Claude Code: Anthropic's AI Terminal Assistant for Developers
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Claude Code: The Agentic Tool for Coding by Anthropic

2025-04-08

Claude Code represents Anthropic’s strong-willed entry into the developer tooling space—a terminal-based AI assistant that seamlessly integrates with your development workflow. Currently available as a beta research preview, this innovative tool transforms how developers interact with their codebases, bringing the power of Anthropic’s Claude 3.7 Sonnet model directly to your terminal.

Claude Code logo.

Claude Code logo.

Bridging the Gap Between AI and Development

Unlike traditional code assistants that operate as IDE extensions, Claude Code takes a different approach by embedding itself in your terminal environment. This architectural choice eliminates the compatibility issues that plague many AI coding extensions, which can cause performance problems in environments like Visual Studio Code.

As Jeff Bennett, a developer who tested Claude Code with test-driven development, notes: “Claude Code can do TDD in principle. This makes me happy, as it leaves me with reasonably safe code without having to hope that my LLM pair partner understands everything.”

Key Capabilities

Claude Code functions as more than just a code generator—it’s designed to be a knowledgeable collaborator that understands your entire project context:

Intelligent Code Understanding

  • Analyzes and explains existing code architecture
  • Responds to natural language questions about implementation details
  • Searches through your codebase with semantic understanding

Examples of queries you might use:

claude > what does the payment processing system do?
claude > find where user permissions are checked
claude > explain how the caching layer works

Active Development Assistance

  • Creates, edits, and fixes code across multiple files
  • Runs and debugs tests, addressing failures with contextual solutions
  • Identifies and resolves bugs with minimal human intervention

Examples of commands:

claude > add input validation to the signup form
claude > refactor the logger to use the new API
claude > fix the race condition in the worker queue
claude > run tests for the auth module and fix failures

Git Workflow Integration

  • Simplifies version control with commit creation and management
  • Searches git history for specific code changes or features
  • Resolves merge conflicts and assists with rebasing operations
  • Creates pull requests based on contextual understanding

Examples of Git operations:

claude > commit my changes
claude > create a pr
claude > which commit added tests for markdown back in December?
claude > rebase on main and resolve any merge conflicts

Extended Thinking Mode

Claude Code leverages Claude 3.7 Sonnet’s reasoning capabilities, allowing it to tackle complex architectural questions. When faced with challenging problems, you can explicitly prompt Claude to “think deeply” about solutions, activating its extended thinking mode for more thorough analysis.

You can trigger this mode with prompts like:

claude > think about how we should architect the new payment service
claude > think hard about the edge cases in our authentication flow

The intensity of thinking is influenced by your phrasing—”think hard” triggers more extended reasoning than simply “think.”

Installation and Setup

Getting started with Claude Code requires minimal setup:

  1. System Requirements:
    • Operating Systems: macOS 10.15+, Ubuntu 20.04+/Debian 10+, or Windows via WSL
    • Node.js 18+ (essential)
    • Git 2.23+ (recommended for full functionality)
    • 4GB RAM minimum
    • Optional tools: GitHub or GitLab CLI (for PR workflows), ripgrep (for enhanced file search)
  2. Installation Process: 
    npm install -g @anthropic-ai/claude-code

    Important: Avoid using sudo with the installation command to prevent permission issues and security risks.

  3. Authentication: Claude Code employs a simple OAuth process that connects to your Anthropic Console account, requiring active billing to use the service.

Troubleshooting WSL Installation

If you’re using Windows with WSL and encounter issues:

  • For OS/platform detection problems: 
    npm config set os linux
npm install -g @anthropic-ai/claude-code --force --no-os-check
  • If you see “node not found” errors, your WSL environment might be using a Windows Node.js installation. Confirm with which npm and which node, which should point to Linux paths starting with /usr/ rather than /mnt/c/.

Getting Started

After installation:

  1. Navigate to your project directory: cd your-project-directory
  2. Start Claude Code: claude
  3. Complete the one-time OAuth authentication process
  4. For first-time users:
    • Try a simple command like summarize this project
    • Generate a CLAUDE.md project guide with /init
    • Ask Claude to commit the generated CLAUDE.md file to your repository

Practical Applications in Development Workflows

Test-Driven Development (TDD)

Claude Code demonstrates particular strength in test-driven development scenarios. In practical testing, it successfully:

  • Understood test requirements defined by the developer
  • Implemented the necessary code to pass those tests
  • Identified and fixed edge cases and bugs in the implementation
  • Maintained the TDD loop without breaking the development flow

This compatibility with TDD is significant because it allows developers to maintain rigorous quality standards while benefiting from AI assistance—something many previous AI coding tools struggled with.

Example: TDD with Claude Code

Let’s examine a practical example of how Claude Code facilitates test-driven development. Suppose we’re developing a simple banking application and want to create a SavingsAccount class with basic functionality.

First, we define our test requirements:

using BankAccount;
using NUnit.Framework;
public class Tests
{
    [SetUp]
    public void Setup()
    {
    }
 
    [Test] 
    public void test_deposit() 
    { 
        SavingsAccount ba = new SavingsAccount(); 
        ba.Deposit(20); 
        Assert.AreEqual("$20", ba.ShowBalance()); 
    } 
 
    [Test] 
    public void test_withdraw_more_than_balance() 
    { 
        SavingsAccount ba = new SavingsAccount(); 
        Assert.Throws<Exception>(() => ba.Withdraw(25)); 
    }
}

When asked to make these tests pass, Claude Code analyzed the requirements and generated appropriate implementation code:

public class SavingsAccount
{
    private decimal balance = 0;
    
    public SavingsAccount(decimal initialBalance = 0)
    {
        balance = initialBalance;
    }
    
    public void Deposit(decimal amount)
    {
        balance += amount;
    }
    
    public void Withdraw(decimal amount)
    {
        if (amount > balance)
        {
            throw new Exception("Insufficient funds");
        }
        
        balance -= amount;
    }
    
    public string ShowBalance()
    {
        return $"${balance}";
    }
    
    public decimal GetBalance()
    {
        return balance;
    }
}

When additional requirements were added to handle interest calculations, Claude Code adapted the implementation accordingly:

[Test]
public void test_daily_interest_rate()
{
    SavingsAccount ba = new SavingsAccount();
    ba.SetDailyInterestRate(0.05m);
    ba.Deposit(100);
    ba.ApplyDailyInterest();
    Assert.AreEqual("$100.05", ba.ShowBalance());
}

Claude Code understood that the daily interest rate should be a percentage and needed to be applied correctly to the balance with proper formatting, demonstrating its ability to not just implement features but also understand the financial domain concepts involved in the application.

Code Exploration and Understanding

For developers working with unfamiliar codebases, Claude Code serves as an invaluable guide:

  • “What does the payment processing system do?”
  • “Find where user permissions are checked”
  • “Explain how the caching layer works”

By responding to these natural language queries with detailed explanations based on actual code analysis, Claude Code reduces the learning curve associated with joining new projects or exploring complex systems.

Automation of Repetitive Tasks

Software development often involves repetitive operations that Claude Code can streamline:

  • Running and fixing test failures
  • Standardizing code based on project conventions
  • Creating documentation from existing code
  • Refactoring for improved readability or performance

Contextual Memory System

One of Claude Code’s most powerful features is its multi-tiered memory system, which allows it to retain important context across sessions:

Project Memory (./CLAUDE.md)

Stores team-shared conventions and project-specific knowledge that all developers should follow, such as architecture decisions and coding standards.

Local Project Memory (./CLAUDE.local.md)

Contains personal project-specific preferences that might not apply to all team members, like sandbox URLs or preferred test data.

User Memory (~/.claude/CLAUDE.md)

Maintains global personal preferences that apply across all projects, including code styling choices and personal tooling shortcuts.

The system intelligently reads these memories recursively, starting from the current working directory and moving upward, ensuring that Claude always has the most relevant context for your specific situation.

Adding Memories

The quickest way to add a memory is with the # shortcut:

# Always use descriptive variable names

When you enter this, Claude Code will prompt you to select which memory file to store it in.

For more extensive additions or organization, you can use the /memory slash command during a session to open any memory file in your system editor.

Memory Best Practices

To get the most out of Claude Code’s memory system:

  1. Be specific: “Use 2-space indentation” is more actionable than “Format code properly”
  2. Use structure: Format each memory as a bullet point and group related memories under descriptive markdown headings
  3. Review periodically: Update memories as your project evolves to ensure Claude is working with current information

This memory system is particularly valuable for onboarding new team members, as it encapsulates project conventions and architecture decisions in a format that Claude Code can directly reference and apply.

Security and Permission Model

Claude Code implements a thoughtful security model that balances power with safety:

Tiered Permissions

  • Read-only operations: No approval required
  • Bash commands: Explicit approval required, with options to remember permissions
  • File modifications: Approval required for each session

Available Tools and Their Permission Levels

Claude Code provides access to a comprehensive set of tools:

Tool Description Permission Required
AgentTool Runs a sub-agent for complex tasks No
BashTool Executes shell commands Yes
GlobTool Finds files using pattern matching No
GrepTool Searches for patterns in files No
LSTool Lists files and directories No
FileReadTool Reads file contents No
FileEditTool Makes targeted edits to files Yes
FileWriteTool Creates or overwrites files Yes
NotebookReadTool Displays Jupyter notebook contents No
NotebookEditTool Modifies Jupyter notebook cells Yes

Protection Against Prompt Injection

The tool incorporates several safeguards against potential prompt injection attacks:

  • Context-aware analysis to detect potentially harmful instructions
  • Input sanitization to prevent command injection
  • Command blocklist for risky operations like curl and wget

Best Practices for Security

When working with Claude Code, especially with untrusted content:

  • Always review suggested commands before approval
  • Avoid piping untrusted content directly to Claude
  • Verify proposed changes to critical files
  • Report suspicious behavior with the /bug command

For headless execution in CI/CD pipelines, you can use the non-interactive mode with specific allowed tools:

export ANTHROPIC_API_KEY=sk_...
claude -p "update the README with the latest changes" --allowedTools "Bash(git diff:*)" "Bash(git log:*)" Edit

Command Reference Guide

Claude Code provides both CLI commands and in-session slash commands to control its behavior.

CLI Commands

Command Description Example
claude Start interactive REPL claude
claude "query" Start REPL with initial prompt claude "explain this project"
claude -p "query" Run one-off query, then exit claude -p "explain this function"
cat file | claude -p "query" Process piped content cat logs.txt | claude -p "explain"
claude config Configure settings claude config set --global theme dark
claude update Update to latest version claude update

Useful CLI flags:

  • --print (-p): Print response without interactive mode
  • --json: Return JSON output in --print mode (useful for scripting)
  • --verbose: Enable verbose logging with full turn-by-turn output
  • --dangerously-skip-permissions: Skip permission prompts (use with caution)

Slash Commands

Control Claude’s behavior within a session:

Command Purpose
/bug Report bugs (sends conversation to Anthropic)
/clear Clear conversation history
/compact [instructions] Compact conversation with optional focus
/config View/modify configuration
/cost Show token usage statistics
/doctor Check Claude Code installation health
/help Get usage help
/init Initialize project with CLAUDE.md guide
/login Switch Anthropic accounts
/logout Sign out from your Anthropic account
/memory Edit CLAUDE.md memory files
/pr_comments View pull request comments
/review Request code review
/terminal-setup Install Shift+Enter key binding for newlines
/vim Enter vim mode for alternating insert and command modes

The Future of Claude Code

As a research preview, Claude Code represents Anthropic’s exploration into how AI can best serve developers. The team has already outlined preliminary plans to enhance several areas based on user feedback:

  • Improving tool execution reliability
  • Supporting long-running commands
  • Enhancing terminal rendering
  • Expanding Claude’s self-knowledge of its capabilities

Conclusion

Claude Code is undoubtedly a significant evolution in AI-assisted development tools. By bringing Claude’s advanced language capabilities directly into the terminal environment, Anthropic has created a tool that fits naturally into existing development workflows while providing powerful new capabilities.

The discipline of working with Claude Code feels familiar to experienced developers—similar to how senior engineers have traditionally guided junior team members, but with the added benefits of tireless assistance and comprehensive codebase knowledge. It is quite certain that this new tool is about to become an increasingly valuable partner in the development process, potentially transforming how we approach complex coding challenges.

If you are interested in this topic, we suggest you check our articles:

Sources: TheNewStack, Anthropic

Written by Alius Noreika

Claude Code: The Agentic Tool for Coding by Anthropic
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