Centralize MIME type initialization into utils/mime_types.py

Move mimetypes.init() and all custom type registrations from server.py
and metadata_extract.py into a single init_mime_types() function called
once at startup in main.py.

Amp-Thread-ID: https://ampcode.com/threads/T-019cbb2a-513a-7458-9962-b4100e4f124d
Co-authored-by: Amp <amp@ampcode.com>

app/assets/services/metadata_extract.py

@@ -20,31 +20,6 @@ SAFETENSORS_EXTENSIONS = frozenset({".safetensors", ".sft"})
 # Maximum safetensors header size to read (8MB)
 MAX_SAFETENSORS_HEADER_SIZE = 8 * 1024 * 1024
 
-def _register_custom_mime_types():
-    """Register custom MIME types for model and config files.
-
-    Called before each use because mimetypes.init() in server.py resets the database.
-    Uses a quick check to avoid redundant registrations.
-    """
-    # Quick check if already registered (avoids redundant add_type calls)
-    test_result, _ = mimetypes.guess_type("test.safetensors")
-    if test_result == "application/safetensors":
-        return
-
-    mimetypes.add_type("application/safetensors", ".safetensors")
-    mimetypes.add_type("application/safetensors", ".sft")
-    mimetypes.add_type("application/pytorch", ".pt")
-    mimetypes.add_type("application/pytorch", ".pth")
-    mimetypes.add_type("application/pickle", ".ckpt")
-    mimetypes.add_type("application/pickle", ".pkl")
-    mimetypes.add_type("application/gguf", ".gguf")
-    mimetypes.add_type("application/yaml", ".yaml")
-    mimetypes.add_type("application/yaml", ".yml")
-
-
-# Register custom types at module load
-_register_custom_mime_types()
-
 
 @dataclass
 class ExtractedMetadata:
@@ -325,8 +300,6 @@ def extract_file_metadata(
     _, ext = os.path.splitext(abs_path)
     meta.format = ext.lstrip(".").lower() if ext else ""
 
-    # MIME type guess (re-register in case mimetypes.init() was called elsewhere)
-    _register_custom_mime_types()
     mime_type, _ = mimetypes.guess_type(abs_path)
     meta.content_type = mime_type
 

main.py

@@ -10,6 +10,7 @@ from app.logger import setup_logger
 from app.assets.seeder import asset_seeder
 import itertools
 import utils.extra_config
+from utils.mime_types import init_mime_types
 import logging
 import sys
 from comfy_execution.progress import get_progress_state
@@ -162,6 +163,7 @@ def execute_prestartup_script():
         logging.info("")
 
 apply_custom_paths()
+init_mime_types()
 
 if args.enable_manager:
     comfyui_manager.prestartup()

server.py

@@ -197,10 +197,6 @@ class PromptServer():
     def __init__(self, loop):
         PromptServer.instance = self
 
-        mimetypes.init()
-        mimetypes.add_type('application/javascript; charset=utf-8', '.js')
-        mimetypes.add_type('image/webp', '.webp')
-
         self.user_manager = UserManager()
         self.model_file_manager = ModelFileManager()
         self.custom_node_manager = CustomNodeManager()

utils/mime_types.py

@@ -0,0 +1,37 @@
+"""Centralized MIME type initialization.
+
+Call init_mime_types() once at startup to initialize the MIME type database
+and register all custom types used across ComfyUI.
+"""
+
+import mimetypes
+
+_initialized = False
+
+
+def init_mime_types():
+    """Initialize the MIME type database and register all custom types.
+
+    Safe to call multiple times; only runs once.
+    """
+    global _initialized
+    if _initialized:
+        return
+    _initialized = True
+
+    mimetypes.init()
+
+    # Web types (used by server.py for static file serving)
+    mimetypes.add_type('application/javascript; charset=utf-8', '.js')
+    mimetypes.add_type('image/webp', '.webp')
+
+    # Model and data file types (used by asset scanning / metadata extraction)
+    mimetypes.add_type("application/safetensors", ".safetensors")
+    mimetypes.add_type("application/safetensors", ".sft")
+    mimetypes.add_type("application/pytorch", ".pt")
+    mimetypes.add_type("application/pytorch", ".pth")
+    mimetypes.add_type("application/pickle", ".ckpt")
+    mimetypes.add_type("application/pickle", ".pkl")
+    mimetypes.add_type("application/gguf", ".gguf")
+    mimetypes.add_type("application/yaml", ".yaml")
+    mimetypes.add_type("application/yaml", ".yml")