Remove useModelRouter experimental flag (#13593)

docs/cli/model-routing.md

@@ -25,18 +25,6 @@ Here's how it works:
     `packages/cli/src/zed-integration/zedIntegration.ts` which checks if
     `isInFallbackMode()` is true.
 
-## Configuration
-
-Model routing is controlled by the `useModelRouter` setting in your
-`settings.json` file.
-
-- **`"experimental.useModelRouter": true` (Default):** Enables the model
-  routing/fallback feature.
-
-- **`"experimental.useModelRouter": false`:** Disables the model
-  routing/fallback feature. If a model fails, the CLI will not attempt to switch
-  to a fallback model.
-
 ### Model Selection Precedence
 
 The model used by Gemini CLI is determined by the following order of precedence:
@@ -50,7 +38,4 @@ The model used by Gemini CLI is determined by the following order of precedence:
     model specified in the `model.name` property of your `settings.json` file
     will be used.
 4.  **Default Model:** If none of the above are set, the default model will be
-    used. The default model is determined by the `useModelRouter` setting:
+    used. The default model is `auto`
-    - If `useModelRouter` is `true`, the default model is `"auto"`.
-    - If `useModelRouter` is `false`, the default model is the standard Gemini
-      model.

docs/cli/settings.md

@@ -107,7 +107,6 @@ they appear in the UI.
 ### Experimental
 
 | UI Label                            | Setting                                                 | Description                                                  | Default |
-| ----------------------------------- | ------------------------------------------------------- | ----------------------------------------------------------------------------- | ------- |
+| ----------------------------------- | ------------------------------------------------------- | ------------------------------------------------------------ | ------- |
-| Use Model Router                    | `experimental.useModelRouter`                           | Enable model routing to route requests to the best model based on complexity. | `true`  |
 | Enable Codebase Investigator        | `experimental.codebaseInvestigatorSettings.enabled`     | Enable the Codebase Investigator agent.                      | `true`  |
 | Codebase Investigator Max Num Turns | `experimental.codebaseInvestigatorSettings.maxNumTurns` | Maximum number of turns for the Codebase Investigator agent. | `10`    |

docs/get-started/configuration.md

@@ -563,12 +563,6 @@ their corresponding top-level category object in your `settings.json` file.
   - **Default:** `false`
   - **Requires restart:** Yes
 
-- **`experimental.useModelRouter`** (boolean):
-  - **Description:** Enable model routing to route requests to the best model
-    based on complexity.
-  - **Default:** `true`
-  - **Requires restart:** Yes
-
 - **`experimental.codebaseInvestigatorSettings.enabled`** (boolean):
   - **Description:** Enable the Codebase Investigator agent.
   - **Default:** `true`

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

@@ -9,8 +9,6 @@ import * as os from 'node:os';
 import * as path from 'node:path';
 import {
   DEFAULT_FILE_FILTERING_OPTIONS,
-  DEFAULT_GEMINI_MODEL,
-  DEFAULT_GEMINI_MODEL_AUTO,
   OutputFormat,
   SHELL_TOOL_NAME,
   WRITE_FILE_TOOL_NAME,
@@ -1364,100 +1362,6 @@ describe('loadCliConfig model selection', () => {
   });
 });
 
-describe('loadCliConfig model selection with model router', () => {
-  beforeEach(() => {
-    vi.spyOn(ExtensionManager.prototype, 'getExtensions').mockReturnValue([]);
-  });
-
-  afterEach(() => {
-    vi.resetAllMocks();
-  });
-
-  it('should use auto model when useModelRouter is true and no model is provided', async () => {
-    process.argv = ['node', 'script.js'];
-    const argv = await parseArguments({} as Settings);
-    const config = await loadCliConfig(
-      {
-        experimental: {
-          useModelRouter: true,
-        },
-      },
-      'test-session',
-      argv,
-    );
-
-    expect(config.getModel()).toBe(DEFAULT_GEMINI_MODEL_AUTO);
-  });
-
-  it('should use default model when useModelRouter is false and no model is provided', async () => {
-    process.argv = ['node', 'script.js'];
-    const argv = await parseArguments({} as Settings);
-    const config = await loadCliConfig(
-      {
-        experimental: {
-          useModelRouter: false,
-        },
-      },
-      'test-session',
-      argv,
-    );
-
-    expect(config.getModel()).toBe(DEFAULT_GEMINI_MODEL);
-  });
-
-  it('should prioritize argv over useModelRouter', async () => {
-    process.argv = ['node', 'script.js', '--model', 'gemini-from-argv'];
-    const argv = await parseArguments({} as Settings);
-    const config = await loadCliConfig(
-      {
-        experimental: {
-          useModelRouter: true,
-        },
-      },
-      'test-session',
-      argv,
-    );
-
-    expect(config.getModel()).toBe('gemini-from-argv');
-  });
-
-  it('should prioritize settings over useModelRouter', async () => {
-    process.argv = ['node', 'script.js'];
-    const argv = await parseArguments({} as Settings);
-    const config = await loadCliConfig(
-      {
-        experimental: {
-          useModelRouter: true,
-        },
-        model: {
-          name: 'gemini-from-settings',
-        },
-      },
-      'test-session',
-      argv,
-    );
-
-    expect(config.getModel()).toBe('gemini-from-settings');
-  });
-
-  it('should prioritize environment variable over useModelRouter', async () => {
-    process.argv = ['node', 'script.js'];
-    vi.stubEnv('GEMINI_MODEL', 'gemini-from-env');
-    const argv = await parseArguments({} as Settings);
-    const config = await loadCliConfig(
-      {
-        experimental: {
-          useModelRouter: true,
-        },
-      },
-      'test-session',
-      argv,
-    );
-
-    expect(config.getModel()).toBe('gemini-from-env');
-  });
-});
-
 describe('loadCliConfig folderTrust', () => {
   beforeEach(() => {
     vi.resetAllMocks();
@@ -1633,32 +1537,6 @@ describe('loadCliConfig useRipgrep', () => {
     const config = await loadCliConfig(settings, 'test-session', argv);
     expect(config.getUseRipgrep()).toBe(true);
   });
-
-  describe('loadCliConfig useModelRouter', () => {
-    it('should be true by default when useModelRouter is not set in settings', async () => {
-      process.argv = ['node', 'script.js'];
-      const argv = await parseArguments({} as Settings);
-      const settings: Settings = {};
-      const config = await loadCliConfig(settings, 'test-session', argv);
-      expect(config.getUseModelRouter()).toBe(true);
-    });
-
-    it('should be true when useModelRouter is set to true in settings', async () => {
-      process.argv = ['node', 'script.js'];
-      const argv = await parseArguments({} as Settings);
-      const settings: Settings = { experimental: { useModelRouter: true } };
-      const config = await loadCliConfig(settings, 'test-session', argv);
-      expect(config.getUseModelRouter()).toBe(true);
-    });
-
-    it('should be false when useModelRouter is explicitly set to false in settings', async () => {
-      process.argv = ['node', 'script.js'];
-      const argv = await parseArguments({} as Settings);
-      const settings: Settings = { experimental: { useModelRouter: false } };
-      const config = await loadCliConfig(settings, 'test-session', argv);
-      expect(config.getUseModelRouter()).toBe(false);
-    });
-  });
 });
 
 describe('screenReader configuration', () => {

packages/cli/src/config/config.ts

@@ -15,7 +15,6 @@ import {
   setGeminiMdFilename as setServerGeminiMdFilename,
   getCurrentGeminiMdFilename,
   ApprovalMode,
-  DEFAULT_GEMINI_MODEL,
   DEFAULT_GEMINI_MODEL_AUTO,
   DEFAULT_GEMINI_EMBEDDING_MODEL,
   DEFAULT_FILE_FILTERING_OPTIONS,
@@ -580,10 +579,7 @@ export async function loadCliConfig(
     extraExcludes.length > 0 ? extraExcludes : undefined,
   );
 
-  const useModelRouter = settings.experimental?.useModelRouter ?? true;
+  const defaultModel = DEFAULT_GEMINI_MODEL_AUTO;
-  const defaultModel = useModelRouter
-    ? DEFAULT_GEMINI_MODEL_AUTO
-    : DEFAULT_GEMINI_MODEL;
   const resolvedModel: string =
     argv.model ||
     process.env['GEMINI_MODEL'] ||
@@ -674,7 +670,6 @@ export async function loadCliConfig(
     output: {
       format: (argv.outputFormat ?? settings.output?.format) as OutputFormat,
     },
-    useModelRouter,
     enableMessageBusIntegration,
     codebaseInvestigatorSettings:
       settings.experimental?.codebaseInvestigatorSettings,

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

@@ -345,21 +345,6 @@ describe('SettingsSchema', () => {
         getSettingsSchema().general.properties.previewFeatures.description,
       ).toBe('Enable preview features (e.g., preview models).');
     });
-
-    it('should have useModelRouter setting in schema', () => {
-      expect(
-        getSettingsSchema().experimental.properties.useModelRouter,
-      ).toBeDefined();
-      expect(
-        getSettingsSchema().experimental.properties.useModelRouter.type,
-      ).toBe('boolean');
-      expect(
-        getSettingsSchema().experimental.properties.useModelRouter.category,
-      ).toBe('Experimental');
-      expect(
-        getSettingsSchema().experimental.properties.useModelRouter.default,
-      ).toBe(true);
-    });
   });
 
   it('has JSON schema definitions for every referenced ref', () => {

packages/cli/src/config/settingsSchema.ts

@@ -1281,16 +1281,6 @@ const SETTINGS_SCHEMA = {
           'Enables extension loading/unloading within the CLI session.',
         showInDialog: false,
       },
-      useModelRouter: {
-        type: 'boolean',
-        label: 'Use Model Router',
-        category: 'Experimental',
-        requiresRestart: true,
-        default: true,
-        description:
-          'Enable model routing to route requests to the best model based on complexity.',
-        showInDialog: true,
-      },
       codebaseInvestigatorSettings: {
         type: 'object',
         label: 'Codebase Investigator Settings',

packages/cli/src/services/BuiltinCommandLoader.test.ts

@@ -95,7 +95,6 @@ describe('BuiltinCommandLoader', () => {
     vi.clearAllMocks();
     mockConfig = {
       getFolderTrust: vi.fn().mockReturnValue(true),
-      getUseModelRouter: () => false,
       getEnableMessageBusIntegration: () => false,
       getEnableExtensionReloading: () => false,
     } as unknown as Config;
@@ -168,28 +167,6 @@ describe('BuiltinCommandLoader', () => {
     expect(permissionsCmd).toBeUndefined();
   });
 
-  it('should include modelCommand when getUseModelRouter is true', async () => {
-    const mockConfigWithModelRouter = {
-      ...mockConfig,
-      getUseModelRouter: () => true,
-    } as unknown as Config;
-    const loader = new BuiltinCommandLoader(mockConfigWithModelRouter);
-    const commands = await loader.loadCommands(new AbortController().signal);
-    const modelCmd = commands.find((c) => c.name === 'model');
-    expect(modelCmd).toBeDefined();
-  });
-
-  it('should not include modelCommand when getUseModelRouter is false', async () => {
-    const mockConfigWithoutModelRouter = {
-      ...mockConfig,
-      getUseModelRouter: () => false,
-    } as unknown as Config;
-    const loader = new BuiltinCommandLoader(mockConfigWithoutModelRouter);
-    const commands = await loader.loadCommands(new AbortController().signal);
-    const modelCmd = commands.find((c) => c.name === 'model');
-    expect(modelCmd).toBeUndefined();
-  });
-
   it('should include policies command when message bus integration is enabled', async () => {
     const mockConfigWithMessageBus = {
       ...mockConfig,
@@ -220,7 +197,6 @@ describe('BuiltinCommandLoader profile', () => {
     vi.resetModules();
     mockConfig = {
       getFolderTrust: vi.fn().mockReturnValue(false),
-      getUseModelRouter: () => false,
       getCheckpointingEnabled: () => false,
       getEnableMessageBusIntegration: () => false,
       getEnableExtensionReloading: () => false,

packages/cli/src/services/BuiltinCommandLoader.ts

@@ -73,7 +73,7 @@ export class BuiltinCommandLoader implements ICommandLoader {
       initCommand,
       mcpCommand,
       memoryCommand,
-      ...(this.config?.getUseModelRouter() ? [modelCommand] : []),
+      modelCommand,
       ...(this.config?.getFolderTrust() ? [permissionsCommand] : []),
       privacyCommand,
       ...(this.config?.getEnableMessageBusIntegration()

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

@@ -51,7 +51,6 @@ const renderComponent = (
         getDebugMode: vi.fn(() => false),
         getContentGeneratorConfig: vi.fn(() => ({ authType: 'mock' })),
         getUseSmartEdit: vi.fn(() => false),
-        getUseModelRouter: vi.fn(() => false),
         getProxy: vi.fn(() => undefined),
         isInteractive: vi.fn(() => false),
 

packages/cli/src/ui/hooks/useGeminiStream.test.tsx

@@ -222,7 +222,6 @@ describe('useGeminiStream', () => {
         .fn()
         .mockReturnValue(contentGeneratorConfig),
       getUseSmartEdit: () => false,
-      getUseModelRouter: () => false,
       isInteractive: () => false,
     } as unknown as Config;
     mockOnDebugMessage = vi.fn();

packages/cli/src/ui/hooks/useToolScheduler.test.ts

@@ -74,7 +74,6 @@ const mockConfig = {
     authType: 'oauth-personal',
   }),
   getUseSmartEdit: () => false,
-  getUseModelRouter: () => false,
   getGeminiClient: () => null, // No client needed for these tests
   getShellExecutionConfig: () => ({ terminalWidth: 80, terminalHeight: 24 }),
   getEnableMessageBusIntegration: () => false,

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

@@ -750,99 +750,6 @@ describe('Server Config (config.ts)', () => {
     });
   });
 
-  describe('Model Router with Auth', () => {
-    it('should disable model router by default for oauth-personal', async () => {
-      const config = new Config({
-        ...baseParams,
-        useModelRouter: true,
-      });
-      await config.refreshAuth(AuthType.LOGIN_WITH_GOOGLE);
-      expect(config.getUseModelRouter()).toBe(true);
-    });
-
-    it('should enable model router by default for other auth types', async () => {
-      const config = new Config({
-        ...baseParams,
-        useModelRouter: true,
-      });
-      await config.refreshAuth(AuthType.USE_GEMINI);
-      expect(config.getUseModelRouter()).toBe(true);
-    });
-
-    it('should disable model router for specified auth type', async () => {
-      const config = new Config({
-        ...baseParams,
-        useModelRouter: true,
-        disableModelRouterForAuth: [AuthType.USE_GEMINI],
-      });
-      await config.refreshAuth(AuthType.USE_GEMINI);
-      expect(config.getUseModelRouter()).toBe(false);
-    });
-
-    it('should enable model router for other auth type', async () => {
-      const config = new Config({
-        ...baseParams,
-        useModelRouter: true,
-        disableModelRouterForAuth: [],
-      });
-      await config.refreshAuth(AuthType.LOGIN_WITH_GOOGLE);
-      expect(config.getUseModelRouter()).toBe(true);
-    });
-
-    it('should keep model router disabled when useModelRouter is false', async () => {
-      const config = new Config({
-        ...baseParams,
-        useModelRouter: false,
-        disableModelRouterForAuth: [AuthType.USE_GEMINI],
-      });
-      await config.refreshAuth(AuthType.LOGIN_WITH_GOOGLE);
-      expect(config.getUseModelRouter()).toBe(false);
-    });
-
-    it('should keep the user-chosen model after refreshAuth, even when model router is disabled for the auth type', async () => {
-      const config = new Config({
-        ...baseParams,
-        useModelRouter: true,
-        disableModelRouterForAuth: [AuthType.USE_GEMINI],
-      });
-      const chosenModel = 'gemini-1.5-pro-latest';
-      config.setModel(chosenModel);
-
-      await config.refreshAuth(AuthType.USE_GEMINI);
-
-      expect(config.getUseModelRouter()).toBe(false);
-      expect(config.getModel()).toBe(chosenModel);
-    });
-
-    it('should keep the user-chosen model after refreshAuth, when model router is enabled for the auth type', async () => {
-      const config = new Config({
-        ...baseParams,
-        useModelRouter: true,
-        disableModelRouterForAuth: [AuthType.USE_GEMINI],
-      });
-      const chosenModel = 'gemini-1.5-pro-latest';
-      config.setModel(chosenModel);
-
-      await config.refreshAuth(AuthType.LOGIN_WITH_GOOGLE);
-
-      expect(config.getUseModelRouter()).toBe(true);
-      expect(config.getModel()).toBe(chosenModel);
-    });
-
-    it('should NOT switch to auto model if cli provides specific model, even if router is enabled', async () => {
-      const config = new Config({
-        ...baseParams,
-        useModelRouter: true,
-        model: 'gemini-flash-latest',
-      });
-
-      await config.refreshAuth(AuthType.LOGIN_WITH_GOOGLE);
-
-      expect(config.getUseModelRouter()).toBe(true);
-      expect(config.getModel()).toBe('gemini-flash-latest');
-    });
-  });
-
   describe('ContinueOnFailedApiCall Configuration', () => {
     it('should default continueOnFailedApiCall to false when not provided', () => {
       const config = new Config(baseParams);

packages/core/src/config/config.ts

@@ -48,7 +48,6 @@ import {
   DEFAULT_GEMINI_EMBEDDING_MODEL,
   DEFAULT_GEMINI_FLASH_MODEL,
   DEFAULT_GEMINI_MODEL,
-  DEFAULT_GEMINI_MODEL_AUTO,
   DEFAULT_THINKING_MODE,
 } from './models.js';
 import { shouldAttemptBrowserLaunch } from '../utils/browser.js';
@@ -288,7 +287,6 @@ export interface ConfigParameters {
   useWriteTodos?: boolean;
   policyEngineConfig?: PolicyEngineConfig;
   output?: OutputSettings;
-  useModelRouter?: boolean;
   enableMessageBusIntegration?: boolean;
   disableModelRouterForAuth?: AuthType[];
   codebaseInvestigatorSettings?: CodebaseInvestigatorSettings;
@@ -402,9 +400,6 @@ export class Config {
   private readonly messageBus: MessageBus;
   private readonly policyEngine: PolicyEngine;
   private readonly outputSettings: OutputSettings;
-  private useModelRouter: boolean;
-  private readonly initialUseModelRouter: boolean;
-  private readonly disableModelRouterForAuth?: AuthType[];
   private readonly enableMessageBusIntegration: boolean;
   private readonly codebaseInvestigatorSettings: CodebaseInvestigatorSettings;
   private readonly continueOnFailedApiCall: boolean;
@@ -519,9 +514,6 @@ export class Config {
     this.enableToolOutputTruncation = params.enableToolOutputTruncation ?? true;
     this.useSmartEdit = params.useSmartEdit ?? true;
     this.useWriteTodos = params.useWriteTodos ?? true;
-    this.initialUseModelRouter = params.useModelRouter ?? false;
-    this.useModelRouter = this.initialUseModelRouter;
-    this.disableModelRouterForAuth = params.disableModelRouterForAuth ?? [];
     this.enableHooks = params.enableHooks ?? false;
 
     // Enable MessageBus integration if:
@@ -643,14 +635,6 @@ export class Config {
   }
 
   async refreshAuth(authMethod: AuthType) {
-    this.useModelRouter = this.initialUseModelRouter;
-    if (this.disableModelRouterForAuth?.includes(authMethod)) {
-      this.useModelRouter = false;
-      if (this.model === DEFAULT_GEMINI_MODEL_AUTO) {
-        this.model = DEFAULT_GEMINI_MODEL;
-      }
-    }
-
     // Vertex and Genai have incompatible encryption and sending history with
     // thoughtSignature from Genai to Vertex will fail, we need to strip them
     if (
@@ -1341,10 +1325,6 @@ export class Config {
       : OutputFormat.TEXT;
   }
 
-  getUseModelRouter(): boolean {
-    return this.useModelRouter;
-  }
-
   async getGitService(): Promise<GitService> {
     if (!this.gitService) {
       this.gitService = new GitService(this.targetDir, this.storage);

packages/core/src/core/client.test.ts

@@ -216,7 +216,6 @@ describe('Gemini Client (client.ts)', () => {
       getChatCompression: vi.fn().mockReturnValue(undefined),
       getSkipNextSpeakerCheck: vi.fn().mockReturnValue(false),
       getUseSmartEdit: vi.fn().mockReturnValue(false),
-      getUseModelRouter: vi.fn().mockReturnValue(false),
       getShowModelInfoInChat: vi.fn().mockReturnValue(false),
       getContinueOnFailedApiCall: vi.fn(),
       getProjectRoot: vi.fn().mockReturnValue('/test/project/root'),

packages/core/src/core/coreToolScheduler.test.ts

@@ -248,7 +248,6 @@ function createMockConfig(overrides: Partial<Config> = {}): Config {
     getTruncateToolOutputLines: () => DEFAULT_TRUNCATE_TOOL_OUTPUT_LINES,
     getToolRegistry: () => defaultToolRegistry,
     getUseSmartEdit: () => false,
-    getUseModelRouter: () => false,
     getGeminiClient: () => null,
     getEnableMessageBusIntegration: () => false,
     getMessageBus: () => null,

packages/core/src/core/nonInteractiveToolExecutor.test.ts

@@ -60,7 +60,6 @@ describe('executeToolCall', () => {
         DEFAULT_TRUNCATE_TOOL_OUTPUT_THRESHOLD,
       getTruncateToolOutputLines: () => DEFAULT_TRUNCATE_TOOL_OUTPUT_LINES,
       getUseSmartEdit: () => false,
-      getUseModelRouter: () => false,
       getGeminiClient: () => null, // No client needed for these tests
       getEnableMessageBusIntegration: () => false,
       getMessageBus: () => null,

packages/core/src/telemetry/clearcut-logger/clearcut-logger.test.ts

@@ -312,7 +312,7 @@ describe('ClearcutLogger', () => {
 
     it('logs all user settings', () => {
       const { logger } = setup({
-        config: { useSmartEdit: true, useModelRouter: true },
+        config: { useSmartEdit: true },
       });
 
       vi.stubEnv('TERM_PROGRAM', 'vscode');

packages/core/src/telemetry/loggers.test.ts

@@ -1544,7 +1544,6 @@ describe('loggers', () => {
       getUsageStatisticsEnabled: () => true,
       getContentGeneratorConfig: () => null,
       getUseSmartEdit: () => null,
-      getUseModelRouter: () => null,
       isInteractive: () => false,
     } as unknown as Config;
 
@@ -1595,7 +1594,6 @@ describe('loggers', () => {
       getUsageStatisticsEnabled: () => true,
       getContentGeneratorConfig: () => null,
       getUseSmartEdit: () => null,
-      getUseModelRouter: () => null,
       isInteractive: () => false,
     } as unknown as Config;
 
@@ -1648,7 +1646,6 @@ describe('loggers', () => {
       getUsageStatisticsEnabled: () => true,
       getContentGeneratorConfig: () => null,
       getUseSmartEdit: () => null,
-      getUseModelRouter: () => null,
       isInteractive: () => false,
     } as unknown as Config;
 

packages/core/src/tools/smart-edit.test.ts

@@ -90,7 +90,6 @@ describe('SmartEditTool', () => {
       getSessionId: vi.fn(() => 'mock-session-id'),
       getContentGeneratorConfig: vi.fn(() => ({ authType: 'mock' })),
       getUseSmartEdit: vi.fn(() => false),
-      getUseModelRouter: vi.fn(() => false),
       getProxy: vi.fn(() => undefined),
       getGeminiClient: vi.fn().mockReturnValue(geminiClient),
       getBaseLlmClient: vi.fn().mockReturnValue(baseLlmClient),

schemas/settings.schema.json

@@ -1201,13 +1201,6 @@
           "default": false,
           "type": "boolean"
         },
-        "useModelRouter": {
-          "title": "Use Model Router",
-          "description": "Enable model routing to route requests to the best model based on complexity.",
-          "markdownDescription": "Enable model routing to route requests to the best model based on complexity.\n\n- Category: `Experimental`\n- Requires restart: `yes`\n- Default: `true`",
-          "default": true,
-          "type": "boolean"
-        },
         "codebaseInvestigatorSettings": {
           "title": "Codebase Investigator Settings",
           "description": "Configuration for Codebase Investigator.",