Summary

• Root cause: tui_gateway/server.py::_apply_model_switch() was converting the providers: dict from config.yaml into a list of {"provider": k, **v} dicts before calling switch_model(). But resolve_user_provider() in hermes_cli/providers.py calls user_config.get(name) — which expects a plain dict keyed by provider slug. The list format always returned None, causing the "Unknown provider 'ollama-local'" error.
• tui_gateway/server.py: Changed the list comprehension to cfg.get("providers") if isinstance(..., dict) else {} — matching how the CLI and web_server.py already pass this value.
• hermes_cli/model_switch.py: Fixed the validation-override block which was written to iterate the (now-removed) list format. It now does a direct dict key lookup on target_provider instead of looping.

Test plan

• test_switch_model_resolves_ollama_local_from_providers_dict — end-to-end switch through the corrected dict path; asserts no "Unknown provider" error and target_provider == "ollama-local"
• test_switch_model_list_format_user_providers_fails_to_resolve — unit proof that the old list shape returns None while the correct dict shape resolves; prevents regression back to the list format
• Full tests/hermes_cli/test_user_providers_model_switch.py suite (27 tests) passes

python -m pytest tests/hermes_cli/test_user_providers_model_switch.py -o 'addopts=' -q
# 27 passed