fix: Add SPA Static Files handler for HuggingFace deployment

- Created SPAStaticFiles class to preserve API routes
- Updated main.py to use SPA handler
- Fixes 404 errors on frontend routes in HuggingFace Spaces

backend/main.py

@@ -21,7 +21,6 @@ from dotenv import load_dotenv
 from fastapi import FastAPI, HTTPException, WebSocket, WebSocketDisconnect, Depends
 from fastapi.middleware.cors import CORSMiddleware
 from fastapi.responses import JSONResponse
-from fastapi.staticfiles import StaticFiles
 from contextlib import asynccontextmanager
 from typing import List, Dict, Optional
 import asyncio
@@ -225,16 +224,19 @@ def get_websocket_manager() -> WebSocketManager:
     return saap_app.websocket_manager
 
 # =====================================================
-# STATIC FILES - Serve Vue.js Frontend
+# STATIC FILES - Serve Vue.js Frontend (SPA Mode)
 # =====================================================
 
+# Import custom SPA Static Files handler
+from spa_static_files import SPAStaticFiles
+
 # Mount static files for frontend (must be AFTER all API routes)
-# This serves the built Vue.js app
+# SPAStaticFiles preserves API routes while serving Vue.js SPA
 import os
 frontend_dist = "/app/frontend/dist"
 if os.path.exists(frontend_dist):
-    app.mount("/", StaticFiles(directory=frontend_dist, html=True), name="static")
-    logger.info(f"✅ Static files mounted: {frontend_dist}")
+    app.mount("/", SPAStaticFiles(directory=frontend_dist, html=True), name="static")
+    logger.info(f"✅ SPA Static files mounted: {frontend_dist}")
 else:
     logger.warning(f"⚠️ Frontend dist directory not found: {frontend_dist}")
 

backend/spa_static_files.py

@@ -0,0 +1,34 @@
+"""
+SPA Static Files Handler for FastAPI
+Serves Vue.js SPA while preserving API routes
+"""
+from fastapi.staticfiles import StaticFiles
+from starlette.responses import FileResponse
+from starlette.types import Scope
+import os
+
+
+class SPAStaticFiles(StaticFiles):
+    """
+    Custom StaticFiles that serves index.html for non-API routes (SPA fallback)
+    while allowing API routes to pass through
+    """
+    
+    async def get_response(self, path: str, scope: Scope):
+        """
+        Handle requests:
+        - API routes (/api/*) → 404 (let FastAPI handle)
+        - Static files (exist) → serve file  
+        - Everything else → index.html (SPA routing)
+        """
+        # Let API routes pass through to FastAPI
+        if path.startswith("api/") or path.startswith("docs") or path.startswith("redoc") or path.startswith("openapi.json"):
+            # Return 404 to let FastAPI handle it
+            raise RuntimeError("Not found")
+        
+        try:
+            # Try to serve the file
+            return await super().get_response(path, scope)
+        except Exception:
+            # File not found → serve index.html for SPA routing
+            return FileResponse(os.path.join(self.directory, "index.html"))