fix(models): preserve preset rename compatibility

tests/webui/test_session_list_index.py

@@ -52,6 +52,20 @@ def test_webui_session_list_reuses_valid_index_without_scanning_files(
     assert rows[0]["model_preset"] == "fast"
 
 
+def test_webui_session_list_refreshes_after_model_preset_rename(tmp_path: Path) -> None:
+    manager = SessionManager(tmp_path)
+    session = manager.get_or_create("websocket:renamed-preset")
+    session.metadata[SESSION_MODEL_PRESET_METADATA_KEY] = "openai"
+    session.add_message("user", "hello")
+    manager.save(session)
+
+    assert list_webui_sessions(manager)[0]["model_preset"] == "openai"
+
+    assert manager.rename_model_preset("openai", "Codex") == 1
+
+    assert list_webui_sessions(manager)[0]["model_preset"] == "Codex"
+
+
 def test_webui_session_index_uses_unique_temp_file(tmp_path: Path) -> None:
     manager = SessionManager(tmp_path)
     session = manager.get_or_create("websocket:unique-index-temp")

tests/webui/test_settings_api.py

@@ -10,6 +10,8 @@ import pytest
 from nanobot.config.loader import load_config, save_config
 from nanobot.config.schema import Config, InlineFallbackConfig, ModelPresetConfig
 from nanobot.providers.registry import find_by_name
+from nanobot.session.manager import SessionManager
+from nanobot.session.model_selection import SESSION_MODEL_PRESET_METADATA_KEY
 from nanobot.webui.settings_api import (
     WebUISettingsError,
     _docs_version,
@@ -434,9 +436,17 @@ def test_update_model_configuration_renames_preset_and_config_references(
     defaults.dream.model_override = "openai"
     save_config(config, config_path)
     monkeypatch.setattr("nanobot.config.loader._current_config_path", config_path)
+    session_manager = SessionManager(
+        tmp_path / "workspace",
+        sessions_root=tmp_path / "sessions",
+    )
+    session = session_manager.get_or_create("websocket:selected")
+    session.metadata[SESSION_MODEL_PRESET_METADATA_KEY] = "openai"
+    session_manager.save(session)
 
     payload = update_model_configuration(
-        {"name": ["openai"], "new_name": ["Codex"]}
+        {"name": ["openai"], "new_name": ["Codex"]},
+        rename_model_preset=session_manager.rename_model_preset,
     )
 
     assert payload["agent"]["model_preset"] == "Codex"
@@ -451,6 +461,11 @@ def test_update_model_configuration_renames_preset_and_config_references(
     assert saved.agents.defaults.model_preset == "Codex"
     assert saved.agents.defaults.fallback_models == ["backup", "Codex"]
     assert saved.agents.defaults.dream.model_override == "Codex"
+    persisted = SessionManager(
+        tmp_path / "workspace",
+        sessions_root=tmp_path / "sessions",
+    ).get_or_create("websocket:selected")
+    assert persisted.metadata[SESSION_MODEL_PRESET_METADATA_KEY] == "Codex"
 
 
 def test_update_model_configuration_rejects_duplicate_rename(
@@ -473,6 +488,33 @@ def test_update_model_configuration_rejects_duplicate_rename(
     assert set(load_config(config_path).model_presets) == {"openai", "Codex"}
 
 
+def test_update_model_configuration_rolls_back_sessions_when_config_save_fails(
+    tmp_path,
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    config_path = tmp_path / "config.json"
+    config = Config(
+        model_presets={"openai": ModelPresetConfig(model="openai/gpt-4.1")}
+    )
+    save_config(config, config_path)
+    calls: list[tuple[str, str]] = []
+
+    def fail_save(_config: Config, _path) -> None:
+        raise OSError("disk full")
+
+    monkeypatch.setattr("nanobot.webui.settings_api._save_settings_config", fail_save)
+
+    with pytest.raises(OSError, match="disk full"):
+        update_model_configuration(
+            {"name": ["openai"], "new_name": ["Codex"]},
+            config_path=config_path,
+            rename_model_preset=lambda old, new: calls.append((old, new)) or 1,
+        )
+
+    assert calls == [("openai", "Codex"), ("Codex", "openai")]
+    assert list(load_config(config_path).model_presets) == ["openai"]
+
+
 def test_settings_payload_exposes_named_model_call_order(
     tmp_path,
     monkeypatch: pytest.MonkeyPatch,

tests/webui/test_settings_routes.py

@@ -24,9 +24,15 @@ def _router(
     config_path: Path | None = None,
     mcp_runtime_status: Callable[[], Mapping[str, str]] | None = None,
     mcp_reload: Callable[[], Awaitable[dict[str, object]]] | None = None,
+    rename_model_preset: Callable[[str, str], int] | None = None,
+    refresh_runtime_config: Callable[[], None] | None = None,
 ) -> WebUISettingsRouter:
     return WebUISettingsRouter(
-        settings=WebUISettingsServices.create(config_path or get_config_path()),
+        settings=WebUISettingsServices.create(
+            config_path or get_config_path(),
+            rename_model_preset=rename_model_preset,
+            refresh_runtime_config=refresh_runtime_config,
+        ),
         bus=SimpleNamespace(),
         logger=SimpleNamespace(exception=lambda *_args: None),
         check_api_token=lambda _request: authorized,
@@ -346,6 +352,38 @@ async def test_model_preset_mutation_routes(
     assert captured["query"] == expected_query
 
 
+@pytest.mark.asyncio
+async def test_model_update_route_forwards_session_rename_dependency(monkeypatch) -> None:
+    rename_model_preset = MagicMock(return_value=2)
+    refresh_runtime_config = MagicMock()
+    captured: dict[str, object] = {}
+
+    def update(query, *, config_path=None, rename_model_preset=None):
+        captured.update(query=query, rename_model_preset=rename_model_preset)
+        return {"updated": True}
+
+    monkeypatch.setattr("nanobot.webui.settings_routes.update_model_configuration", update)
+    path = "/api/settings/model-configurations/update"
+    request = _mutation_request(path, {"name": "openai", "new_name": "Codex"})
+
+    response = await _router(
+        rename_model_preset=rename_model_preset,
+        refresh_runtime_config=refresh_runtime_config,
+    ).dispatch(
+        None,
+        request,
+        path,
+    )
+
+    assert response is not None
+    assert response.status_code == 200
+    assert captured == {
+        "query": {"name": ["openai"], "new_name": ["Codex"]},
+        "rename_model_preset": rename_model_preset,
+    }
+    refresh_runtime_config.assert_called_once_with()
+
+
 @pytest.mark.asyncio
 async def test_settings_get_mutation_route_is_method_not_allowed() -> None:
     path = "/api/settings/provider/update"