Example config with fallback strategy

{
  "strategy": {
    "mode": "fallback"
  },
  "targets": [
    {
      "virtual_key": "openai-virtual-key"
    },
    {
      "virtual_key": "anthropic-virtual-key",
      "override_params": {
        "model": "claude-1"
      }
    }
  ]
}