fix: avoid deprecated FIDO2 capability query

proton/vpn/core/api.py

@@ -217,8 +217,9 @@ def supports_fido2(self) -> bool:
         This only returns True if both conditions are met and if the user
         is currently authenticating a session that requires 2FA.
         """
-        lib_available = self.is_fido2_lib_available
-        supports_fido2 = self._session_holder.session.supports_fido2
+        session = self._session_holder.session
+        lib_available = session.fido2_lib_available
+        supports_fido2 = session.supports_fido2
         return bool(lib_available and supports_fido2)
 
     async def generate_2fa_fido2_assertion(

tests/python/core/test_api.py

@@ -0,0 +1,47 @@
+"""
+Copyright (c) 2026 Proton AG
+
+This file is part of Proton VPN.
+
+Proton VPN is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+"""
+from types import SimpleNamespace
+
+import pytest
+
+from proton.vpn.core.api import ProtonVPNAPI
+
+
+@pytest.mark.parametrize(
+    "library_available,registered_key,expected",
+    [
+        (False, False, False),
+        (False, True, False),
+        (True, False, False),
+        (True, True, True),
+    ],
+)
+def test_supports_fido2_uses_current_session_capabilities(
+        monkeypatch, library_available, registered_key, expected
+):
+    api = object.__new__(ProtonVPNAPI)
+    api._session_holder = SimpleNamespace(
+        session=SimpleNamespace(
+            fido2_lib_available=library_available,
+            supports_fido2=registered_key,
+        )
+    )
+
+    def fail_if_deprecated_property_is_used(_api):
+        pytest.fail("supports_fido2 called the deprecated capability property")
+
+    monkeypatch.setattr(
+        ProtonVPNAPI,
+        "is_fido2_lib_available",
+        property(fail_if_deprecated_property_is_used),
+    )
+
+    assert api.supports_fido2 is expected