How to Switch from Claude Code to Aider (2026 Migration Guide)

Updated: June 2026 · How we test tools →

You've decided to switch from Claude Code to Aider. Most likely reason: you're tired of paying $20/month flat for a tool that hits rate limits during intensive sessions, or you need to run AI coding assistance on local models for privacy. Aider gives you the same terminal-first agentic workflow — using the same Claude models if you want — but you pay only for what you use, with no subscription and no usage caps.

This guide walks you through the full migration in under an hour.

What You're Gaining and Losing

You'll gain:

No subscription rate limits — usage capped only by your API budget
Full model freedom: Claude (same models as Claude Code), GPT, Gemini, DeepSeek, or fully local via Ollama
Pay-per-token billing — light weeks cost less, heavy weeks scale naturally
MIT licence — open-source, auditable, self-hostable
Architect mode: plan with a powerful model, execute with a faster/cheaper one
Offline capability with local models (Ollama)

You'll lose:

Claude Code's polished out-of-the-box experience — Aider requires more initial configuration
Claude Code's 1M token context window (Aider uses repo map instead)
Smoother error recovery on long autonomous sessions

The break-even point: If you'd spend less than $20/month in raw Claude API tokens, Aider is cheaper. Most moderate users spend $5–15/month with BYOK.

If you're undecided, read Claude Code vs Aider → first. If cost was your main driver, see Claude Code Too Expensive? →.

Step 1: Install Aider

Aider is a Python package — installation is straightforward.

# Install Aider (requires Python 3.10+)
pip install aider-chat

# Verify installation
aider --version

# If pip isn't available or you want a clean environment:
pipx install aider-chat

Python version check:

python3 --version
# Should be 3.10 or higher

If you're on an older Python, use pyenv to install a newer version first:

brew install pyenv  # macOS
pyenv install 3.12
pyenv global 3.12

Step 2: Set Up Your API Key

Aider supports multiple providers. To get the same Claude model quality you had in Claude Code:

Option A: Use Claude (same models, pay-per-token)

# Get your API key from console.anthropic.com/settings/keys
export ANTHROPIC_API_KEY=your-key-here

# Add to your shell profile to persist across sessions
echo 'export ANTHROPIC_API_KEY=your-key-here' >> ~/.zshrc  # or ~/.bashrc
source ~/.zshrc

Recommended models:

claude-sonnet-4-5 — best balance of quality and cost (same model as Claude Code Pro)
claude-opus-4 — maximum quality, higher cost (same as Claude Code Max)

Option B: Use a free/cheaper alternative

# Gemini (free tier via Google AI Studio)
export GEMINI_API_KEY=your-key-here

# OpenAI
export OPENAI_API_KEY=your-key-here

# DeepSeek (very cheap)
export DEEPSEEK_API_KEY=your-key-here

Option C: Local models (free, fully private)

Skip to the bonus section at the end for the Ollama setup. This is the right path if you're switching for privacy reasons.

Step 3: Migrate Your CLAUDE.md Configuration

Claude Code uses CLAUDE.md for project-specific instructions. Aider uses .aider.conf.yml for tool configuration and passes project context differently.

Find and export your CLAUDE.md files

# Find all CLAUDE.md files
find ~/projects -name "CLAUDE.md" -type f -exec echo {} \;

# View the content of each
find ~/projects -name "CLAUDE.md" -exec cat {} \;

Create Aider's config file

Aider looks for .aider.conf.yml in your project root or ~/.aider.conf.yml for global settings:

# Create global Aider config
cat > ~/.aider.conf.yml << 'EOF'
# Aider global configuration
# Migrated from Claude Code setup

model: claude-sonnet-4-5
# editor-model: claude-haiku-4    # cheaper model for simple edits in architect mode

# Git settings
auto-commits: true
commit-prompt: "feat: "    # customize your commit message prefix

# Output settings
pretty: true
stream: true

# Context
map-tokens: 2048    # repo map size (adjust based on codebase size)
EOF

Port your CLAUDE.md instructions

Claude Code reads CLAUDE.md automatically. In Aider, you pass project context differently:

Method 1 — Read-only file (best for project conventions):

# Add CLAUDE.md as a read-only context file
aider --read CLAUDE.md src/main.py

Method 2 — Convert to .aiderignore + system message: Create a .aider.system.md file (Aider reads this automatically in some versions):

cat CLAUDE.md > .aider.system.md

Method 3 — Pass context inline:

# Reference your conventions at session start
aider --message "Before we start: $(cat CLAUDE.md)" src/main.py

Practical recommendation: Keep your CLAUDE.md files as-is and pass them with --read at the start of sessions. This is the least friction approach:

# Session start: load project conventions + target files
aider --read CLAUDE.md src/auth/login.py src/auth/session.py

Step 4: Learn the Core Aider Commands

Claude Code has a conversational interface. Aider uses slash commands inside the session. Here's the mapping:

Claude Code	Aider equivalent
`claude "implement X"`	`aider file.py` then describe task
`/add file.py`	`/add file.py` (same!)
`/clear` context	`/clear` (same!)
Review via `git diff`	Auto-committed — `git log` + `git diff HEAD~1`
Multi-file task	`/add file1.py file2.py` then describe
"Don't touch X"	`/drop X.py` to remove from context
Exit	`/exit` or Ctrl+D

Starting a session:

# Work on specific files
aider src/auth/login.py src/auth/session.py

# Work on whole project (uses repo map)
aider

# With model specified
aider --model claude-sonnet-4-5 src/main.py

Inside the Aider session:

> /add tests/test_auth.py          # add file to context
> /drop utils/deprecated.py        # remove file from context
> /ls                               # see what's in context
> Write a JWT authentication function with refresh token rotation
> /run pytest tests/test_auth.py    # run tests from within session
> /commit                           # commit changes with AI-generated message
> /undo                             # undo last commit if needed

Step 5: Set Up Architect Mode (Your Agentic Power Feature)

Claude Code's agentic sessions handle complex multi-step tasks. Aider's equivalent is Architect mode — it separates planning from execution, using a powerful model for reasoning and a cheaper/faster model for implementation.

# Architect mode: Opus plans, Sonnet executes
aider --architect \
  --model claude-opus-4 \
  --editor-model claude-sonnet-4-5 \
  src/payments/processor.py src/payments/validators.py

# For complex refactors (cost-optimised version)
aider --architect \
  --model claude-sonnet-4-5 \
  --editor-model claude-haiku-4 \
  src/legacy_module.py

When to use Architect mode:

Large refactors spanning multiple files
Complex feature implementation where you want a reasoning step before code is written
Any task where Claude Code's Max plan would have been your choice

Cost of Architect mode vs Claude Code Max:

Scenario	Claude Code Max	Aider Architect (Opus+Sonnet)
Monthly subscription	$100–200	$0 (tool is free)
Per complex session	Included	~$0.50–3.00
Light usage month	$100	$5–15
Heavy usage month	$200	$30–60

For most developers who hit Claude Code's rate limits but don't use it 8 hours daily, Aider BYOK is meaningfully cheaper.

Step 6: Configure Your Repo Map

Aider builds a repo map — a compact structural summary of your codebase — instead of loading everything into a massive context window. This is efficient but different from Claude Code's whole-context approach.

# Default repo map (2K tokens) — good for small projects
aider

# Larger repo map for bigger codebases
aider --map-tokens 4096

# For very large monorepos: disable map, add files manually
aider --map-tokens 0
# Then: /add specific/files/you/need.py

For large codebases where Claude Code's 1M context was an advantage:

Create a .aiderignore file to exclude irrelevant directories from the repo map:

cat > .aiderignore << 'EOF'
node_modules/
dist/
build/
.git/
*.lock
coverage/
__pycache__/
*.pyc
vendor/
EOF

This keeps the repo map focused on what matters, approximating Claude Code's context quality within Aider's different architecture.

Step 7: Set Up Git Integration

Aider is Git-native — every change is auto-committed with a descriptive message. This is actually better than Claude Code's Git integration for auditability.

# Ensure Git is configured (Aider requires this)
git config --global user.email "you@example.com"
git config --global user.name "Your Name"

# Verify you're in a Git repo
git status

# First time in a project: Aider will create commits automatically
# Review AI commits: 
git log --oneline -5

# Revert an Aider commit you don't like:
git revert HEAD

# Or undo from within Aider:
# > /undo

Pro tip: Use Aider's --dirty-commits flag if you want to start a session with uncommitted changes:

aider --dirty-commits src/main.py

Bonus: Local Model Setup (Fully Private, $0 Cost)

If privacy was your reason for switching — here's how to run Aider completely locally.

# Step 1: Install Ollama
curl -fsSL https://ollama.com/install.sh | sh

# Step 2: Pull a coding model
# Best quality on 32GB RAM:
ollama pull qwen2.5-coder:32b

# Good on 16GB RAM:
ollama pull qwen2.5-coder:14b

# Fast on 8GB RAM (lower quality):
ollama pull qwen2.5-coder:7b

# Step 3: Run Aider with local model
aider --model ollama/qwen2.5-coder:32b

# Step 4 (optional): Architect mode with local models
aider --architect \
  --model ollama/qwen2.5-coder:32b \
  --editor-model ollama/qwen2.5-coder:7b

Honest performance note: qwen2.5-coder:32b handles routine coding tasks well — 80–85% of Claude Sonnet quality on everyday work. For complex multi-file refactors or nuanced reasoning, cloud models are stronger. Many teams use local models for routine work and switch to Claude API for hard tasks.

See Self-Hosted Claude Code Alternatives → for the complete local setup guide including hardware requirements and model benchmarks.

What to Expect in Your First Week

Day 1: Aider's interactive session feel is familiar if you've used Claude Code — it's also a conversational terminal interface. The main adjustment is using /add and /drop to manage context explicitly rather than relying on Claude Code's automatic context loading.

Day 2–3: You'll start appreciating Git auto-commits. Every Aider change is a Git commit — you can always git revert if something goes wrong. This is more granular control than Claude Code's approval prompts.

Day 4–5: Set up your .aider.conf.yml with your preferred model and settings. After this, starting a session is as fast as Claude Code was.

Week 1 end: Check your API bill. For most moderate Claude Code users switching to Aider with Claude API, the first month costs $8–18 — less than Claude Code's $20 floor, with no rate limits.

Quick Reference: Aider Cheat Sheet for Claude Code Switchers

# Start session with Claude (same quality as Claude Code)
aider --model claude-sonnet-4-5

# Start with specific files
aider --model claude-sonnet-4-5 src/main.py tests/

# Complex task (Architect mode)
aider --architect --model claude-opus-4 --editor-model claude-sonnet-4-5

# Local models (private, free)
aider --model ollama/qwen2.5-coder:32b

# Load project conventions
aider --read CLAUDE.md src/target.py

# Inside session
/add file.py        # add file to context
/drop file.py       # remove from context
/ls                 # list context
/run command        # run shell command
/undo               # undo last commit
/diff               # show changes
/commit             # commit with message
/exit               # end session

FAQ

Will Aider with Claude API give me the same output quality as Claude Code? Yes, for the same model. Aider with claude-sonnet-4-5 uses the identical model as Claude Code Pro. The output quality is the same — what differs is the agent loop's polish and the context management approach.

How much will Aider cost compared to Claude Code? It depends on your usage. Light users (1–2 hours/day): $5–12/month. Moderate users (3–5 hours/day): $12–25/month. Heavy users (6+ hours/day with complex tasks): $25–60/month. Claude Code's equivalent would be $20 (Pro, with rate limits) or $100–200 (Max). See Claude Code Pricing → for the full comparison.

Can I use Aider without internet? With local models via Ollama — yes, fully offline. With cloud API models — no. See the bonus section above for local model setup.

Does Aider auto-commit like Claude Code? Yes. Every Aider change that modifies files is auto-committed with a descriptive message. You can view the commit in git log and revert with git revert HEAD if needed. Use /undo inside the session to revert the last commit immediately.

What's the biggest difference from Claude Code day-to-day? Context management. Claude Code loads context automatically (and sometimes loads too much). Aider uses a repo map plus explicit /add and /drop commands. After a few days, explicit context control feels more precise than Claude Code's automatic approach.

Can I switch back to Claude Code if needed? Yes. Aider and Claude Code don't conflict. Running both is fine — use whichever fits the task. Many developers keep both installed and use Claude Code for complex tasks that benefit from its polished agent loop, and Aider for everything else.

Browse other migration guides →, explore CLI Agents →, or see the full Claude Code alternatives directory →

How to Switch from Claude Code to Aider: BYOK Migration Guide (2026)