Accept provider-prefixed model selection

backend/api/server.py

@@ -524,7 +524,10 @@ class AgentState:
         with self._lock:
             config = self._config_for(account_id)
             if model is not None:
-                config = replace(config, model=_normalize_chat_model_name(model))
+                normalized_model = _normalize_model_id(model)
+                if normalized_model is None:
+                    raise ValueError('model must not be empty')
+                config = replace(config, model=normalized_model)
             if base_url is not None:
                 config = replace(config, base_url=base_url)
             if api_key is not None:

tests/test_gui_server.py

@@ -71,6 +71,16 @@ class GuiServerTests(unittest.TestCase):
             self.assertTrue(data['allow_shell'])
             self.assertEqual(data['model'], 'other-model')
 
+    def test_state_update_accepts_provider_prefixed_model(self) -> None:
+        with tempfile.TemporaryDirectory() as d:
+            client, _ = _build_client(Path(d))
+            updated = client.post(
+                '/api/state',
+                json={'model': 'azure_openai/gpt-4o-mini'},
+            )
+            self.assertEqual(updated.status_code, 200)
+            self.assertEqual(updated.json()['model'], 'azure_openai/gpt-4o-mini')
+
     def test_state_snapshot_can_scope_to_account(self) -> None:
         with tempfile.TemporaryDirectory() as d:
             client, _ = _build_client(Path(d))