diff --git a/docs/DESIGN.md b/docs/DESIGN.md
index 11496b7..6b34a2b 100644
--- a/docs/DESIGN.md
+++ b/docs/DESIGN.md
@@ -104,9 +104,12 @@
 4) Send Engine 驗證 tenant scope，更新本地名單快照
 
 ### 6.7 Send Engine 退信/黑名單回寫（選用）
-1) Send Engine 判定黑名單（例如 hard bounce / complaint）
-2) 呼叫 Member Center API 將 email 加入 `email_blacklist`
-3) Member Center 對該 email 的訂閱事件全部忽略且不再推送
+1) Send Engine 依事件類型決定回寫時機與原因碼：
+2) `hard_bounce` / `soft_bounce_threshold` / `suppression`：設黑名單後回寫
+3) `complaint`：先取消訂閱，再回寫黑名單
+4) 呼叫 Member Center API 將 email 加入 `email_blacklist`
+5) Member Center 對該 email 的訂閱事件全部忽略且不再推送
+6) 回寫請求需帶 `tenant_id + subscriber_id + list_id`，Member Center 端做租戶邊界驗證
 
 ### 6.5 註冊後銜接
 1) 使用者完成註冊
@@ -128,14 +131,14 @@
 - POST `/newsletter/preferences`
 - POST `/webhooks/subscriptions`（Send Engine 端點，Member Center 呼叫）
 - POST `/webhooks/lists/full-sync`（Send Engine 端點，Member Center 呼叫）
-- POST `/api/subscriptions/disable`（Member Center 端點，Send Engine 呼叫）
+- POST `/subscriptions/disable`（Member Center 端點，Send Engine 呼叫）
 
 ## 7.1 待新增 API / Auth（規劃中）
 ### API
 - `GET /newsletter/subscriptions?list_id=...`：供發送引擎同步訂閱清單
 - `POST /webhooks/subscriptions`：Member Center → Send Engine 事件推送
 - `POST /webhooks/lists/full-sync`：Member Center → Send Engine 全量同步
-- `POST /api/subscriptions/disable`：Send Engine → Member Center 黑名單回寫
+- `POST /subscriptions/disable`：Send Engine → Member Center 黑名單回寫
 
 ### Auth / Scope
 - OAuth Client 綁定 `tenant_id`，所有清單/事件 API 需驗證租戶邊界
diff --git a/docs/FLOWS.md b/docs/FLOWS.md
index 243e687..7425666 100644
--- a/docs/FLOWS.md
+++ b/docs/FLOWS.md
@@ -45,8 +45,10 @@
 - [API] Send Engine 更新名單快照
 
 ## F-11 黑名單回寫（Send Engine → Member Center）
-- [API] Send Engine 判定黑名單（例如 hard bounce / complaint）
-- [API] 呼叫 `POST /api/subscriptions/disable`（scope: `newsletter:events.write`）
+- [API] Send Engine 依事件規則處理：
+- [API] `hard_bounce` / `soft_bounce_threshold` / `suppression`：設黑名單後回寫
+- [API] `complaint`：先在 Send Engine 取消訂閱，再回寫黑名單
+- [API] 呼叫 `POST /subscriptions/disable`（scope: `newsletter:events.write`），body 需含 `tenant_id + subscriber_id + list_id + reason + disabled_by + occurred_at`
 - [API] Member Center 將 email 寫入 `email_blacklist`，停用寄送並停止事件推送
 
 ## F-07 會員資料查看
diff --git a/docs/OPENAPI.md b/docs/OPENAPI.md
index 02c65a6..fb41009 100644
--- a/docs/OPENAPI.md
+++ b/docs/OPENAPI.md
@@ -55,7 +55,9 @@
 - 驗證規則：
   - timestamp 在允許時間窗（例如 ±5 分鐘）
   - nonce 不可重複（防重放）
-  - `X-Client-Id` 必須存在且 active，且 tenant 綁定一致
+  - `X-Client-Id` 必須存在且 active，且 `auth_clients.tenant_id` 與 payload `tenant_id` 一致
+  - 不使用 `X-Client-Id` fallback；缺少 tenant 對應 client 時應略過發送
+  - 預設拒絕 `auth_clients.tenant_id = NULL` 的通用 client（除非 Send Engine 明確開啟）
   - signature 必須匹配
 
 ## OAuth Client 用途分離（強制）
@@ -70,12 +72,12 @@
   - 每個 tenant 至少 2 組憑證（`tenant_api` / `webhook_outbound`）
   - secret 分開輪替，禁止共用
 
-## 待新增 API / Auth（規劃中）
+## 整合 API / Auth（狀態）
 ### API
-- `GET /newsletter/subscriptions?list_id=...`：回傳清單內所有訂閱（供發送引擎同步用）
-- `POST /webhooks/subscriptions`：Member Center → Send Engine 事件推送（Send Engine 端點，scope: `newsletter:events.write`）
-- `POST /webhooks/lists/full-sync`：Member Center → Send Engine 全量同步（Send Engine 端點，scope: `newsletter:events.write`）
-- `POST /api/subscriptions/disable`：Send Engine → Member Center 黑名單回寫（全租戶 email，scope: `newsletter:events.write`）
+- `GET /newsletter/subscriptions?list_id=...`：已實作（供發送引擎同步）
+- `POST /webhooks/subscriptions`：已實作（Member Center 發送；Send Engine 接收）
+- `POST /webhooks/lists/full-sync`：規格已定義（Member Center 發送；Send Engine 接收）
+- `POST /subscriptions/disable`：已實作（Send Engine 回寫黑名單）
 
 ### Auth / Scope
 - OAuth Client 需綁定 `tenant_id`
@@ -84,3 +86,21 @@
   - `newsletter:events.read`
   - `newsletter:events.write`
 - 發送引擎僅能用上述 scope，禁止 admin 權限
+- `POST /subscriptions/disable` 需 Bearer token 且包含 `newsletter:events.write`
+- 建議 Send Engine 使用 client credentials 取 token，不建議使用長效固定 token
+
+### 回寫原因碼（Send Engine -> Member Center）
+- `hard_bounce`
+- `soft_bounce_threshold`
+- `complaint`
+- `suppression`
+
+### `/subscriptions/disable` 請求欄位（Send Engine -> Member Center）
+- `tenant_id`（UUID）
+- `subscriber_id`（UUID）
+- `list_id`（UUID）
+- `reason`（`hard_bounce | soft_bounce_threshold | complaint | suppression`）
+- `disabled_by`（建議固定 `send_engine`）
+- `occurred_at`（RFC3339）
+
+Member Center 會用 `subscriber_id + list_id` 查詢訂閱，再驗證 `tenant_id` 邊界；驗證通過後才寫入全域 email 黑名單。
diff --git a/docs/openapi.yaml b/docs/openapi.yaml
index bd41a33..3d94bcb 100644
--- a/docs/openapi.yaml
+++ b/docs/openapi.yaml
@@ -436,11 +436,11 @@ paths:
               schema:
                 $ref: '#/components/schemas/ErrorResponse'
 
-  /api/subscriptions/disable:
+  /subscriptions/disable:
     post:
       summary: Disable email (global blacklist)
       security: [{ BearerAuth: [] }]
-      description: Requires scope `newsletter:events.write`.
+      description: Requires scope `newsletter:events.write`. Request must include `tenant_id`, `subscriber_id`, and `list_id` for tenant-boundary validation. Expected reason codes: `hard_bounce`, `soft_bounce_threshold`, `complaint`, `suppression`.
       requestBody:
         required: true
         content:
@@ -466,7 +466,7 @@ paths:
   /webhooks/subscriptions:
     post:
       summary: (NOTE) Member Center -> Send Engine subscription events webhook
-      description: This endpoint is implemented by Send Engine; listed here as an integration note. Required headers are X-Signature, X-Timestamp, X-Nonce, X-Client-Id. X-Client-Id must be Send Engine `auth_clients.id` (UUID).
+      description: This endpoint is implemented by Send Engine; listed here as an integration note. Required headers are X-Signature, X-Timestamp, X-Nonce, X-Client-Id. X-Client-Id must be Send Engine `auth_clients.id` (UUID), tenant-bound, no fallback client id.
       security: []
       parameters:
         - in: header
@@ -498,7 +498,7 @@ paths:
   /webhooks/lists/full-sync:
     post:
       summary: (NOTE) Member Center -> Send Engine full list sync webhook
-      description: This endpoint is implemented by Send Engine; listed here as an integration note. Required headers are X-Signature, X-Timestamp, X-Nonce, X-Client-Id. X-Client-Id must be Send Engine `auth_clients.id` (UUID).
+      description: This endpoint is implemented by Send Engine; listed here as an integration note. Required headers are X-Signature, X-Timestamp, X-Nonce, X-Client-Id. X-Client-Id must be Send Engine `auth_clients.id` (UUID), tenant-bound, no fallback client id.
       security: []
       parameters:
         - in: header
@@ -829,10 +829,14 @@ components:
 
     DisableSubscriptionRequest:
       type: object
-      required: [email, reason, disabled_by, occurred_at]
+      required: [tenant_id, subscriber_id, list_id, reason, disabled_by, occurred_at]
       properties:
-        email: { type: string, format: email }
-        reason: { type: string }
+        tenant_id: { type: string, format: uuid }
+        subscriber_id: { type: string, format: uuid }
+        list_id: { type: string, format: uuid }
+        reason:
+          type: string
+          enum: [hard_bounce, soft_bounce_threshold, complaint, suppression]
         disabled_by: { type: string }
         occurred_at: { type: string, format: date-time }
 
diff --git a/src/MemberCenter.Api/Contracts/NewsletterRequests.cs b/src/MemberCenter.Api/Contracts/NewsletterRequests.cs
index b425692..4ab63ba 100644
--- a/src/MemberCenter.Api/Contracts/NewsletterRequests.cs
+++ b/src/MemberCenter.Api/Contracts/NewsletterRequests.cs
@@ -21,7 +21,9 @@ public sealed record UpdatePreferencesRequest(
     [property: JsonPropertyName("preferences")] Dictionary<string, object> Preferences);
 
 public sealed record DisableSubscriptionRequest(
-    [property: JsonPropertyName("email")] string Email,
+    [property: JsonPropertyName("tenant_id")] Guid TenantId,
+    [property: JsonPropertyName("subscriber_id")] Guid SubscriberId,
+    [property: JsonPropertyName("list_id")] Guid ListId,
     [property: JsonPropertyName("reason")] string Reason,
     [property: JsonPropertyName("disabled_by")] string DisabledBy,
     [property: JsonPropertyName("occurred_at")] DateTimeOffset OccurredAt);
diff --git a/src/MemberCenter.Api/Controllers/SubscriptionsController.cs b/src/MemberCenter.Api/Controllers/SubscriptionsController.cs
index 40df088..f98902d 100644
--- a/src/MemberCenter.Api/Controllers/SubscriptionsController.cs
+++ b/src/MemberCenter.Api/Controllers/SubscriptionsController.cs
@@ -1,20 +1,34 @@
 using MemberCenter.Api.Contracts;
 using MemberCenter.Application.Abstractions;
+using MemberCenter.Infrastructure.Persistence;
 using Microsoft.AspNetCore.Authorization;
 using Microsoft.AspNetCore.Mvc;
+using Microsoft.EntityFrameworkCore;
 using OpenIddict.Abstractions;
 
 namespace MemberCenter.Api.Controllers;
 
 [ApiController]
-[Route("api/subscriptions")]
+[Route("subscriptions")]
 public class SubscriptionsController : ControllerBase
 {
-    private readonly IEmailBlacklistService _emailBlacklistService;
+    private static readonly HashSet<string> AllowedReasons = new(StringComparer.OrdinalIgnoreCase)
+    {
+        "hard_bounce",
+        "soft_bounce_threshold",
+        "complaint",
+        "suppression"
+    };
 
-    public SubscriptionsController(IEmailBlacklistService emailBlacklistService)
+    private readonly IEmailBlacklistService _emailBlacklistService;
+    private readonly MemberCenterDbContext _dbContext;
+
+    public SubscriptionsController(
+        IEmailBlacklistService emailBlacklistService,
+        MemberCenterDbContext dbContext)
     {
         _emailBlacklistService = emailBlacklistService;
+        _dbContext = dbContext;
     }
 
     [Authorize]
@@ -26,20 +40,48 @@ public class SubscriptionsController : ControllerBase
             return Forbid();
         }
 
-        if (string.IsNullOrWhiteSpace(request.Email) ||
+        if (request.TenantId == Guid.Empty ||
+            request.SubscriberId == Guid.Empty ||
+            request.ListId == Guid.Empty ||
             string.IsNullOrWhiteSpace(request.Reason) ||
             string.IsNullOrWhiteSpace(request.DisabledBy))
         {
-            return BadRequest("email, reason, disabled_by are required.");
+            return BadRequest("tenant_id, subscriber_id, list_id, reason, disabled_by are required.");
+        }
+
+        if (!AllowedReasons.Contains(request.Reason))
+        {
+            return BadRequest("reason must be one of: hard_bounce, soft_bounce_threshold, complaint, suppression.");
+        }
+
+        var target = await (
+            from subscription in _dbContext.NewsletterSubscriptions
+            join list in _dbContext.NewsletterLists on subscription.ListId equals list.Id
+            where subscription.Id == request.SubscriberId && subscription.ListId == request.ListId
+            select new
+            {
+                subscription.Email,
+                list.TenantId
+            })
+            .FirstOrDefaultAsync();
+
+        if (target is null)
+        {
+            return NotFound("Subscription not found.");
+        }
+
+        if (target.TenantId != request.TenantId)
+        {
+            return BadRequest("tenant_id does not match subscription/list tenant boundary.");
         }
 
         await _emailBlacklistService.AddOrUpdateAsync(
-            request.Email,
+            target.Email,
             request.Reason,
             request.DisabledBy,
             request.OccurredAt);
 
-        return Ok(new { email = request.Email, status = "blacklisted" });
+        return Ok(new { email = target.Email, status = "blacklisted" });
     }
 
     private static bool HasScope(System.Security.Claims.ClaimsPrincipal user, string scope)