Aider is an open-source AI pair-programming tool for the terminal, with deep git integration. It can point at any OpenAI-compatible endpoint via environment variables, so once it's aimed at CrossModel you can use the entire catalog.

Quickstart

1. Install Aider

python -m pip install aider-install
aider-install

Or with pipx:

pipx install aider-chat

2. Create an API key

Sign in to the Console and create a key that starts with cm- on the API Keys page. The key is shown only once, so copy it somewhere safe.

3. Set the environment variables

macOS / Linux:

export OPENAI_API_BASE=https://api.crossmodel.ai/v1
export OPENAI_API_KEY=cm-YOUR_KEY

Windows (PowerShell):

$env:OPENAI_API_BASE = "https://api.crossmodel.ai/v1"
$env:OPENAI_API_KEY  = "cm-YOUR_KEY"

To make them permanent, add the two lines to ~/.zshrc, ~/.bashrc, or your system environment variables, then reopen the terminal.

4. Launch Aider

From your project directory, pick a model using the openai/<model-id> form:

aider --model openai/deepseek/deepseek-v4-pro

Lock it in with a config file

Create .aider.conf.yml in your project root so you don't have to pass flags every time:

openai-api-base: https://api.crossmodel.ai/v1
openai-api-key: cm-YOUR_KEY
model: openai/deepseek/deepseek-v4-pro

After that, just run aider with no extra arguments.

Common model examples

# DeepSeek V4 Pro (recommended — great price/performance)
aider --model openai/deepseek/deepseek-v4-pro
 
# Claude Sonnet 4.6
aider --model openai/anthropic/claude-sonnet-4.6
 
# GPT-5.5
aider --model openai/openai/gpt-5.5

See the full list of model IDs in the model catalog.

Troubleshooting