feat(models): support Gemini 3.1 custom tool model (#131)

* feat(models): add support for Gemini 3.1 and custom tool models

* test(routing): fix classifier and numerical classifier strategy tests

* test(routing): add Gemini 3.1 tests for classifier strategy

* fix(models): correctly filter active Gemini 3.1 models

* fix(routing): ensure useCustomToolModel is only true when Gemini 3.1 is enabled

* fix(test-utils): prevent double newline in lastFrame() on Windows

* fix(test-utils): surgically fix double newline in lastFrame() on Windows

* use custom_tools_model string for api key only

* fix(ui): correct useCustomToolModel logic and update tests

* fix(ui): correct useCustomToolModel logic in StatsDisplay

* fix(routing): ensure test models are active and sync useCustomToolModel logic

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

@@ -14,8 +14,14 @@ import {
   DEFAULT_GEMINI_MODEL_AUTO,
   DEFAULT_GEMINI_FLASH_MODEL,
   DEFAULT_GEMINI_FLASH_LITE_MODEL,
+  PREVIEW_GEMINI_MODEL,
+  PREVIEW_GEMINI_3_1_MODEL,
+  PREVIEW_GEMINI_3_1_CUSTOM_TOOLS_MODEL,
+  PREVIEW_GEMINI_FLASH_MODEL,
+  AuthType,
 } from '@google/gemini-cli-core';
 import type { Config, ModelSlashCommandEvent } from '@google/gemini-cli-core';
+import { createMockSettings } from '../../test-utils/settings.js';
 
 // Mock dependencies
 const mockGetDisplayString = vi.fn();
@@ -42,12 +48,14 @@ describe('<ModelDialog />', () => {
   const mockGetModel = vi.fn();
   const mockOnClose = vi.fn();
   const mockGetHasAccessToPreviewModel = vi.fn();
+  const mockGetGemini31LaunchedSync = vi.fn();
 
   interface MockConfig extends Partial<Config> {
     setModel: (model: string, isTemporary?: boolean) => void;
     getModel: () => string;
     getHasAccessToPreviewModel: () => boolean;
     getIdeMode: () => boolean;
+    getGemini31LaunchedSync: () => boolean;
   }
 
   const mockConfig: MockConfig = {
@@ -55,12 +63,14 @@ describe('<ModelDialog />', () => {
     getModel: mockGetModel,
     getHasAccessToPreviewModel: mockGetHasAccessToPreviewModel,
     getIdeMode: () => false,
+    getGemini31LaunchedSync: mockGetGemini31LaunchedSync,
   };
 
   beforeEach(() => {
     vi.resetAllMocks();
     mockGetModel.mockReturnValue(DEFAULT_GEMINI_MODEL_AUTO);
     mockGetHasAccessToPreviewModel.mockReturnValue(false);
+    mockGetGemini31LaunchedSync.mockReturnValue(false);
 
     // Default implementation for getDisplayString
     mockGetDisplayString.mockImplementation((val: string) => {
@@ -70,11 +80,24 @@ describe('<ModelDialog />', () => {
     });
   });
 
-  const renderComponent = (configValue = mockConfig as Config) =>
-    renderWithProviders(<ModelDialog onClose={mockOnClose} />, {
-      config: configValue,
+  const renderComponent = (
+    configValue = mockConfig as Config,
+    authType = AuthType.LOGIN_WITH_GOOGLE,
+  ) => {
+    const settings = createMockSettings({
+      security: {
+        auth: {
+          selectedType: authType,
+        },
+      },
     });
 
+    return renderWithProviders(<ModelDialog onClose={mockOnClose} />, {
+      config: configValue,
+      settings,
+    });
+  };
+
   it('renders the initial "main" view correctly', () => {
     const { lastFrame } = renderComponent();
     expect(lastFrame()).toContain('Select Model');
@@ -210,4 +233,96 @@ describe('<ModelDialog />', () => {
       expect(lastFrame()).toContain('Manual');
     });
   });
+
+  it('shows the preferred manual model in the main view option', () => {
+    mockGetModel.mockReturnValue(DEFAULT_GEMINI_MODEL);
+    const { lastFrame, unmount } = renderComponent();
+
+    expect(lastFrame()).toContain(`Manual (${DEFAULT_GEMINI_MODEL})`);
+    unmount();
+  });
+
+  describe('Preview Models', () => {
+    beforeEach(() => {
+      mockGetHasAccessToPreviewModel.mockReturnValue(true);
+    });
+
+    it('shows Auto (Preview) in main view when access is granted', () => {
+      const { lastFrame, unmount } = renderComponent();
+      expect(lastFrame()).toContain('Auto (Preview)');
+      unmount();
+    });
+
+    it('shows Gemini 3 models in manual view when Gemini 3.1 is NOT launched', async () => {
+      mockGetGemini31LaunchedSync.mockReturnValue(false);
+      const { lastFrame, stdin, unmount } = renderComponent();
+
+      // Go to manual view
+      await act(async () => {
+        stdin.write('\u001B[B'); // Manual
+      });
+      await act(async () => {
+        stdin.write('\r');
+      });
+
+      await waitFor(() => {
+        const output = lastFrame();
+        expect(output).toContain(PREVIEW_GEMINI_MODEL);
+        expect(output).toContain(PREVIEW_GEMINI_FLASH_MODEL);
+      });
+      unmount();
+    });
+
+    it('shows Gemini 3.1 models in manual view when Gemini 3.1 IS launched', async () => {
+      mockGetGemini31LaunchedSync.mockReturnValue(true);
+      const { lastFrame, stdin, unmount } = renderComponent(
+        mockConfig as Config,
+        AuthType.USE_VERTEX_AI,
+      );
+
+      // Go to manual view
+      await act(async () => {
+        stdin.write('\u001B[B'); // Manual
+      });
+      await act(async () => {
+        stdin.write('\r');
+      });
+
+      await waitFor(() => {
+        const output = lastFrame();
+        expect(output).toContain(PREVIEW_GEMINI_3_1_MODEL);
+        expect(output).toContain(PREVIEW_GEMINI_FLASH_MODEL);
+      });
+      unmount();
+    });
+
+    it('uses custom tools model when Gemini 3.1 IS launched and auth is Gemini API Key', async () => {
+      mockGetGemini31LaunchedSync.mockReturnValue(true);
+      const { stdin, unmount } = renderComponent(
+        mockConfig as Config,
+        AuthType.USE_GEMINI,
+      );
+
+      // Go to manual view
+      await act(async () => {
+        stdin.write('\u001B[B'); // Manual
+      });
+      await act(async () => {
+        stdin.write('\r');
+      });
+
+      // Select Gemini 3.1 (first item in preview section)
+      await act(async () => {
+        stdin.write('\r');
+      });
+
+      await waitFor(() => {
+        expect(mockSetModel).toHaveBeenCalledWith(
+          PREVIEW_GEMINI_3_1_CUSTOM_TOOLS_MODEL,
+          true,
+        );
+      });
+      unmount();
+    });
+  });
 });

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

@@ -19,11 +19,14 @@ import {
   ModelSlashCommandEvent,
   logModelSlashCommand,
   getDisplayString,
+  AuthType,
+  PREVIEW_GEMINI_3_1_CUSTOM_TOOLS_MODEL,
 } from '@google/gemini-cli-core';
 import { useKeypress } from '../hooks/useKeypress.js';
 import { theme } from '../semantic-colors.js';
 import { DescriptiveRadioButtonSelect } from './shared/DescriptiveRadioButtonSelect.js';
 import { ConfigContext } from '../contexts/ConfigContext.js';
+import { useSettings } from '../contexts/SettingsContext.js';
 
 interface ModelDialogProps {
   onClose: () => void;
@@ -31,6 +34,7 @@ interface ModelDialogProps {
 
 export function ModelDialog({ onClose }: ModelDialogProps): React.JSX.Element {
   const config = useContext(ConfigContext);
+  const settings = useSettings();
   const [view, setView] = useState<'main' | 'manual'>('main');
   const [persistMode, setPersistMode] = useState(false);
 
@@ -39,6 +43,9 @@ export function ModelDialog({ onClose }: ModelDialogProps): React.JSX.Element {
 
   const shouldShowPreviewModels = config?.getHasAccessToPreviewModel();
   const useGemini31 = config?.getGemini31LaunchedSync?.() ?? false;
+  const selectedAuthType = settings.merged.security.auth.selectedType;
+  const useCustomToolModel =
+    useGemini31 && selectedAuthType !== AuthType.USE_VERTEX_AI;
 
   const manualModelSelected = useMemo(() => {
     const manualModels = [
@@ -47,6 +54,7 @@ export function ModelDialog({ onClose }: ModelDialogProps): React.JSX.Element {
       DEFAULT_GEMINI_FLASH_LITE_MODEL,
       PREVIEW_GEMINI_MODEL,
       PREVIEW_GEMINI_3_1_MODEL,
+      PREVIEW_GEMINI_3_1_CUSTOM_TOOLS_MODEL,
       PREVIEW_GEMINI_FLASH_MODEL,
     ];
     if (manualModels.includes(preferredModel)) {
@@ -126,11 +134,19 @@ export function ModelDialog({ onClose }: ModelDialogProps): React.JSX.Element {
     ];
 
     if (shouldShowPreviewModels) {
+      const previewProModel = useGemini31
+        ? PREVIEW_GEMINI_3_1_MODEL
+        : PREVIEW_GEMINI_MODEL;
+
+      const previewProValue = useCustomToolModel
+        ? PREVIEW_GEMINI_3_1_CUSTOM_TOOLS_MODEL
+        : previewProModel;
+
       list.unshift(
         {
-          value: useGemini31 ? PREVIEW_GEMINI_3_1_MODEL : PREVIEW_GEMINI_MODEL,
-          title: useGemini31 ? PREVIEW_GEMINI_3_1_MODEL : PREVIEW_GEMINI_MODEL,
-          key: useGemini31 ? PREVIEW_GEMINI_3_1_MODEL : PREVIEW_GEMINI_MODEL,
+          value: previewProValue,
+          title: previewProModel,
+          key: previewProModel,
         },
         {
           value: PREVIEW_GEMINI_FLASH_MODEL,
@@ -140,7 +156,7 @@ export function ModelDialog({ onClose }: ModelDialogProps): React.JSX.Element {
       );
     }
     return list;
-  }, [shouldShowPreviewModels, useGemini31]);
+  }, [shouldShowPreviewModels, useGemini31, useCustomToolModel]);
 
   const options = view === 'main' ? mainOptions : manualOptions;
 

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

@@ -26,6 +26,7 @@ import {
   isActiveModel,
   getDisplayString,
   isAutoModel,
+  AuthType,
 } from '@google/gemini-cli-core';
 import { useSettings } from '../contexts/SettingsContext.js';
 import { useConfig } from '../contexts/ConfigContext.js';
@@ -84,9 +85,12 @@ const buildModelRows = (
   models: Record<string, ModelMetrics>,
   quotas?: RetrieveUserQuotaResponse,
   useGemini3_1 = false,
+  useCustomToolModel = false,
 ) => {
   const getBaseModelName = (name: string) => name.replace('-001', '');
-  const usedModelNames = new Set(Object.keys(models).map(getBaseModelName));
+  const usedModelNames = new Set(
+    Object.keys(models).map(getBaseModelName).map(getDisplayString),
+  );
 
   // 1. Models with active usage
   const activeRows = Object.entries(models).map(([name, metrics]) => {
@@ -95,7 +99,7 @@ const buildModelRows = (
     const inputTokens = metrics.tokens.input;
     return {
       key: name,
-      modelName,
+      modelName: getDisplayString(modelName),
       requests: metrics.api.totalRequests,
       cachedTokens: cachedTokens.toLocaleString(),
       inputTokens: inputTokens.toLocaleString(),
@@ -111,12 +115,12 @@ const buildModelRows = (
       ?.filter(
         (b) =>
           b.modelId &&
-          isActiveModel(b.modelId, useGemini3_1) &&
-          !usedModelNames.has(b.modelId),
+          isActiveModel(b.modelId, useGemini3_1, useCustomToolModel) &&
+          !usedModelNames.has(getDisplayString(b.modelId)),
       )
       .map((bucket) => ({
         key: bucket.modelId!,
-        modelName: bucket.modelId!,
+        modelName: getDisplayString(bucket.modelId!),
         requests: '-',
         cachedTokens: '-',
         inputTokens: '-',
@@ -138,6 +142,7 @@ const ModelUsageTable: React.FC<{
   pooledLimit?: number;
   pooledResetTime?: string;
   useGemini3_1?: boolean;
+  useCustomToolModel?: boolean;
 }> = ({
   models,
   quotas,
@@ -147,9 +152,10 @@ const ModelUsageTable: React.FC<{
   pooledRemaining,
   pooledLimit,
   pooledResetTime,
-  useGemini3_1 = false,
+  useGemini3_1,
+  useCustomToolModel,
 }) => {
-  const rows = buildModelRows(models, quotas, useGemini3_1);
+  const rows = buildModelRows(models, quotas, useGemini3_1, useCustomToolModel);
 
   if (rows.length === 0) {
     return null;
@@ -407,7 +413,9 @@ export const StatsDisplay: React.FC<StatsDisplayProps> = ({
   const settings = useSettings();
   const config = useConfig();
   const useGemini3_1 = config.getGemini31LaunchedSync?.() ?? false;
-
+  const useCustomToolModel =
+    useGemini3_1 &&
+    config.getContentGeneratorConfig().authType !== AuthType.USE_VERTEX_AI;
   const pooledRemaining = quotaStats?.remaining;
   const pooledLimit = quotaStats?.limit;
   const pooledResetTime = quotaStats?.resetTime;
@@ -542,6 +550,7 @@ export const StatsDisplay: React.FC<StatsDisplayProps> = ({
         pooledLimit={pooledLimit}
         pooledResetTime={pooledResetTime}
         useGemini3_1={useGemini3_1}
+        useCustomToolModel={useCustomToolModel}
       />
     </Box>
   );

packages/cli/src/ui/components/messages/ModelMessage.tsx

@@ -7,6 +7,7 @@
 import type React from 'react';
 import { Text, Box } from 'ink';
 import { theme } from '../../semantic-colors.js';
+import { getDisplayString } from '@google/gemini-cli-core';
 
 interface ModelMessageProps {
   model: string;
@@ -15,7 +16,7 @@ interface ModelMessageProps {
 export const ModelMessage: React.FC<ModelMessageProps> = ({ model }) => (
   <Box marginLeft={2}>
     <Text color={theme.ui.comment} italic>
-      Responding with {model}
+      Responding with {getDisplayString(model)}
     </Text>
   </Box>
 );

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

@@ -155,9 +155,10 @@ describe('useQuotaAndFallback', () => {
         expect(request?.isTerminalQuotaError).toBe(true);
 
         const message = request!.message;
-        expect(message).toContain('Usage limit reached for gemini-pro.');
+        expect(message).toContain('Usage limit reached for all Pro models.');
         expect(message).toContain('Access resets at'); // From getResetTimeMessage
         expect(message).toContain('/stats model for usage details');
+        expect(message).toContain('/model to switch models.');
         expect(message).toContain('/auth to switch to API key.');
 
         expect(mockHistoryManager.addItem).not.toHaveBeenCalled();
@@ -176,6 +177,77 @@ describe('useQuotaAndFallback', () => {
         expect(mockHistoryManager.addItem).toHaveBeenCalledTimes(1);
       });
 
+      it('should show the model name for a terminal quota error on a non-pro model', async () => {
+        const { result } = renderHook(() =>
+          useQuotaAndFallback({
+            config: mockConfig,
+            historyManager: mockHistoryManager,
+            userTier: UserTierId.FREE,
+            setModelSwitchedFromQuotaError: mockSetModelSwitchedFromQuotaError,
+            onShowAuthSelection: mockOnShowAuthSelection,
+          }),
+        );
+
+        const handler = setFallbackHandlerSpy.mock
+          .calls[0][0] as FallbackModelHandler;
+
+        let promise: Promise<FallbackIntent | null>;
+        const error = new TerminalQuotaError(
+          'flash quota',
+          mockGoogleApiError,
+          1000 * 60 * 5,
+        );
+        act(() => {
+          promise = handler('gemini-flash', 'gemini-pro', error);
+        });
+
+        const request = result.current.proQuotaRequest;
+        expect(request).not.toBeNull();
+        expect(request?.failedModel).toBe('gemini-flash');
+
+        const message = request!.message;
+        expect(message).toContain('Usage limit reached for gemini-flash.');
+        expect(message).not.toContain('all Pro models');
+
+        act(() => {
+          result.current.handleProQuotaChoice('retry_later');
+        });
+
+        await promise!;
+      });
+
+      it('should handle terminal quota error without retry delay', async () => {
+        const { result } = renderHook(() =>
+          useQuotaAndFallback({
+            config: mockConfig,
+            historyManager: mockHistoryManager,
+            userTier: UserTierId.FREE,
+            setModelSwitchedFromQuotaError: mockSetModelSwitchedFromQuotaError,
+            onShowAuthSelection: mockOnShowAuthSelection,
+          }),
+        );
+
+        const handler = setFallbackHandlerSpy.mock
+          .calls[0][0] as FallbackModelHandler;
+
+        let promise: Promise<FallbackIntent | null>;
+        const error = new TerminalQuotaError('no delay', mockGoogleApiError);
+        act(() => {
+          promise = handler('gemini-pro', 'gemini-flash', error);
+        });
+
+        const request = result.current.proQuotaRequest;
+        const message = request!.message;
+        expect(message).not.toContain('Access resets at');
+        expect(message).toContain('Usage limit reached for all Pro models.');
+
+        act(() => {
+          result.current.handleProQuotaChoice('retry_later');
+        });
+
+        await promise!;
+      });
+
       it('should handle race conditions by stopping subsequent requests', async () => {
         const { result } = renderHook(() =>
           useQuotaAndFallback({

packages/cli/src/ui/hooks/useQuotaAndFallback.ts

@@ -16,6 +16,7 @@ import {
   type UserTierId,
   VALID_GEMINI_MODELS,
   isProModel,
+  getDisplayString,
 } from '@google/gemini-cli-core';
 import { useCallback, useEffect, useRef, useState } from 'react';
 import { type UseHistoryManagerReturn } from './useHistoryManager.js';
@@ -86,7 +87,7 @@ export function useQuotaAndFallback({
       ) {
         isModelNotFoundError = true;
         const messageLines = [
-          `It seems like you don't have access to ${failedModel}.`,
+          `It seems like you don't have access to ${getDisplayString(failedModel)}.`,
           `Your admin might have disabled the access. Contact them to enable the Preview Release Channel.`,
         ];
         message = messageLines.join('\n');