fix: add X-Accel-Buffering header to fix ERR_HTTP2_PROTOCOL_ERROR on HF Spaces SSE stream

src/api/routes/rag.py

@@ -86,9 +86,19 @@ async def chat_with_rag_stream(
 
         user_id = current_user.id if current_user else None
 
+        # SSE headers: X-Accel-Buffering: no is critical for HF Spaces nginx
+        # to disable proxy buffering which causes ERR_HTTP2_PROTOCOL_ERROR
+        headers = {
+            "X-Accel-Buffering": "no",
+            "Cache-Control": "no-cache, no-transform",
+            "Connection": "keep-alive",
+            "Transfer-Encoding": "chunked",
+        }
+
         return StreamingResponse(
             router_use_case.execute_stream(request, is_guest=(current_user is None), user_id=user_id),
-            media_type="text/event-stream"
+            media_type="text/event-stream",
+            headers=headers,
         )
     except Exception as e:
         raise HTTPException(status_code=500, detail=str(e))