Serve React SPA at root so /assets/* resolve (fix white screen)

app.py

@@ -4,8 +4,13 @@ The Space uses the Docker SDK, so we serve everything from one plain FastAPI
 app on port 7860:
 
   * ``/api/v1/*``  -> the real 9XAIPal backend router
-  * ``/ui/*``      -> the compiled React build (SPA, with client-side routing)
-  * ``/``          -> redirects to ``/ui/``
+  * ``/*``         -> the compiled React build (SPA, with client-side routing)
+
+The React build (``dist/index.html``) references its bundles with absolute
+root paths (``/assets/index-*.js``), so the SPA MUST be served from the root.
+Mounting it under a sub-path (e.g. ``/ui``) makes those asset requests 404 and
+the page renders blank. The API router is registered before the static mount,
+so ``/api/v1`` and ``/api/docs`` still win over the catch-all.
 
 We deliberately do NOT use Gradio as a wrapper: as of Gradio 6.0 the FastAPI
 instance exposed as ``demo.app`` is no longer the app that ``launch()`` serves,
@@ -20,7 +25,6 @@ from pathlib import Path
 
 import uvicorn
 from fastapi import FastAPI
-from fastapi.responses import RedirectResponse
 from fastapi.staticfiles import StaticFiles
 from starlette.responses import FileResponse
 
@@ -73,9 +77,17 @@ except Exception as exc:  # pragma: no cover
     logger.warning("Backend package not importable (%s); serving static UI only", exc)
 
 
+@app.get("/healthz", include_in_schema=False)
+def healthz() -> dict:
+    """Lightweight liveness probe for the container itself."""
+    return {"status": "ok"}
+
+
 # -----------------------------------------------------------------------------
-# Serve the compiled React build under /ui with SPA fallback so client-side
-# routes (deep links) resolve to index.html instead of 404.
+# Serve the compiled React build at the ROOT with SPA fallback so client-side
+# routes (deep links) resolve to index.html instead of 404. This MUST be the
+# last route added: as a "/" mount it matches every path, so the API router and
+# /healthz above (registered first) take precedence.
 # -----------------------------------------------------------------------------
 _index = UI_DIR / "index.html"
 if UI_DIR.is_dir() and _index.exists():
@@ -84,35 +96,23 @@ if UI_DIR.is_dir() and _index.exists():
         async def get_response(self, path, scope):
             response = await super().get_response(path, scope)
             if response.status_code == 404:
-                # Unknown sub-path: hand it back to the SPA router.
+                # Unknown client-side route: hand it back to the SPA router.
                 return FileResponse(_index)
             return response
 
     app.mount(
-        "/ui",
+        "/",
         SPAStaticFiles(directory=str(UI_DIR), html=True, check_dir=False),
         name="ui",
     )
-    logger.info("React UI mounted at /ui (source: %s)", UI_DIR)
+    logger.info("React UI mounted at / (source: %s)", UI_DIR)
 else:
     logger.warning(
-        "No compiled React build found at %s; /ui will be unavailable. "
+        "No compiled React build found at %s; the UI will be unavailable. "
         "Run `npm run build` in the frontend and copy `dist/` here.",
         UI_DIR,
     )
 
 
-@app.get("/", include_in_schema=False)
-def root() -> RedirectResponse:
-    """Send visitors from the Space root to the React UI."""
-    return RedirectResponse(url="/ui/")
-
-
-@app.get("/healthz", include_in_schema=False)
-def healthz() -> dict:
-    """Lightweight liveness probe for the container itself."""
-    return {"status": "ok"}
-
-
 if __name__ == "__main__":
     uvicorn.run(app, host=HOST, port=PORT, log_level="info")