diff --git a/api/auth.py b/api/auth.py
index fa10e6fb..fef5dc95 100644
--- a/api/auth.py
+++ b/api/auth.py
@@ -512,7 +512,18 @@ def get_oidc_startup_warning() -> str | None:
     issuer = bool(pick("issuer", "HERMES_WEBUI_OIDC_ISSUER"))
     client_id = bool(pick("client_id", "HERMES_WEBUI_OIDC_CLIENT_ID"))
     allow_claim = bool(pick("allow_claim", "HERMES_WEBUI_OIDC_ALLOW_CLAIM"))
-    allow_values = bool(pick("allow_values", "HERMES_WEBUI_OIDC_ALLOW_VALUES"))
+    raw_allow_env = os.getenv("HERMES_WEBUI_OIDC_ALLOW_VALUES")
+    raw_allow = raw_allow_env if raw_allow_env is not None else raw.get("allow_values")
+    normalized_allow_values = []
+    allow_values_warning = None
+    try:
+        from api import auth_oidc
+
+        normalized_allow_values = auth_oidc._normalize_allow_values(raw_allow)
+        allow_values_warning = auth_oidc._ALLOW_VALUES_WHITESPACE_WARNING
+    except Exception:
+        logger.debug("Failed to normalize OIDC allow_values", exc_info=True)
+    allow_values = bool(normalized_allow_values)
 
     if not any((issuer, client_id, allow_claim, allow_values)):
         return None
@@ -538,16 +549,13 @@ def get_oidc_startup_warning() -> str | None:
     # Detect whitespace-only allow_values scalar that may contain multiple intended values.
     # Runs unconditionally so the warning reaches startup even when other auth methods
     # short-circuit is_auth_enabled() before the OIDC branch is evaluated.
-    raw_allow_env = os.getenv("HERMES_WEBUI_OIDC_ALLOW_VALUES")
-    raw_allow = raw_allow_env if raw_allow_env is not None else raw.get("allow_values")
-    if raw_allow is not None and not isinstance(raw_allow, (list, tuple, set)):
-        try:
-            from api.auth_oidc import _normalize_allow_values, _ALLOW_VALUES_WHITESPACE_WARNING
-            normalized = _normalize_allow_values(raw_allow)
-            if any(any(ch.isspace() for ch in v) for v in normalized):
-                warnings.append(_ALLOW_VALUES_WHITESPACE_WARNING)
-        except Exception:
-            logger.debug("Failed to check OIDC allow_values for whitespace", exc_info=True)
+    if (
+        allow_values_warning is not None
+        and raw_allow is not None
+        and not isinstance(raw_allow, (list, tuple, set))
+        and any(any(ch.isspace() for ch in v) for v in normalized_allow_values)
+    ):
+        warnings.append(allow_values_warning)
 
     return "\n".join(warnings) if warnings else None
 
diff --git a/tests/test_auth_oidc.py b/tests/test_auth_oidc.py
index 74bd91c1..d36a0dd8 100644
--- a/tests/test_auth_oidc.py
+++ b/tests/test_auth_oidc.py
@@ -16,6 +16,17 @@ import api.auth_oidc as auth_oidc
 from api.auth_oidc import _enforce_allowlist, _normalize_allow_values, OIDCAuthError
 
 
+@pytest.fixture(autouse=True)
+def _clear_oidc_environment(monkeypatch):
+    for name in (
+        "HERMES_WEBUI_OIDC_ISSUER",
+        "HERMES_WEBUI_OIDC_CLIENT_ID",
+        "HERMES_WEBUI_OIDC_ALLOW_CLAIM",
+        "HERMES_WEBUI_OIDC_ALLOW_VALUES",
+    ):
+        monkeypatch.delenv(name, raising=False)
+
+
 @pytest.fixture(autouse=True)
 def _reset_warned_cache():
     auth_oidc._warned_allow_values.clear()
@@ -23,6 +34,58 @@ def _reset_warned_cache():
     auth_oidc._warned_allow_values.clear()
 
 
+def _startup_warning(monkeypatch, allow_values):
+    import api.auth as auth
+
+    monkeypatch.setattr(
+        auth,
+        "get_config",
+        lambda: {
+            "webui_oidc": {
+                "issuer": "https://issuer.example",
+                "client_id": "webui-client",
+                "allow_claim": "email",
+                "allow_values": allow_values,
+            }
+        },
+    )
+    return auth.get_oidc_startup_warning()
+
+
+@pytest.mark.parametrize("allow_values", [[], [""]])
+def test_startup_warning_treats_empty_allowlist_shapes_as_missing(monkeypatch, allow_values):
+    warning = _startup_warning(monkeypatch, allow_values)
+
+    assert warning is not None
+    assert "allow_values" in warning
+    assert auth_oidc._ALLOW_VALUES_WHITESPACE_WARNING not in warning
+
+
+def test_startup_warning_accepts_multi_word_list(monkeypatch):
+    assert _startup_warning(monkeypatch, ["Hermes Users"]) is None
+
+
+def test_startup_warning_accepts_comma_scalar(monkeypatch):
+    assert _startup_warning(monkeypatch, "alice@example.com,bob@example.com") is None
+
+
+def test_startup_warning_reports_whitespace_scalar_migration(monkeypatch):
+    warning = _startup_warning(monkeypatch, "alice@example.com bob@example.com")
+
+    assert warning is not None
+    assert "partially configured" not in warning
+    assert auth_oidc._ALLOW_VALUES_WHITESPACE_WARNING in warning
+
+
+def test_startup_warning_uses_environment_allow_values_precedence(monkeypatch):
+    monkeypatch.setenv("HERMES_WEBUI_OIDC_ALLOW_VALUES", "")
+
+    warning = _startup_warning(monkeypatch, ["alice@example.com"])
+
+    assert warning is not None
+    assert "allow_values" in warning
+
+
 def _resolve(monkeypatch, *, env=None, cfg_list=None):
     """Call _resolve_oidc_config with controlled allow_values input.