diff --git a/tests/tools/test_tool_backend_helpers.py b/tests/tools/test_tool_backend_helpers.py
index e3d6cf0711c..03bb7f20d7a 100644
--- a/tests/tools/test_tool_backend_helpers.py
+++ b/tests/tools/test_tool_backend_helpers.py
@@ -242,6 +242,20 @@ class TestHasDirectModalCredentials:
         with patch.object(Path, "home", return_value=tmp_path):
             assert has_direct_modal_credentials() is True
 
+    def test_home_dir_permission_denied(self, monkeypatch):
+        """PermissionError on Path.home() should not crash (issue #33525)."""
+        monkeypatch.delenv("MODAL_TOKEN_ID", raising=False)
+        monkeypatch.delenv("MODAL_TOKEN_SECRET", raising=False)
+        with patch.object(Path, "home", side_effect=PermissionError("denied")):
+            assert has_direct_modal_credentials() is False
+
+    def test_home_dir_permission_denied_with_env_vars(self, monkeypatch):
+        """PermissionError on Path.home() should not prevent env var detection."""
+        monkeypatch.setenv("MODAL_TOKEN_ID", "id-123")
+        monkeypatch.setenv("MODAL_TOKEN_SECRET", "sec-456")
+        with patch.object(Path, "home", side_effect=PermissionError("denied")):
+            assert has_direct_modal_credentials() is True
+
 
 # ---------------------------------------------------------------------------
 # prefers_gateway
diff --git a/tools/tool_backend_helpers.py b/tools/tool_backend_helpers.py
index c4320c68432..b1e0f834c7e 100644
--- a/tools/tool_backend_helpers.py
+++ b/tools/tool_backend_helpers.py
@@ -84,9 +84,13 @@ def normalize_modal_mode(value: object | None) -> str:
 
 def has_direct_modal_credentials() -> bool:
     """Return True when direct Modal credentials/config are available."""
+    try:
+        modal_file_exists = (Path.home() / ".modal.toml").exists()
+    except (PermissionError, OSError):
+        modal_file_exists = False
     return bool(
         (os.getenv("MODAL_TOKEN_ID") and os.getenv("MODAL_TOKEN_SECRET"))
-        or (Path.home() / ".modal.toml").exists()
+        or modal_file_exists
     )