diff --git a/api/onnx_web/convert/__main__.py b/api/onnx_web/convert/__main__.py
index 437dc0394..7e3315c68 100644
--- a/api/onnx_web/convert/__main__.py
+++ b/api/onnx_web/convert/__main__.py
@@ -22,6 +22,7 @@
 from .upscaling.resrgan import convert_upscale_resrgan
 from .upscaling.swinir import convert_upscaling_swinir
 from .utils import (
+    DEFAULT_OPSET,
     ConversionContext,
     download_progress,
     remove_prefix,
@@ -572,7 +573,7 @@ def main(args=None) -> int:
     )
     parser.add_argument(
         "--opset",
-        default=14,
+        default=DEFAULT_OPSET,
         type=int,
         help="The version of the ONNX operator set to use.",
     )
diff --git a/api/onnx_web/convert/diffusion/diffusers.py b/api/onnx_web/convert/diffusion/diffusers.py
index a59b696ad..a56f21970 100644
--- a/api/onnx_web/convert/diffusion/diffusers.py
+++ b/api/onnx_web/convert/diffusion/diffusers.py
@@ -120,6 +120,7 @@ def convert_diffusion_diffusers_cnet(
         pipe_cnet = UNet2DConditionModel_CNet.from_pretrained(source, subfolder="unet")
 
     pipe_cnet = pipe_cnet.to(device=device, dtype=dtype)
+    run_gc()
 
     if is_torch_2_0:
         pipe_cnet.set_attn_processor(AttnProcessor())
diff --git a/api/onnx_web/convert/utils.py b/api/onnx_web/convert/utils.py
index 9d22fbad2..bd219d90f 100644
--- a/api/onnx_web/convert/utils.py
+++ b/api/onnx_web/convert/utils.py
@@ -17,6 +17,7 @@
 
 from ..constants import ONNX_WEIGHTS
 from ..server import ServerContext
+from ..utils import get_boolean
 
 logger = getLogger(__name__)
 
@@ -28,6 +29,8 @@
 ModelDict = Dict[str, Union[str, int]]
 LegacyModel = Tuple[str, str, Optional[bool], Optional[bool], Optional[int]]
 
+DEFAULT_OPSET = 14
+
 
 class ConversionContext(ServerContext):
     def __init__(
@@ -36,7 +39,7 @@ def __init__(
         cache_path: Optional[str] = None,
         device: Optional[str] = None,
         half: bool = False,
-        opset: Optional[int] = None,
+        opset: int = DEFAULT_OPSET,
         token: Optional[str] = None,
         prune: Optional[List[str]] = None,
         control: bool = True,
@@ -57,6 +60,12 @@ def __init__(
 
         self.map_location = torch.device(self.training_device)
 
+    @classmethod
+    def from_environ(cls):
+        context = super().from_environ()
+        context.control = get_boolean(environ, "ONNX_WEB_CONVERT_CONTROL", True)
+        context.opset = int(environ.get("ONNX_WEB_CONVERT_OPSET", DEFAULT_OPSET))
+
 
 def download_progress(urls: List[Tuple[str, str]]):
     for url, dest in urls:
diff --git a/api/onnx_web/server/hacks.py b/api/onnx_web/server/hacks.py
index 1c33953cb..b59bb73a3 100644
--- a/api/onnx_web/server/hacks.py
+++ b/api/onnx_web/server/hacks.py
@@ -4,8 +4,8 @@
 from os import path
 from urllib.parse import urlparse
 
-from .context import ServerContext
 from ..utils import run_gc
+from .context import ServerContext
 
 logger = getLogger(__name__)
 
@@ -135,6 +135,7 @@ def patch_cache_path(server: ServerContext, url: str, **kwargs) -> str:
 def apply_patch_basicsr(server: ServerContext):
     logger.debug("patching BasicSR module")
     import basicsr.utils.download_util
+
     basicsr.utils.download_util.download_file_from_google_drive = patch_not_impl
     basicsr.utils.download_util.load_file_from_url = partial(patch_cache_path, server)
 
@@ -142,6 +143,7 @@ def apply_patch_basicsr(server: ServerContext):
 def apply_patch_codeformer(server: ServerContext):
     logger.debug("patching CodeFormer module")
     import codeformer.facelib.utils.misc
+
     codeformer.facelib.utils.misc.download_pretrained_models = patch_not_impl
     codeformer.facelib.utils.misc.load_file_from_url = partial(patch_cache_path, server)
 
@@ -149,6 +151,7 @@ def apply_patch_codeformer(server: ServerContext):
 def apply_patch_facexlib(server: ServerContext):
     logger.debug("patching Facexlib module")
     import facexlib.utils
+
     facexlib.utils.load_file_from_url = partial(patch_cache_path, server)