Update implementation to make it cleaner

tests/test_tui_gateway_server.py

@@ -1091,6 +1091,21 @@ def test_config_sync_switches_unpinned_session(monkeypatch):
     assert session["config_model_seen"] == ("new/model", "nous")
 
 
+def test_config_sync_treats_auto_provider_as_unset(monkeypatch):
+    _patch_config_model(monkeypatch, "new/model", provider="auto")
+    session = _sync_test_session(config_model_seen=("old/model", ""))
+    calls = []
+    monkeypatch.setattr(
+        server,
+        "_apply_model_switch",
+        lambda sid, sess, raw, **kw: calls.append(raw),
+    )
+
+    server._sync_agent_model_with_config("sid", session)
+
+    assert calls == ["new/model"]
+
+
 def test_config_sync_skips_session_pinned_by_model_command(monkeypatch):
     _patch_config_model(monkeypatch, "new/model")
     session = _sync_test_session(