fix: detect Ollama models directory using platform-specific defaults

  Previously, get_ollama_models_dir() only checked ~/.ollama/models, which
  doesn't exist on Linux systems using the systemd-managed Ollama install
  (which stores models in /usr/share/ollama/.ollama/models).

  Now checks in order:
  1. OLLAMA_MODELS environment variable
  2. Platform-specific directories:
     - macOS: ~/.ollama/models
     - Linux: /usr/share/ollama/.ollama/models (systemd), ~/.ollama/models (user)
     - Windows: ~/.ollama/models

  Updated tests to mock get_ollama_models_dir to avoid using real system models.

Author: storkwrangler

merle/model_split.py

@@ -14,6 +14,7 @@
 import os
 import shutil
 import subprocess
+import sys
 from pathlib import Path
 
 import boto3
@@ -34,10 +35,61 @@
 SPLIT_METADATA_FILE = "split_metadata.json"
 
 
+def _get_platform_models_dirs() -> list[Path]:
+    """
+    Get platform-specific Ollama models directories to search.
+
+    Returns directories in priority order:
+    - macOS: ~/.ollama/models
+    - Linux: /usr/share/ollama/.ollama/models (systemd), ~/.ollama/models (user)
+    - Windows: ~/.ollama/models
+    """
+    if sys.platform == "darwin":
+        # macOS: ~/.ollama/models
+        return [Path.home() / ".ollama" / "models"]
+
+    if sys.platform == "win32":
+        # Windows: C:\Users\%username%\.ollama\models
+        return [Path.home() / ".ollama" / "models"]
+
+    # Linux: check systemd install first, then user install
+    return [
+        Path("/usr/share/ollama/.ollama/models"),  # systemd install
+        Path.home() / ".ollama" / "models",  # user install
+    ]
+
+
 def get_ollama_models_dir() -> Path:
-    """Get the default Ollama models directory."""
-    home = Path.home()
-    return home / ".ollama" / "models"
+    """
+    Get the Ollama models directory.
+
+    Checks in order:
+    1. OLLAMA_MODELS environment variable (if set)
+    2. Platform-specific directories (first existing one):
+       - macOS: ~/.ollama/models
+       - Linux: /usr/share/ollama/.ollama/models (systemd) or ~/.ollama/models (user)
+       - Windows: ~/.ollama/models
+
+    Returns:
+        Path to the Ollama models directory
+    """
+    # Check environment variable first
+    env_models_dir = os.environ.get("OLLAMA_MODELS")
+    if env_models_dir:
+        models_path = Path(env_models_dir)
+        logger.debug(f"Using OLLAMA_MODELS from environment: {models_path}")
+        return models_path
+
+    # Search platform-specific directories
+    for models_dir in _get_platform_models_dirs():
+        if models_dir.exists():
+            logger.debug(f"Found models directory: {models_dir}")
+            return models_dir
+
+    # Fall back to first platform default (even if it doesn't exist yet)
+    default_dir = _get_platform_models_dirs()[0]
+    logger.debug(f"Using default models directory: {default_dir}")
+    return default_dir
 
 
 def calculate_directory_size(path: Path) -> int:

tests/conftest.py

@@ -21,6 +21,25 @@ def temp_cache_dir(tmp_path: Path) -> Path:
     return cache_dir
 
 
+@pytest.fixture
+def mock_models_dir(tmp_path: Path) -> Path:
+    """
+    Create a mock Ollama models directory for testing.
+
+    Creates an empty models directory structure to avoid tests
+    using the real system Ollama models.
+
+    Args:
+        tmp_path: pytest tmp_path fixture
+
+    Returns:
+        Path to mock models directory
+    """
+    models_dir = tmp_path / ".ollama" / "models"
+    models_dir.mkdir(parents=True, exist_ok=True)
+    return models_dir
+
+
 @pytest.fixture
 def sample_config() -> dict:
     """

tests/test_deployment_completeness.py

@@ -10,14 +10,21 @@
 class TestDeploymentCompleteness:
     """Test that verifies what's missing for successful deployment."""
 
+    @patch("merle.model_split.get_ollama_models_dir")
     @patch("merle.functions.validate_ollama_model")
     @patch("merle.cli.get_default_project_name")
     def test_prepare_creates_expected_files(
-        self, mock_get_default_project: MagicMock, mock_validate: MagicMock, temp_cache_dir: Path
+        self,
+        mock_get_default_project: MagicMock,
+        mock_validate: MagicMock,
+        mock_models_dir_fn: MagicMock,
+        temp_cache_dir: Path,
+        mock_models_dir: Path,
     ) -> None:
         """Test that prepare command creates expected deployment files."""
         mock_validate.return_value = True
         mock_get_default_project.return_value = "testproject"
+        mock_models_dir_fn.return_value = mock_models_dir
 
         # Prepare deployment files
         args = argparse.Namespace(
@@ -53,14 +60,21 @@ def test_prepare_creates_expected_files(
         config_path = temp_cache_dir / "testproject" / "config.json"
         assert config_path.exists(), "config.json should be created"
 
+    @patch("merle.model_split.get_ollama_models_dir")
     @patch("merle.functions.validate_ollama_model")
     @patch("merle.cli.get_default_project_name")
     def test_deployment_is_now_complete(  # noqa: PLR0915, PLR0912
-        self, mock_get_default_project: MagicMock, mock_validate: MagicMock, temp_cache_dir: Path
+        self,
+        mock_get_default_project: MagicMock,
+        mock_validate: MagicMock,
+        mock_models_dir_fn: MagicMock,
+        temp_cache_dir: Path,
+        mock_models_dir: Path,
     ) -> None:
         """Verify that deployment is now complete with all required components."""
         mock_validate.return_value = True
         mock_get_default_project.return_value = "testproject"
+        mock_models_dir_fn.return_value = mock_models_dir
 
         # Prepare deployment files
         args = argparse.Namespace(

tests/test_functions.py

@@ -394,10 +394,14 @@ def test_generate_zappa_settings_with_tags(self, tmp_path: Path, sample_tags: di
 class TestPrepareDeploymentFiles:
     """Tests for prepare_deployment_files function."""
 
+    @patch("merle.model_split.get_ollama_models_dir")
     @patch("merle.functions.validate_ollama_model")
-    def test_prepare_deployment_files_basic(self, mock_validate: MagicMock, temp_cache_dir: Path):
+    def test_prepare_deployment_files_basic(
+        self, mock_validate: MagicMock, mock_models_dir_fn: MagicMock, temp_cache_dir: Path, mock_models_dir: Path
+    ):
         """Test preparing deployment files with basic parameters."""
         mock_validate.return_value = True
+        mock_models_dir_fn.return_value = mock_models_dir
 
         # Create template directory with mock templates
         template_dir = Path(__file__).parent.parent / "merle" / "templates"
@@ -426,12 +430,19 @@ def test_prepare_deployment_files_basic(self, mock_validate: MagicMock, temp_cac
         assert config["models"]["llama2"]["dev"]["auth_token"] == "test-token"
         assert config["models"]["llama2"]["dev"]["region"] == "us-east-1"
 
+    @patch("merle.model_split.get_ollama_models_dir")
     @patch("merle.functions.validate_ollama_model")
     def test_prepare_deployment_files_with_tags(
-        self, mock_validate: MagicMock, temp_cache_dir: Path, sample_tags: dict
+        self,
+        mock_validate: MagicMock,
+        mock_models_dir_fn: MagicMock,
+        temp_cache_dir: Path,
+        sample_tags: dict,
+        mock_models_dir: Path,
     ):
         """Test preparing deployment files with tags."""
         mock_validate.return_value = True
+        mock_models_dir_fn.return_value = mock_models_dir
 
         model_cache_dir = prepare_deployment_files(
             model_name="llama2",
@@ -454,10 +465,14 @@ def test_prepare_deployment_files_with_tags(
         config = load_config(temp_cache_dir)
         assert config["models"]["llama2"]["dev"]["tags"] == sample_tags
 
+    @patch("merle.model_split.get_ollama_models_dir")
     @patch("merle.functions.validate_ollama_model")
-    def test_prepare_deployment_files_without_tags(self, mock_validate: MagicMock, temp_cache_dir: Path):
+    def test_prepare_deployment_files_without_tags(
+        self, mock_validate: MagicMock, mock_models_dir_fn: MagicMock, temp_cache_dir: Path, mock_models_dir: Path
+    ):
         """Test preparing deployment files without tags."""
         mock_validate.return_value = True
+        mock_models_dir_fn.return_value = mock_models_dir
 
         model_cache_dir = prepare_deployment_files(
             model_name="llama2",