diff --git a/packages/cli/src/ui/auth/useAuth.ts b/packages/cli/src/ui/auth/useAuth.ts
index 05f811741..8e5b28499 100644
--- a/packages/cli/src/ui/auth/useAuth.ts
+++ b/packages/cli/src/ui/auth/useAuth.ts
@@ -4,7 +4,11 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import type { Config, ModelProvidersConfig } from '@qwen-code/qwen-code-core';
+import type {
+  Config,
+  ContentGeneratorConfig,
+  ModelProvidersConfig,
+} from '@qwen-code/qwen-code-core';
 import {
   AuthEvent,
   AuthType,
@@ -214,11 +218,19 @@ export const useAuthCommand = (
 
       if (authType === AuthType.USE_OPENAI) {
         if (credentials) {
-          config.updateCredentials({
-            apiKey: credentials.apiKey,
-            baseUrl: credentials.baseUrl,
-            model: credentials.model,
-          });
+          // Pass settings.model.generationConfig to updateCredentials so it can be merged
+          // after clearing provider-sourced config. This ensures settings.json generationConfig
+          // fields (e.g., samplingParams, timeout) are preserved.
+          const settingsGenerationConfig = settings.merged.model
+            ?.generationConfig as Partial<ContentGeneratorConfig> | undefined;
+          config.updateCredentials(
+            {
+              apiKey: credentials.apiKey,
+              baseUrl: credentials.baseUrl,
+              model: credentials.model,
+            },
+            settingsGenerationConfig,
+          );
           await performAuth(authType, credentials);
         }
         return;
@@ -226,7 +238,13 @@ export const useAuthCommand = (
 
       await performAuth(authType);
     },
-    [config, performAuth, isProviderManagedModel, onAuthError],
+    [
+      config,
+      performAuth,
+      isProviderManagedModel,
+      onAuthError,
+      settings.merged.model?.generationConfig,
+    ],
   );
 
   const openAuthDialog = useCallback(() => {
diff --git a/packages/cli/src/ui/components/ModelDialog.tsx b/packages/cli/src/ui/components/ModelDialog.tsx
index 42b85438a..06c002070 100644
--- a/packages/cli/src/ui/components/ModelDialog.tsx
+++ b/packages/cli/src/ui/components/ModelDialog.tsx
@@ -275,7 +275,7 @@ export function ModelDialog({ onClose }: ModelDialogProps): React.JSX.Element {
         persistModelSelection(settings, effectiveModelId);
         persistAuthTypeSelection(settings, effectiveAuthType);
 
-        const baseUrl = after?.baseUrl ?? '(default)';
+        const baseUrl = after?.baseUrl ?? t('(default)');
         const maskedKey = maskApiKey(after?.apiKey);
         uiState?.historyManager.addItem(
           {
@@ -322,7 +322,7 @@ export function ModelDialog({ onClose }: ModelDialogProps): React.JSX.Element {
             <>
               <ConfigRow
                 label="Base URL"
-                value={effectiveConfig?.baseUrl ?? ''}
+                value={effectiveConfig?.baseUrl ?? t('(default)')}
                 badge={formatSourceBadge(sources['baseUrl'])}
               />
               <ConfigRow
diff --git a/packages/cli/src/utils/modelConfigUtils.test.ts b/packages/cli/src/utils/modelConfigUtils.test.ts
new file mode 100644
index 000000000..0bf0acdcb
--- /dev/null
+++ b/packages/cli/src/utils/modelConfigUtils.test.ts
@@ -0,0 +1,721 @@
+/**
+ * @license
+ * Copyright 2025 Qwen Team
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { describe, it, expect, beforeEach, afterEach, vi } from 'vitest';
+import {
+  AuthType,
+  resolveModelConfig,
+  type ProviderModelConfig,
+} from '@qwen-code/qwen-code-core';
+import {
+  getAuthTypeFromEnv,
+  resolveCliGenerationConfig,
+} from './modelConfigUtils.js';
+import type { Settings } from '../config/settings.js';
+
+vi.mock('@qwen-code/qwen-code-core', async (importOriginal) => {
+  const original =
+    await importOriginal<typeof import('@qwen-code/qwen-code-core')>();
+  return {
+    ...original,
+    resolveModelConfig: vi.fn(),
+  };
+});
+
+describe('modelConfigUtils', () => {
+  describe('getAuthTypeFromEnv', () => {
+    const originalEnv = process.env;
+
+    beforeEach(() => {
+      vi.resetModules();
+      process.env = { ...originalEnv };
+    });
+
+    afterEach(() => {
+      process.env = originalEnv;
+    });
+
+    it('should return USE_OPENAI when all OpenAI env vars are set', () => {
+      process.env['OPENAI_API_KEY'] = 'test-key';
+      process.env['OPENAI_MODEL'] = 'gpt-4';
+      process.env['OPENAI_BASE_URL'] = 'https://api.openai.com';
+
+      expect(getAuthTypeFromEnv()).toBe(AuthType.USE_OPENAI);
+    });
+
+    it('should return undefined when OpenAI env vars are incomplete', () => {
+      process.env['OPENAI_API_KEY'] = 'test-key';
+      process.env['OPENAI_MODEL'] = 'gpt-4';
+      // Missing OPENAI_BASE_URL
+
+      expect(getAuthTypeFromEnv()).toBeUndefined();
+    });
+
+    it('should return QWEN_OAUTH when QWEN_OAUTH is set', () => {
+      process.env['QWEN_OAUTH'] = 'true';
+
+      expect(getAuthTypeFromEnv()).toBe(AuthType.QWEN_OAUTH);
+    });
+
+    it('should return USE_GEMINI when Gemini env vars are set', () => {
+      process.env['GEMINI_API_KEY'] = 'test-key';
+      process.env['GEMINI_MODEL'] = 'gemini-pro';
+
+      expect(getAuthTypeFromEnv()).toBe(AuthType.USE_GEMINI);
+    });
+
+    it('should return undefined when Gemini env vars are incomplete', () => {
+      process.env['GEMINI_API_KEY'] = 'test-key';
+      // Missing GEMINI_MODEL
+
+      expect(getAuthTypeFromEnv()).toBeUndefined();
+    });
+
+    it('should return USE_VERTEX_AI when Google env vars are set', () => {
+      process.env['GOOGLE_API_KEY'] = 'test-key';
+      process.env['GOOGLE_MODEL'] = 'vertex-model';
+
+      expect(getAuthTypeFromEnv()).toBe(AuthType.USE_VERTEX_AI);
+    });
+
+    it('should return undefined when Google env vars are incomplete', () => {
+      process.env['GOOGLE_API_KEY'] = 'test-key';
+      // Missing GOOGLE_MODEL
+
+      expect(getAuthTypeFromEnv()).toBeUndefined();
+    });
+
+    it('should return USE_ANTHROPIC when Anthropic env vars are set', () => {
+      process.env['ANTHROPIC_API_KEY'] = 'test-key';
+      process.env['ANTHROPIC_MODEL'] = 'claude-3';
+      process.env['ANTHROPIC_BASE_URL'] = 'https://api.anthropic.com';
+
+      expect(getAuthTypeFromEnv()).toBe(AuthType.USE_ANTHROPIC);
+    });
+
+    it('should return undefined when Anthropic env vars are incomplete', () => {
+      process.env['ANTHROPIC_API_KEY'] = 'test-key';
+      process.env['ANTHROPIC_MODEL'] = 'claude-3';
+      // Missing ANTHROPIC_BASE_URL
+
+      expect(getAuthTypeFromEnv()).toBeUndefined();
+    });
+
+    it('should prioritize QWEN_OAUTH over other auth types when explicitly set', () => {
+      process.env['QWEN_OAUTH'] = 'true';
+      process.env['OPENAI_API_KEY'] = 'test-key';
+      process.env['OPENAI_MODEL'] = 'gpt-4';
+      process.env['OPENAI_BASE_URL'] = 'https://api.openai.com';
+
+      // QWEN_OAUTH is checked first, so it should be returned even when other auth vars are set
+      expect(getAuthTypeFromEnv()).toBe(AuthType.QWEN_OAUTH);
+    });
+
+    it('should return undefined when no auth env vars are set', () => {
+      expect(getAuthTypeFromEnv()).toBeUndefined();
+    });
+  });
+
+  describe('resolveCliGenerationConfig', () => {
+    const originalEnv = process.env;
+    const originalConsoleWarn = console.warn;
+
+    beforeEach(() => {
+      vi.resetModules();
+      process.env = { ...originalEnv };
+      console.warn = vi.fn();
+    });
+
+    afterEach(() => {
+      process.env = originalEnv;
+      console.warn = originalConsoleWarn;
+      vi.clearAllMocks();
+    });
+
+    function makeMockSettings(overrides?: Partial<Settings>): Settings {
+      return {
+        model: { name: 'default-model' },
+        security: {
+          auth: {
+            apiKey: 'settings-api-key',
+            baseUrl: 'https://settings.example.com',
+          },
+        },
+        ...overrides,
+      } as Settings;
+    }
+
+    it('should resolve config from argv with highest precedence', () => {
+      const argv = {
+        model: 'argv-model',
+        openaiApiKey: 'argv-key',
+        openaiBaseUrl: 'https://argv.example.com',
+      };
+      const settings = makeMockSettings();
+      const selectedAuthType = AuthType.USE_OPENAI;
+
+      vi.mocked(resolveModelConfig).mockReturnValue({
+        config: {
+          model: 'argv-model',
+          apiKey: 'argv-key',
+          baseUrl: 'https://argv.example.com',
+        },
+        sources: {
+          model: { kind: 'cli', detail: '--model' },
+          apiKey: { kind: 'cli', detail: '--openaiApiKey' },
+          baseUrl: { kind: 'cli', detail: '--openaiBaseUrl' },
+        },
+        warnings: [],
+      });
+
+      const result = resolveCliGenerationConfig({
+        argv,
+        settings,
+        selectedAuthType,
+      });
+
+      expect(result.model).toBe('argv-model');
+      expect(result.apiKey).toBe('argv-key');
+      expect(result.baseUrl).toBe('https://argv.example.com');
+      expect(vi.mocked(resolveModelConfig)).toHaveBeenCalledWith(
+        expect.objectContaining({
+          cli: {
+            model: 'argv-model',
+            apiKey: 'argv-key',
+            baseUrl: 'https://argv.example.com',
+          },
+        }),
+      );
+    });
+
+    it('should resolve config from settings when argv is not provided', () => {
+      const argv = {};
+      const settings = makeMockSettings({
+        model: { name: 'settings-model' },
+        security: {
+          auth: {
+            apiKey: 'settings-key',
+            baseUrl: 'https://settings.example.com',
+          },
+        },
+      });
+      const selectedAuthType = AuthType.USE_OPENAI;
+
+      vi.mocked(resolveModelConfig).mockReturnValue({
+        config: {
+          model: 'settings-model',
+          apiKey: 'settings-key',
+          baseUrl: 'https://settings.example.com',
+        },
+        sources: {
+          model: { kind: 'settings', detail: 'model.name' },
+          apiKey: { kind: 'settings', detail: 'security.auth.apiKey' },
+          baseUrl: { kind: 'settings', detail: 'security.auth.baseUrl' },
+        },
+        warnings: [],
+      });
+
+      const result = resolveCliGenerationConfig({
+        argv,
+        settings,
+        selectedAuthType,
+      });
+
+      expect(result.model).toBe('settings-model');
+      expect(result.apiKey).toBe('settings-key');
+      expect(result.baseUrl).toBe('https://settings.example.com');
+    });
+
+    it('should merge generationConfig from settings', () => {
+      const argv = {};
+      const settings = makeMockSettings({
+        model: {
+          name: 'test-model',
+          generationConfig: {
+            samplingParams: {
+              temperature: 0.7,
+              max_tokens: 1000,
+            },
+            timeout: 5000,
+          } as Record<string, unknown>,
+        },
+      });
+      const selectedAuthType = AuthType.USE_OPENAI;
+
+      vi.mocked(resolveModelConfig).mockReturnValue({
+        config: {
+          model: 'test-model',
+          apiKey: '',
+          baseUrl: '',
+          samplingParams: {
+            temperature: 0.7,
+            max_tokens: 1000,
+          },
+          timeout: 5000,
+        },
+        sources: {},
+        warnings: [],
+      });
+
+      const result = resolveCliGenerationConfig({
+        argv,
+        settings,
+        selectedAuthType,
+      });
+
+      expect(result.generationConfig.samplingParams?.temperature).toBe(0.7);
+      expect(result.generationConfig.samplingParams?.max_tokens).toBe(1000);
+      expect(result.generationConfig.timeout).toBe(5000);
+    });
+
+    it('should resolve OpenAI logging from argv', () => {
+      const argv = {
+        openaiLogging: true,
+        openaiLoggingDir: '/custom/log/dir',
+      };
+      const settings = makeMockSettings();
+      const selectedAuthType = AuthType.USE_OPENAI;
+
+      vi.mocked(resolveModelConfig).mockReturnValue({
+        config: {
+          model: 'test-model',
+          apiKey: '',
+          baseUrl: '',
+        },
+        sources: {},
+        warnings: [],
+      });
+
+      const result = resolveCliGenerationConfig({
+        argv,
+        settings,
+        selectedAuthType,
+      });
+
+      expect(result.generationConfig.enableOpenAILogging).toBe(true);
+      expect(result.generationConfig.openAILoggingDir).toBe('/custom/log/dir');
+    });
+
+    it('should resolve OpenAI logging from settings when argv is undefined', () => {
+      const argv = {};
+      const settings = makeMockSettings({
+        model: {
+          name: 'test-model',
+          enableOpenAILogging: true,
+          openAILoggingDir: '/settings/log/dir',
+        },
+      });
+      const selectedAuthType = AuthType.USE_OPENAI;
+
+      vi.mocked(resolveModelConfig).mockReturnValue({
+        config: {
+          model: 'test-model',
+          apiKey: '',
+          baseUrl: '',
+        },
+        sources: {},
+        warnings: [],
+      });
+
+      const result = resolveCliGenerationConfig({
+        argv,
+        settings,
+        selectedAuthType,
+      });
+
+      expect(result.generationConfig.enableOpenAILogging).toBe(true);
+      expect(result.generationConfig.openAILoggingDir).toBe(
+        '/settings/log/dir',
+      );
+    });
+
+    it('should default OpenAI logging to false when not provided', () => {
+      const argv = {};
+      const settings = makeMockSettings();
+      const selectedAuthType = AuthType.USE_OPENAI;
+
+      vi.mocked(resolveModelConfig).mockReturnValue({
+        config: {
+          model: 'test-model',
+          apiKey: '',
+          baseUrl: '',
+        },
+        sources: {},
+        warnings: [],
+      });
+
+      const result = resolveCliGenerationConfig({
+        argv,
+        settings,
+        selectedAuthType,
+      });
+
+      expect(result.generationConfig.enableOpenAILogging).toBe(false);
+    });
+
+    it('should find modelProvider from settings when authType and model match', () => {
+      const argv = { model: 'provider-model' };
+      const modelProvider: ProviderModelConfig = {
+        id: 'provider-model',
+        name: 'Provider Model',
+        generationConfig: {
+          samplingParams: { temperature: 0.8 },
+        },
+      };
+      const settings = makeMockSettings({
+        modelProviders: {
+          [AuthType.USE_OPENAI]: [modelProvider],
+        },
+      });
+      const selectedAuthType = AuthType.USE_OPENAI;
+
+      vi.mocked(resolveModelConfig).mockReturnValue({
+        config: {
+          model: 'provider-model',
+          apiKey: '',
+          baseUrl: '',
+        },
+        sources: {},
+        warnings: [],
+      });
+
+      resolveCliGenerationConfig({
+        argv,
+        settings,
+        selectedAuthType,
+      });
+
+      expect(vi.mocked(resolveModelConfig)).toHaveBeenCalledWith(
+        expect.objectContaining({
+          modelProvider,
+        }),
+      );
+    });
+
+    it('should find modelProvider from settings.model.name when argv.model is not provided', () => {
+      const argv = {};
+      const modelProvider: ProviderModelConfig = {
+        id: 'settings-model',
+        name: 'Settings Model',
+        generationConfig: {
+          samplingParams: { temperature: 0.9 },
+        },
+      };
+      const settings = makeMockSettings({
+        model: { name: 'settings-model' },
+        modelProviders: {
+          [AuthType.USE_OPENAI]: [modelProvider],
+        },
+      });
+      const selectedAuthType = AuthType.USE_OPENAI;
+
+      vi.mocked(resolveModelConfig).mockReturnValue({
+        config: {
+          model: 'settings-model',
+          apiKey: '',
+          baseUrl: '',
+        },
+        sources: {},
+        warnings: [],
+      });
+
+      resolveCliGenerationConfig({
+        argv,
+        settings,
+        selectedAuthType,
+      });
+
+      expect(vi.mocked(resolveModelConfig)).toHaveBeenCalledWith(
+        expect.objectContaining({
+          modelProvider,
+        }),
+      );
+    });
+
+    it('should not find modelProvider when authType is undefined', () => {
+      const argv = { model: 'test-model' };
+      const settings = makeMockSettings({
+        modelProviders: {
+          [AuthType.USE_OPENAI]: [{ id: 'test-model', name: 'Test Model' }],
+        },
+      });
+      const selectedAuthType = undefined;
+
+      vi.mocked(resolveModelConfig).mockReturnValue({
+        config: {
+          model: 'test-model',
+          apiKey: '',
+          baseUrl: '',
+        },
+        sources: {},
+        warnings: [],
+      });
+
+      resolveCliGenerationConfig({
+        argv,
+        settings,
+        selectedAuthType,
+      });
+
+      expect(vi.mocked(resolveModelConfig)).toHaveBeenCalledWith(
+        expect.objectContaining({
+          modelProvider: undefined,
+        }),
+      );
+    });
+
+    it('should not find modelProvider when modelProviders is not an array', () => {
+      const argv = { model: 'test-model' };
+      const settings = makeMockSettings({
+        modelProviders: {
+          [AuthType.USE_OPENAI]: null as unknown as ProviderModelConfig[],
+        },
+      });
+      const selectedAuthType = AuthType.USE_OPENAI;
+
+      vi.mocked(resolveModelConfig).mockReturnValue({
+        config: {
+          model: 'test-model',
+          apiKey: '',
+          baseUrl: '',
+        },
+        sources: {},
+        warnings: [],
+      });
+
+      resolveCliGenerationConfig({
+        argv,
+        settings,
+        selectedAuthType,
+      });
+
+      expect(vi.mocked(resolveModelConfig)).toHaveBeenCalledWith(
+        expect.objectContaining({
+          modelProvider: undefined,
+        }),
+      );
+    });
+
+    it('should log warnings from resolveModelConfig', () => {
+      const argv = {};
+      const settings = makeMockSettings();
+      const selectedAuthType = AuthType.USE_OPENAI;
+
+      vi.mocked(resolveModelConfig).mockReturnValue({
+        config: {
+          model: 'test-model',
+          apiKey: '',
+          baseUrl: '',
+        },
+        sources: {},
+        warnings: ['Warning 1', 'Warning 2'],
+      });
+
+      resolveCliGenerationConfig({
+        argv,
+        settings,
+        selectedAuthType,
+      });
+
+      expect(console.warn).toHaveBeenCalledWith('Warning 1');
+      expect(console.warn).toHaveBeenCalledWith('Warning 2');
+    });
+
+    it('should use custom env when provided', () => {
+      const argv = {};
+      const settings = makeMockSettings();
+      const selectedAuthType = AuthType.USE_OPENAI;
+      const customEnv = {
+        OPENAI_API_KEY: 'custom-key',
+        OPENAI_MODEL: 'custom-model',
+      };
+
+      vi.mocked(resolveModelConfig).mockReturnValue({
+        config: {
+          model: 'custom-model',
+          apiKey: 'custom-key',
+          baseUrl: '',
+        },
+        sources: {},
+        warnings: [],
+      });
+
+      resolveCliGenerationConfig({
+        argv,
+        settings,
+        selectedAuthType,
+        env: customEnv,
+      });
+
+      expect(vi.mocked(resolveModelConfig)).toHaveBeenCalledWith(
+        expect.objectContaining({
+          env: customEnv,
+        }),
+      );
+    });
+
+    it('should use process.env when env is not provided', () => {
+      const argv = {};
+      const settings = makeMockSettings();
+      const selectedAuthType = AuthType.USE_OPENAI;
+
+      vi.mocked(resolveModelConfig).mockReturnValue({
+        config: {
+          model: 'test-model',
+          apiKey: '',
+          baseUrl: '',
+        },
+        sources: {},
+        warnings: [],
+      });
+
+      resolveCliGenerationConfig({
+        argv,
+        settings,
+        selectedAuthType,
+      });
+
+      expect(vi.mocked(resolveModelConfig)).toHaveBeenCalledWith(
+        expect.objectContaining({
+          env: process.env,
+        }),
+      );
+    });
+
+    it('should return empty strings for missing model, apiKey, and baseUrl', () => {
+      const argv = {};
+      const settings = makeMockSettings();
+      const selectedAuthType = AuthType.USE_OPENAI;
+
+      vi.mocked(resolveModelConfig).mockReturnValue({
+        config: {
+          model: '',
+          apiKey: '',
+          baseUrl: '',
+        },
+        sources: {},
+        warnings: [],
+      });
+
+      const result = resolveCliGenerationConfig({
+        argv,
+        settings,
+        selectedAuthType,
+      });
+
+      expect(result.model).toBe('');
+      expect(result.apiKey).toBe('');
+      expect(result.baseUrl).toBe('');
+    });
+
+    it('should merge resolved config with logging settings', () => {
+      const argv = {
+        openaiLogging: true,
+      };
+      const settings = makeMockSettings({
+        model: {
+          name: 'test-model',
+          generationConfig: {
+            timeout: 5000,
+          } as Record<string, unknown>,
+        },
+      });
+      const selectedAuthType = AuthType.USE_OPENAI;
+
+      vi.mocked(resolveModelConfig).mockReturnValue({
+        config: {
+          model: 'test-model',
+          apiKey: 'test-key',
+          baseUrl: 'https://test.com',
+          samplingParams: { temperature: 0.5 },
+        },
+        sources: {},
+        warnings: [],
+      });
+
+      const result = resolveCliGenerationConfig({
+        argv,
+        settings,
+        selectedAuthType,
+      });
+
+      expect(result.generationConfig).toEqual({
+        model: 'test-model',
+        apiKey: 'test-key',
+        baseUrl: 'https://test.com',
+        samplingParams: { temperature: 0.5 },
+        enableOpenAILogging: true,
+        openAILoggingDir: undefined,
+      });
+    });
+
+    it('should handle settings without model property', () => {
+      const argv = {};
+      const settings = makeMockSettings({
+        model: undefined as unknown as Settings['model'],
+      });
+      const selectedAuthType = AuthType.USE_OPENAI;
+
+      vi.mocked(resolveModelConfig).mockReturnValue({
+        config: {
+          model: '',
+          apiKey: '',
+          baseUrl: '',
+        },
+        sources: {},
+        warnings: [],
+      });
+
+      const result = resolveCliGenerationConfig({
+        argv,
+        settings,
+        selectedAuthType,
+      });
+
+      expect(result.model).toBe('');
+      expect(vi.mocked(resolveModelConfig)).toHaveBeenCalledWith(
+        expect.objectContaining({
+          settings: expect.objectContaining({
+            model: undefined,
+          }),
+        }),
+      );
+    });
+
+    it('should handle settings without security.auth property', () => {
+      const argv = {};
+      const settings = makeMockSettings({
+        security: undefined,
+      });
+      const selectedAuthType = AuthType.USE_OPENAI;
+
+      vi.mocked(resolveModelConfig).mockReturnValue({
+        config: {
+          model: '',
+          apiKey: '',
+          baseUrl: '',
+        },
+        sources: {},
+        warnings: [],
+      });
+
+      resolveCliGenerationConfig({
+        argv,
+        settings,
+        selectedAuthType,
+      });
+
+      expect(vi.mocked(resolveModelConfig)).toHaveBeenCalledWith(
+        expect.objectContaining({
+          settings: expect.objectContaining({
+            apiKey: undefined,
+            baseUrl: undefined,
+          }),
+        }),
+      );
+    });
+  });
+});
diff --git a/packages/cli/src/utils/modelConfigUtils.ts b/packages/cli/src/utils/modelConfigUtils.ts
index 305e50d15..e9cd050c3 100644
--- a/packages/cli/src/utils/modelConfigUtils.ts
+++ b/packages/cli/src/utils/modelConfigUtils.ts
@@ -44,20 +44,31 @@ export interface ResolvedCliGenerationConfig {
 }
 
 export function getAuthTypeFromEnv(): AuthType | undefined {
-  if (process.env['OPENAI_API_KEY']) {
-    return AuthType.USE_OPENAI;
-  }
   if (process.env['QWEN_OAUTH']) {
     return AuthType.QWEN_OAUTH;
   }
 
-  if (process.env['GEMINI_API_KEY']) {
+  if (
+    process.env['OPENAI_API_KEY'] &&
+    process.env['OPENAI_MODEL'] &&
+    process.env['OPENAI_BASE_URL']
+  ) {
+    return AuthType.USE_OPENAI;
+  }
+
+  if (process.env['GEMINI_API_KEY'] && process.env['GEMINI_MODEL']) {
     return AuthType.USE_GEMINI;
   }
-  if (process.env['GOOGLE_API_KEY']) {
+
+  if (process.env['GOOGLE_API_KEY'] && process.env['GOOGLE_MODEL']) {
     return AuthType.USE_VERTEX_AI;
   }
-  if (process.env['ANTHROPIC_API_KEY']) {
+
+  if (
+    process.env['ANTHROPIC_API_KEY'] &&
+    process.env['ANTHROPIC_MODEL'] &&
+    process.env['ANTHROPIC_BASE_URL']
+  ) {
     return AuthType.USE_ANTHROPIC;
   }
 
diff --git a/packages/core/src/config/config.ts b/packages/core/src/config/config.ts
index 581e3a347..54d8f795a 100644
--- a/packages/core/src/config/config.ts
+++ b/packages/core/src/config/config.ts
@@ -708,12 +708,15 @@ export class Config {
    * Exclusive for `OpenAIKeyPrompt` to update credentials via `/auth`
    * Delegates to ModelsConfig.
    */
-  updateCredentials(credentials: {
-    apiKey?: string;
-    baseUrl?: string;
-    model?: string;
-  }): void {
-    this._modelsConfig.updateCredentials(credentials);
+  updateCredentials(
+    credentials: {
+      apiKey?: string;
+      baseUrl?: string;
+      model?: string;
+    },
+    settingsGenerationConfig?: Partial<ContentGeneratorConfig>,
+  ): void {
+    this._modelsConfig.updateCredentials(credentials, settingsGenerationConfig);
   }
 
   /**
diff --git a/packages/core/src/models/modelsConfig.test.ts b/packages/core/src/models/modelsConfig.test.ts
index 06896a382..36e40cfe8 100644
--- a/packages/core/src/models/modelsConfig.test.ts
+++ b/packages/core/src/models/modelsConfig.test.ts
@@ -191,7 +191,7 @@ describe('ModelsConfig', () => {
     expect(gc.apiKeyEnvKey).toBe('API_KEY_SHARED');
   });
 
-  it('should preserve settings generationConfig when model is updated via updateCredentials even if it matches modelProviders', () => {
+  it('should use provider config when modelId exists in registry even after updateCredentials', () => {
     const modelProvidersConfig: ModelProvidersConfig = {
       openai: [
         {
@@ -213,7 +213,7 @@ describe('ModelsConfig', () => {
       initialAuthType: AuthType.USE_OPENAI,
       modelProvidersConfig,
       generationConfig: {
-        model: 'model-a',
+        model: 'custom-model',
         samplingParams: { temperature: 0.9, max_tokens: 999 },
         timeout: 9999,
         maxRetries: 9,
@@ -235,30 +235,30 @@ describe('ModelsConfig', () => {
       },
     });
 
-    // User manually updates the model via updateCredentials (e.g. key prompt flow).
-    // Even if the model ID matches a modelProviders entry, we must not apply provider defaults
-    // that would overwrite settings.model.generationConfig.
-    modelsConfig.updateCredentials({ model: 'model-a' });
+    // User manually updates credentials via updateCredentials.
+    // Note: In practice, handleAuthSelect prevents using a modelId that matches a provider model,
+    // but if syncAfterAuthRefresh is called with a modelId that exists in registry,
+    // we should use provider config.
+    modelsConfig.updateCredentials({ apiKey: 'manual-key' });
 
-    modelsConfig.syncAfterAuthRefresh(
-      AuthType.USE_OPENAI,
-      modelsConfig.getModel(),
-    );
+    // syncAfterAuthRefresh with a modelId that exists in registry should use provider config
+    modelsConfig.syncAfterAuthRefresh(AuthType.USE_OPENAI, 'model-a');
 
     const gc = currentGenerationConfig(modelsConfig);
     expect(gc.model).toBe('model-a');
-    expect(gc.samplingParams?.temperature).toBe(0.9);
-    expect(gc.samplingParams?.max_tokens).toBe(999);
-    expect(gc.timeout).toBe(9999);
-    expect(gc.maxRetries).toBe(9);
+    // Provider config should be applied
+    expect(gc.samplingParams?.temperature).toBe(0.1);
+    expect(gc.samplingParams?.max_tokens).toBe(123);
+    expect(gc.timeout).toBe(111);
+    expect(gc.maxRetries).toBe(1);
   });
 
-  it('should preserve settings generationConfig across multiple auth refreshes after updateCredentials', () => {
+  it('should preserve settings generationConfig when modelId does not exist in registry', () => {
     const modelProvidersConfig: ModelProvidersConfig = {
       openai: [
         {
-          id: 'model-a',
-          name: 'Model A',
+          id: 'provider-model',
+          name: 'Provider Model',
           baseUrl: 'https://api.example.com/v1',
           envKey: 'API_KEY_A',
           generationConfig: {
@@ -270,11 +270,12 @@ describe('ModelsConfig', () => {
       ],
     };
 
+    // Simulate settings with a custom model (not in registry)
     const modelsConfig = new ModelsConfig({
       initialAuthType: AuthType.USE_OPENAI,
       modelProvidersConfig,
       generationConfig: {
-        model: 'model-a',
+        model: 'custom-model',
         samplingParams: { temperature: 0.9, max_tokens: 999 },
         timeout: 9999,
         maxRetries: 9,
@@ -296,25 +297,21 @@ describe('ModelsConfig', () => {
       },
     });
 
+    // User manually sets credentials for a custom model (not in registry)
     modelsConfig.updateCredentials({
       apiKey: 'manual-key',
       baseUrl: 'https://manual.example.com/v1',
-      model: 'model-a',
+      model: 'custom-model',
     });
 
-    // First auth refresh
-    modelsConfig.syncAfterAuthRefresh(
-      AuthType.USE_OPENAI,
-      modelsConfig.getModel(),
-    );
+    // First auth refresh - modelId doesn't exist in registry, so credentials should be preserved
+    modelsConfig.syncAfterAuthRefresh(AuthType.USE_OPENAI, 'custom-model');
     // Second auth refresh should still preserve settings generationConfig
-    modelsConfig.syncAfterAuthRefresh(
-      AuthType.USE_OPENAI,
-      modelsConfig.getModel(),
-    );
+    modelsConfig.syncAfterAuthRefresh(AuthType.USE_OPENAI, 'custom-model');
 
     const gc = currentGenerationConfig(modelsConfig);
-    expect(gc.model).toBe('model-a');
+    expect(gc.model).toBe('custom-model');
+    // Settings-sourced generation config should be preserved since modelId doesn't exist in registry
     expect(gc.samplingParams?.temperature).toBe(0.9);
     expect(gc.samplingParams?.max_tokens).toBe(999);
     expect(gc.timeout).toBe(9999);
@@ -681,4 +678,120 @@ describe('ModelsConfig', () => {
     expect(modelsConfig.getModel()).toBe('updated-model');
     expect(modelsConfig.getGenerationConfig().model).toBe('updated-model');
   });
+
+  describe('getAllAvailableModels', () => {
+    it('should return all models across all authTypes', () => {
+      const modelProvidersConfig: ModelProvidersConfig = {
+        openai: [
+          {
+            id: 'openai-model-1',
+            name: 'OpenAI Model 1',
+            baseUrl: 'https://api.openai.com/v1',
+            envKey: 'OPENAI_API_KEY',
+          },
+          {
+            id: 'openai-model-2',
+            name: 'OpenAI Model 2',
+            baseUrl: 'https://api.openai.com/v1',
+            envKey: 'OPENAI_API_KEY',
+          },
+        ],
+        anthropic: [
+          {
+            id: 'anthropic-model-1',
+            name: 'Anthropic Model 1',
+            baseUrl: 'https://api.anthropic.com/v1',
+            envKey: 'ANTHROPIC_API_KEY',
+          },
+        ],
+        gemini: [
+          {
+            id: 'gemini-model-1',
+            name: 'Gemini Model 1',
+            baseUrl: 'https://generativelanguage.googleapis.com/v1',
+            envKey: 'GEMINI_API_KEY',
+          },
+        ],
+      };
+
+      const modelsConfig = new ModelsConfig({
+        modelProvidersConfig,
+      });
+
+      const allModels = modelsConfig.getAllAvailableModels();
+
+      // Should include qwen-oauth models (hard-coded)
+      const qwenModels = allModels.filter(
+        (m) => m.authType === AuthType.QWEN_OAUTH,
+      );
+      expect(qwenModels.length).toBeGreaterThan(0);
+
+      // Should include openai models
+      const openaiModels = allModels.filter(
+        (m) => m.authType === AuthType.USE_OPENAI,
+      );
+      expect(openaiModels.length).toBe(2);
+      expect(openaiModels.map((m) => m.id)).toContain('openai-model-1');
+      expect(openaiModels.map((m) => m.id)).toContain('openai-model-2');
+
+      // Should include anthropic models
+      const anthropicModels = allModels.filter(
+        (m) => m.authType === AuthType.USE_ANTHROPIC,
+      );
+      expect(anthropicModels.length).toBe(1);
+      expect(anthropicModels[0].id).toBe('anthropic-model-1');
+
+      // Should include gemini models
+      const geminiModels = allModels.filter(
+        (m) => m.authType === AuthType.USE_GEMINI,
+      );
+      expect(geminiModels.length).toBe(1);
+      expect(geminiModels[0].id).toBe('gemini-model-1');
+    });
+
+    it('should return empty array when no models are registered', () => {
+      const modelsConfig = new ModelsConfig();
+
+      const allModels = modelsConfig.getAllAvailableModels();
+
+      // Should still include qwen-oauth models (hard-coded)
+      expect(allModels.length).toBeGreaterThan(0);
+      const qwenModels = allModels.filter(
+        (m) => m.authType === AuthType.QWEN_OAUTH,
+      );
+      expect(qwenModels.length).toBeGreaterThan(0);
+    });
+
+    it('should return models with correct structure', () => {
+      const modelProvidersConfig: ModelProvidersConfig = {
+        openai: [
+          {
+            id: 'test-model',
+            name: 'Test Model',
+            description: 'A test model',
+            baseUrl: 'https://api.example.com/v1',
+            envKey: 'TEST_API_KEY',
+            capabilities: {
+              vision: true,
+            },
+          },
+        ],
+      };
+
+      const modelsConfig = new ModelsConfig({
+        modelProvidersConfig,
+      });
+
+      const allModels = modelsConfig.getAllAvailableModels();
+      const testModel = allModels.find((m) => m.id === 'test-model');
+
+      expect(testModel).toBeDefined();
+      expect(testModel?.id).toBe('test-model');
+      expect(testModel?.label).toBe('Test Model');
+      expect(testModel?.description).toBe('A test model');
+      expect(testModel?.authType).toBe(AuthType.USE_OPENAI);
+      expect(testModel?.isVision).toBe(true);
+      expect(testModel?.capabilities?.vision).toBe(true);
+    });
+  });
 });
diff --git a/packages/core/src/models/modelsConfig.ts b/packages/core/src/models/modelsConfig.ts
index 36435143f..d33618c21 100644
--- a/packages/core/src/models/modelsConfig.ts
+++ b/packages/core/src/models/modelsConfig.ts
@@ -203,6 +203,18 @@ export class ModelsConfig {
     return this.modelRegistry.getModelsForAuthType(authType);
   }
 
+  /**
+   * Get all available models across all authTypes
+   */
+  getAllAvailableModels(): AvailableModel[] {
+    const allModels: AvailableModel[] = [];
+    for (const authType of Object.values(AuthType)) {
+      const models = this.modelRegistry.getModelsForAuthType(authType);
+      allModels.push(...models);
+    }
+    return allModels;
+  }
+
   /**
    * Check if a model exists for the given authType
    */
@@ -307,6 +319,33 @@ export class ModelsConfig {
     return this.generationConfigSources;
   }
 
+  /**
+   * Merge settings generation config, preserving existing values.
+   * Used when provider-sourced config is cleared but settings should still apply.
+   */
+  mergeSettingsGenerationConfig(
+    settingsGenerationConfig?: Partial<ContentGeneratorConfig>,
+  ): void {
+    if (!settingsGenerationConfig) {
+      return;
+    }
+
+    for (const field of MODEL_GENERATION_CONFIG_FIELDS) {
+      if (
+        !(field in this._generationConfig) &&
+        field in settingsGenerationConfig
+      ) {
+        // eslint-disable-next-line @typescript-eslint/no-explicit-any
+        (this._generationConfig as any)[field] =
+          settingsGenerationConfig[field];
+        this.generationConfigSources[field] = {
+          kind: 'settings',
+          detail: `model.generationConfig.${field}`,
+        };
+      }
+    }
+  }
+
   /**
    * Update credentials in generation config.
    * Sets a flag to prevent syncAfterAuthRefresh from overriding these credentials.
@@ -314,12 +353,20 @@ export class ModelsConfig {
    * When credentials are manually set, we clear all provider-sourced configuration
    * to maintain provider atomicity (either fully applied or not at all).
    * Other layers (CLI, env, settings, defaults) will participate in resolve.
+   *
+   * @param settingsGenerationConfig Optional generation config from settings.json
+   *                                  to merge after clearing provider-sourced config.
+   *                                  This ensures settings.model.generationConfig fields
+   *                                  (e.g., samplingParams, timeout) are preserved.
    */
-  updateCredentials(credentials: {
-    apiKey?: string;
-    baseUrl?: string;
-    model?: string;
-  }): void {
+  updateCredentials(
+    credentials: {
+      apiKey?: string;
+      baseUrl?: string;
+      model?: string;
+    },
+    settingsGenerationConfig?: Partial<ContentGeneratorConfig>,
+  ): void {
     /**
      * If any fields are updated here, we treat the resulting config as manually overridden
      * and avoid applying modelProvider defaults during the next auth refresh.
@@ -359,6 +406,14 @@ export class ModelsConfig {
     this.strictModelProviderSelection = false;
     // Clear apiKeyEnvKey to prevent validation from requiring environment variable
     this._generationConfig.apiKeyEnvKey = undefined;
+
+    // After clearing provider-sourced config, merge settings.model.generationConfig
+    // to ensure fields like samplingParams, timeout, etc. are preserved.
+    // This follows the resolution strategy where settings.model.generationConfig
+    // has lower priority than programmatic overrides but should still be applied.
+    if (settingsGenerationConfig) {
+      this.mergeSettingsGenerationConfig(settingsGenerationConfig);
+    }
   }
 
   /**
@@ -587,50 +642,88 @@ export class ModelsConfig {
   }
 
   /**
-   * Called by Config.refreshAuth to sync state after auth refresh.
-   *
-   * IMPORTANT: If credentials were manually set via updateCredentials(),
-   * we should NOT override them with modelProvider defaults.
-   * This handles the case where user inputs credentials via OpenAIKeyPrompt
-   * after removing environment variables for a previously selected model.
+   * Sync state after auth refresh with fallback strategy:
+   * 1. If modelId can be found in modelRegistry, use the config from modelRegistry.
+   * 2. Otherwise, if existing credentials exist in resolved generationConfig from other sources
+   *    (not modelProviders), preserve them and update authType/modelId only.
+   * 3. Otherwise, fall back to default model for the authType.
+   * 4. If no default is available, leave the generationConfig incomplete and let
+   *    resolveContentGeneratorConfigWithSources throw exceptions as expected.
    */
   syncAfterAuthRefresh(authType: AuthType, modelId?: string): void {
-    // Check if we have manually set credentials that should be preserved
-    const preserveManualCredentials = this.hasManualCredentials;
+    this.strictModelProviderSelection = false;
+    const previousAuthType = this.currentAuthType;
+    this.currentAuthType = authType;
 
-    // If credentials were manually set, don't apply modelProvider defaults
-    // Just update the authType and preserve the manually set credentials
-    if (preserveManualCredentials && authType === AuthType.USE_OPENAI) {
-      this.strictModelProviderSelection = false;
-      this.currentAuthType = authType;
+    // Step 1: If modelId exists in registry, always use config from modelRegistry
+    // Manual credentials won't have a modelId that matches a provider model (handleAuthSelect prevents it),
+    // so if modelId exists in registry, we should always use provider config.
+    // This handles provider switching even within the same authType.
+    if (modelId && this.modelRegistry.hasModel(authType, modelId)) {
+      const resolved = this.modelRegistry.getModel(authType, modelId);
+      if (resolved) {
+        this.applyResolvedModelDefaults(resolved);
+        this.strictModelProviderSelection = true;
+        return;
+      }
+    }
+
+    // Step 2: Check if there are existing credentials from other sources (not modelProviders)
+    const apiKeySource = this.generationConfigSources['apiKey'];
+    const baseUrlSource = this.generationConfigSources['baseUrl'];
+    const hasExistingCredentials =
+      (this._generationConfig.apiKey &&
+        apiKeySource?.kind !== 'modelProviders') ||
+      (this._generationConfig.baseUrl &&
+        baseUrlSource?.kind !== 'modelProviders');
+
+    // Only preserve credentials if:
+    // 1. AuthType hasn't changed (credentials are authType-specific), AND
+    // 2. The modelId doesn't exist in the registry (if it did, we would have used provider config in Step 1), AND
+    // 3. Either:
+    //    a. We have manual credentials (set via updateCredentials), OR
+    //    b. We have existing credentials
+    // Note: Even if authType hasn't changed, switching to a different provider model (that exists in registry)
+    // will use provider config (Step 1), not preserve old credentials. This ensures credentials change when
+    // switching providers, independent of authType changes.
+    const isAuthTypeChange = previousAuthType !== authType;
+    const shouldPreserveCredentials =
+      !isAuthTypeChange &&
+      (modelId === undefined ||
+        !this.modelRegistry.hasModel(authType, modelId)) &&
+      (this.hasManualCredentials || hasExistingCredentials);
+
+    if (shouldPreserveCredentials) {
+      // Preserve existing credentials, just update authType and modelId if provided
       if (modelId) {
         this._generationConfig.model = modelId;
+        if (!this.generationConfigSources['model']) {
+          this.generationConfigSources['model'] = {
+            kind: 'programmatic',
+            detail: 'auth refresh (preserved credentials)',
+          };
+        }
       }
       return;
     }
 
-    this.strictModelProviderSelection = false;
+    // Step 3: Fall back to default model for the authType
+    const defaultModel =
+      this.modelRegistry.getDefaultModelForAuthType(authType);
+    if (defaultModel) {
+      this.applyResolvedModelDefaults(defaultModel);
+      return;
+    }
 
-    if (modelId && this.modelRegistry.hasModel(authType, modelId)) {
-      const resolved = this.modelRegistry.getModel(authType, modelId);
-      if (resolved) {
-        // Ensure applyResolvedModelDefaults can correctly apply authType-specific
-        // behavior (e.g., Qwen OAuth placeholder token) by setting currentAuthType
-        // before applying defaults.
-        this.currentAuthType = authType;
-        this.applyResolvedModelDefaults(resolved);
-      }
-    } else {
-      // If the provided modelId doesn't exist in the registry for the new authType,
-      // use the default model for that authType instead of keeping the old model.
-      // This handles the case where switching from one authType (e.g., OPENAI with
-      // env vars) to another (e.g., qwen-oauth) - we should use the default model
-      // for the new authType, not the old model.
-      this.currentAuthType = authType;
-      const defaultModel =
-        this.modelRegistry.getDefaultModelForAuthType(authType);
-      if (defaultModel) {
-        this.applyResolvedModelDefaults(defaultModel);
+    // Step 4: No default available - leave generationConfig incomplete
+    // resolveContentGeneratorConfigWithSources will throw exceptions as expected
+    if (modelId) {
+      this._generationConfig.model = modelId;
+      if (!this.generationConfigSources['model']) {
+        this.generationConfigSources['model'] = {
+          kind: 'programmatic',
+          detail: 'auth refresh (no default model)',
+        };
       }
     }
   }
diff --git a/packages/core/src/qwen/qwenOAuth2.test.ts b/packages/core/src/qwen/qwenOAuth2.test.ts
index 6596e12d3..920ca85e3 100644
--- a/packages/core/src/qwen/qwenOAuth2.test.ts
+++ b/packages/core/src/qwen/qwenOAuth2.test.ts
@@ -751,6 +751,7 @@ describe('getQwenOAuthClient', () => {
   beforeEach(() => {
     mockConfig = {
       isBrowserLaunchSuppressed: vi.fn().mockReturnValue(false),
+      isInteractive: vi.fn().mockReturnValue(true),
     } as unknown as Config;
 
     originalFetch = global.fetch;
@@ -839,9 +840,7 @@ describe('getQwenOAuthClient', () => {
           requireCachedCredentials: true,
         }),
       ),
-    ).rejects.toThrow(
-      'No cached Qwen-OAuth credentials found. Please re-authenticate.',
-    );
+    ).rejects.toThrow('Please use /auth to re-authenticate.');
 
     expect(global.fetch).not.toHaveBeenCalled();
 
@@ -1007,6 +1006,7 @@ describe('getQwenOAuthClient - Enhanced Error Scenarios', () => {
   beforeEach(() => {
     mockConfig = {
       isBrowserLaunchSuppressed: vi.fn().mockReturnValue(false),
+      isInteractive: vi.fn().mockReturnValue(true),
     } as unknown as Config;
 
     originalFetch = global.fetch;
@@ -1202,6 +1202,7 @@ describe('authWithQwenDeviceFlow - Comprehensive Testing', () => {
   beforeEach(() => {
     mockConfig = {
       isBrowserLaunchSuppressed: vi.fn().mockReturnValue(false),
+      isInteractive: vi.fn().mockReturnValue(true),
     } as unknown as Config;
 
     originalFetch = global.fetch;
@@ -1405,6 +1406,7 @@ describe('Browser Launch and Error Handling', () => {
   beforeEach(() => {
     mockConfig = {
       isBrowserLaunchSuppressed: vi.fn().mockReturnValue(false),
+      isInteractive: vi.fn().mockReturnValue(true),
     } as unknown as Config;
 
     originalFetch = global.fetch;
@@ -2043,6 +2045,7 @@ describe('SharedTokenManager Integration in QwenOAuth2Client', () => {
   it('should handle TokenManagerError types correctly in getQwenOAuthClient', async () => {
     const mockConfig = {
       isBrowserLaunchSuppressed: vi.fn().mockReturnValue(true),
+      isInteractive: vi.fn().mockReturnValue(true),
     } as unknown as Config;
 
     // Test different TokenManagerError types
diff --git a/packages/core/src/qwen/qwenOAuth2.ts b/packages/core/src/qwen/qwenOAuth2.ts
index ab89cdfcf..b18c0319d 100644
--- a/packages/core/src/qwen/qwenOAuth2.ts
+++ b/packages/core/src/qwen/qwenOAuth2.ts
@@ -516,9 +516,7 @@ export async function getQwenOAuthClient(
     }
 
     if (options?.requireCachedCredentials) {
-      throw new Error(
-        'No cached Qwen-OAuth credentials found. Please re-authenticate.',
-      );
+      throw new Error('Please use /auth to re-authenticate.');
     }
 
     // If we couldn't obtain valid credentials via SharedTokenManager, fall back to
@@ -740,11 +738,9 @@ async function authWithQwenDeviceFlow(
     // Emit device authorization event for UI integration immediately
     qwenOAuth2Events.emit(QwenOAuth2Event.AuthUri, deviceAuth);
 
-    // Always show the fallback message in non-interactive environments to ensure
-    // users can see the authorization URL even if browser launching is attempted.
-    // This is critical for headless/remote environments where browser launching
-    // may silently fail without throwing an error.
-    showFallbackMessage(deviceAuth.verification_uri_complete);
+    if (config.isBrowserLaunchSuppressed() || !config.isInteractive()) {
+      showFallbackMessage(deviceAuth.verification_uri_complete);
+    }
 
     // Try to open browser if not suppressed
     if (!config.isBrowserLaunchSuppressed()) {