---
title: "Aider API: Use FreeTheAI Models"
description: "Run the Aider AI pair programmer on AI models with FreeTheAI: OPENAI_API_BASE, OPENAI_API_KEY, and the openai/ model prefix."
url: https://freetheai.org/setup/aider
language: en
updated: 2026-09-29
---

# Aider API: Use FreeTheAI Models

Aider uses FreeTheAI through its OpenAI compatible setting: two environment variables and the openai/ model prefix.

## Settings

- OPENAI_API_BASE: `https://api.freetheai.org/v1`
- OPENAI_API_KEY: `your FreeTheAI key (ftai_..., 53 characters)`
- --model: `openai/glm-5.3`

## Steps

1. **Set the environment variables.** On macOS and Linux:

```bash
export OPENAI_API_BASE=https://api.freetheai.org/v1
export OPENAI_API_KEY=ftai_your_key_here
```
2. **On Windows.** Run these, then open a new terminal:

```powershell
setx OPENAI_API_BASE https://api.freetheai.org/v1
setx OPENAI_API_KEY ftai_your_key_here
```
3. **Start Aider.** In your project folder, add openai/ in front of the FreeTheAI model ID:

```bash
aider --model openai/glm-5.3
```

## Tips

- Aider warns about unknown model settings for FreeTheAI models. It still works; the warning is about context size defaults.

## Troubleshooting

**Why does Aider need openai/ before the model?**

The prefix tells Aider to use the OpenAI compatible client with your OPENAI_API_BASE.

Checked: Checked against Aider's docs (OpenAI compatible APIs) on 2026-09-29.