Register CORS before Gradio app startup

app.py

@@ -9,8 +9,9 @@ from typing import Any
 
 import gradio as gr
 from fastapi import File, UploadFile
-from fastapi.middleware.cors import CORSMiddleware
 from fastapi.responses import RedirectResponse
+from starlette.middleware import Middleware
+from fastapi.middleware.cors import CORSMiddleware
 
 from src.api.main import detect_image as api_detect_image
 from src.api.main import detect_video as api_detect_video
@@ -51,13 +52,6 @@ def _build_demo() -> gr.Blocks:
 
 
 def _attach_api_routes(app: Any) -> None:
-    app.add_middleware(
-        CORSMiddleware,
-        allow_origins=["*"],
-        allow_methods=["*"],
-        allow_headers=["*"],
-    )
-
     async def health() -> dict:
         return await api_health()
 
@@ -128,7 +122,18 @@ if __name__ == "__main__":
             prevent_thread_lock=True,
             show_error=True,
             ssr_mode=False,
-            app_kwargs={"docs_url": "/docs", "redoc_url": "/redoc"},
+            app_kwargs={
+                "docs_url": "/docs",
+                "redoc_url": "/redoc",
+                "middleware": [
+                    Middleware(
+                        CORSMiddleware,
+                        allow_origins=["*"],
+                        allow_methods=["*"],
+                        allow_headers=["*"],
+                    )
+                ],
+            },
         )
         _attach_api_routes(app)
         while True:

tests/test_zero_gpu_contract.py

@@ -38,7 +38,10 @@ def test_app_mounts_gradio_onto_fastapi():
     assert "demo = _build_demo().queue()" in source
     assert "prevent_thread_lock=True" in source
     assert "while True:" in source
-    assert 'app_kwargs={"docs_url": "/docs", "redoc_url": "/redoc"}' in source
+    assert '"docs_url": "/docs"' in source
+    assert '"redoc_url": "/redoc"' in source
+    assert "Middleware(" in source
+    assert "CORSMiddleware" in source
     assert 'app.add_api_route("/api/health"' in source
     assert "/api/detect/image" in source
     assert "/api/detect/video" in source