diff --git a/miniapp/pages/counseling-request/counseling-request.ts b/miniapp/pages/counseling-request/counseling-request.ts
index 0836224..2870ea1 100644
--- a/miniapp/pages/counseling-request/counseling-request.ts
+++ b/miniapp/pages/counseling-request/counseling-request.ts
@@ -1,5 +1,6 @@
 export {}
 import { request } from '../../utils/requestPromise'
+import api from '../../utils/api'
 const app = getApp<{ globalData: { apiBase: string; token: string } }>();
 
 Page({
@@ -45,6 +46,9 @@ Page({
       return;
     }
     this.setData({ submitting: true, errorMsg: '' });
+    // 幂等键在「一次提交」内保持稳定：网络异常后用户重试复用同一把键，
+    // 后端据此识别为重复投递（重放首次结果）而不是第二次申请。
+    const idempotencyKey = api.idempotencyKey('counseling-apply', serviceType);
     try {
       const res = await request<any>({
         url: `${app.globalData.apiBase}/counseling/services`,
@@ -58,10 +62,13 @@ Page({
           summary,
           requestSource: 'user_self',
           // 幂等键：同一次填写重复提交不会产生两条申请
-          idempotencyKey: `counseling-${serviceType}-${Date.now()}`
+          // 幂等键由 api 层托管（见 onSubmit 开头的说明）
+          idempotencyKey
         }
       });
       if (res.statusCode === 200 && res.data && res.data.success) {
+        // 提交已落地：释放幂等键，下一次申请是新的一次
+        api.releaseIdempotencyKey(idempotencyKey);
         wx.showToast({ title: '申请已提交', icon: 'success' });
         setTimeout(() => wx.redirectTo({ url: '/pages/my-counseling/my-counseling' }), 1500);
       } else {
diff --git a/miniapp/pages/premarital-request/premarital-request.ts b/miniapp/pages/premarital-request/premarital-request.ts
index 3b4d09b..3fa238d 100644
--- a/miniapp/pages/premarital-request/premarital-request.ts
+++ b/miniapp/pages/premarital-request/premarital-request.ts
@@ -1,5 +1,6 @@
 export {}
 import { request } from '../../utils/requestPromise'
+import api from '../../utils/api'
 const app = getApp<{ globalData: { apiBase: string; token: string } }>();
 
 Page({
@@ -22,6 +23,9 @@ Page({
       return;
     }
     this.setData({ submitting: true, errorMsg: '' });
+    // 幂等键在「一次提交」内保持稳定：网络异常后用户重试复用同一把键，
+    // 后端据此识别为重复投递（重放首次结果）而不是第二次申请。
+    const idempotencyKey = api.idempotencyKey('premarital-apply', name);
     try {
       const res = await request<any>({
         url: `${app.globalData.apiBase}/counseling/services`,
@@ -35,10 +39,13 @@ Page({
           requestSource: 'user_self',
           // INV-005：伴侣须**本人**确认。此处只登记受邀伴侣 ID，确认动作由伴侣本人另行完成。
           companionUserId: hasCompanion ? (companionUserId || null) : null,
-          idempotencyKey: `premarital-${name}-${Date.now()}`
+          // 幂等键由 api 层托管（见 onSubmit 开头的说明）
+          idempotencyKey
         }
       });
       if (res.statusCode === 200 && res.data && res.data.success) {
+        // 提交已落地：释放幂等键，下一次申请是新的一次
+        api.releaseIdempotencyKey(idempotencyKey);
         wx.showToast({ title: hasCompanion ? '已提交，伴侣需本人确认' : '申请已提交', icon: 'success' });
         setTimeout(() => wx.redirectTo({ url: '/pages/my-counseling/my-counseling' }), 1800);
       } else {
diff --git a/miniapp/services/activityService.js b/miniapp/services/activityService.js
index 6d96363..63c125b 100644
--- a/miniapp/services/activityService.js
+++ b/miniapp/services/activityService.js
@@ -36,7 +36,7 @@ function getActivityDetail(activityId) {
  * @returns {Promise<{ registrationStatus: 'pending', registrationId: string }>}
  */
 function register(activityId, payload = {}) {
-  const idempotencyKey = `activity-register:${activityId}:${Date.now()}`;
+  const idempotencyKey = api.idempotencyKey('activity-register', activityId);
   return api.post(`/activities/${encodeURIComponent(activityId)}/register`, payload, undefined, idempotencyKey);
 }
 
@@ -66,21 +66,17 @@ function getMyActivities(params = {}) {
  * @param {{ rating: number, content: string }} payload
  * @returns {Promise<{ submitted: true }>}
  */
-function submitFeedback(activityId, payload) {
-  const idempotencyKey = `activity-feedback:${activityId}:${Date.now()}`;
-  return api.post(`/activities/${encodeURIComponent(activityId)}/feedback`, payload, undefined, idempotencyKey);
-}
-
 /**
- * 提交活动互选意向（API_INVENTORY 行 98，AGENTS 第 6 条：单向意向保密）
- * @param {string} activityId
- * @param {{ likedUserIds: string[] }} payload
- * @returns {Promise<{ submitted: true, matchedUserIds: string[] }>}
- *         matchedUserIds 仅包含双向匹配成功的人；未匹配的人不会泄露是否被对方选择。
+ * 提交活动反馈（含表达意向 via interestTargetUserIds）
+ *
+ * 注意：此前的 `submitInterests()` → `POST /activities/{id}/interests`
+ * **后端不存在该端点**（Phase 16 已把表达意向合并进本流程），调用必然 404。
+ * 全仓确认无页面调用方，属设计残留，已删除。若需要独立的互选提交接口，
+ * 须先由产品定义语义并补后端端点。
  */
-function submitInterests(activityId, payload) {
-  const idempotencyKey = `activity-interests:${activityId}:${Date.now()}`;
-  return api.post(`/activities/${encodeURIComponent(activityId)}/interests`, payload, undefined, idempotencyKey);
+function submitFeedback(activityId, payload) {
+  const idempotencyKey = api.idempotencyKey('activity-feedback', activityId);
+  return api.post(`/activities/${encodeURIComponent(activityId)}/feedback`, payload, undefined, idempotencyKey);
 }
 
 module.exports = {
@@ -90,5 +86,4 @@ module.exports = {
   cancelRegistration,
   getMyActivities,
   submitFeedback,
-  submitInterests,
 };
diff --git a/miniapp/services/appealService.js b/miniapp/services/appealService.js
index 6cc7ffb..1b4be4c 100644
--- a/miniapp/services/appealService.js
+++ b/miniapp/services/appealService.js
@@ -18,7 +18,7 @@ const api = require('../utils/api');
 function submitAppeal(payload) {
   // 幂等键：申诉类型 + 关联处置 ID + 当前秒，防止用户多次点击重复提交
   const actionKey = payload.relatedActionId || 'no_action';
-  const idempotencyKey = `appeal:${payload.appealType}:${actionKey}:${Math.floor(Date.now() / 1000)}`;
+  const idempotencyKey = api.idempotencyKey('appeal', `${payload.appealType}:${actionKey}`);
   return api.post('/appeals', payload, undefined, idempotencyKey);
 }
 
diff --git a/miniapp/services/authService.js b/miniapp/services/authService.js
index 0cf794d..95eba59 100644
--- a/miniapp/services/authService.js
+++ b/miniapp/services/authService.js
@@ -36,11 +36,11 @@ function refresh() {
 
 /**
  * 登出（API_INVENTORY 行 11）
- * 幂等：Idempotency-Key = "logout:" + 当前毫秒时间，便于后端去重。
+ * 幂等：键由 api 层托管，网络异常重试时复用同一把，避免后端重复记账。
  * @returns {Promise<void>}
  */
 function logout() {
-  return api.post('/auth/logout', {}, undefined, 'logout:' + Date.now());
+  return api.post('/auth/logout', {}, undefined, api.idempotencyKey('logout'));
 }
 
 module.exports = {
diff --git a/miniapp/services/matchService.js b/miniapp/services/matchService.js
index 380b075..b1d5b03 100644
--- a/miniapp/services/matchService.js
+++ b/miniapp/services/matchService.js
@@ -26,7 +26,7 @@ const api = require('../utils/api');
  * @returns {Promise<import('../types').LikeResult>}
  */
 function like(userId) {
-  const idempotencyKey = `like:${userId}:${Date.now()}`;
+  const idempotencyKey = api.idempotencyKey('like', userId);
   return api.post('/likes', { targetUserId: userId }, undefined, idempotencyKey);
 }
 
@@ -51,7 +51,7 @@ function unlike(userId) {
  * @returns {Promise<void>}
  */
 function pass(userId) {
-  const idempotencyKey = `pass:${userId}:${Date.now()}`;
+  const idempotencyKey = api.idempotencyKey('pass', userId);
   return api.post('/passes', { targetUserId: userId }, undefined, idempotencyKey);
 }
 
@@ -65,7 +65,7 @@ function pass(userId) {
  * @returns {Promise<void>}
  */
 function block(userId, payload = {}) {
-  const idempotencyKey = `block:${userId}:${Date.now()}`;
+  const idempotencyKey = api.idempotencyKey('block', userId);
   return api.post('/blocks', { targetUserId: userId, reason: payload.reason }, undefined, idempotencyKey);
 }
 
@@ -145,7 +145,7 @@ function getMatches(params = {}) {
  * @returns {Promise<void>}
  */
 function unmatch(matchId) {
-  const idempotencyKey = `unmatch:${matchId}:${Date.now()}`;
+  const idempotencyKey = api.idempotencyKey('unmatch', matchId);
   return api.post(`/matches/${encodeURIComponent(matchId)}/unmatch`, {}, undefined, idempotencyKey);
 }
 
@@ -158,7 +158,7 @@ function unmatch(matchId) {
  * @returns {Promise<{ requestId: string, initiatedBy: string, status: 'pending' }>}
  */
 function requestSuccess(matchId) {
-  const idempotencyKey = `success-req:${matchId}:${Date.now()}`;
+  const idempotencyKey = api.idempotencyKey('success-req', matchId);
   return api.post(`/matches/${encodeURIComponent(matchId)}/success/request`, {}, undefined, idempotencyKey);
 }
 
@@ -171,7 +171,7 @@ function requestSuccess(matchId) {
  * @returns {Promise<{ relationshipStatus: string }>}
  */
 function confirmSuccess(matchId) {
-  const idempotencyKey = `success-confirm:${matchId}:${Date.now()}`;
+  const idempotencyKey = api.idempotencyKey('success-confirm', matchId);
   return api.post(`/matches/${encodeURIComponent(matchId)}/success/confirm`, {}, undefined, idempotencyKey);
 }
 
@@ -182,7 +182,7 @@ function confirmSuccess(matchId) {
  * @returns {Promise<void>}
  */
 function declineSuccess(matchId) {
-  const idempotencyKey = `success-decline:${matchId}:${Date.now()}`;
+  const idempotencyKey = api.idempotencyKey('success-decline', matchId);
   return api.post(`/matches/${encodeURIComponent(matchId)}/success/decline`, {}, undefined, idempotencyKey);
 }
 
diff --git a/miniapp/services/matchmakerService.js b/miniapp/services/matchmakerService.js
index ab10fb7..1c433a9 100644
--- a/miniapp/services/matchmakerService.js
+++ b/miniapp/services/matchmakerService.js
@@ -15,7 +15,7 @@ const api = require('../utils/api');
  * @returns {Promise<{ serviceId: string, status: 'submitted' }>}
  */
 function applyService(payload) {
-  const idempotencyKey = `matchmaker-apply:${Date.now()}`;
+  const idempotencyKey = api.idempotencyKey('matchmaker-apply');
   return api.post('/matchmaker/services', payload, undefined, idempotencyKey);
 }
 
diff --git a/miniapp/services/profileService.js b/miniapp/services/profileService.js
index 7df19b2..dcee610 100644
--- a/miniapp/services/profileService.js
+++ b/miniapp/services/profileService.js
@@ -22,7 +22,7 @@ function getProfile() {
  */
 function updateProfile(payload) {
   // PUT 默认幂等：用 userId + 字段指纹作为幂等键，避免重复提交时脏写
-  const idempotencyKey = 'profile-put:' + (payload && payload.userId || 'me') + ':' + Date.now();
+  const idempotencyKey = api.idempotencyKey('profile-put', (payload && payload.userId) || 'me');
   return api.put('/me/profile', payload, undefined, idempotencyKey);
 }
 
@@ -40,7 +40,7 @@ function getPreferences() {
  * @returns {Promise<import('../types').PartnerPreference>}
  */
 function updatePreferences(payload) {
-  const idempotencyKey = 'preferences-put:' + Date.now();
+  const idempotencyKey = api.idempotencyKey('preferences-put');
   return api.put('/me/preferences', payload, undefined, idempotencyKey);
 }
 
@@ -67,7 +67,7 @@ function deletePhoto(photoId) {
  * @returns {Promise<{ avatarUrl: string }>}
  */
 function setMainPhoto(photoId) {
-  const idempotencyKey = 'photo-main:' + photoId + ':' + Date.now();
+  const idempotencyKey = api.idempotencyKey('photo-main', photoId);
   return api.put(`/me/photos/${photoId}/main`, {}, undefined, idempotencyKey);
 }
 
@@ -94,7 +94,7 @@ function getPrivacySettings() {
  * @returns {Promise<import('../types').PrivacySettings>}
  */
 function updatePrivacySettings(payload) {
-  const idempotencyKey = 'privacy-put:' + Date.now();
+  const idempotencyKey = api.idempotencyKey('privacy-put');
   return api.put('/me/privacy-settings', payload, undefined, idempotencyKey);
 }
 
@@ -129,7 +129,7 @@ function getReviewStatus() {
  * @returns {Promise<{ reviewStatus: 'pending', submittedAt: number }>}
  */
 function submitReview() {
-  const idempotencyKey = 'review-submit:' + Date.now();
+  const idempotencyKey = api.idempotencyKey('review-submit');
   return api.post('/me/profile/submit-review', {}, undefined, idempotencyKey);
 }
 
@@ -147,7 +147,7 @@ function getRelationshipStatus() {
  * @returns {Promise<{ status: 'paused', recommendationEnabled: boolean }>}
  */
 function pauseSearching() {
-  const idempotencyKey = 'rel-pause:' + Date.now();
+  const idempotencyKey = api.idempotencyKey('rel-pause');
   return api.patch('/me/relationship-status', { status: 'paused' }, undefined, idempotencyKey);
 }
 
@@ -156,7 +156,7 @@ function pauseSearching() {
  * @returns {Promise<{ status: 'searching', recommendationEnabled: boolean }>}
  */
 function resumeSearching() {
-  const idempotencyKey = 'rel-resume:' + Date.now();
+  const idempotencyKey = api.idempotencyKey('rel-resume');
   return api.patch('/me/relationship-status', { status: 'searching' }, undefined, idempotencyKey);
 }
 
@@ -165,7 +165,7 @@ function resumeSearching() {
  * @returns {Promise<{ status: 'getting_to_know', recommendationEnabled: boolean }>}
  */
 function markGettingToKnow() {
-  const idempotencyKey = 'rel-gtk:' + Date.now();
+  const idempotencyKey = api.idempotencyKey('rel-gtk');
   return api.patch('/me/relationship-status', { status: 'getting_to_know' }, undefined, idempotencyKey);
 }
 
diff --git a/miniapp/services/safetyService.js b/miniapp/services/safetyService.js
index d4a7769..f3ae9dc 100644
--- a/miniapp/services/safetyService.js
+++ b/miniapp/services/safetyService.js
@@ -21,7 +21,7 @@ const api = require('../utils/api');
  */
 function submitReport(payload) {
   // 幂等键：目标用户 + 举报类型 + 当前秒，防止用户多次点击重复提交
-  const idempotencyKey = `report:${payload.targetUserId}:${payload.reportType}:${Math.floor(Date.now() / 1000)}`;
+  const idempotencyKey = api.idempotencyKey('report', `${payload.targetUserId}:${payload.reportType}`);
   return api.post('/reports', payload, undefined, idempotencyKey);
 }
 
diff --git a/miniapp/services/verificationService.js b/miniapp/services/verificationService.js
index 1c86da7..4af2013 100644
--- a/miniapp/services/verificationService.js
+++ b/miniapp/services/verificationService.js
@@ -15,7 +15,7 @@ const api = require('../utils/api');
 function submit(payload) {
   // 幂等键：身份证号后4位 + 当前秒，避免用户多次点击
   const tail = (payload.idCardNumber || '').slice(-4).toUpperCase();
-  const idempotencyKey = 'verification-submit:' + tail + ':' + Math.floor(Date.now() / 1000);
+  const idempotencyKey = api.idempotencyKey('verification-submit', tail);
   return api.post('/verification/submit', payload, undefined, idempotencyKey);
 }
 
diff --git a/miniapp/stores/activityStore.js b/miniapp/stores/activityStore.js
index 56622da..37c4047 100644
--- a/miniapp/stores/activityStore.js
+++ b/miniapp/stores/activityStore.js
@@ -8,8 +8,9 @@
  *
  * 不变量（AGENTS.md）：
  *   - 第 1 条：用户永久免费——活动 feeType=paid 字段仅作展示，前端不实现任何支付入口。
- *   - 第 6 条：活动单向意向保密——submitInterests 返回的 matchedUserIds 仅含双向匹配，
- *     未匹配的人不在前端可见；Store 不缓存"谁单独选了我"的字段。
+ *   - 第 6 条：活动单向意向保密——表达意向走 submitFeedback 的 interestTargetUserIds，
+ *     其返回的 newMutuals 仅含双向匹配成功的人；未匹配的人不在前端可见；
+ *     Store 不缓存"谁单独选了我"的字段。
  */
 const BaseStore = require('./baseStore');
 const { activityService } = require('../services');
@@ -166,16 +167,15 @@ class ActivityStore extends BaseStore {
   }
 
   /**
-   * 提交活动互选意向（AGENTS 第 6 条：单向意向保密）
-   * @param {string} activityId
-   * @param {string[]} likedUserIds
-   * @returns {Promise<{ matchedUserIds: string[] }>} 仅返回双向匹配的 userIds
+   * 提交活动反馈（含表达意向）
+   *
+   * 原有一个 `submitInterests(activityId, likedUserIds)` 已删除：它请求
+   * `POST /activities/{id}/interests` —— **后端没有这个端点**（Phase 16 把
+   * 表达意向合并进反馈流程，即本方法的 `interestTargetUserIds`），调用必然 404。
+   * 全仓已确认它没有任何页面调用方，属 Phase 16 前的设计残留。
+   * 若将来确实需要独立的"提交互选"接口，须由产品先定义语义再补后端端点，
+   * 不应让前端留一个指向 404 的方法。
    */
-  async submitInterests(activityId, likedUserIds) {
-    return activityService.submitInterests(activityId, { likedUserIds });
-  }
-
-  /** 提交活动反馈 */
   async submitFeedback(activityId, payload) {
     return activityService.submitFeedback(activityId, payload);
   }
diff --git a/miniapp/utils/api.js b/miniapp/utils/api.js
index ccb3fc0..ae63711 100644
--- a/miniapp/utils/api.js
+++ b/miniapp/utils/api.js
@@ -7,6 +7,14 @@
 const { BUSINESS_LIMITS, REQUEST_ERROR } = require('../constants');
 const { API_BASE_URL } = require('../env');
 
+/**
+ * 未成功操作的幂等键保留时长。
+ *
+ * 取 10 分钟：足够覆盖用户「看到失败 → 重试」的常规间隔，又不至于让一把
+ * 早该作废的键长期占据缓存、把两次真正独立的操作误认成同一次。
+ */
+const IDEMPOTENCY_KEY_TTL_MS = 10 * 60 * 1000;
+
 class ApiClient {
   constructor() {
     this.baseURL = API_BASE_URL;
@@ -16,6 +24,52 @@ class ApiClient {
     this.onSessionExpired = null;
     /** @type {((config: object) => void)|null} 维护态拦截回调，由 AppStore 注入 */
     this.onMaintenance = null;
+    /** 未确认成功的幂等键缓存：操作指纹 -> {key, createdAt}。语义见 idempotencyKey()。 */
+    this._pendingIdempotency = {};
+  }
+
+  /**
+   * 取一次逻辑操作的幂等键。
+   *
+   * @param {string} scope 操作域，如 'activity-register'
+   * @param {string} [subject] 操作对象（活动 ID / 目标用户 ID 等）
+   * @returns {string} 幂等键
+   *
+   * 幂等键的语义是「同一次逻辑操作的重复投递用同一把键」，而不是「每次调用
+   * 一把新键」。此前各 service 自行拼 `xxx:${Date.now()}`，每次调用都是新键
+   * —— 后端即便实现了幂等也永远命中不了，「弱网重发」照样产生重复数据。
+   *
+   * 这里由 api 层统一托管：同一次**尚未成功**的操作复用同一把键，
+   * 成功后才释放，下一次点击才是新的一次操作。
+   */
+  idempotencyKey(scope, subject) {
+    const fingerprint = `${scope}::${subject == null ? '' : subject}`;
+    const now = Date.now();
+    const cached = this._pendingIdempotency[fingerprint];
+    if (cached && now - cached.createdAt < IDEMPOTENCY_KEY_TTL_MS) {
+      return cached.key;
+    }
+    const key = `${scope}:${subject == null ? '' : subject}:${this.generateRequestId()}`;
+    this._pendingIdempotency[fingerprint] = { key, createdAt: now };
+    return key;
+  }
+
+  /**
+   * 释放幂等键：一次逻辑操作成功后调用，下一次同域操作属新的一次。
+   *
+   * 公开方法：`request()` 内部在业务成功后自动调用；直接使用
+   * `utils/requestPromise` 绕开本层封装的页面（如 counseling-request）
+   * 需在成功后自行调用，否则一把旧键会被一直复用。
+   */
+  releaseIdempotencyKey(key) {
+    if (!key) return;
+    const fingerprints = Object.keys(this._pendingIdempotency);
+    for (let i = 0; i < fingerprints.length; i += 1) {
+      if (this._pendingIdempotency[fingerprints[i]].key === key) {
+        delete this._pendingIdempotency[fingerprints[i]];
+        return;
+      }
+    }
   }
 
   /** 读取本地存储的 access token */
@@ -98,6 +152,10 @@ class ApiClient {
           if (res.statusCode === 200) {
             const body = res.data || {};
             if (body.success) {
+              // 操作已成功落地：释放幂等键，下一次同域操作是新的一次。
+              // 失败时刻意**不释放** —— 用户重试时复用同一把键，
+              // 后端才能识别出这是重复投递而不是第二次操作。
+              this._releaseIdempotencyKey(idempotencyKey);
               resolve(body.data);
             } else {
               reject({