Patch Gradio's video-conversion race that kills the generation connection

convert_video_to_playable_mp4() writes ffmpeg output to
Path(video_path).with_suffix(".mp4"), a no-op rename when the upload
is already *.mp4 (e.g. HEVC-in-mp4). It overwrites that file in place
while the browser is still streaming it for the preview widget, which
corrupts the response and — since HF Spaces multiplexes a tab over one
HTTP/2 connection — takes the whole connection down, including the
live generation job's SSE queue. Convert a copy instead so the file
being served is never mutated mid-stream.

app.py

@@ -29,6 +29,31 @@ import spaces
 import gradio as gr
 from huggingface_hub import HfApi, hf_hub_download, snapshot_download
 
+# ------------------------------------------------------------------ #
+# Gradio's own Video component (processing_utils.convert_video_to_    #
+# playable_mp4) writes its ffmpeg output to Path(video_path)          #
+# .with_suffix(".mp4") — a no-op rename whenever the upload is        #
+# already named *.mp4 (e.g. HEVC-in-mp4). That makes it overwrite the #
+# exact file the browser is concurrently streaming for the live       #
+# preview widget, corrupting the response mid-flight. Since HF Spaces #
+# multiplexes a whole browser tab over one HTTP/2 connection, that    #
+# corrupted stream takes the *entire* connection down with it — even  #
+# unrelated in-flight requests like the generation job's SSE queue.   #
+# Patch it to convert a same-named copy instead, so the file the      #
+# browser already has a handle on is never mutated in place.          #
+import gradio.processing_utils as _gr_processing_utils
+_gr_convert_video_to_playable_mp4 = _gr_processing_utils.convert_video_to_playable_mp4
+
+def _patched_convert_video_to_playable_mp4(video_path: str) -> str:
+    p = Path(video_path)
+    if p.suffix.lower() == ".mp4":
+        copy_path = str(p.with_name(p.stem + "_gr_conv.mp4"))
+        shutil.copy2(video_path, copy_path)
+        video_path = copy_path
+    return _gr_convert_video_to_playable_mp4(video_path)
+
+_gr_processing_utils.convert_video_to_playable_mp4 = _patched_convert_video_to_playable_mp4
+
 # ================================================================== #
 #                     CHECKPOINT CONFIGURATION                        #
 # ================================================================== #