diff --git a/samples/models/dummy/model.py b/samples/models/dummy/model.py
index 1586d61..43be902 100644
--- a/samples/models/dummy/model.py
+++ b/samples/models/dummy/model.py
@@ -1,4 +1,3 @@
-import json
 import typing
 
 
@@ -8,5 +7,5 @@ def load(model) -> None:
 def unload(model) -> None:
     pass
 
-def infer(model, file) -> typing.Iterator[bytes]:
-    yield json.dumps({"hello": "world!"}).encode("utf-8")
+async def infer(model, file) -> typing.AsyncIterator[bytes]:
+    yield await file.read()
\ No newline at end of file
diff --git a/source/manager/ModelManager.py b/source/manager/ModelManager.py
index 2c7106c..f6e7268 100644
--- a/source/manager/ModelManager.py
+++ b/source/manager/ModelManager.py
@@ -23,6 +23,9 @@ class ModelManager:
         # TODO(Faraphel): load more than one model at a time ? require a way more complex manager to handle memory issue
         self.current_loaded_model: typing.Optional[model.base.BaseModel] = None
 
+        # lock to avoid concurrent inference and concurrent model loading and unloading
+        self.inference_lock = asyncio.Lock()
+
         @self.application.get("/models")
         async def get_models() -> list[str]:
             """
diff --git a/source/model/PythonModel.py b/source/model/PythonModel.py
index 0d47fc6..2d91df1 100644
--- a/source/model/PythonModel.py
+++ b/source/model/PythonModel.py
@@ -50,7 +50,7 @@ class PythonModel(base.BaseModel):
         parameters = utils.parameters.load(configuration.get("inputs", {}))
 
         # create an endpoint wrapping the inference inside a fastapi call
-        async def infer_api(**kwargs):
+        async def infer_api(**kwargs) -> fastapi.responses.StreamingResponse:
             # NOTE: fix an issue where it is not possible to give an UploadFile to a StreamingResponse
             # NOTE: perform a naive type(value).__name__ == "type_name" because fastapi do not use it own
             #   fastapi.UploadFile class, but instead the starlette UploadFile class that is more of an implementation
@@ -61,8 +61,12 @@ class PythonModel(base.BaseModel):
             }
 
             return fastapi.responses.StreamingResponse(
-                content=self.infer(**kwargs),
+                content=await self.infer(**kwargs),
                 media_type=self.output_type,
+                headers={
+                    # if the data is not text-like, mark it as an attachment to avoid display issue with Swagger UI
+                    "content-disposition": "inline" if utils.mimetypes.is_textlike(self.output_type) else "attachment"
+                }
             )
 
         infer_api.__signature__ = inspect.Signature(parameters=parameters)
@@ -81,5 +85,5 @@ class PythonModel(base.BaseModel):
     def _unload(self) -> None:
         return self.module.unload(self)
 
-    def _infer(self, **kwargs) -> typing.Iterator[bytes]:
+    def _infer(self, **kwargs) -> typing.Iterator[bytes] | typing.Iterator[bytes]:
         return self.module.infer(self, **kwargs)
diff --git a/source/model/base/BaseModel.py b/source/model/base/BaseModel.py
index d39d7d2..9072e97 100644
--- a/source/model/base/BaseModel.py
+++ b/source/model/base/BaseModel.py
@@ -106,20 +106,21 @@ class BaseModel(abc.ABC):
         Do not call manually, use `unload` instead.
         """
 
-    def infer(self, **kwargs) -> typing.Iterator[bytes]:
+    async def infer(self, **kwargs) -> typing.Iterator[bytes] | typing.AsyncIterator[bytes]:
         """
         Infer our payload through the model within the model manager
         :return: the response of the model
         """
 
-        # make sure we are loaded before an inference
-        self.load()
+        async with self.manager.inference_lock:
+            # make sure we are loaded before an inference
+            self.load()
 
-        # model specific inference part
-        return self._infer(**kwargs)
+            # model specific inference part
+            return self._infer(**kwargs)
 
     @abc.abstractmethod
-    def _infer(self, **kwargs) -> typing.Iterator[bytes]:
+    def _infer(self, **kwargs) -> typing.Iterator[bytes] | typing.AsyncIterator[bytes]:
         """
         Infer our payload through the model
         :return: the response of the model