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,
+    );
+  }
+}

packages/cli/src/ui/components/ModelDialog.test.tsx

@@ -89,6 +89,9 @@ describe('<ModelDialog />', () => {
   it('renders the initial "main" view correctly', () => {
     const { lastFrame } = renderComponent();
     expect(lastFrame()).toContain('Select Model');
+    expect(lastFrame()).toContain(
+      'Applies to this session and future Gemini CLI sessions.',
+    );
     expect(lastFrame()).toContain('Auto');
     expect(lastFrame()).toContain('Manual');
   });

packages/cli/src/ui/components/ModelDialog.tsx

@@ -204,7 +204,6 @@ export function ModelDialog({ onClose }: ModelDialogProps): React.JSX.Element {
         )}
         {subheader && <Text>{subheader}</Text>}
       </Box>
-
       <Box marginTop={1}>
         <DescriptiveRadioButtonSelect
           items={options}
@@ -215,7 +214,12 @@ export function ModelDialog({ onClose }: ModelDialogProps): React.JSX.Element {
       </Box>
       <Box marginTop={1} flexDirection="column">
         <Text color={theme.text.secondary}>
-          {'To use a specific Gemini model on startup, use the --model flag.'}
+          Applies to this session and future Gemini CLI sessions.
+        </Text>
+      </Box>
+      <Box marginTop={1} flexDirection="column">
+        <Text color={theme.text.secondary}>
+          {'> To use a specific Gemini model on startup, use the --model flag.'}
         </Text>
       </Box>
       <Box marginTop={1} flexDirection="column">

packages/core/src/config/config.test.ts

@@ -1629,6 +1629,18 @@ describe('Config getHooks', () => {
       expect(config.getModel()).toBe(originalModel);
       expect(config.getActiveModel()).toBe(originalModel);
     });
+
+    it('should call onModelChange when a new model is set', () => {
+      const onModelChange = vi.fn();
+      const config = new Config({
+        ...baseParams,
+        onModelChange,
+      });
+
+      config.setModel(DEFAULT_GEMINI_MODEL);
+
+      expect(onModelChange).toHaveBeenCalledWith(DEFAULT_GEMINI_MODEL);
+    });
   });
 });
 

packages/core/src/config/config.ts

@@ -337,6 +337,7 @@ export interface ConfigParameters {
   previewFeatures?: boolean;
   enableAgents?: boolean;
   experimentalJitContext?: boolean;
+  onModelChange?: (model: string) => void;
 }
 
 export class Config {
@@ -457,6 +458,7 @@ export class Config {
   private experiments: Experiments | undefined;
   private experimentsPromise: Promise<void> | undefined;
   private hookSystem?: HookSystem;
+  private readonly onModelChange: ((model: string) => void) | undefined;
 
   private readonly enableAgents: boolean;
 
@@ -623,6 +625,7 @@ export class Config {
     this.disableYoloMode = params.disableYoloMode ?? false;
     this.hooks = params.hooks;
     this.experiments = params.experiments;
+    this.onModelChange = params.onModelChange;
 
     if (params.contextFileName) {
       setGeminiMdFilename(params.contextFileName);
@@ -879,6 +882,9 @@ export class Config {
       // When the user explicitly sets a model, that becomes the active model.
       this._activeModel = newModel;
       coreEvents.emitModelChanged(newModel);
+      if (this.onModelChange) {
+        this.onModelChange(newModel);
+      }
     }
     this.modelAvailabilityService.reset();
   }