diff --git a/src/modules/ai-runtime/quiz-execution-router.spec.ts b/src/modules/ai-runtime/quiz-execution-router.spec.ts
new file mode 100644
index 0000000..4bfa00c
--- /dev/null
+++ b/src/modules/ai-runtime/quiz-execution-router.spec.ts
@@ -0,0 +1,159 @@
+import { Test, TestingModule } from '@nestjs/testing';
+import { QuizExecutionRouter } from './quiz-execution-router';
+import { FeatureFlagService } from '../config/feature-flag.service';
+import { QuizGenerationSnapshotBuilder } from '../ai-job/quiz-generation-snapshot-builder';
+import { AiJobCreationService } from '../ai-job/ai-job-creation.service';
+import { UserAiService } from './user-ai.service';
+import * as crypto from 'crypto';
+
+function dto(overrides?: any) {
+  return {
+    jobType: 'quiz_generation',
+    targetType: 'knowledge_base',
+    targetId: 'kb-001',
+    questionCount: 3,
+    questionTypes: ['choice', 'judge'],
+    difficultyLevel: 'medium',
+    ...overrides,
+  };
+}
+
+describe('QuizExecutionRouter', () => {
+  let router: QuizExecutionRouter;
+  let mockFlag: any;
+  let mockSnapshot: any;
+  let mockCreation: any;
+  let mockLegacy: any;
+
+  beforeEach(async () => {
+    mockFlag = { isEnabled: jest.fn().mockResolvedValue(true) };
+    mockSnapshot = {
+      build: jest.fn().mockResolvedValue({
+        schemaVersion: 'v1',
+        snapshot: { userId: 'u1', targetId: 'kb-001', questionCount: 3 },
+      }),
+    };
+    mockCreation = {
+      createJob: jest.fn().mockImplementation(async (input: any) => ({
+        id: 'job-' + Math.random().toString(36).slice(2, 8),
+        createdAt: new Date(),
+        ...input,
+      })),
+    };
+    mockLegacy = { createAnalysisJob: jest.fn() };
+
+    const module: TestingModule = await Test.createTestingModule({
+      providers: [
+        QuizExecutionRouter,
+        { provide: FeatureFlagService, useValue: mockFlag },
+        { provide: QuizGenerationSnapshotBuilder, useValue: mockSnapshot },
+        { provide: AiJobCreationService, useValue: mockCreation },
+        { provide: UserAiService, useValue: mockLegacy },
+      ],
+    }).compile();
+
+    router = module.get(QuizExecutionRouter);
+    jest.spyOn(require('@nestjs/common').Logger.prototype, 'log').mockImplementation(() => {});
+    jest.spyOn(require('@nestjs/common').Logger.prototype, 'warn').mockImplementation(() => {});
+  });
+
+  describe('幂等：显式 idempotencyKey', () => {
+    it('相同 idempotencyKey → 相同 jobId', async () => {
+      const key = 'my-stable-key-001';
+      mockCreation.createJob.mockResolvedValue({ id: 'job-stable', createdAt: new Date() });
+
+      const r1 = await router.generateQuiz('u1', dto({ idempotencyKey: key }));
+      const r2 = await router.generateQuiz('u1', dto({ idempotencyKey: key }));
+
+      // Same idempotencyKey passed to creation service
+      const calls = mockCreation.createJob.mock.calls;
+      expect(calls[0][0].idempotencyKey).toBe(`quiz-generation:${key}`);
+      expect(calls[1][0].idempotencyKey).toBe(`quiz-generation:${key}`);
+    });
+  });
+
+  describe('幂等：无 idempotencyKey（内容哈希 + 窗口）', () => {
+    it('相同参数 → 相同内容哈希（窗口内）', async () => {
+      const r1 = await router.generateQuiz('u1', dto());
+      const r2 = await router.generateQuiz('u1', dto());
+
+      // Same content → same idempotencyKey (same window)
+      const calls = mockCreation.createJob.mock.calls;
+      expect(calls[0][0].idempotencyKey).toBe(calls[1][0].idempotencyKey);
+    });
+
+    it('不同参数 → 不同内容哈希', async () => {
+      const r1 = await router.generateQuiz('u1', dto({ questionCount: 3 }));
+      const r2 = await router.generateQuiz('u1', dto({ questionCount: 5 }));
+
+      const calls = mockCreation.createJob.mock.calls;
+      // Different questionCount → different hash
+      expect(calls[0][0].idempotencyKey).not.toBe(calls[1][0].idempotencyKey);
+    });
+
+    it('questionTypes 排序后相同 → 相同哈希', async () => {
+      // Unsorted input should normalize
+      await router.generateQuiz('u1', dto({ questionTypes: ['judge', 'choice'] }));
+      await router.generateQuiz('u1', dto({ questionTypes: ['choice', 'judge'] }));
+
+      const calls = mockCreation.createJob.mock.calls;
+      expect(calls[0][0].idempotencyKey).toBe(calls[1][0].idempotencyKey);
+    });
+  });
+
+  describe('幂等：不包含 Date.now / random', () => {
+    it('idempotencyKey 不含随机值格式', async () => {
+      // Run 5 times with same params
+      const keys = new Set<string>();
+      for (let i = 0; i < 5; i++) {
+        const result = await router.generateQuiz('u1', dto());
+        const key = mockCreation.createJob.mock.calls[i][0].idempotencyKey;
+        keys.add(key);
+      }
+      // Same params within same window → all identical keys
+      expect(keys.size).toBe(1);
+
+      const theKey = [...keys][0];
+      // Must match quiz-generation:<sha256-24chars>:w<window>
+      expect(theKey).toMatch(/^quiz-generation:[0-9a-f]{24}:w\d+$/);
+    });
+  });
+
+  describe('主动重新生成', () => {
+    it('新 idempotencyKey → 新 Job', async () => {
+      const r1 = await router.generateQuiz('u1', dto({ idempotencyKey: 'gen-1' }));
+      const r2 = await router.generateQuiz('u1', dto({ idempotencyKey: 'gen-2' }));
+
+      const calls = mockCreation.createJob.mock.calls;
+      expect(calls[0][0].idempotencyKey).toBe('quiz-generation:gen-1');
+      expect(calls[1][0].idempotencyKey).toBe('quiz-generation:gen-2');
+      expect(calls[0][0].idempotencyKey).not.toBe(calls[1][0].idempotencyKey);
+    });
+  });
+
+  describe('Legacy 兼容', () => {
+    it('legacy 模式不经过 Unified', async () => {
+      mockFlag.isEnabled.mockResolvedValue(false);
+      mockLegacy.createAnalysisJob.mockResolvedValue({ jobId: 'legacy-1' });
+
+      const result = await router.generateQuiz('u1', dto());
+
+      expect(result).toEqual({ jobId: 'legacy-1' });
+      expect(mockCreation.createJob).not.toHaveBeenCalled();
+    });
+  });
+
+  describe('contentKey 确定性', () => {
+    it('submissionId 可由 contentKey 验证', async () => {
+      // Build expected key manually
+      const types = ['choice', 'judge'].sort().join(',');
+      const normalized = ['knowledge_base', 'kb-001', '3', types, 'medium'].join('|');
+      const expectedHash = crypto.createHash('sha256').update(normalized).digest('hex').substring(0, 24);
+
+      await router.generateQuiz('u1', dto());
+
+      const key = mockCreation.createJob.mock.calls[0][0].idempotencyKey;
+      expect(key).toContain(expectedHash);
+    });
+  });
+});
diff --git a/src/modules/ai-runtime/quiz-execution-router.ts b/src/modules/ai-runtime/quiz-execution-router.ts
index ed04423..15fcd42 100644
--- a/src/modules/ai-runtime/quiz-execution-router.ts
+++ b/src/modules/ai-runtime/quiz-execution-router.ts
@@ -1,4 +1,5 @@
 import { Injectable, Logger } from '@nestjs/common';
+import * as crypto from 'crypto';
 import { FeatureFlagService } from '../config/feature-flag.service';
 import { QuizGenerationSnapshotBuilder } from '../ai-job/quiz-generation-snapshot-builder';
 import type { QuizGenerationSnapshotInput } from '../ai-job/quiz-generation-snapshot-builder';
@@ -7,15 +8,23 @@ import { UserAiService } from './user-ai.service';
 import type { CreateAnalysisJobDto } from './user-ai.dto';
 
 /**
- * M-AI-07-05: Quiz Execution Router
+ * M-AI-07-05 / M-AI-07-CLEANUP: Quiz Execution Router
  *
  * 根据 QUIZ_GENERATION_ENGINE_MODE Feature Flag 路由 Quiz 生成请求。
  *   - 'legacy'  → UserAiService.createAnalysisJob()
  *   - 'unified' → SnapshotBuilder → AiJobCreationService
+ *
+ * 幂等策略（M-AI-07-CLEANUP）：
+ *   Priority 1: 客户端显式 idempotencyKey → 直接使用
+ *   Priority 2: 规范化内容哈希 + 10min 窗口 → 兼容旧客户端重试
+ *   主动重新生成：客户端提供新 idempotencyKey
  */
 
 const FLAG_NAME = 'QUIZ_GENERATION_ENGINE_MODE';
 
+/** 短窗口去重窗口（毫秒），仅用于旧客户端兼容 */
+const IDEMPOTENCY_WINDOW_MS = 10 * 60 * 1000; // 10 minutes
+
 @Injectable()
 export class QuizExecutionRouter {
   private readonly logger = new Logger(QuizExecutionRouter.name);
@@ -28,7 +37,6 @@ export class QuizExecutionRouter {
   ) {}
 
   async generateQuiz(userId: string, dto: CreateAnalysisJobDto) {
-    // 1. 判断模式
     const useUnified = await this.shouldUseUnified(userId);
 
     if (!useUnified) {
@@ -36,17 +44,34 @@ export class QuizExecutionRouter {
       return this.legacyService.createAnalysisJob(userId, dto);
     }
 
-    // ═════════════════════════════════════════════════════════
-    // Unified 路径
-    // ═════════════════════════════════════════════════════════
-
     this.logger.log(`QUIZ_GENERATION_ENGINE_MODE=unified for userId=${userId}`);
 
-    // 2. 确定 submissionId（幂等键来源）
-    const submissionId = dto.idempotencyKey ??
-      `${dto.targetType}:${dto.targetId}:${Date.now().toString(36)}`;
+    // ═════════════════════════════════════════════════════════
+    // 幂等标识解析（M-AI-07-CLEANUP）
+    // ═════════════════════════════════════════════════════════
+
+    let effectiveId: string;
+    let idSource: 'client' | 'compatibility_window';
+
+    if (dto.idempotencyKey) {
+      // Priority 1: 客户端显式操作标识
+      effectiveId = dto.idempotencyKey;
+      idSource = 'client';
+    } else {
+      // Priority 2: 规范化内容哈希 + 短窗口（兼容旧客户端重试）
+      const contentKey = this.buildContentKey(dto);
+      const windowTs = Math.floor(Date.now() / IDEMPOTENCY_WINDOW_MS);
+      effectiveId = `${contentKey}:w${windowTs}`;
+      idSource = 'compatibility_window';
+    }
+
+    const submissionId = effectiveId;
+    const idempotencyKey = `quiz-generation:${effectiveId}`;
+
+    // ═════════════════════════════════════════════════════════
+    // Snapshot + Job 创建
+    // ═════════════════════════════════════════════════════════
 
-    // 3. 构建 Snapshot
     const snapshotInput: QuizGenerationSnapshotInput = {
       userId,
       targetType: dto.targetType,
@@ -60,10 +85,6 @@ export class QuizExecutionRouter {
 
     const snapshot = await this.snapshotBuilder.build(snapshotInput);
 
-    // 4. 幂等键
-    const idempotencyKey = dto.idempotencyKey ?? `quiz-generation:${submissionId}`;
-
-    // 5. 通过 AiJobCreationService 创建 Job（原子：Job + Snapshot + Outbox）
     const job = await this.creationService.createJob({
       userId,
       jobType: 'quiz_generation',
@@ -74,22 +95,45 @@ export class QuizExecutionRouter {
       retrySnapshotContent: snapshot as unknown as Record<string, unknown>,
     });
 
+    const isIdempotentHit = job.createdAt?.getTime?.() !== undefined &&
+      (Date.now() - new Date(job.createdAt).getTime()) > 1000;
+
     this.logger.log(
       `Quiz Unified: jobId=${job.id} userId=${userId} ` +
+      `idSource=${idSource} idempotencyHit=${isIdempotentHit} ` +
       `targetType=${dto.targetType} targetId=${dto.targetId} ` +
       `questionCount=${snapshot.snapshot.questionCount}`,
     );
 
-    // 6. 返回兼容响应
     return {
       jobId: job.id,
       status: 'queued',
       engineMode: 'unified' as const,
       lifecycleStatus: 'queued',
-      planId: undefined, // Unified 不创建 QuestionGenerationPlan
+      planId: undefined,
     };
   }
 
+  // ── Private ──
+
+  /**
+   * 构建确定性内容键（SHA-256 前 24 字符）。
+   *
+   * 规范化参数：targetType, targetId, questionCount, questionTypes(sorted), difficultyLevel。
+   * 不包含：时间戳、随机值、完整学习资料、PII。
+   */
+  private buildContentKey(dto: CreateAnalysisJobDto): string {
+    const types = (dto.questionTypes ?? []).slice().sort().join(',');
+    const normalized = [
+      dto.targetType,
+      dto.targetId,
+      String(dto.questionCount ?? 5),
+      types || 'choice,fill,judge',
+      dto.difficultyLevel ?? 'medium',
+    ].join('|');
+    return crypto.createHash('sha256').update(normalized).digest('hex').substring(0, 24);
+  }
+
   private async shouldUseUnified(userId: string): Promise<boolean> {
     try {
       return await this.featureFlag.isEnabled(FLAG_NAME, userId);