diff --git a/tests/routes/test_preview_routes.py b/tests/routes/test_preview_routes.py
index 9ec798ce..639c3b5b 100644
--- a/tests/routes/test_preview_routes.py
+++ b/tests/routes/test_preview_routes.py
@@ -1,5 +1,7 @@
+import os
 import urllib.parse
 from pathlib import Path
+from unittest.mock import patch
 
 import pytest
 from aiohttp import web
@@ -110,3 +112,80 @@ async def test_config_updates_preview_roots_after_switch(tmp_path):
     assert preview_url.startswith("/api/lm/previews?path=")
     decoded = urllib.parse.unquote(preview_url.split("path=", 1)[1])
     assert decoded.replace("\\", "/").endswith("model.webp")
+
+
+def test_is_preview_path_allowed_case_insensitive_on_windows(tmp_path):
+    """Test that preview path validation is case-insensitive on Windows.
+
+    On Windows, drive letters and paths are case-insensitive. This test verifies
+    that paths like 'a:/folder/file' match roots stored as 'A:/folder'.
+
+    See: https://github.com/willmiao/ComfyUI-Lora-Manager/issues/772
+    See: https://github.com/willmiao/ComfyUI-Lora-Manager/issues/774
+    """
+    # Create actual files for the test
+    library_root = tmp_path / "loras"
+    library_root.mkdir()
+    preview_file = library_root / "model.preview.jpeg"
+    preview_file.write_bytes(b"preview")
+
+    config = Config()
+
+    # Simulate Windows behavior by mocking os.path.normcase to lowercase paths
+    # and os.sep to backslash, regardless of the actual platform
+    def windows_normcase(path):
+        return path.lower().replace("/", "\\")
+
+    with patch("py.config.os.path.normcase", side_effect=windows_normcase), \
+         patch("py.config.os.sep", "\\"):
+
+        # Manually set _preview_root_paths with uppercase drive letter style path
+        uppercase_root = Path(str(library_root).upper())
+        config._preview_root_paths = {uppercase_root}
+
+        # Test: lowercase version of the path should still be allowed
+        lowercase_path = str(preview_file).lower()
+        assert config.is_preview_path_allowed(lowercase_path), \
+            f"Path '{lowercase_path}' should be allowed when root is '{uppercase_root}'"
+
+        # Test: mixed case should also work
+        mixed_case_path = str(preview_file).swapcase()
+        assert config.is_preview_path_allowed(mixed_case_path), \
+            f"Path '{mixed_case_path}' should be allowed when root is '{uppercase_root}'"
+
+        # Test: path outside root should still be rejected
+        outside_path = str(tmp_path / "other" / "file.jpeg")
+        assert not config.is_preview_path_allowed(outside_path), \
+            f"Path '{outside_path}' should NOT be allowed"
+
+
+def test_is_preview_path_allowed_rejects_prefix_without_separator(tmp_path):
+    """Test that 'A:/folder' does not match 'A:/folderextra/file'.
+
+    This ensures we check for the path separator after the root to avoid
+    false positives with paths that share a common prefix.
+    """
+    library_root = tmp_path / "loras"
+    library_root.mkdir()
+
+    # Create a sibling folder that starts with the same prefix
+    sibling_root = tmp_path / "loras_extra"
+    sibling_root.mkdir()
+    sibling_file = sibling_root / "model.jpeg"
+    sibling_file.write_bytes(b"x")
+
+    config = Config()
+    config.apply_library_settings(
+        {
+            "folder_paths": {
+                "loras": [str(library_root)],
+                "checkpoints": [],
+                "unet": [],
+                "embeddings": [],
+            }
+        }
+    )
+
+    # The sibling path should NOT be allowed even though it shares a prefix
+    assert not config.is_preview_path_allowed(str(sibling_file)), \
+        f"Path in '{sibling_root}' should NOT be allowed when root is '{library_root}'"