diff --git a/packages/cli/test-setup.ts b/packages/cli/test-setup.ts
index e64e553ede..b7a6a1863e 100644
--- a/packages/cli/test-setup.ts
+++ b/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();
 
diff --git a/packages/core/src/config/config.ts b/packages/core/src/config/config.ts
index bae1fe483e..d5105b2fd5 100644
--- a/packages/core/src/config/config.ts
+++ b/packages/core/src/config/config.ts
@@ -2802,7 +2802,7 @@ export class Config implements McpContext, AgentLoopContext {
   }
 
   getAuthType(): string | undefined {
-    return this.contentGeneratorConfig.authType;
+    return this.contentGeneratorConfig?.authType;
   }
 
   getPendingIncludeDirectories(): string[] {
diff --git a/packages/core/src/config/models_auth.test.ts b/packages/core/src/config/models_auth.test.ts
index 68e01c839e..0363750cc4 100644
--- a/packages/core/src/config/models_auth.test.ts
+++ b/packages/core/src/config/models_auth.test.ts
@@ -10,17 +10,17 @@ import {
   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';
-import type { Config } from './config.js';
 
 const modelConfigService = new ModelConfigService(DEFAULT_MODEL_CONFIGS);
 
 const dynamicConfig = {
   getExperimentalDynamicModelConfiguration: () => true,
   modelConfigService,
-} as unknown as Config;
+} as unknown as ModelCapabilityContext;
 
 describe('resolveModel with authType', () => {
   it('should resolve auto-gemini-3 to gemini-3-pro-preview for non-personal auth', () => {
@@ -55,7 +55,7 @@ describe('resolveModel with authType', () => {
     const configWithAuth = {
       ...dynamicConfig,
       getAuthType: () => 'oauth-personal',
-    } as unknown as Config;
+    } as unknown as ModelCapabilityContext;
 
     const model = resolveModel(
       PREVIEW_GEMINI_MODEL_AUTO,
diff --git a/packages/core/test-setup.ts b/packages/core/test-setup.ts
index d730369578..cd8b67ffd9 100644
--- a/packages/core/test-setup.ts
+++ b/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();
 });