy lifting while you stay in control.

If you are building applications that involve AI-generated media, such as images, videos, or audio, Hypereal AI provides developer-friendly APIs that work seamlessly alongside tools like Claude Code. Generate images, create videos, and more through simple API calls.