Two bugs in get_available_models() conspired to duplicate the active
provider's auto-detected models under a phantom 'Custom' group whenever
custom_providers was also declared in config.yaml:
1. custom:* PIDs not in _named_custom_groups (e.g. stale slugs left from
prior configs) fell through to the auto_detected_models fallback, copying
the active provider's whole catalog into a phantom Custom: <slug> group.
Fix: continue unconditionally for ANY custom:* PID — the named-group
branch is the only legitimate population path.
2. The bare 'custom' PID, with the active provider being concrete (e.g.
ai-gateway), hit 'elif auto_detected_models: copy.deepcopy(...)' and
built a duplicate Custom group of the active provider's models with
mismatched provider prefixes. Fix: when pid == 'custom' and the active
provider is non-custom, leave models_for_group empty.
The reporter also suggested a third fix gating resolve_model_provider() on
config_provider — that's intentionally NOT applied because it conflicts with
the long-standing model-specific-override semantics covered by
test_model_resolver.py::test_custom_provider_*_routes_to_named_custom_provider
(custom_providers entries explicitly override the active provider's routing
when the user opted-in). The reporter's symptom (duplicate UI group) lives
entirely in get_available_models()'s group construction and is fully fixed
by the two changes above.
Tests: 6 new regression tests (3 in #1881 file + reuse), 774 broader
tests still green (model/provider/custom/config domain).
Sanjay Santhanam