Aider Configuration for OpenRouter API

Configure Aider to use OpenRouter's API with flexible model selection and cost-saving features.

Description

This skill shows you how to set up Aider with OpenRouter as your AI provider, allowing access to multiple models (Deepseek, Gemini, Mistral, etc.) through a single API key. Includes optional prompt caching to reduce costs on repeated operations.

Instructions

Step 1: Obtain OpenRouter API Key

1. Navigate to the OpenRouter settings page at https://openrouter.ai/settings/keys

2. Create a new API key if you don't have one

3. Copy the API key (starts with `sk-`)

4. Store it securely - you'll need it for configuration

Step 2: Create Aider Configuration File

1. Create or edit the Aider configuration file at `~/.aider.conf.yml`

2. Add the following configuration structure:

```yaml

Add your OpenRouter API key

api-key:

- openrouter=sk-YOUR_ACTUAL_KEY_HERE

Set your default model

model: openrouter/mistralai/devstral-2512:free

Enable caching to save on costs

cache-prompts: true

```

3. Replace `sk-YOUR_ACTUAL_KEY_HERE` with your actual OpenRouter API key from Step 1

Step 3: Choose Your Model

Select a model from OpenRouter's available options. Common choices include:

**Mistral Devstral (free tier)**: `openrouter/mistralai/devstral-2512:free`

**Deepseek models**: `openrouter/deepseek/deepseek-chat`

**Google Gemini models**: `openrouter/google/gemini-2.0-flash-exp:free`

**Other models**: Check https://openrouter.ai/docs/models for full list

Update the `model:` field with your preferred model identifier.

Step 4: Configure Optional Settings

**Prompt Caching** (Recommended):

Keep `cache-prompts: true` to enable caching

This reduces costs by reusing common prompt components across sessions

Particularly useful for repeated operations on the same codebase

Step 5: Verify Configuration

1. Open a terminal

2. Run `aider --help` to confirm Aider recognizes your configuration

3. Start an Aider session: `aider` (or `aider <file>` to edit specific files)

4. Confirm the model loads and responds correctly

Important Notes

**Security**: Never commit your `~/.aider.conf.yml` file with API keys to version control

**Model Selection**: Free-tier models have rate limits; consider paid models for production use

**Cost Management**: Prompt caching can reduce API costs by 50-90% for repetitive tasks

**Model Compatibility**: Not all OpenRouter models support all Aider features; test your selection

**Alternative Providers**: You can configure multiple API keys for different providers in the same config file

Examples

**Example 1: Using Deepseek Model**

```yaml

api-key:

- openrouter=sk-or-v1-abc123...

model: openrouter/deepseek/deepseek-chat

cache-prompts: true

```

**Example 2: Multiple Providers**

```yaml

api-key:

- openrouter=sk-or-v1-abc123...

- anthropic=sk-ant-abc123...

model: openrouter/google/gemini-2.0-flash-exp:free

cache-prompts: true

```

**Example 3: Cost-Optimized Setup**

```yaml

api-key:

- openrouter=sk-or-v1-abc123...

model: openrouter/mistralai/devstral-2512:free

cache-prompts: true

cache-keepalive-pings: 5

```

Constraints

Requires active Aider installation

Valid OpenRouter API key required

Internet connection needed for API calls

Model availability subject to OpenRouter's current offerings

Free-tier models may have rate limits or reduced capabilities

Aider Configuration for OpenRouter API

Aider Configuration for OpenRouter API

Description

Instructions

Step 1: Obtain OpenRouter API Key

Step 2: Create Aider Configuration File

Add your OpenRouter API key

Set your default model

Enable caching to save on costs

Step 3: Choose Your Model

Step 4: Configure Optional Settings

Step 5: Verify Configuration

Important Notes

Examples

Constraints

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