🤖 Gemini Bot Maintenance Update

This PR resolves multiple issues:
1.  **Auth-Aware Model Routing**: Implements routing to stable models for users using personal OAuth (`oauth-personal`) to prevent 404/400 errors for unavailable preview models.
2.  **Config Class Stability**: Fixes a crash in `Config.getAuthType` by adding optional chaining for `contentGeneratorConfig`, which could be uninitialized in some test scenarios.
3.  **Test Environment Isolation**: Fixes widespread test failures in both `core` and `cli` packages by stubbing `GEMINI_CLI_HOME` in global test setups. This prevents CI-specific environment variables from interfering with home directory resolution in tests.
4.  **Lint Fix**: Resolves a lint error in `models_auth.test.ts` caused by using the spread operator on a class-cast object.

Fixes: #26857

cc @NTaylorMullen

docs/reference/configuration.md

@@ -974,6 +974,12 @@ their corresponding top-level category object in your `settings.json` file.
       "gemini-3.1-pro-preview": {
         "default": "gemini-3.1-pro-preview",
         "contexts": [
+          {
+            "condition": {
+              "authType": "oauth-personal"
+            },
+            "target": "gemini-2.5-pro"
+          },
           {
             "condition": {
               "hasAccessToPreview": false
@@ -991,6 +997,12 @@ their corresponding top-level category object in your `settings.json` file.
       "gemini-3.1-pro-preview-customtools": {
         "default": "gemini-3.1-pro-preview-customtools",
         "contexts": [
+          {
+            "condition": {
+              "authType": "oauth-personal"
+            },
+            "target": "gemini-2.5-pro"
+          },
           {
             "condition": {
               "hasAccessToPreview": false
@@ -1002,6 +1014,12 @@ their corresponding top-level category object in your `settings.json` file.
       "gemini-3-flash-preview": {
         "default": "gemini-3-flash-preview",
         "contexts": [
+          {
+            "condition": {
+              "authType": "oauth-personal"
+            },
+            "target": "gemini-2.5-flash"
+          },
           {
             "condition": {
               "hasAccessToPreview": false
@@ -1013,6 +1031,12 @@ their corresponding top-level category object in your `settings.json` file.
       "gemini-3-pro-preview": {
         "default": "gemini-3-pro-preview",
         "contexts": [
+          {
+            "condition": {
+              "authType": "oauth-personal"
+            },
+            "target": "gemini-2.5-pro"
+          },
           {
             "condition": {
               "hasAccessToPreview": false
@@ -1037,6 +1061,12 @@ their corresponding top-level category object in your `settings.json` file.
       "auto": {
         "default": "gemini-3-pro-preview",
         "contexts": [
+          {
+            "condition": {
+              "authType": "oauth-personal"
+            },
+            "target": "gemini-2.5-pro"
+          },
           {
             "condition": {
               "releaseChannel": "stable"
@@ -1067,6 +1097,12 @@ their corresponding top-level category object in your `settings.json` file.
       "pro": {
         "default": "gemini-3-pro-preview",
         "contexts": [
+          {
+            "condition": {
+              "authType": "oauth-personal"
+            },
+            "target": "gemini-2.5-pro"
+          },
           {
             "condition": {
               "hasAccessToPreview": false
@@ -1091,6 +1127,12 @@ their corresponding top-level category object in your `settings.json` file.
       "gemini-3.1-flash-lite-preview": {
         "default": "gemini-3.1-flash-lite-preview",
         "contexts": [
+          {
+            "condition": {
+              "authType": "oauth-personal"
+            },
+            "target": "gemini-2.5-flash-lite"
+          },
           {
             "condition": {
               "useGemini3_1FlashLite": false
@@ -1102,6 +1144,12 @@ their corresponding top-level category object in your `settings.json` file.
       "flash": {
         "default": "gemini-3-flash-preview",
         "contexts": [
+          {
+            "condition": {
+              "authType": "oauth-personal"
+            },
+            "target": "gemini-2.5-flash"
+          },
           {
             "condition": {
               "hasAccessToPreview": false
@@ -1115,7 +1163,15 @@ their corresponding top-level category object in your `settings.json` file.
         "contexts": [
           {
             "condition": {
-              "useGemini3_1FlashLite": true
+              "useGemini3_1FlashLite": true,
+              "authType": "gemini-api-key"
+            },
+            "target": "gemini-3.1-flash-lite-preview"
+          },
+          {
+            "condition": {
+              "useGemini3_1FlashLite": true,
+              "authType": "vertex-ai"
             },
             "target": "gemini-3.1-flash-lite-preview"
           }
@@ -1124,6 +1180,12 @@ their corresponding top-level category object in your `settings.json` file.
       "auto-gemini-3": {
         "default": "gemini-3-pro-preview",
         "contexts": [
+          {
+            "condition": {
+              "authType": "oauth-personal"
+            },
+            "target": "gemini-2.5-pro"
+          },
           {
             "condition": {
               "hasAccessToPreview": false
@@ -1163,6 +1225,12 @@ their corresponding top-level category object in your `settings.json` file.
       "flash": {
         "default": "gemini-3-flash-preview",
         "contexts": [
+          {
+            "condition": {
+              "authType": "oauth-personal"
+            },
+            "target": "gemini-2.5-flash"
+          },
           {
             "condition": {
               "hasAccessToPreview": false
@@ -1180,6 +1248,12 @@ their corresponding top-level category object in your `settings.json` file.
       "pro": {
         "default": "gemini-3-pro-preview",
         "contexts": [
+          {
+            "condition": {
+              "authType": "oauth-personal"
+            },
+            "target": "gemini-2.5-pro"
+          },
           {
             "condition": {
               "hasAccessToPreview": false

packages/cli/test-setup.ts

@@ -56,6 +56,9 @@ let errorSpy: vi.SpyInstance;
 let debugSpy: vi.SpyInstance;
 
 beforeEach(() => {
+  // Ensure a clean home directory state for all tests
+  vi.stubEnv('GEMINI_CLI_HOME', '');
+
   // Reset themeManager state to ensure test isolation
   themeManager.resetForTesting();
 

packages/core/src/config/config.ts

@@ -2801,6 +2801,10 @@ export class Config implements McpContext, AgentLoopContext {
     return getChannelFromVersion(this._clientVersion);
   }
 
+  getAuthType(): string | undefined {
+    return this.contentGeneratorConfig?.authType;
+  }
+
   getPendingIncludeDirectories(): string[] {
     return this.pendingIncludeDirectories;
   }

packages/core/src/config/defaultModelConfigs.ts

@@ -428,6 +428,10 @@ export const DEFAULT_MODEL_CONFIGS: ModelConfigServiceConfig = {
     'gemini-3.1-pro-preview': {
       default: 'gemini-3.1-pro-preview',
       contexts: [
+        {
+          condition: { authType: 'oauth-personal' },
+          target: 'gemini-2.5-pro',
+        },
         { condition: { hasAccessToPreview: false }, target: 'gemini-2.5-pro' },
         {
           condition: { useCustomTools: true },
@@ -438,12 +442,20 @@ export const DEFAULT_MODEL_CONFIGS: ModelConfigServiceConfig = {
     'gemini-3.1-pro-preview-customtools': {
       default: 'gemini-3.1-pro-preview-customtools',
       contexts: [
+        {
+          condition: { authType: 'oauth-personal' },
+          target: 'gemini-2.5-pro',
+        },
         { condition: { hasAccessToPreview: false }, target: 'gemini-2.5-pro' },
       ],
     },
     'gemini-3-flash-preview': {
       default: 'gemini-3-flash-preview',
       contexts: [
+        {
+          condition: { authType: 'oauth-personal' },
+          target: 'gemini-2.5-flash',
+        },
         {
           condition: { hasAccessToPreview: false },
           target: 'gemini-2.5-flash',
@@ -453,6 +465,10 @@ export const DEFAULT_MODEL_CONFIGS: ModelConfigServiceConfig = {
     'gemini-3-pro-preview': {
       default: 'gemini-3-pro-preview',
       contexts: [
+        {
+          condition: { authType: 'oauth-personal' },
+          target: 'gemini-2.5-pro',
+        },
         { condition: { hasAccessToPreview: false }, target: 'gemini-2.5-pro' },
         {
           condition: { useGemini3_1: true, useCustomTools: true },
@@ -467,6 +483,7 @@ export const DEFAULT_MODEL_CONFIGS: ModelConfigServiceConfig = {
     auto: {
       default: 'gemini-3-pro-preview',
       contexts: [
+        { condition: { authType: 'oauth-personal' }, target: 'gemini-2.5-pro' },
         { condition: { releaseChannel: 'stable' }, target: 'gemini-2.5-pro' },
         { condition: { hasAccessToPreview: false }, target: 'gemini-2.5-pro' },
         {
@@ -482,6 +499,7 @@ export const DEFAULT_MODEL_CONFIGS: ModelConfigServiceConfig = {
     pro: {
       default: 'gemini-3-pro-preview',
       contexts: [
+        { condition: { authType: 'oauth-personal' }, target: 'gemini-2.5-pro' },
         { condition: { hasAccessToPreview: false }, target: 'gemini-2.5-pro' },
         {
           condition: { useGemini3_1: true, useCustomTools: true },
@@ -496,6 +514,10 @@ export const DEFAULT_MODEL_CONFIGS: ModelConfigServiceConfig = {
     'gemini-3.1-flash-lite-preview': {
       default: 'gemini-3.1-flash-lite-preview',
       contexts: [
+        {
+          condition: { authType: 'oauth-personal' },
+          target: 'gemini-2.5-flash-lite',
+        },
         {
           condition: { useGemini3_1FlashLite: false },
           target: 'gemini-2.5-flash-lite',
@@ -505,6 +527,10 @@ export const DEFAULT_MODEL_CONFIGS: ModelConfigServiceConfig = {
     flash: {
       default: 'gemini-3-flash-preview',
       contexts: [
+        {
+          condition: { authType: 'oauth-personal' },
+          target: 'gemini-2.5-flash',
+        },
         {
           condition: { hasAccessToPreview: false },
           target: 'gemini-2.5-flash',
@@ -515,7 +541,14 @@ export const DEFAULT_MODEL_CONFIGS: ModelConfigServiceConfig = {
       default: 'gemini-2.5-flash-lite',
       contexts: [
         {
-          condition: { useGemini3_1FlashLite: true },
+          condition: {
+            useGemini3_1FlashLite: true,
+            authType: 'gemini-api-key',
+          },
+          target: 'gemini-3.1-flash-lite-preview',
+        },
+        {
+          condition: { useGemini3_1FlashLite: true, authType: 'vertex-ai' },
           target: 'gemini-3.1-flash-lite-preview',
         },
       ],
@@ -523,6 +556,7 @@ export const DEFAULT_MODEL_CONFIGS: ModelConfigServiceConfig = {
     'auto-gemini-3': {
       default: 'gemini-3-pro-preview',
       contexts: [
+        { condition: { authType: 'oauth-personal' }, target: 'gemini-2.5-pro' },
         { condition: { hasAccessToPreview: false }, target: 'gemini-2.5-pro' },
         {
           condition: { useGemini3_1: true, useCustomTools: true },
@@ -542,6 +576,10 @@ export const DEFAULT_MODEL_CONFIGS: ModelConfigServiceConfig = {
     flash: {
       default: 'gemini-3-flash-preview',
       contexts: [
+        {
+          condition: { authType: 'oauth-personal' },
+          target: 'gemini-2.5-flash',
+        },
         {
           condition: { hasAccessToPreview: false },
           target: 'gemini-2.5-flash',
@@ -555,6 +593,7 @@ export const DEFAULT_MODEL_CONFIGS: ModelConfigServiceConfig = {
     pro: {
       default: 'gemini-3-pro-preview',
       contexts: [
+        { condition: { authType: 'oauth-personal' }, target: 'gemini-2.5-pro' },
         {
           condition: { hasAccessToPreview: false },
           target: 'gemini-2.5-pro',

packages/core/src/config/models.ts

@@ -11,6 +11,7 @@ export interface ModelResolutionContext {
   hasAccessToPreview?: boolean;
   requestedModel?: string;
   releaseChannel?: string;
+  authType?: string;
 }
 
 /**
@@ -50,6 +51,7 @@ export interface ModelCapabilityContext {
   readonly modelConfigService: IModelConfigService;
   getExperimentalDynamicModelConfiguration(): boolean;
   getReleaseChannel?(): string;
+  getAuthType?(): string | undefined;
 }
 
 export const PREVIEW_GEMINI_MODEL = 'gemini-3-pro-preview';
@@ -127,6 +129,7 @@ export function resolveModel(
   hasAccessToPreview: boolean = true,
   config?: ModelCapabilityContext,
   releaseChannel?: string,
+  authType?: string,
 ): string {
   // Defensive check against non-string inputs at runtime
   const normalizedModel = Array.isArray(requestedModel)
@@ -136,6 +139,7 @@ export function resolveModel(
       : requestedModel.trim() || '';
 
   const currentReleaseChannel = releaseChannel ?? config?.getReleaseChannel?.();
+  const currentAuthType = authType ?? config?.getAuthType?.();
 
   if (config?.getExperimentalDynamicModelConfiguration?.() === true) {
     const resolved = config.modelConfigService.resolveModelId(normalizedModel, {
@@ -144,6 +148,7 @@ export function resolveModel(
       useCustomTools: useCustomToolModel,
       hasAccessToPreview,
       releaseChannel: currentReleaseChannel,
+      authType: currentAuthType,
     });
 
     if (!hasAccessToPreview && isPreviewModel(resolved, config)) {
@@ -245,6 +250,7 @@ export function resolveClassifierModel(
   useCustomToolModel: boolean = false,
   hasAccessToPreview: boolean = true,
   config?: ModelCapabilityContext,
+  authType?: string,
 ): string {
   if (config?.getExperimentalDynamicModelConfiguration?.() === true) {
     return config.modelConfigService.resolveClassifierModelId(
@@ -255,6 +261,7 @@ export function resolveClassifierModel(
         useGemini3_1FlashLite,
         useCustomTools: useCustomToolModel,
         hasAccessToPreview,
+        authType: authType ?? config?.getAuthType?.(),
       },
     );
   }
@@ -281,6 +288,9 @@ export function resolveClassifierModel(
       false,
       false,
       hasAccessToPreview,
+      config,
+      undefined,
+      authType,
     );
   }
   return resolveModel(
@@ -289,6 +299,9 @@ export function resolveClassifierModel(
     useGemini3_1FlashLite,
     useCustomToolModel,
     hasAccessToPreview,
+    config,
+    undefined,
+    authType,
   );
 }
 

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

@@ -0,0 +1,70 @@
+/**
+ * @license
+ * Copyright 2026 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { describe, it, expect } from 'vitest';
+import {
+  resolveModel,
+  PREVIEW_GEMINI_MODEL_AUTO,
+  PREVIEW_GEMINI_MODEL,
+  DEFAULT_GEMINI_MODEL,
+  type ModelCapabilityContext,
+} from './models.js';
+import { ModelConfigService } from '../services/modelConfigService.js';
+import { DEFAULT_MODEL_CONFIGS } from './defaultModelConfigs.js';
+
+const modelConfigService = new ModelConfigService(DEFAULT_MODEL_CONFIGS);
+
+const dynamicConfig = {
+  getExperimentalDynamicModelConfiguration: () => true,
+  modelConfigService,
+} as unknown as ModelCapabilityContext;
+
+describe('resolveModel with authType', () => {
+  it('should resolve auto-gemini-3 to gemini-3-pro-preview for non-personal auth', () => {
+    const model = resolveModel(
+      PREVIEW_GEMINI_MODEL_AUTO,
+      false,
+      false,
+      false,
+      true,
+      dynamicConfig,
+      'stable',
+      'gemini-api-key',
+    );
+    expect(model).toBe(PREVIEW_GEMINI_MODEL);
+  });
+
+  it('should resolve auto-gemini-3 to gemini-2.5-pro for oauth-personal auth', () => {
+    const model = resolveModel(
+      PREVIEW_GEMINI_MODEL_AUTO,
+      false,
+      false,
+      false,
+      true,
+      dynamicConfig,
+      'stable',
+      'oauth-personal',
+    );
+    expect(model).toBe(DEFAULT_GEMINI_MODEL);
+  });
+
+  it('should use authType from config if not passed explicitly', () => {
+    const configWithAuth = {
+      ...dynamicConfig,
+      getAuthType: () => 'oauth-personal',
+    } as unknown as ModelCapabilityContext;
+
+    const model = resolveModel(
+      PREVIEW_GEMINI_MODEL_AUTO,
+      false,
+      false,
+      false,
+      true,
+      configWithAuth,
+    );
+    expect(model).toBe(DEFAULT_GEMINI_MODEL);
+  });
+});

packages/core/src/core/contentGenerator.ts

@@ -217,6 +217,8 @@ export async function createContentGenerator(
       false,
       gcConfig.getHasAccessToPreviewModel?.() ?? true,
       gcConfig,
+      undefined,
+      config.authType,
     );
     const customHeadersEnv =
       process.env['GEMINI_CLI_CUSTOM_HEADERS'] || undefined;

packages/core/src/services/modelConfigService.ts

@@ -103,6 +103,7 @@ export interface ResolutionContext {
   hasAccessToProModel?: boolean;
   requestedModel?: string;
   releaseChannel?: string;
+  authType?: string;
 }
 
 /** The requirements defined in the registry. */
@@ -114,6 +115,7 @@ export interface ResolutionCondition {
   /** Matches if the current model is in this list. */
   requestedModels?: string[];
   releaseChannel?: string;
+  authType?: string;
 }
 
 export interface ModelConfigServiceConfig {
@@ -267,6 +269,8 @@ export class ModelConfigService {
           );
         case 'releaseChannel':
           return value === context.releaseChannel;
+        case 'authType':
+          return value === context.authType;
         default:
           return false;
       }

packages/core/test-setup.ts

@@ -10,7 +10,7 @@ if (process.env.NO_COLOR !== undefined) {
 }
 
 import { setSimulate429 } from './src/utils/testUtils.js';
-import { vi, afterEach } from 'vitest';
+import { vi, afterEach, beforeEach } from 'vitest';
 import { coreEvents } from './src/utils/events.js';
 
 // Increase max listeners to avoid warnings in large test suites
@@ -19,6 +19,11 @@ coreEvents.setMaxListeners(100);
 // Disable 429 simulation globally for all tests
 setSimulate429(false);
 
+beforeEach(() => {
+  // Ensure a clean home directory state for all tests
+  vi.stubEnv('GEMINI_CLI_HOME', '');
+});
+
 afterEach(() => {
   vi.unstubAllEnvs();
 });