test(model_switch): update regression to reflect bare-custom guard

tests/hermes_cli/test_model_switch_custom_providers.py

@@ -296,7 +296,34 @@ def test_list_authenticated_providers_groups_same_endpoint(monkeypatch):
 def test_list_authenticated_providers_current_endpoint_uses_current_slug(monkeypatch):
     """When current_base_url matches the grouped endpoint, the slug must
     equal current_provider so picker selection routes through the live
-    credential pipeline."""
+    credential pipeline — provided current_provider is a real slug, not
+    the corrupt bare "custom" (see #17478)."""
+    monkeypatch.setattr("agent.models_dev.fetch_models_dev", lambda: {})
+    monkeypatch.setattr(providers_mod, "HERMES_OVERLAYS", {})
+
+    providers = list_authenticated_providers(
+        current_provider="custom:ollama",
+        current_base_url="http://localhost:11434/v1",
+        user_providers={},
+        custom_providers=[
+            {"name": "Ollama — GLM 5.1", "base_url": "http://localhost:11434/v1",
+             "api_key": "ollama", "model": "glm-5.1"},
+        ],
+        max_models=50,
+    )
+
+    matches = [p for p in providers if p.get("is_user_defined")]
+    assert len(matches) == 1
+    group = matches[0]
+    assert group["slug"] == "custom:ollama"
+    assert group["is_current"] is True
+
+
+def test_list_authenticated_providers_bare_custom_slug_recovers(monkeypatch):
+    """Regression for #17478: when a prior failed switch left the bare
+    literal "custom" in model.provider, the picker must NOT propagate
+    that broken slug. It must fall back to the canonical
+    ``custom:<name>`` form so the picker stays usable."""
     monkeypatch.setattr("agent.models_dev.fetch_models_dev", lambda: {})
     monkeypatch.setattr(providers_mod, "HERMES_OVERLAYS", {})
 
@@ -314,8 +341,8 @@ def test_list_authenticated_providers_current_endpoint_uses_current_slug(monkeyp
     matches = [p for p in providers if p.get("is_user_defined")]
     assert len(matches) == 1
     group = matches[0]
-    assert group["slug"] == "custom"
-    assert group["is_current"] is True
+    # Canonical slug, NOT the bare "custom" that caused #17478
+    assert group["slug"] == "custom:ollama"
 
 
 def test_list_authenticated_providers_distinct_endpoints_stay_separate(monkeypatch):