diff --git a/csaxs_bec/bec_ipython_client/plugins/omny/omny.py b/csaxs_bec/bec_ipython_client/plugins/omny/omny.py
index 0ff2437a..b8530a5b 100644
--- a/csaxs_bec/bec_ipython_client/plugins/omny/omny.py
+++ b/csaxs_bec/bec_ipython_client/plugins/omny/omny.py
@@ -1338,7 +1338,13 @@ class OMNY(
                 )
 
     def _is_superuser_account(self) -> bool:
-        """Whether the active BEC account is allowed to select advanced tomo modes."""
+        """Whether the active BEC account is allowed to select advanced tomo modes.
+
+        bec.active_account is a pgroup set explicitly via `bec-set-account`; when no
+        pgroup has been set yet (e.g. a fresh dev/test session), fall back to the OS
+        login (matches the account/system-user comparison convention already used in
+        OMNY_shared/omny_general_tools.py's _accounts_match()).
+        """
         bec = builtins.__dict__.get("bec")
         try:
             account = bec.active_account
@@ -1346,6 +1352,8 @@ class OMNY(
             return False
         if isinstance(account, bytes):
             account = account.decode()
+        if not account:
+            account = os.getenv("USER") or ""
         return bool(account) and account in _SUPERUSER_ACCOUNTS
 
     def tomo_parameters(self):
diff --git a/tests/tests_bec_ipython_client/test_omny_tomo_angles.py b/tests/tests_bec_ipython_client/test_omny_tomo_angles.py
index c1c25255..f71e5184 100644
--- a/tests/tests_bec_ipython_client/test_omny_tomo_angles.py
+++ b/tests/tests_bec_ipython_client/test_omny_tomo_angles.py
@@ -192,6 +192,24 @@ def test_is_superuser_account_false_when_empty_allowlist(monkeypatch, fake_bec):
     assert omny._is_superuser_account() is False
 
 
+def test_is_superuser_account_falls_back_to_os_user_when_no_pgroup_set(monkeypatch, fake_bec):
+    """bec.active_account is a pgroup, only set explicitly via bec-set-account. A
+    fresh dev/test session with no pgroup set must fall back to the OS login."""
+    monkeypatch.setattr(omny_module, "_SUPERUSER_ACCOUNTS", frozenset({"gac-x01dc"}))
+    fake_bec.active_account = ""
+    monkeypatch.setenv("USER", "gac-x01dc")
+    omny = make_omny()
+    assert omny._is_superuser_account() is True
+
+
+def test_is_superuser_account_no_pgroup_and_unlisted_os_user(monkeypatch, fake_bec):
+    monkeypatch.setattr(omny_module, "_SUPERUSER_ACCOUNTS", frozenset({"gac-x01dc"}))
+    fake_bec.active_account = ""
+    monkeypatch.setenv("USER", "someone-else")
+    omny = make_omny()
+    assert omny._is_superuser_account() is False
+
+
 def test_tomo_parameters_forces_type_1_for_non_superuser(monkeypatch, fake_bec):
     """A non-superuser account that ends up picking an advanced tomo_type via
     the interactive prompt must be forced back to tomo_type 1."""