diff --git a/packages/reflex-base/src/reflex_base/config.py b/packages/reflex-base/src/reflex_base/config.py
index 9a522628e6a..9ff2895f5ce 100644
--- a/packages/reflex-base/src/reflex_base/config.py
+++ b/packages/reflex-base/src/reflex_base/config.py
@@ -348,6 +348,9 @@ def _post_init(self, **kwargs):
         for key, env_value in env_kwargs.items():
             setattr(self, key, env_value)
 
+        # Normalize route prefixes to ensure they start with a slash.
+        self._normalize_paths()
+
         # Normalize disable_plugins: convert strings and Plugin subclasses to instances.
         self._normalize_disable_plugins()
 
@@ -418,6 +421,14 @@ def _normalize_disable_plugins(self):
                 )
         self.disable_plugins = normalized
 
+    def _normalize_paths(self):
+        """Ensure frontend and backend paths start with a slash if provided."""
+        if self.frontend_path and not self.frontend_path.startswith("/"):
+            self.frontend_path = f"/{self.frontend_path}"
+
+        if self.backend_path and not self.backend_path.startswith("/"):
+            self.backend_path = f"/{self.backend_path}"
+
     def _add_builtin_plugins(self):
         """Add the builtin plugins to the config."""
         for plugin in _PLUGINS_ENABLED_BY_DEFAULT:
diff --git a/reflex/utils/exec.py b/reflex/utils/exec.py
index 0889e9359e1..451607e9bb2 100644
--- a/reflex/utils/exec.py
+++ b/reflex/utils/exec.py
@@ -13,7 +13,6 @@
 from collections.abc import Sequence
 from pathlib import Path
 from typing import Any, NamedTuple, TypedDict
-from urllib.parse import urljoin
 
 from reflex_base import constants
 from reflex_base.config import get_config
@@ -227,8 +226,6 @@ def run_process_and_launch_url(
                 if match:
                     if first_run:
                         url = match.group(1)
-                        if get_config().frontend_path != "":
-                            url = urljoin(url, get_config().frontend_path)
 
                         notify_frontend(url, backend_present)
                         if backend_present:
diff --git a/tests/integration/tests_playwright/test_frontend_path.py b/tests/integration/tests_playwright/test_frontend_path.py
index 8434938a894..e4e52aba22b 100644
--- a/tests/integration/tests_playwright/test_frontend_path.py
+++ b/tests/integration/tests_playwright/test_frontend_path.py
@@ -214,8 +214,14 @@ def bouncer_dynamic():
 
 @pytest.fixture(
     scope="module",
-    params=["", "/prefix", "/prefix/nested"],
-    ids=["no-prefix", "single-level", "two-level"],
+    params=["", "/prefix", "/prefix/nested", "noslash", "noslash/nested"],
+    ids=[
+        "no-prefix",
+        "single-level",
+        "two-level",
+        "noslash-single-level",
+        "noslash-two-level",
+    ],
 )
 def frontend_path(request: pytest.FixtureRequest) -> str:
     """Parametrise over no-prefix and various prefix depths.
@@ -450,3 +456,23 @@ def test_navigate_back_and_forth(frontend_path_app: AppHarness, page: Page):
     expect(log).to_contain_text("index")
     expect(log).to_contain_text("static")
     expect(log).to_contain_text("dynamic-7")
+
+
+def test_frontend_url_format(frontend_path_app: AppHarness, frontend_path: str):
+    """Verify that the frontend_url correctly incorporates the frontend_path."""
+    url = frontend_path_app.frontend_url
+    assert url is not None
+
+    from urllib.parse import urlparse
+
+    parsed = urlparse(url)
+
+    expected_path = frontend_path
+    if expected_path and not expected_path.startswith("/"):
+        expected_path = f"/{expected_path}"
+    if expected_path and not expected_path.endswith("/"):
+        expected_path = f"{expected_path}/"
+    if not expected_path:
+        expected_path = "/"
+
+    assert parsed.path == expected_path