Fix file list cache invalidation on exFAT filesystems

On exFAT volumes, directory mtime does not update when files are
added or removed, causing ComfyUI's mtime-based cache invalidation
in folder_paths to never detect changes. This means newly added
model files do not appear in node dropdowns until the server is
restarted.

Fix: detect exFAT volumes via Win32 API and use directory entry
count as an additional cache invalidation signal on such
filesystems. NTFS and other platforms are unaffected.

folder_paths.py

@@ -1,4 +1,5 @@
 import os
+import sys
 import time
 import mimetypes
 import logging
@@ -7,6 +8,34 @@ from collections.abc import Collection
 
 from comfy.cli_args import args
 
+# exFAT does not update directory mtime when files are added/removed,
+# so the cache invalidation needs an extra check on such filesystems.
+_exfat_checked = False
+_is_exfat_cache: dict[str, bool] = {}
+
+def _is_exfat(path: str) -> bool:
+    """Check if the given path resides on an exFAT volume (Windows only)."""
+    global _exfat_checked, _is_exfat_cache
+    if sys.platform != "win32":
+        return False
+    # Cache per drive letter
+    drive = os.path.splitdrive(path)[0]
+    if drive in _is_exfat_cache:
+        return _is_exfat_cache[drive]
+    try:
+        import ctypes
+        kernel32 = ctypes.windll.kernel32
+        # Get volume information
+        fs_name = ctypes.create_unicode_buffer(256)
+        if kernel32.GetVolumeInformationW(drive + "\\", None, 0, None, None, None, fs_name, 256):
+            result = fs_name.value.upper() == "EXFAT"
+        else:
+            result = False
+    except Exception:
+        result = False
+    _is_exfat_cache[drive] = result
+    return result
+
 supported_pt_extensions: set[str] = {'.ckpt', '.pt', '.pt2', '.bin', '.pth', '.safetensors', '.pkl', '.sft'}
 
 folder_names_and_paths: dict[str, tuple[list[str], set[str]]] = {}
@@ -308,19 +337,22 @@ def get_folder_paths(folder_name: str) -> list[str]:
     folder_name = map_legacy(folder_name)
     return folder_names_and_paths[folder_name][0][:]
 
-def recursive_search(directory: str, excluded_dir_names: list[str] | None=None) -> tuple[list[str], dict[str, float]]:
+def recursive_search(directory: str, excluded_dir_names: list[str] | None=None) -> tuple[list[str], dict[str, float], dict[str, int]]:
     if not os.path.isdir(directory):
-        return [], {}
+        return [], {}, {}
 
     if excluded_dir_names is None:
         excluded_dir_names = []
 
     result = []
     dirs = {}
+    entry_counts = {}
 
     # Attempt to add the initial directory to dirs with error handling
     try:
         dirs[directory] = os.path.getmtime(directory)
+        if _is_exfat(directory):
+            entry_counts[directory] = len(os.listdir(directory))
     except FileNotFoundError:
         logging.warning(f"Warning: Unable to access {directory}. Skipping this path.")
 
@@ -343,11 +375,13 @@ def recursive_search(directory: str, excluded_dir_names: list[str] | None=None)
             path: str = os.path.join(dirpath, d)
             try:
                 dirs[path] = os.path.getmtime(path)
+                if _is_exfat(path):
+                    entry_counts[path] = len(os.listdir(path))
             except FileNotFoundError:
                 logging.warning(f"Warning: Unable to access {path}. Skipping this path.")
                 continue
     logging.debug("found {} files".format(len(result)))
-    return result, dirs
+    return result, dirs, entry_counts
 
 def filter_files_extensions(files: Collection[str], extensions: Collection[str]) -> list[str]:
     return sorted(list(filter(lambda a: os.path.splitext(a)[-1].lower() in extensions or len(extensions) == 0, files)))
@@ -390,11 +424,16 @@ def get_filename_list_(folder_name: str) -> tuple[list[str], dict[str, float], f
     output_list = set()
     folders = folder_names_and_paths[folder_name]
     output_folders = {}
+    all_entry_counts = {}
     for x in folders[0]:
-        files, folders_all = recursive_search(x, excluded_dir_names=[".git"])
+        files, folders_all, entry_counts = recursive_search(x, excluded_dir_names=[".git"])
         output_list.update(filter_files_extensions(files, folders[1]))
         output_folders = {**output_folders, **folders_all}
+        # Store entry counts with a key suffix to avoid colliding with mtime keys
+        for k, v in entry_counts.items():
+            all_entry_counts[k + "::entry_count"] = v
 
+    output_folders.update(all_entry_counts)
     return sorted(list(output_list)), output_folders, time.perf_counter()
 
 def cached_filename_list_(folder_name: str) -> tuple[list[str], dict[str, float], float] | None:
@@ -410,9 +449,24 @@ def cached_filename_list_(folder_name: str) -> tuple[list[str], dict[str, float]
     out = filename_list_cache[folder_name]
 
     for x in out[1]:
+        # Skip entry count keys used for exFAT cache invalidation
+        if x.endswith("::entry_count"):
+            continue
         time_modified = out[1][x]
         folder = x
-        if os.path.getmtime(folder) != time_modified:
+        try:
+            current_mtime = os.path.getmtime(folder)
+        except FileNotFoundError:
+            return None
+        if current_mtime != time_modified:
+            return None
+        # exFAT does not update directory mtime on file changes;
+        # use entry count as a fallback invalidation signal.
+        if _is_exfat(folder):
+            try:
+                if len(os.listdir(folder)) != out[1][folder + "::entry_count"]:
+                    return None
+            except (KeyError, FileNotFoundError):
                 return None
 
     folders = folder_names_and_paths[folder_name]