feat: automatic /model persistence across Gemini CLI sessions (#13199)

Co-authored-by: Jack Wotherspoon <jackwoth@google.com>

packages/cli/src/config/config.test.ts

@@ -25,13 +25,11 @@ import { ExtensionManager } from './extension-manager.js';
 import { RESUME_LATEST } from '../utils/sessionUtils.js';
 
 vi.mock('./trustedFolders.js', () => ({
-  isWorkspaceTrusted: vi
-    .fn()
-    .mockReturnValue({ isTrusted: true, source: 'file' }), // Default to trusted
+  isWorkspaceTrusted: vi.fn(() => ({ isTrusted: true, source: 'file' })), // Default to trusted
 }));
 
 vi.mock('./sandboxConfig.js', () => ({
-  loadSandboxConfig: vi.fn().mockResolvedValue(undefined),
+  loadSandboxConfig: vi.fn(async () => undefined),
 }));
 
 vi.mock('fs', async (importOriginal) => {

packages/cli/src/config/config.ts

@@ -35,6 +35,7 @@ import {
   PREVIEW_GEMINI_MODEL_AUTO,
 } from '@google/gemini-cli-core';
 import type { Settings } from './settings.js';
+import { saveModelChange, loadSettings } from './settings.js';
 
 import { loadSandboxConfig } from './sandboxConfig.js';
 import { resolvePath } from '../utils/resolvePath.js';
@@ -387,6 +388,8 @@ export async function loadCliConfig(
 ): Promise<Config> {
   const debugMode = isDebugMode(argv);
 
+  const loadedSettings = loadSettings(cwd);
+
   if (argv.sandbox) {
     process.env['GEMINI_SANDBOX'] = 'true';
   }
@@ -693,6 +696,7 @@ export async function loadCliConfig(
     // TODO: loading of hooks based on workspace trust
     enableHooks: settings.tools?.enableHooks ?? false,
     hooks: settings.hooks || {},
+    onModelChange: (model: string) => saveModelChange(loadedSettings, model),
   });
 }
 

packages/cli/src/config/settings.ts

@@ -874,3 +874,18 @@ export function saveSettings(settingsFile: SettingsFile): void {
     );
   }
 }
+
+export function saveModelChange(
+  loadedSettings: LoadedSettings,
+  model: string,
+): void {
+  try {
+    loadedSettings.setValue(SettingScope.User, 'model.name', model);
+  } catch (error) {
+    coreEvents.emitFeedback(
+      'error',
+      'There was an error saving your preferred model.',
+      error,
+    );
+  }
+}