diff --git a/packages/core/src/models/content-generator-config.test.ts b/packages/core/src/models/content-generator-config.test.ts
new file mode 100644
index 000000000..e090d0daf
--- /dev/null
+++ b/packages/core/src/models/content-generator-config.test.ts
@@ -0,0 +1,243 @@
+/**
+ * @license
+ * Copyright 2025 Qwen
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { describe, it, expect, vi, beforeEach, afterEach } from 'vitest';
+import {
+  buildAgentContentGeneratorConfig,
+  resolveCredentialField,
+} from './content-generator-config.js';
+import type { ContentGeneratorConfig } from '../core/contentGenerator.js';
+import type { Config } from '../config/config.js';
+import type { ResolvedModelConfig } from './types.js';
+
+function createMockConfig(
+  parentConfig: ContentGeneratorConfig,
+  resolvedModel?: ResolvedModelConfig,
+) {
+  return {
+    getContentGeneratorConfig: () => parentConfig,
+    getModelsConfig: () => ({
+      getResolvedModel: vi.fn().mockReturnValue(resolvedModel),
+    }),
+  } as unknown as Config;
+}
+
+describe('buildAgentContentGeneratorConfig', () => {
+  const parentConfig: ContentGeneratorConfig = {
+    model: 'parent-model',
+    authType: 'openai' as ContentGeneratorConfig['authType'],
+    apiKey: 'parent-key',
+    apiKeyEnvKey: 'PARENT_KEY_ENV',
+    baseUrl: 'https://parent.example.com',
+    samplingParams: { temperature: 0.7, top_p: 0.9 },
+    reasoning: { effort: 'high' as const },
+    timeout: 30000,
+    maxRetries: 3,
+    contextWindowSize: 128000,
+    extra_body: { custom: 'value' },
+  };
+
+  describe('same-provider, bare model ID, no registry match', () => {
+    it('should override the model but keep parent generation config', () => {
+      const config = createMockConfig(parentConfig);
+
+      const result = buildAgentContentGeneratorConfig(config, 'custom-model', {
+        authType: 'openai',
+      });
+
+      expect(result.model).toBe('custom-model');
+      expect(result.authType).toBe('openai');
+      expect(result.apiKey).toBe('parent-key');
+      expect(result.baseUrl).toBe('https://parent.example.com');
+      expect(result.apiKeyEnvKey).toBe('PARENT_KEY_ENV');
+      // Generation config inherited from parent
+      expect(result.samplingParams).toEqual({ temperature: 0.7, top_p: 0.9 });
+      expect(result.reasoning).toEqual({ effort: 'high' });
+      expect(result.timeout).toBe(30000);
+      expect(result.maxRetries).toBe(3);
+      expect(result.contextWindowSize).toBe(128000);
+      expect(result.extra_body).toEqual({ custom: 'value' });
+    });
+  });
+
+  describe('cross-provider, no registry match', () => {
+    it('should clear generation config fields to prevent leaking', () => {
+      const config = createMockConfig(parentConfig);
+
+      const result = buildAgentContentGeneratorConfig(config, 'claude-sonnet', {
+        authType: 'anthropic',
+      });
+
+      expect(result.model).toBe('claude-sonnet');
+      expect(result.authType).toBe('anthropic');
+      // Generation config cleared
+      expect(result.samplingParams).toBeUndefined();
+      expect(result.reasoning).toBeUndefined();
+      expect(result.timeout).toBeUndefined();
+      expect(result.maxRetries).toBeUndefined();
+      expect(result.contextWindowSize).toBeUndefined();
+      expect(result.extra_body).toBeUndefined();
+      // Parent credentials NOT inherited (different provider)
+      expect(result.apiKeyEnvKey).toBeUndefined();
+    });
+
+    it('should use explicit auth overrides', () => {
+      const config = createMockConfig(parentConfig);
+
+      const result = buildAgentContentGeneratorConfig(config, 'claude-sonnet', {
+        authType: 'anthropic',
+        apiKey: 'explicit-key',
+        baseUrl: 'https://explicit.example.com',
+      });
+
+      expect(result.apiKey).toBe('explicit-key');
+      expect(result.baseUrl).toBe('https://explicit.example.com');
+    });
+  });
+
+  describe('cross-provider with env var fallback', () => {
+    beforeEach(() => {
+      vi.stubEnv('ANTHROPIC_API_KEY', 'env-anthropic-key');
+      vi.stubEnv('ANTHROPIC_BASE_URL', 'https://env-anthropic.example.com');
+    });
+
+    afterEach(() => {
+      vi.unstubAllEnvs();
+    });
+
+    it('should resolve credentials from provider env vars', () => {
+      const config = createMockConfig(parentConfig);
+
+      const result = buildAgentContentGeneratorConfig(config, 'claude-sonnet', {
+        authType: 'anthropic',
+      });
+
+      expect(result.apiKey).toBe('env-anthropic-key');
+    });
+  });
+
+  describe('with registry-resolved model', () => {
+    const resolvedModel: ResolvedModelConfig = {
+      id: 'registry-model-id',
+      name: 'Registry Model',
+      authType: 'anthropic' as ResolvedModelConfig['authType'],
+      baseUrl: 'https://registry.example.com',
+      envKey: 'REGISTRY_API_KEY',
+      generationConfig: {
+        samplingParams: { temperature: 0.5 },
+        contextWindowSize: 200000,
+        reasoning: { effort: 'medium' as const },
+      },
+      capabilities: {},
+    };
+
+    beforeEach(() => {
+      vi.stubEnv('REGISTRY_API_KEY', 'registry-key-from-env');
+    });
+
+    afterEach(() => {
+      vi.unstubAllEnvs();
+    });
+
+    it('should apply registry generation config over cleared parent config', () => {
+      const config = createMockConfig(parentConfig, resolvedModel);
+
+      const result = buildAgentContentGeneratorConfig(
+        config,
+        'registry-model-id',
+        { authType: 'anthropic' },
+      );
+
+      expect(result.model).toBe('registry-model-id');
+      expect(result.authType).toBe('anthropic');
+      expect(result.baseUrl).toBe('https://registry.example.com');
+      expect(result.apiKey).toBe('registry-key-from-env');
+      expect(result.apiKeyEnvKey).toBe('REGISTRY_API_KEY');
+      // Registry generation config applied
+      expect(result.samplingParams).toEqual({ temperature: 0.5 });
+      expect(result.contextWindowSize).toBe(200000);
+      expect(result.reasoning).toEqual({ effort: 'medium' });
+      // Fields not in registry stay cleared (cross-provider)
+      expect(result.extra_body).toBeUndefined();
+    });
+
+    it('should prefer explicit auth overrides over registry values', () => {
+      const config = createMockConfig(parentConfig, resolvedModel);
+
+      const result = buildAgentContentGeneratorConfig(
+        config,
+        'registry-model-id',
+        {
+          authType: 'anthropic',
+          apiKey: 'explicit-key',
+          baseUrl: 'https://explicit.example.com',
+        },
+      );
+
+      expect(result.apiKey).toBe('explicit-key');
+      expect(result.baseUrl).toBe('https://explicit.example.com');
+    });
+  });
+
+  describe('edge cases', () => {
+    it('should fall back to parent model when modelId is undefined', () => {
+      const config = createMockConfig(parentConfig);
+
+      const result = buildAgentContentGeneratorConfig(config, undefined, {
+        authType: 'openai',
+      });
+
+      expect(result.model).toBe('parent-model');
+    });
+
+    it('should keep proxy and userAgent from parent regardless of provider', () => {
+      const configWithProxy: ContentGeneratorConfig = {
+        ...parentConfig,
+        proxy: 'http://proxy.example.com',
+        userAgent: 'custom-agent/1.0',
+      };
+      const config = createMockConfig(configWithProxy);
+
+      const result = buildAgentContentGeneratorConfig(config, 'claude-sonnet', {
+        authType: 'anthropic',
+      });
+
+      expect(result.proxy).toBe('http://proxy.example.com');
+      expect(result.userAgent).toBe('custom-agent/1.0');
+    });
+  });
+});
+
+describe('resolveCredentialField', () => {
+  afterEach(() => {
+    vi.unstubAllEnvs();
+  });
+
+  it('should prefer explicit value', () => {
+    expect(
+      resolveCredentialField('explicit', 'inherited', 'openai', 'apiKey'),
+    ).toBe('explicit');
+  });
+
+  it('should fall back to inherited value', () => {
+    expect(
+      resolveCredentialField(undefined, 'inherited', 'openai', 'apiKey'),
+    ).toBe('inherited');
+  });
+
+  it('should fall back to env var', () => {
+    vi.stubEnv('OPENAI_API_KEY', 'env-key');
+    expect(
+      resolveCredentialField(undefined, undefined, 'openai', 'apiKey'),
+    ).toBe('env-key');
+  });
+
+  it('should return undefined when nothing matches', () => {
+    expect(
+      resolveCredentialField(undefined, undefined, 'unknown', 'apiKey'),
+    ).toBeUndefined();
+  });
+});