fix: include frontend_path in sirv prod command for correct 404.html fallback

reflex/constants/installer.py

@@ -106,7 +106,20 @@ class Commands(SimpleNamespace):
 
         DEV = "react-router dev --host"
         EXPORT = "react-router build"
-        PROD = "sirv ./build/client --single 404.html --host"
+
+        @staticmethod
+        def get_prod_command(frontend_path: str = "") -> str:
+            """Get the prod command with the correct 404.html path for the given frontend_path.
+
+            Args:
+                frontend_path: The frontend path prefix (e.g. "/app").
+
+            Returns:
+                The sirv command with the correct --single fallback path.
+            """
+            stripped = frontend_path.strip("/")
+            fallback = f"{stripped}/404.html" if stripped else "404.html"
+            return f"sirv ./build/client --single {fallback} --host"
 
     PATH = "package.json"
 

reflex/utils/frontend_skeleton.py

@@ -168,11 +168,14 @@ def _update_react_router_config(config: Config, prerender_routes: bool = False):
 
 
 def _compile_package_json():
+    config = get_config()
     return templates.package_json_template(
         scripts={
             "dev": constants.PackageJson.Commands.DEV,
             "export": constants.PackageJson.Commands.EXPORT,
-            "prod": constants.PackageJson.Commands.PROD,
+            "prod": constants.PackageJson.Commands.get_prod_command(
+                config.frontend_path
+            ),
         },
         dependencies=constants.PackageJson.DEPENDENCIES,
         dev_dependencies=constants.PackageJson.DEV_DEPENDENCIES,

tests/units/test_prerequisites.py

@@ -6,10 +6,12 @@
 from click.testing import CliRunner
 
 from reflex.config import Config
+from reflex.constants.installer import PackageJson
 from reflex.reflex import cli
 from reflex.testing import chdir
 from reflex.utils.decorator import cached_procedure
 from reflex.utils.frontend_skeleton import (
+    _compile_package_json,
     _compile_vite_config,
     _update_react_router_config,
 )
@@ -90,6 +92,47 @@ def test_initialise_vite_config(config, expected_output):
     assert expected_output in output
 
 
+@pytest.mark.parametrize(
+    ("frontend_path", "expected_command"),
+    [
+        ("", "sirv ./build/client --single 404.html --host"),
+        ("/", "sirv ./build/client --single 404.html --host"),
+        ("/app", "sirv ./build/client --single app/404.html --host"),
+        ("/app/", "sirv ./build/client --single app/404.html --host"),
+        ("app", "sirv ./build/client --single app/404.html --host"),
+        (
+            "/deep/nested/path",
+            "sirv ./build/client --single deep/nested/path/404.html --host",
+        ),
+    ],
+)
+def test_get_prod_command(frontend_path, expected_command):
+    assert PackageJson.Commands.get_prod_command(frontend_path) == expected_command
+
+
+@pytest.mark.parametrize(
+    ("config", "expected_prod_script"),
+    [
+        (
+            Config(app_name="test"),
+            "sirv ./build/client --single 404.html --host",
+        ),
+        (
+            Config(app_name="test", frontend_path="/app"),
+            "sirv ./build/client --single app/404.html --host",
+        ),
+        (
+            Config(app_name="test", frontend_path="/deep/nested"),
+            "sirv ./build/client --single deep/nested/404.html --host",
+        ),
+    ],
+)
+def test_compile_package_json_prod_command(config, expected_prod_script, monkeypatch):
+    monkeypatch.setattr("reflex.utils.frontend_skeleton.get_config", lambda: config)
+    output = _compile_package_json()
+    assert f'"prod": "{expected_prod_script}"' in output
+
+
 def test_cached_procedure():
     call_count = 0