Aider: AI Pair Programming in Your Terminal

What is Aider?

Created by Paul Gauthier (@paulgauthier), Aider (https://aider.chat/) is a terminal-based AI pair programming tool that lets you chat with LLMs to edit code directly in your local git repository. Unlike web-based AI coding assistants that require copying and pasting code back and forth, Aider integrates seamlessly into your existing development workflow, working with your local files and git history.

Since Aider uses your own API keys directly with LLM providers, you don’t have to worry about usage quotas or artificial limits that plague other tools. You pay only for what you use and can code as much as you need.

Why Aider Stands Out

Git-Native Approach: Aider automatically commits changes with sensible commit messages (though this can be disabled with auto-commits: false in the config), allowing you to use familiar git tools to easily diff, manage and undo AI changes. This creates a safety net where every change is tracked and reversible.

Repository Intelligence: Aider makes a map of your entire codebase, which helps it work well in larger projects. This repository mapping gives the AI context about your project structure, dependencies, and relationships between files.

Universal Compatibility: Aider works with most popular programming languages: python, javascript, rust, ruby, go, cpp, php, html, css, and dozens more. It also works best with Claude 3.7 Sonnet, Gemini & Chat V3, OpenAI o1, o3-mini & GPT-4o, but can connect to almost any LLM, including local models.

Bring Your Own Key: Unlike tools like Cursor that impose usage quotas, Aider uses your own API keys directly with LLM providers. This means no artificial limits on your usage - you pay only for what you use and can code as much as you need.

Getting Started: Installation and Setup

Prerequisites

Before installing Aider, ensure you have:

Python 3.8-3.13 installed on your system
A local git repository for your project
An API key from a supported LLM provider (OpenAI, Anthropic, etc.)

Quick Installation

If you already have python 3.8-3.13 installed, you can get started quickly with this command:

pip install --upgrade --no-input aider-chat

First Launch

Once installed, navigate to your project directory and launch Aider with your preferred model:

# Change directory into your codebase
cd /to/your/project

# Using default model (usually claude depending on the API keys in your env variables)
aider

# Using Claude 3.7 Sonnet
aider --model sonnet --api-key anthropic=<key>

# Using OpenAI o3-mini
aider --model o3-mini --api-key openai=<key>

Your First Coding Session

Let’s walk through a typical Aider session to understand how it works in practice.

Adding Files to the Chat

When you launch Aider, you can either specify files on the command line or add them during the session:

# Launch with specific files
aider main.py utils.py

# Or add files during the chat session
> /add src/components/Button.js
> /add tests/test_button.py

You can check what files are currently included in the conversation context with the /tokens command, which shows you exactly what’s being tracked as well as how many tokens Aider is consuming.

Making Your First Request

Once your files are loaded, you can start making requests in natural language:

> Add error handling to the login function. It should catch network timeouts and display a user-friendly message.

Aider will:

Analyze your code to understand the current login function
Generate the necessary changes with proper error handling
Show you exactly what it plans to modify
Apply the changes to your files
Automatically commit with a descriptive message like “Add timeout error handling to login function”

Understanding the Output

When Aider makes changes, it clearly shows:

Which files are being modified
The exact changes being made (similar to a git diff)
Why it’s making specific decisions
Any assumptions or considerations

You can review these changes before they’re applied, and easily undo them using standard git commands if needed.

Core Usage Patterns

Working with Multiple Files

One of Aider’s strengths is coordinating changes across multiple files. For example:

> Refactor the User class to use dependency injection. Update all the files that instantiate User objects to use the new pattern.

Aider will:

Identify all files that need changes
Modify the User class definition
Update every instantiation across your codebase
Ensure imports and dependencies are correctly adjusted
Commit everything as a single, coherent changeset

Chat Commands

Aider provides many in-chat commands for managing your session. Here are some of the most commonly used:

/add <file> - Add files to the chat session
/drop <file> - Remove files from the session
/ask - Ask questions without making code changes
/diff - Show pending changes before applying
/undo - Undo the last change
/commit - Commit current changes with a custom message
/help - Show available commands

Advanced Features

Repository Mapping

Aider makes a map of your entire codebase, which helps it work well in larger projects. This mapping allows the AI to understand:

Project structure and architecture
Dependencies between modules
Coding patterns and conventions
Context from related files not directly in the chat

Multiple Chat Modes

Code Mode: The default mode for making direct edits to your code.

Architect Mode: For high-level planning and design discussions before implementation.

Ask Mode: For questions about your code without making changes.

Help Mode: For assistance with Aider itself.

Voice and Visual Context

Aider supports advanced input methods:

Voice commands: Speak your requests instead of typing
Image context: Add screenshots, diagrams, or mockups to guide development
Web page context: Reference documentation or examples from URLs

Integration with Development Tools

IDE Integration: While Aider runs in the terminal, it works seamlessly with any editor. You can make manual edits while chatting with Aider, and it will automatically detect and incorporate your changes.

Linting and Testing: Aider now lints code after every LLM edit and automatically fixes errors, using tree-sitter and AST-aware code context.

Automated Workflows: Use Aider in scripts to automate repetitive coding tasks or batch operations across multiple files.

Best Practices for Success

Effective Communication

Be Specific: Instead of “make this better,” try “optimize this function for memory usage” or “add input validation for email addresses.”

Provide Context: Explain the business logic, constraints, or requirements that might not be obvious from the code alone.

Break Down Complex Tasks: Large changes work better when broken into logical steps that can be implemented and tested incrementally.

Ask Questions First: Don’t hesitate to ask Aider to explain code, analyze potential issues, or suggest approaches before making changes. Use the /ask command for questions that don’t require code edits, like “What does this function do?” or “Are there any potential security issues in this authentication code?”

File Management Strategy

Start Focused: Begin with just the files you know need changes, then add related files as needed.

Think About Dependencies: If you’re modifying a core component, consider adding files that depend on it to catch necessary updates.

Use Repository Discovery: Let Aider suggest relevant files when you mention them in conversation.

Quality Control

Review Before Accepting: Always review the proposed changes, especially for critical code paths.

Test Incrementally: Use the automatic git commits to test changes in small increments.

Leverage Git: Use git diff, git log, and git revert to understand and manage AI-generated changes.

Configuration and Customization

Configuration Methods

Aider offers multiple ways to customize its behavior:

Command Line Options: For one-time settings

aider --auto-commits --no-pretty

YAML Configuration: For persistent settings

# .aider.conf.yml
model: claude-3-sonnet-20240229
auto-commits: true
gitignore: true

Environment Variables: For API keys and sensitive settings

export ANTHROPIC_API_KEY=your_key_here
export AIDER_MODEL=claude-3-sonnet-20240229

Model Selection

Different models excel at different tasks:

Claude 3.7 Sonnet: Excellent balance of capability and cost
GPT-4o: Strong at complex reasoning and edge cases
Gemini: Cost-effective option with good performance
Local models: For privacy-sensitive projects or offline work

Advanced Settings

Prompt Caching: Reduce costs by caching repository context between sessions.

Custom Editors: Configure your preferred editor for complex edits.

Model Aliases: Create shortcuts for frequently used model configurations.

Comparison with Other AI Coding Tools

Terminal vs. Web-Based Tools

Advantages of Aider’s Terminal Approach:

No context switching between browser and development environment
Direct integration with git workflow
Works with any editor or IDE
Handles large codebases efficiently
Maintains session state and history

Terminal vs. AI-Enabled IDEs

Compared to Cursor, Windsurf, and Similar Tools:

Bring Your Own Key: No usage quotas or subscription tiers - use any model with your own API key
Git-First Design: Built around git workflow with automatic commits and version control
Model Flexibility: Switch between different AI models (Claude, GPT-4, Gemini, local models) within the same session
Repository Understanding: Deep codebase mapping that works across the entire project, not just open files
Terminal Native: Integrates seamlessly with existing command-line workflows and automation

Unique Capabilities

Repository Intelligence: Unlike tools that work with individual files, Aider understands your entire project structure.

Multi-Model Support: Switch between different AI models within the same session to leverage their unique strengths.

Git-Native Design: Every change is automatically versioned, making it safe to experiment and easy to revert.

Getting the Most from Aider

Who Should Use Aider

Ideal Users:

Developers comfortable with terminal workflows
Teams working on larger codebases that benefit from repository mapping
Anyone who wants AI assistance without leaving their development environment
Developers working with multiple programming languages in the same project

Perfect Use Cases:

Feature implementation across multiple files
Code refactoring and modernization
Bug fixes requiring coordination between modules
Adding tests and documentation
Exploring and understanding unfamiliar codebases

Troubleshooting Common Issues

Installation Problems

Python Version Conflicts: Use the aider-install method to create an isolated environment.

API Key Issues: Ensure your API key has sufficient credits and proper permissions for your chosen model.

Git Repository Requirements: Aider requires a git repository. Initialize one with git init if needed.

Performance Considerations

Large Repositories: Use .aiderignore files to exclude unnecessary directories like node_modules or build artifacts.

Token Limits: Be selective about which files to include in the chat session to stay within model context limits.

Cost Management: Use prompt caching and consider cost-effective models for routine tasks.

The Future of AI-Assisted Development

Aider represents a significant step toward seamless AI integration in software development. By working directly with your local files and git repository, it maintains the familiar development workflow while adding powerful AI capabilities.

Recent developments show Aider achieving strong results mainly through its existing features that focus on static code analysis, reliable LLM code editing, and pragmatic UX for AI pair programming. The tool continues to evolve with improvements in model integration, performance optimization, and developer experience.

Getting Started Today

Ready to try AI pair programming? Start with these steps:

Install Aider following the installation guide
Set up an API key with your preferred LLM provider
Navigate to a small project to experiment with basic features
Start simple with single-file edits before moving to complex multi-file changes
Explore the documentation at https://aider.chat/docs/ for advanced features

Aider transforms the relationship between developers and AI from occasional consultation to continuous collaboration. By integrating directly into your terminal workflow, it becomes a natural extension of your development toolkit rather than a separate tool requiring context switching.

Whether you’re implementing new features, fixing bugs, or exploring unfamiliar code, having an AI pair programmer in your terminal can dramatically accelerate your development workflow while maintaining the control and visibility that professional developers require.

For the latest updates, documentation, and community discussions, visit aider.chat and explore the extensive documentation and examples available.

Aider: Seamless AI Pair Programming in Your Terminal

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