```json
{
  "files": [
    "client.py",
    "test_client.py"
  ],
  "edits": [
    {
      "file": "client.py",
      "description": "Update ApiClient to initialize httpx.Client with a default timeout and wrap the request method to handle httpx.TimeoutException without altering the method signature.",
      "code": "import httpx\n\nclass ApiClient:\n    def __init__(self, default_timeout=5.0):\n        self.default_timeout = default_timeout\n        self.client = httpx.Client(timeout=self.default_timeout)\n\n    def request(self, method, url, **kwargs):\n        # Maintain signature by using kwargs for optional overrides\n        # Ensure a timeout is always present\n        kwargs.setdefault('timeout', self.default_timeout)\n        \n        try:\n            return self.client.request(method, url, **kwargs)\n        except httpx.TimeoutException as e:\n            # Wrap httpx timeout into a standard Python TimeoutError or custom domain exception\n            raise TimeoutError(f\"Request to {url} timed out after {kwargs['timeout']}s\") from e"
    }
  ],
  "tests": [
    {
      "file": "test_client.py",
      "description": "Verify that timeout exceptions are caught and re-raised as TimeoutError, and that default timeouts are applied.",
      "code": "import pytest\nimport httpx\nfrom unittest.mock import patch\nfrom client import ApiClient\n\ndef test_timeout_exception_handling():\n    client = ApiClient(default_timeout=1.0)\n    with patch('httpx.Client.request', side_effect=httpx.TimeoutException('Request timed out')):\n        with pytest.raises(TimeoutError) as excinfo:\n            client.request('GET', 'http://example.com')\n        assert 'timed out' in str(excinfo.value)\n\ndef test_timeout_passed_to_httpx():\n    client = ApiClient(default_timeout=5.0)\n    with patch('httpx.Client.request') as mock_request:\n        client.request('GET', 'http://example.com')\n        # Verify the default timeout was passed in kwargs\n        args, kwargs = mock_request.call_args\n        assert kwargs['timeout'] == 5.0"
    }
  ],
  "risks": [
    "Replacing specific httpx timeout subtypes (ConnectTimeout, ReadTimeout) with a generic TimeoutError may hide the root cause of the failure from the caller.",
    "Setting a global default timeout may cause unexpected failures for endpoints that naturally require longer processing times.",
    "If the wrapper is used in an async context, httpx.AsyncClient must be used instead of httpx.Client."
  ]
}
```