OpenRouter Free Tier Setup for Aider

Configures Aider to use OpenRouter's free tier models instead of premium APIs, preserving your Claude or other paid API credits while maintaining full coding assistant functionality.

What This Does

Sets up an `.aider.conf.yaml` configuration that routes Aider through OpenRouter using Qwen 2.5 Coder 32B Instruct (free tier) as the primary model, with fallback options for other free models. Includes sensible defaults for auto-commits, file handling, and development workflow.

Instructions

1. **Check for existing configuration**

- Look for `.aider.conf.yaml` or `.aider.yml` in the project root

- If found, ask user whether to overwrite or merge settings

2. **Verify OpenRouter API key**

- Check if `OPENROUTER_API_KEY` environment variable is set

- If not set, instruct user to:

- Sign up at https://openrouter.ai

- Get free API key from dashboard

- Set environment variable: `export OPENROUTER_API_KEY=your_key_here`

- Confirm key is available before proceeding

3. **Create configuration file**

- Create `.aider.conf.yaml` in project root with:

- OpenRouter API endpoint (`https://openrouter.ai/api/v1`)

- Primary model: `openrouter/qwen/qwen-2.5-coder-32b-instruct`

- Fallback models list in comments for easy switching

- Auto-commits enabled, dirty commits disabled

- Git integration enabled

- Pretty printing and streaming enabled

- Show diffs for review

4. **Configure file handling**

- Set include patterns based on project type:

- Python projects: `**/*.py`, `*.md`, `*.yml`, `*.yaml`

- JavaScript/TypeScript: `**/*.js`, `**/*.ts`, `**/*.jsx`, `**/*.tsx`, `*.md`, `*.json`

- Full-stack: Combine relevant patterns

- Add standard exclude patterns:

- `__pycache__/`, `*.pyc` (Python)

- `node_modules/`, `.git/`

- `venv/`, `.venv/`, `.env`

- Build directories: `dist/`, `build/`, `.next/`

5. **Set editor preference**

- Default to `code` (VS Code)

- If user has different preference (vim, emacs, nano), update `editor` field

- Set `dark_mode: auto` for terminal theme detection

6. **Add usage instructions**

- Create or update README section with:

- How to verify configuration is working

- Command to test: `aider --model openrouter/qwen/qwen-2.5-coder-32b-instruct --test`

- How to switch to fallback models if primary is rate-limited

- Link to OpenRouter free tier limits and model documentation

7. **Validate configuration**

- Ensure YAML syntax is valid

- Verify all paths in include/exclude patterns exist or are relevant

- Check that environment variable interpolation syntax is correct for the shell

Example Configuration Structure

```yaml

Model configuration

model: openrouter/qwen/qwen-2.5-coder-32b-instruct

api_base: https://openrouter.ai/api/v1

openrouter_api_key: ${OPENROUTER_API_KEY}

Fallback options (commented)

- openrouter/microsoft/phi-3-mini-128k-instruct:free

- openrouter/google/gemma-2-9b-it:free

Behavior

auto_commits: true

dirty_commits: false

git: true

stream: true

pretty: true

show_diffs: true

Environment

editor: code

dark_mode: auto

File patterns (customize per project)

include:

- "**/*.py"

- "*.md"

exclude:

- "__pycache__/"

- ".git/"

- "node_modules/"

```

Important Notes

Constraints