feat: Enhance Send Engine API with JWT and OIDC support, update OpenAPI documentation. Complete send flow with mock.

- Updated authentication to support OAuth2 Client Credentials and JWT with OIDC/JWKS verification.
- Added necessary claims for JWT, including `aud` and fallback for JWT metadata.
- Improved error response format and added additional claims for webhook events.
- Introduced new request body structure for creating send jobs, supporting both snake_case and camelCase.
- Implemented DevMockSenderWorker for simulating email sending during development.
- Integrated Amazon SES for email delivery, with bulk sending capabilities.
- Updated OpenAPI documentation to reflect changes in request and response schemas.
- Enhanced error handling and logging for better traceability.

.env.example

@@ -3,9 +3,12 @@ ConnectionStrings__Default=Host=localhost;Database=send_engine;Username=postgres
 ESP__Provider=ses
 ESP__ApiKey=change_me
 Db__AutoMigrate=true
-Jwt__Issuer=member_center
-Jwt__Audience=send_engine
-Jwt__SigningKey=change_me_jwt_signing_key
+Jwt__Issuer=http://localhost:7850/
+Jwt__Audience=send_engine_api
+Jwt__Authority=
+Jwt__MetadataAddress=
+Jwt__RequireHttpsMetadata=false
+Jwt__SigningKey=
 Webhook__Secrets__member_center=change_me_webhook_secret
 Webhook__TimestampSkewSeconds=300
 Webhook__AllowNullTenantClient=false
@@ -14,10 +17,15 @@ Bounce__SoftBounceThreshold=5
 MemberCenter__BaseUrl=
 MemberCenter__DisableSubscriptionPath=/subscriptions/disable
 MemberCenter__TokenPath=/oauth/token
-MemberCenter__DisableSubscriptionUrl=
-MemberCenter__TokenUrl=
+MemberCenter__OneClickUnsubscribeTokensPath=/newsletter/one-click-unsubscribe-tokens
 MemberCenter__ClientId=
 MemberCenter__ClientSecret=
 MemberCenter__Scope=newsletter:events.write
 MemberCenter__ApiToken=
 TestFriendly__Enabled=false
+DevSender__Enabled=false
+DevSender__PollIntervalSeconds=5
+Ses__Region=us-east-1
+Ses__FromEmail=
+Ses__ConfigurationSet=
+Ses__TemplateName=

docs/DESIGN.md

@@ -23,14 +23,19 @@ ESP 介接暫定為 Amazon SES。
 - List-Unsubscribe one-click endpoint 本身的服務實作
 - 會員最終名單權威資料庫
 
-### 狀態機（規劃）
-Job 狀態：
+### 狀態機
+Job 狀態（目前實作）：
+- pending
+- running
+- completed
+- failed
+- cancelled
+
+Job 狀態（規劃擴充）：
 - queued
 - sending
 - sent
 - partially_failed
-- failed
-- completed
 
 Recipient 狀態：
 - pending
@@ -49,6 +54,10 @@ Recipient 狀態：
 - 更新 DB 狀態
 - 必要時呼叫 Member Center 停用/註記 API
 
+目前實作：
+- 先以 `POST /webhooks/ses` 接收事件並更新資料
+- `SNS -> SQS -> Worker` 尚未落地
+
 ## 信任邊界與 Auth 模型
 ### 外部角色
 - Member Center：事件來源與名單權威來源（authority）

docs/FLOWS.md

@@ -40,9 +40,9 @@ Member Center 為多租戶架構，信件內容由各租戶網站產生後送入
 - 可於 Send Engine 端提供 `sync_received` 回應與進度回報
 
 ## 2. 發送排程流程
-目的：從租戶網站送入的內容建立 Send Job，切分送信任務並控速。
+目的：從租戶網站送入的內容建立 Send Job，並由背景 worker 執行發送。
 
-流程：
+目前實作流程：
 1. 租戶網站以 Member Center 簽發的 token 呼叫 Send Engine API 建立 Campaign/Send Job：
    - 必填：tenant_id、list_id、內容（subject/body/template 其一或組合）
    - 選填：排程時間、發送窗口、追蹤設定（open/click）
@@ -50,17 +50,16 @@ Member Center 為多租戶架構，信件內容由各租戶網站產生後送入
    - tenant_id 以 token 為準，body 的 tenant_id 僅作一致性檢查
    - tenant 必須預先存在（建議由 Installer 建立）
    - list_id 若不存在，Send Engine 會在該 tenant 下自動建立 list（placeholder）
-3. Scheduler 在排程時間點啟動 Send Job：
-   - 讀取 List Store 快照
-   - 依規則過濾（已退訂、bounced、黑名單）
-4. 切分成可控批次（batch），寫入 Outbox。
-5. Sender Worker 取出 batch，轉成 SES API 請求。
-6. 發送時必帶：
-   - SES Configuration Set
-   - Message Tags（至少含 campaign_id / site_id / list_id）
-   - Newsletter 類型需帶 `List-Unsubscribe` 與 `List-Unsubscribe-Post` headers
-7. SES 回應 message_id → 記錄 delivery log。
-8. 更新 Send Job 進度（成功/失敗/重試）。
+3. `DevMockSenderWorker` 輪詢 `send_jobs(status=pending)`，執行時先改為 `running`。
+4. worker 讀取 `subscriptions(status=active)`，並過濾不可發送對象：
+   - unsubscribed / suppressed 不發送
+   - 若啟用 one-click token endpoint，僅發送 `status=issued` 的收件者
+5. 發送執行：
+   - `ESP__Provider=mock`：僅模擬發送，寫入預覽事件並輸出 console log
+   - `ESP__Provider=ses`：使用 SES v2 `SendBulkEmail`（每批最多 50）
+6. 更新 Send Job 狀態：
+   - 全部成功：`completed`
+   - 例外或部分失敗：`failed`
 
 控速策略（範例）：
 - 全域 TPS 上限 + tenant TPS 上限
@@ -74,9 +73,9 @@ Member Center 為多租戶架構，信件內容由各租戶網站產生後送入
 ## 3. 退信處理流程
 目的：處理 ESP 回報的 bounce/complaint，並回寫本地名單狀態。
 
-流程：
-1. SES 事件由 Configuration Set 發送至 SNS，再落到 SQS。
-2. ECS Worker 輪詢 SQS，解析 SNS envelope 與 SES payload。
+目前實作流程（Webhook）：
+1. 由 `POST /webhooks/ses` 接收 SES 事件 payload。
+2. 驗證（可透過 `Ses__SkipSignatureValidation` 控制是否要求簽章）。
 3. 將事件寫入 Inbox（append-only）。
 4. Consumer 解析事件：
    - hard bounce → 立即標記 blacklisted（同義於 `suppressed`）
@@ -93,6 +92,7 @@ Member Center 為多租戶架構，信件內容由各租戶網站產生後送入
 補充：
 - Unknown event 不應使 worker crash，應記錄後送入 DLQ
 - Throttle/暫時性網路錯誤使用指數退避重試
+- `SNS -> SQS -> Worker` 架構為正式環境建議，尚未在目前程式碼中落地
 
 回寫規則：
 - Send Engine 僅回寫「停用原因」與必要欄位

docs/INSTALL.md

@@ -27,13 +27,35 @@
   - `MemberCenter__BaseUrl`（建議）
   - `MemberCenter__DisableSubscriptionPath`（預設 `/subscriptions/disable`）
   - `MemberCenter__TokenPath`（預設 `/oauth/token`）
+  - `MemberCenter__OneClickUnsubscribeTokensPath`（預設 `/newsletter/one-click-unsubscribe-tokens`）
   - `MemberCenter__ClientId`
   - `MemberCenter__ClientSecret`
   - `MemberCenter__Scope=newsletter:events.write`
-  - `MemberCenter__DisableSubscriptionUrl` 與 `MemberCenter__TokenUrl` 可用完整 URL 覆蓋（fallback）
   - `MemberCenter__ApiToken` 僅作暫時 fallback（非首選）
+- Send Job API 驗證（JWT）：
+  - `Jwt__Issuer`
+  - `Jwt__Audience`
+  - 建議（Member Center OIDC/JWKS）：
+  - `Jwt__Authority`（例如 `http://member-center`）
+  - 或 `Jwt__MetadataAddress`（例如 `http://member-center/.well-known/openid-configuration`）
+  - 若兩者都未設定，會自動回退使用 `MemberCenter__BaseUrl + /.well-known/openid-configuration`
+  - `Jwt__RequireHttpsMetadata`（本機可設 `false`）
+  - 相容舊模式（不建議）：`Jwt__SigningKey`（HS 對稱驗簽）
 - 本機測試輔助（臨時）：
   - `TestFriendly__Enabled=true` 時：
   - webhook 收到未知 tenant 會自動建立 tenant
-  - `/webhooks/ses` 不做任何 DB 存取（僅用於測試流程打通）
+  - `/webhooks/ses` 不做任何 DB 存取，但會保留 Member Center callback 流程（僅用於測試流程打通）
+  - Dev Sender（Mock 發信）：
+  - `DevSender__Enabled=true`：背景 worker 會處理 `pending` send jobs，並將每位收件人的預計發送內容寫入 `events_inbox`（`source=dev_sender`, `event_type=send.preview`）
+  - `DevSender__PollIntervalSeconds`：輪詢間隔秒數（預設 5）
+  - `ESP__Provider=ses` 時，背景 worker 會改用 SES `SendBulkEmail` 發送
+  - SES 相關參數：`Ses__Region`、`Ses__FromEmail`、`Ses__ConfigurationSet`（可選）、`Ses__TemplateName`
+  - `SendBulkEmail` 會使用 SES 模板名稱：
+  - 先讀 `campaign.template.ses_template_name`
+  - 若未提供則回退 `Ses__TemplateName`
+  - 若設定了 Member Center one-click token endpoint，sender 會在發送前批次呼叫 `/newsletter/one-click-unsubscribe-tokens`，僅發送 `status=issued` 的收件者
+  - 內容替換合約（Mock 與 SES 共用）：
+  - `{{email}}`
+  - `{{unsubscribe_url}}`（可在 `template` JSON 中提供 `unsubscribe_url` 模板，例如 `https://member.example/unsub?email={{email}}`）
+  - `{{tenant_id}}` / `{{list_id}}` / `{{campaign_id}}` / `{{send_job_id}}`
   - 正式環境建議維持 `false`

docs/OPENAPI.md

@@ -5,11 +5,13 @@
 
 ## Auth 與驗證
 ### 1. 租戶網站 → Send Engine API
-使用 OAuth2 Client Credentials 或 JWT（由 Member Center 簽發）。
+使用 OAuth2 Client Credentials（token 由 Member Center 簽發，Send Engine 以 OIDC/JWKS 驗簽驗證）。
+若未明確設定 JWT metadata/authority，會回退使用 `MemberCenter__BaseUrl + /.well-known/openid-configuration`。
 
 必要 claims：
 - `tenant_id`
 - `scope`（至少 `newsletter:send.write`）
+- 必須包含 `aud`（需符合 `Jwt__Audience`）
 
 規則：
 - `tenant_id` 只能取自 token，不接受 body 覆寫
@@ -55,11 +57,12 @@ scope 最小化：
 ## 通用錯誤格式
 ```json
 {
-  "error": "string_code",
-  "message": "human readable message",
-  "request_id": "uuid"
+  "error": "string_code"
 }
 ```
+補充：
+- 部分錯誤會附帶 `reason` 或 `message`（例如 webhook 驗證失敗）
+- `message`、`request_id` 目前非固定欄位
 
 ## Webhook：Member Center → Send Engine
 ### A. 訂閱事件（增量）
@@ -163,43 +166,73 @@ Request Body：
 - `window_start` 必須小於 `window_end`（若有提供）
 - `tenant_id` 必須已存在（不存在回 `422 tenant_not_found`）
 - `list_id` 若不存在，會在該 tenant 下自動建立 placeholder list 後建立 send job
+- `template` 可攜帶替換參數（例如：`{"unsubscribe_url":"https://member.example/unsub?email={{email}}","ses_template_name":"newsletter_default"}`）
+
+替換合約（Mock/SES 一致）：
+- `{{email}}`
+- `{{unsubscribe_url}}`
+- `{{unsubscribe_token}}`
+- `{{tenant_id}}`
+- `{{list_id}}`
+- `{{campaign_id}}`
+- `{{send_job_id}}`
 
 Response：
 ```json
 {
   "send_job_id": "uuid",
+  "sendJobId": "uuid",
+  "status": "pending"
+}
+```
+說明：回應同時提供 `snake_case` 與 `camelCase`（向後相容不同語言客戶端）。
+
+### C-1. Tenant Site Integration（已實作）
+用途：內容網站以 Member Center 發出的 JWT 呼叫 Send Engine 建立發送工作。
+
+步驟：
+1. 取得 access token（scope 至少 `newsletter:send.write`）
+2. 呼叫 `POST /api/send-jobs`
+3. 查詢 `GET /api/send-jobs/{id}`（需 `newsletter:send.read`）
+
+token 需包含：
+- `tenant_id`（UUID）
+- `scope`（空白分隔字串）
+
+範例（建立 send job）：
+```bash
+curl -X POST "http://localhost:6060/api/send-jobs" \
+  -H "Authorization: Bearer <ACCESS_TOKEN>" \
+  -H "Content-Type: application/json" \
+  -d '{
+    "tenant_id": "c9034414-43d6-404e-8d41-e80922420bf1",
+    "list_id": "22222222-2222-2222-2222-222222222222",
+    "name": "Weekly Update",
+    "subject": "Hi {{email}}",
+    "body_html": "<p>Hello {{email}}</p><p><a href=\"{{unsubscribe_url}}\">unsubscribe</a></p>",
+    "body_text": "Hello {{email}} | unsubscribe: {{unsubscribe_url}}",
+    "template": {
+      "unsubscribe_url": "https://member.example/unsubscribe?email={{email}}",
+      "ses_template_name": "newsletter_default"
+    }
+  }'
+```
+
+回應：
+```json
+{
+  "send_job_id": "uuid",
+  "sendJobId": "uuid",
   "status": "pending"
 }
 ```
 
-### C-1. Sending Proxy Submit Job（整合規格）
-用途：對齊內容網站/會員平台呼叫發信代理的標準接口。
-
-Endpoint：
-- `POST /v1/send-jobs`
-
-Request Body（欄位）：
-- `message_type`：`newsletter` | `transactional`
-- `from`：發件人
-- `to`：收件人陣列
-- `subject`：主旨
-- `html`：HTML 內容
-- `text`：純文字內容
-- `headers`：自定義 header（白名單）
-- `list_unsubscribe.url`：退訂 URL
-- `list_unsubscribe.mailto`：可選
-- `tags.campaign_id` / `tags.site_id` / `tags.list_id` / `tags.segment`
-- `idempotency_key`：冪等鍵
-
-Response：
-- `job_id`
-- `status=queued`
-
-規則：
-- 必須帶 Configuration Set + Message Tags 後才能呼叫 SES
-- `newsletter` 類型需帶：
-- `List-Unsubscribe`
-- `List-Unsubscribe-Post: List-Unsubscribe=One-Click`
+說明：
+- `ESP__Provider=mock`（非 ses）時，會由 Dev Sender 產生 `send.preview` 事件供你檢查替換結果
+- `ESP__Provider=mock` 時，也會把每位收件人的模擬發送內容輸出到 console log（`MOCK send preview`）
+- `ESP__Provider=ses` 時，背景 sender 會用 SES `SendBulkEmail`（每批最多 50）
+- 若已設定 Member Center one-click token endpoint，發送前會批次呼叫 `POST /newsletter/one-click-unsubscribe-tokens`
+- 僅 `status=issued` 的收件者會被送出，並把 `unsubscribe_token` 注入替換內容
 
 ### D. 查詢 Send Job
 Endpoint：
@@ -213,12 +246,18 @@ Response：
 {
   "id": "uuid",
   "tenant_id": "uuid",
+  "tenantId": "uuid",
   "list_id": "uuid",
+  "listId": "uuid",
   "campaign_id": "uuid",
+  "campaignId": "uuid",
   "status": "running",
   "scheduled_at": "2026-02-11T02:00:00Z",
+  "scheduledAt": "2026-02-11T02:00:00Z",
   "window_start": "2026-02-11T02:00:00Z",
-  "window_end": "2026-02-11T05:00:00Z"
+  "windowStart": "2026-02-11T02:00:00Z",
+  "window_end": "2026-02-11T05:00:00Z",
+  "windowEnd": "2026-02-11T05:00:00Z"
 }
 ```
 
@@ -249,7 +288,8 @@ Response：
 - `POST /webhooks/ses`
 
 驗證：
-- 依 SES/SNS 規格驗簽（可用 `Ses__SkipSignatureValidation=true` 暫時略過）
+- 目前實作：`Ses__SkipSignatureValidation=false` 時僅要求 `X-Amz-Sns-Signature` header 存在
+- 正式建議：補上 SES/SNS 憑證鏈與簽章內容驗證
 
 Request Body（示意）：
 ```json

docs/TECH_STACK.md

@@ -2,4 +2,4 @@
 
 - C# .NET Core
 - PostgreSQL
-- ESP: SES / SendGrid / Mailgun
+- ESP: Amazon SES（實作）+ Mock Sender（開發測試）

docs/openapi.yaml

@@ -11,55 +11,6 @@ security:
   - bearerAuth: []
 
 paths:
-  /v1/send-jobs:
-    post:
-      summary: Submit send job (sending proxy)
-      security:
-        - bearerAuth: []
-      requestBody:
-        required: true
-        content:
-          application/json:
-            schema:
-              $ref: '#/components/schemas/SubmitSendJobRequest'
-      responses:
-        '200':
-          description: Queued
-          content:
-            application/json:
-              schema:
-                $ref: '#/components/schemas/SubmitSendJobResponse'
-        '401':
-          description: Unauthorized
-          content:
-            application/json:
-              schema:
-                $ref: '#/components/schemas/ErrorResponse'
-        '403':
-          description: Forbidden
-          content:
-            application/json:
-              schema:
-                $ref: '#/components/schemas/ErrorResponse'
-        '422':
-          description: Unprocessable Entity (e.g. tenant not found)
-          content:
-            application/json:
-              schema:
-                $ref: '#/components/schemas/ErrorResponse'
-        '409':
-          description: Idempotency conflict
-          content:
-            application/json:
-              schema:
-                $ref: '#/components/schemas/ErrorResponse'
-        '422':
-          description: Validation error
-          content:
-            application/json:
-              schema:
-                $ref: '#/components/schemas/ErrorResponse'
-
   /api/send-jobs:
     post:
       summary: Create send job (legacy/internal)
@@ -318,14 +269,23 @@ components:
   schemas:
     CreateSendJobRequest:
       type: object
-      required: [list_id, subject]
+      required: [subject]
+      description: |
+        Request accepts both snake_case and camelCase keys.
+        Recommended contract is snake_case for cross-language consistency.
       properties:
         tenant_id:
           type: string
           format: uuid
+        tenantId:
+          type: string
+          format: uuid
         list_id:
           type: string
           format: uuid
+        listId:
+          type: string
+          format: uuid
         name:
           type: string
         subject:
@@ -333,41 +293,68 @@ components:
           minLength: 1
         body_html:
           type: string
+        bodyHtml:
+          type: string
         body_text:
           type: string
+        bodyText:
+          type: string
         template:
           type: object
           additionalProperties: true
+          description: |
+            Optional template metadata used by sender runtime.
+            Supported keys:
+            - unsubscribe_url: URL template, e.g. https://member.example/unsubscribe?token={{unsubscribe_token}}
+            - ses_template_name: SES template name override
         scheduled_at:
           type: string
           format: date-time
+        scheduledAt:
+          type: string
+          format: date-time
         window_start:
           type: string
           format: date-time
+        windowStart:
+          type: string
+          format: date-time
         window_end:
           type: string
           format: date-time
+        windowEnd:
+          type: string
+          format: date-time
         tracking:
           $ref: '#/components/schemas/TrackingOptions'
-      oneOf:
-        - required: [body_html]
-        - required: [body_text]
-        - required: [template]
+      allOf:
+        - anyOf:
+            - required: [list_id]
+            - required: [listId]
+        - anyOf:
+            - required: [body_html]
+            - required: [bodyHtml]
+            - required: [body_text]
+            - required: [bodyText]
+            - required: [template]
 
     CreateSendJobResponse:
       type: object
-      required: [send_job_id, status]
+      required: [send_job_id, sendJobId, status]
       properties:
         send_job_id:
           type: string
           format: uuid
+        sendJobId:
+          type: string
+          format: uuid
         status:
           type: string
           enum: [pending, running, completed, failed, cancelled]
 
     SendJob:
       type: object
-      required: [id, tenant_id, list_id, campaign_id, status]
+      required: [id, tenant_id, tenantId, list_id, listId, campaign_id, campaignId, status]
       properties:
         id:
           type: string
@@ -375,24 +362,42 @@ components:
         tenant_id:
           type: string
           format: uuid
+        tenantId:
+          type: string
+          format: uuid
         list_id:
           type: string
           format: uuid
+        listId:
+          type: string
+          format: uuid
         campaign_id:
           type: string
           format: uuid
+        campaignId:
+          type: string
+          format: uuid
         status:
           type: string
           enum: [pending, running, completed, failed, cancelled]
         scheduled_at:
           type: string
           format: date-time
+        scheduledAt:
+          type: string
+          format: date-time
         window_start:
           type: string
           format: date-time
+        windowStart:
+          type: string
+          format: date-time
         window_end:
           type: string
           format: date-time
+        windowEnd:
+          type: string
+          format: date-time
 
     SendJobStatusResponse:
       type: object
@@ -405,76 +410,6 @@ components:
           type: string
           enum: [pending, running, completed, failed, cancelled]
 
-    SubmitSendJobRequest:
-      type: object
-      required: [message_type, from, to, subject, html, text, tags, idempotency_key]
-      properties:
-        message_type:
-          type: string
-          enum: [newsletter, transactional]
-        from:
-          type: string
-          format: email
-        to:
-          type: array
-          items:
-            type: string
-            format: email
-          minItems: 1
-        subject:
-          type: string
-          minLength: 1
-        html:
-          type: string
-        text:
-          type: string
-        headers:
-          type: object
-          additionalProperties:
-            type: string
-        list_unsubscribe:
-          $ref: '#/components/schemas/ListUnsubscribe'
-        tags:
-          $ref: '#/components/schemas/MessageTags'
-        idempotency_key:
-          type: string
-          minLength: 1
-
-    SubmitSendJobResponse:
-      type: object
-      required: [job_id, status]
-      properties:
-        job_id:
-          type: string
-          format: uuid
-        status:
-          type: string
-          enum: [queued]
-
-    ListUnsubscribe:
-      type: object
-      required: [url]
-      properties:
-        url:
-          type: string
-          format: uri
-        mailto:
-          type: string
-          format: email
-
-    MessageTags:
-      type: object
-      required: [campaign_id, site_id, list_id, segment]
-      properties:
-        campaign_id:
-          type: string
-        site_id:
-          type: string
-        list_id:
-          type: string
-        segment:
-          type: string
-
     TrackingOptions:
       type: object
       properties:
@@ -573,11 +508,13 @@ components:
 
     ErrorResponse:
       type: object
-      required: [error, message, request_id]
+      required: [error]
       properties:
         error:
           type: string
         message:
           type: string
+        reason:
+          type: string
         request_id:
           type: string

src/SendEngine.Api/Models/SendJobModels.cs

@@ -1,19 +1,44 @@
 using System.Text.Json;
+using System.Text.Json.Serialization;
 
 namespace SendEngine.Api.Models;
 
 public sealed class CreateSendJobRequest
 {
     public Guid TenantId { get; set; }
+    [JsonPropertyName("tenant_id")]
+    public Guid TenantIdSnakeCase { set => TenantId = value; }
+
     public Guid ListId { get; set; }
+    [JsonPropertyName("list_id")]
+    public Guid ListIdSnakeCase { set => ListId = value; }
+
     public string? Name { get; set; }
+
     public string? Subject { get; set; }
+
     public string? BodyHtml { get; set; }
+    [JsonPropertyName("body_html")]
+    public string? BodyHtmlSnakeCase { set => BodyHtml = value; }
+
     public string? BodyText { get; set; }
+    [JsonPropertyName("body_text")]
+    public string? BodyTextSnakeCase { set => BodyText = value; }
+
     public JsonElement? Template { get; set; }
+    [JsonPropertyName("scheduled_at")]
+    public DateTimeOffset? ScheduledAtSnakeCase { set => ScheduledAt = value; }
+
     public DateTimeOffset? ScheduledAt { get; set; }
+    [JsonPropertyName("window_start")]
+    public DateTimeOffset? WindowStartSnakeCase { set => WindowStart = value; }
+
     public DateTimeOffset? WindowStart { get; set; }
+    [JsonPropertyName("window_end")]
+    public DateTimeOffset? WindowEndSnakeCase { set => WindowEnd = value; }
+
     public DateTimeOffset? WindowEnd { get; set; }
+
     public TrackingOptions? Tracking { get; set; }
 }
 
@@ -26,6 +51,9 @@ public sealed class TrackingOptions
 public sealed class CreateSendJobResponse
 {
     public Guid SendJobId { get; set; }
+    [JsonPropertyName("send_job_id")]
+    public Guid SendJobIdSnakeCase => SendJobId;
+
     public string Status { get; set; } = "pending";
 }
 
@@ -33,12 +61,29 @@ public sealed class SendJobResponse
 {
     public Guid Id { get; set; }
     public Guid TenantId { get; set; }
+    [JsonPropertyName("tenant_id")]
+    public Guid TenantIdSnakeCase => TenantId;
+
     public Guid ListId { get; set; }
+    [JsonPropertyName("list_id")]
+    public Guid ListIdSnakeCase => ListId;
+
     public Guid CampaignId { get; set; }
+    [JsonPropertyName("campaign_id")]
+    public Guid CampaignIdSnakeCase => CampaignId;
+
     public string Status { get; set; } = "pending";
     public DateTimeOffset? ScheduledAt { get; set; }
+    [JsonPropertyName("scheduled_at")]
+    public DateTimeOffset? ScheduledAtSnakeCase => ScheduledAt;
+
     public DateTimeOffset? WindowStart { get; set; }
+    [JsonPropertyName("window_start")]
+    public DateTimeOffset? WindowStartSnakeCase => WindowStart;
+
     public DateTimeOffset? WindowEnd { get; set; }
+    [JsonPropertyName("window_end")]
+    public DateTimeOffset? WindowEndSnakeCase => WindowEnd;
 }
 
 public sealed class SendJobStatusResponse

src/SendEngine.Api/Program.cs

@@ -6,6 +6,7 @@ using Microsoft.AspNetCore.Authentication.JwtBearer;
 using Microsoft.EntityFrameworkCore;
 using Microsoft.IdentityModel.Tokens;
 using SendEngine.Api.Models;
+using SendEngine.Api.Services;
 using SendEngine.Api.Security;
 using SendEngine.Domain.Entities;
 using SendEngine.Infrastructure;
@@ -16,24 +17,93 @@ var builder = WebApplication.CreateBuilder(args);
 builder.Services.AddEndpointsApiExplorer();
 builder.Services.AddSwaggerGen();
 builder.Services.AddInfrastructure(builder.Configuration);
+builder.Services.AddHostedService<DevMockSenderWorker>();
 
-var signingKey = builder.Configuration["Jwt:SigningKey"];
-if (string.IsNullOrWhiteSpace(signingKey))
+var jwtAuthority = builder.Configuration["Jwt:Authority"];
+var jwtMetadataAddress = builder.Configuration["Jwt:MetadataAddress"];
+var memberCenterBaseUrl = builder.Configuration["MemberCenter:BaseUrl"];
+if (string.IsNullOrWhiteSpace(jwtAuthority) &&
+    string.IsNullOrWhiteSpace(jwtMetadataAddress) &&
+    !string.IsNullOrWhiteSpace(memberCenterBaseUrl) &&
+    Uri.TryCreate(memberCenterBaseUrl, UriKind.Absolute, out var memberCenterBaseUri))
 {
-    throw new InvalidOperationException("Jwt:SigningKey is required.");
+    jwtMetadataAddress = new Uri(memberCenterBaseUri, "/.well-known/openid-configuration").ToString();
+}
+var signingKey = builder.Configuration["Jwt:SigningKey"];
+var useOidcJwks = !string.IsNullOrWhiteSpace(jwtAuthority) || !string.IsNullOrWhiteSpace(jwtMetadataAddress);
+
+if (!useOidcJwks && string.IsNullOrWhiteSpace(signingKey))
+{
+    throw new InvalidOperationException(
+        "JWT config missing. Set Jwt:Authority or Jwt:MetadataAddress for JWKS validation, " +
+        "or set Jwt:SigningKey for symmetric key validation.");
 }
 
 builder.Services.AddAuthentication(JwtBearerDefaults.AuthenticationScheme)
     .AddJwtBearer(options =>
     {
-        options.TokenValidationParameters = new TokenValidationParameters
+        var expectedIssuer = builder.Configuration["Jwt:Issuer"];
+        var expectedAudience = builder.Configuration["Jwt:Audience"];
+        var requireHttpsMetadata = builder.Configuration.GetValue("Jwt:RequireHttpsMetadata", false);
+
+        if (useOidcJwks)
         {
-            ValidateIssuer = true,
-            ValidateAudience = true,
-            ValidateIssuerSigningKey = true,
-            ValidIssuer = builder.Configuration["Jwt:Issuer"],
-            ValidAudience = builder.Configuration["Jwt:Audience"],
-            IssuerSigningKey = new SymmetricSecurityKey(Encoding.UTF8.GetBytes(signingKey))
+            if (!string.IsNullOrWhiteSpace(jwtAuthority))
+            {
+                options.Authority = jwtAuthority;
+            }
+
+            if (!string.IsNullOrWhiteSpace(jwtMetadataAddress))
+            {
+                options.MetadataAddress = jwtMetadataAddress;
+            }
+
+            options.RequireHttpsMetadata = requireHttpsMetadata;
+            options.TokenValidationParameters = new TokenValidationParameters
+            {
+                ValidateIssuer = true,
+                ValidateAudience = true,
+                ValidAudience = expectedAudience
+            };
+
+            if (!string.IsNullOrWhiteSpace(expectedIssuer))
+            {
+                options.TokenValidationParameters.ValidIssuer = expectedIssuer;
+            }
+        }
+        else
+        {
+            options.TokenValidationParameters = new TokenValidationParameters
+            {
+                ValidateIssuer = true,
+                ValidateAudience = true,
+                ValidateIssuerSigningKey = true,
+                ValidIssuer = expectedIssuer,
+                ValidAudience = expectedAudience,
+                IssuerSigningKey = new SymmetricSecurityKey(Encoding.UTF8.GetBytes(signingKey!))
+            };
+        }
+        options.Events = new JwtBearerEvents
+        {
+            OnAuthenticationFailed = context =>
+            {
+                if (!context.Request.Path.StartsWithSegments("/api"))
+                {
+                    return Task.CompletedTask;
+                }
+
+                var logger = context.HttpContext.RequestServices
+                    .GetRequiredService<ILoggerFactory>()
+                    .CreateLogger("SendEngine.Api.Auth");
+                logger.LogWarning(
+                    context.Exception,
+                    "JWT authentication failed. path={Path} expected_issuer={ExpectedIssuer} expected_audience={ExpectedAudience} mode={Mode}",
+                    context.Request.Path.Value,
+                    expectedIssuer ?? string.Empty,
+                    expectedAudience ?? string.Empty,
+                    useOidcJwks ? "jwks" : "symmetric");
+                return Task.CompletedTask;
+            }
         };
     });
 
@@ -84,6 +154,10 @@ app.MapPost("/api/send-jobs", async (
     ILoggerFactory loggerFactory) =>
 {
     var logger = loggerFactory.CreateLogger("SendEngine.Api.SendJobs");
+    if (!HasScope(httpContext.User, "newsletter:send.write"))
+    {
+        return Results.StatusCode(StatusCodes.Status403Forbidden);
+    }
     var tenantId = GetTenantId(httpContext.User);
     if (tenantId is null)
     {
@@ -187,6 +261,10 @@ app.MapPost("/api/send-jobs", async (
 
 app.MapGet("/api/send-jobs/{id:guid}", async (HttpContext httpContext, Guid id, SendEngineDbContext db) =>
 {
+    if (!HasScope(httpContext.User, "newsletter:send.read"))
+    {
+        return Results.StatusCode(StatusCodes.Status403Forbidden);
+    }
     var tenantId = GetTenantId(httpContext.User);
     if (tenantId is null)
     {
@@ -215,6 +293,10 @@ app.MapGet("/api/send-jobs/{id:guid}", async (HttpContext httpContext, Guid id,
 
 app.MapPost("/api/send-jobs/{id:guid}/cancel", async (HttpContext httpContext, Guid id, SendEngineDbContext db) =>
 {
+    if (!HasScope(httpContext.User, "newsletter:send.write"))
+    {
+        return Results.StatusCode(StatusCodes.Status403Forbidden);
+    }
     var tenantId = GetTenantId(httpContext.User);
     if (tenantId is null)
     {
@@ -587,6 +669,18 @@ static Guid? GetTenantId(ClaimsPrincipal user)
     return Guid.TryParse(value, out var tenantId) ? tenantId : null;
 }
 
+static bool HasScope(ClaimsPrincipal user, string scope)
+{
+    var raw = user.FindFirst("scope")?.Value;
+    if (string.IsNullOrWhiteSpace(raw))
+    {
+        return false;
+    }
+
+    return raw.Split(' ', StringSplitOptions.RemoveEmptyEntries)
+        .Contains(scope, StringComparer.Ordinal);
+}
+
 static bool IsSupportedSubscriptionEvent(string eventType)
 {
     return eventType is "subscription.activated" or "subscription.unsubscribed" or "preferences.updated";
@@ -953,7 +1047,7 @@ static async Task NotifyMemberCenterDisableAsync(
 
     var url = ResolveMemberCenterUrl(
         configuration,
-        "MemberCenter:DisableSubscriptionUrl",
+        null,
         "MemberCenter:BaseUrl",
         "MemberCenter:DisableSubscriptionPath",
         "/subscriptions/disable");
@@ -1015,7 +1109,7 @@ static async Task<string?> ResolveMemberCenterAccessTokenAsync(IConfiguration co
 {
     var tokenUrl = ResolveMemberCenterUrl(
         configuration,
-        "MemberCenter:TokenUrl",
+        null,
         "MemberCenter:BaseUrl",
         "MemberCenter:TokenPath",
         "/oauth/token");
@@ -1087,15 +1181,18 @@ static async Task<string?> ResolveMemberCenterAccessTokenAsync(IConfiguration co
 
 static string? ResolveMemberCenterUrl(
     IConfiguration configuration,
-    string fullUrlKey,
+    string? fullUrlKey,
     string baseUrlKey,
     string pathKey,
     string defaultPath)
 {
-    var fullUrl = configuration[fullUrlKey];
-    if (!string.IsNullOrWhiteSpace(fullUrl))
+    if (!string.IsNullOrWhiteSpace(fullUrlKey))
     {
-        return fullUrl;
+        var fullUrl = configuration[fullUrlKey];
+        if (!string.IsNullOrWhiteSpace(fullUrl))
+        {
+            return fullUrl;
+        }
     }
 
     var baseUrl = configuration[baseUrlKey];

src/SendEngine.Api/SendEngine.Api.csproj

@@ -9,6 +9,7 @@
   <ItemGroup>
     <PackageReference Include="Microsoft.AspNetCore.Authentication.JwtBearer" Version="8.0.0" />
     <PackageReference Include="Microsoft.AspNetCore.OpenApi" Version="8.0.23" />
+    <PackageReference Include="AWSSDK.SimpleEmailV2" Version="3.7.401.2" />
     <PackageReference Include="Microsoft.EntityFrameworkCore.Design" Version="8.0.0">
       <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
       <PrivateAssets>all</PrivateAssets>

src/SendEngine.Api/Services/DevMockSenderWorker.cs

@@ -0,0 +1,603 @@
+using System.Text.Json;
+using System.Text.Json.Serialization;
+using System.Net.Http.Headers;
+using System.Net.Http.Json;
+using Amazon;
+using Amazon.SimpleEmailV2;
+using Amazon.SimpleEmailV2.Model;
+using Microsoft.EntityFrameworkCore;
+using SendEngine.Domain.Entities;
+using SendEngine.Infrastructure.Data;
+
+namespace SendEngine.Api.Services;
+
+public sealed class DevMockSenderWorker : BackgroundService
+{
+    private readonly IServiceScopeFactory _scopeFactory;
+    private readonly IConfiguration _configuration;
+    private readonly ILogger<DevMockSenderWorker> _logger;
+
+    public DevMockSenderWorker(
+        IServiceScopeFactory scopeFactory,
+        IConfiguration configuration,
+        ILogger<DevMockSenderWorker> logger)
+    {
+        _scopeFactory = scopeFactory;
+        _configuration = configuration;
+        _logger = logger;
+    }
+
+    protected override async Task ExecuteAsync(CancellationToken stoppingToken)
+    {
+        var devEnabled = _configuration.GetValue("DevSender:Enabled", false);
+        var provider = (_configuration["ESP:Provider"] ?? "mock").Trim().ToLowerInvariant();
+        var sesEnabled = provider == "ses";
+        if (!devEnabled && !sesEnabled)
+        {
+            _logger.LogInformation("Sender worker disabled. esp_provider={Provider} dev_sender_enabled={DevEnabled}", provider, devEnabled);
+            return;
+        }
+
+        var intervalSeconds = Math.Max(1, _configuration.GetValue("DevSender:PollIntervalSeconds", 5));
+        _logger.LogInformation(
+            "Sender worker started. esp_provider={Provider} dev_sender_enabled={DevEnabled} poll_interval_seconds={IntervalSeconds}",
+            provider,
+            devEnabled,
+            intervalSeconds);
+
+        while (!stoppingToken.IsCancellationRequested)
+        {
+            try
+            {
+                await ProcessPendingJobsAsync(stoppingToken);
+            }
+            catch (Exception ex)
+            {
+                _logger.LogError(ex, "DevMockSenderWorker process loop failed.");
+            }
+
+            await Task.Delay(TimeSpan.FromSeconds(intervalSeconds), stoppingToken);
+        }
+    }
+
+    private async Task ProcessPendingJobsAsync(CancellationToken cancellationToken)
+    {
+        using var scope = _scopeFactory.CreateScope();
+        var db = scope.ServiceProvider.GetRequiredService<SendEngineDbContext>();
+
+        var now = DateTimeOffset.UtcNow;
+        var jobs = await db.SendJobs
+            .Where(x => x.Status == "pending" && (!x.ScheduledAt.HasValue || x.ScheduledAt <= now))
+            .OrderBy(x => x.CreatedAt)
+            .Take(20)
+            .ToListAsync(cancellationToken);
+
+        foreach (var job in jobs)
+        {
+            await ProcessSingleJobAsync(db, job, cancellationToken);
+        }
+    }
+
+    private async Task ProcessSingleJobAsync(SendEngineDbContext db, SendJob job, CancellationToken cancellationToken)
+    {
+        var now = DateTimeOffset.UtcNow;
+        job.Status = "running";
+        job.UpdatedAt = now;
+        await db.SaveChangesAsync(cancellationToken);
+
+        try
+        {
+            var campaign = await db.Campaigns.AsNoTracking()
+                .FirstOrDefaultAsync(x => x.Id == job.CampaignId, cancellationToken);
+            if (campaign is null)
+            {
+                job.Status = "failed";
+                job.UpdatedAt = DateTimeOffset.UtcNow;
+                await db.SaveChangesAsync(cancellationToken);
+                _logger.LogWarning("DevMockSenderWorker failed job: campaign not found. send_job_id={SendJobId}", job.Id);
+                return;
+            }
+
+            var subscriptions = await db.Subscriptions.AsNoTracking()
+                .Where(x => x.ListId == job.ListId && x.Status == "active")
+                .ToListAsync(cancellationToken);
+
+            var issuedTokens = await FetchOneClickUnsubscribeTokensAsync(job.TenantId, job.ListId, subscriptions, cancellationToken);
+            var oneClickUrlConfigured = HasOneClickTokenEndpointConfigured();
+
+            var replacements = subscriptions
+            .Where(subscription =>
+            {
+                if (!oneClickUrlConfigured)
+                {
+                    return true;
+                }
+
+                if (!subscription.ExternalSubscriberId.HasValue)
+                {
+                    return false;
+                }
+
+                return issuedTokens.ContainsKey(subscription.ExternalSubscriberId.Value);
+            })
+            .Select(subscription =>
+            {
+                var unsubscribeToken = subscription.ExternalSubscriberId.HasValue &&
+                                       issuedTokens.TryGetValue(subscription.ExternalSubscriberId.Value, out var token)
+                    ? token
+                    : null;
+                var values = BuildPlaceholderValues(job, campaign, subscription, unsubscribeToken);
+                var subject = Personalize(campaign.Subject, values);
+                var bodyHtml = Personalize(campaign.BodyHtml, values);
+                var bodyText = Personalize(campaign.BodyText, values);
+                return new RecipientPreview(subscription.Email, values, subject, bodyHtml, bodyText);
+            }).ToList();
+
+            if (oneClickUrlConfigured)
+            {
+                var skipped = subscriptions.Count - replacements.Count;
+                if (skipped > 0)
+                {
+                    _logger.LogInformation(
+                        "Sender worker skipped recipients without issued one-click token. send_job_id={SendJobId} skipped_count={SkippedCount}",
+                        job.Id,
+                        skipped);
+                }
+            }
+
+            var provider = (_configuration["ESP:Provider"] ?? "mock").Trim().ToLowerInvariant();
+            var deliveredCount = 0;
+            if (provider == "ses")
+            {
+                deliveredCount = await SendViaSesBulkAsync(campaign, replacements, cancellationToken);
+            }
+            else
+            {
+                deliveredCount = replacements.Count;
+                foreach (var preview in replacements)
+                {
+                    preview.Placeholders.TryGetValue("unsubscribe_url", out var unsubscribeUrl);
+                    _logger.LogInformation(
+                        "MOCK send preview. send_job_id={SendJobId} email={Email} subject={Subject} unsubscribe_url={UnsubscribeUrl} body_html={BodyHtml} body_text={BodyText}",
+                        job.Id,
+                        preview.Email,
+                        preview.Subject,
+                        unsubscribeUrl ?? string.Empty,
+                        preview.BodyHtml,
+                        preview.BodyText);
+                }
+            }
+
+            if (_configuration.GetValue("DevSender:Enabled", false))
+            {
+                var previewEvents = replacements.Select(preview =>
+                {
+                    var unsubscribeUrl = preview.Placeholders.GetValueOrDefault("unsubscribe_url", string.Empty);
+                    var payload = JsonSerializer.Serialize(new
+                    {
+                        send_job_id = job.Id,
+                        campaign_id = campaign.Id,
+                        tenant_id = job.TenantId,
+                        list_id = job.ListId,
+                        email = preview.Email,
+                        subject = preview.Subject,
+                        body_html = preview.BodyHtml,
+                        body_text = preview.BodyText,
+                        unsubscribe_url = unsubscribeUrl,
+                        placeholders = preview.Placeholders,
+                        generated_at = DateTimeOffset.UtcNow
+                    });
+
+                    return new EventInbox
+                    {
+                        Id = Guid.NewGuid(),
+                        TenantId = job.TenantId,
+                        EventType = "send.preview",
+                        Source = "dev_sender",
+                        Payload = payload,
+                        ReceivedAt = DateTimeOffset.UtcNow,
+                        Status = "processed",
+                        ProcessedAt = DateTimeOffset.UtcNow
+                    };
+                }).ToList();
+
+                db.EventsInbox.AddRange(previewEvents);
+            }
+
+            var summary = await db.DeliverySummaries
+                .FirstOrDefaultAsync(x => x.TenantId == job.TenantId && x.SendJobId == job.Id, cancellationToken);
+            if (summary is null)
+            {
+                summary = new DeliverySummary
+                {
+                    Id = Guid.NewGuid(),
+                    TenantId = job.TenantId,
+                    SendJobId = job.Id,
+                    CreatedAt = DateTimeOffset.UtcNow
+                };
+                db.DeliverySummaries.Add(summary);
+            }
+
+            summary.Total = replacements.Count;
+            summary.Delivered = deliveredCount;
+            summary.Bounced = 0;
+            summary.Complained = 0;
+            summary.UpdatedAt = DateTimeOffset.UtcNow;
+
+            job.Status = deliveredCount == replacements.Count ? "completed" : "failed";
+            job.UpdatedAt = DateTimeOffset.UtcNow;
+            await db.SaveChangesAsync(cancellationToken);
+
+            _logger.LogInformation(
+                "Sender worker completed send job. provider={Provider} send_job_id={SendJobId} tenant_id={TenantId} recipient_count={RecipientCount} delivered_count={DeliveredCount}",
+                provider,
+                job.Id,
+                job.TenantId,
+                replacements.Count,
+                deliveredCount);
+        }
+        catch (Exception ex)
+        {
+            job.Status = "failed";
+            job.UpdatedAt = DateTimeOffset.UtcNow;
+            await db.SaveChangesAsync(cancellationToken);
+            _logger.LogError(ex, "Sender worker failed job. send_job_id={SendJobId}", job.Id);
+        }
+    }
+
+    private async Task<int> SendViaSesBulkAsync(Campaign campaign, IReadOnlyCollection<RecipientPreview> recipients, CancellationToken cancellationToken)
+    {
+        var region = _configuration["Ses:Region"] ?? "us-east-1";
+        var fromEmail = _configuration["Ses:FromEmail"] ?? string.Empty;
+        var templateName = ExtractTemplateString(campaign.Template, "ses_template_name")
+            ?? _configuration["Ses:TemplateName"]
+            ?? string.Empty;
+        if (string.IsNullOrWhiteSpace(fromEmail))
+        {
+            _logger.LogWarning("SES send skipped: Ses__FromEmail is empty.");
+            return 0;
+        }
+        if (string.IsNullOrWhiteSpace(templateName))
+        {
+            _logger.LogWarning("SES send skipped: ses template name is empty (template.ses_template_name / Ses__TemplateName).");
+            return 0;
+        }
+
+        using var ses = new AmazonSimpleEmailServiceV2Client(RegionEndpoint.GetBySystemName(region));
+
+        var delivered = 0;
+        foreach (var batch in recipients.Chunk(50))
+        {
+            var request = new SendBulkEmailRequest
+            {
+                FromEmailAddress = fromEmail,
+                ConfigurationSetName = _configuration["Ses:ConfigurationSet"],
+                DefaultContent = new BulkEmailContent
+                {
+                    Template = new Template
+                    {
+                        TemplateName = templateName,
+                        TemplateData = "{}"
+                    }
+                },
+                BulkEmailEntries = batch.Select(preview => new BulkEmailEntry
+                {
+                    Destination = new Destination
+                    {
+                        ToAddresses = new List<string> { preview.Email }
+                    },
+                    ReplacementEmailContent = new ReplacementEmailContent
+                    {
+                        ReplacementTemplate = new ReplacementTemplate
+                        {
+                            ReplacementTemplateData = JsonSerializer.Serialize(preview.Placeholders)
+                        }
+                    }
+                }).ToList()
+            };
+
+            var response = await ses.SendBulkEmailAsync(request, cancellationToken);
+            foreach (var result in response.BulkEmailEntryResults)
+            {
+                if (string.Equals(result.Status?.Value, "SUCCESS", StringComparison.OrdinalIgnoreCase))
+                {
+                    delivered++;
+                }
+                else
+                {
+                    _logger.LogWarning(
+                        "SES bulk entry failed. status={Status} error={Error} message_id={MessageId}",
+                        result.Status?.Value,
+                        result.Error,
+                        result.MessageId);
+                }
+            }
+        }
+
+        return delivered;
+    }
+
+    private async Task<Dictionary<Guid, string>> FetchOneClickUnsubscribeTokensAsync(
+        Guid tenantId,
+        Guid listId,
+        IReadOnlyCollection<Subscription> subscriptions,
+        CancellationToken cancellationToken)
+    {
+        var endpointUrl = ResolveMemberCenterUrl(
+            _configuration,
+            null,
+            "MemberCenter:BaseUrl",
+            "MemberCenter:OneClickUnsubscribeTokensPath",
+            "/newsletter/one-click-unsubscribe-tokens");
+        if (string.IsNullOrWhiteSpace(endpointUrl))
+        {
+            return new Dictionary<Guid, string>();
+        }
+
+        var subscriberIds = subscriptions
+            .Where(x => x.ExternalSubscriberId.HasValue)
+            .Select(x => x.ExternalSubscriberId!.Value)
+            .Distinct()
+            .ToArray();
+        if (subscriberIds.Length == 0)
+        {
+            return new Dictionary<Guid, string>();
+        }
+
+        using var client = new HttpClient();
+        var token = await ResolveMemberCenterAccessTokenAsync(_configuration, client, _logger, cancellationToken);
+        if (string.IsNullOrWhiteSpace(token))
+        {
+            _logger.LogWarning("Skip one-click token fetch: unable to resolve Member Center access token.");
+            return new Dictionary<Guid, string>();
+        }
+        client.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Bearer", token);
+
+        var result = new Dictionary<Guid, string>();
+        foreach (var batch in subscriberIds.Chunk(200))
+        {
+            var body = new
+            {
+                tenant_id = tenantId,
+                list_id = listId,
+                subscriber_ids = batch
+            };
+
+            try
+            {
+                using var response = await client.PostAsJsonAsync(endpointUrl, body, cancellationToken);
+                if (!response.IsSuccessStatusCode)
+                {
+                    var errorBody = await response.Content.ReadAsStringAsync(cancellationToken);
+                    _logger.LogWarning(
+                        "One-click token batch request failed. status={StatusCode} body={Body}",
+                        (int)response.StatusCode,
+                        Truncate(errorBody, 1000));
+                    continue;
+                }
+
+                var payload = await response.Content.ReadFromJsonAsync<OneClickTokensResponse>(cancellationToken: cancellationToken);
+                if (payload?.Items is null)
+                {
+                    continue;
+                }
+
+                foreach (var item in payload.Items)
+                {
+                    if (item.SubscriberId == Guid.Empty ||
+                        !string.Equals(item.Status, "issued", StringComparison.OrdinalIgnoreCase) ||
+                        string.IsNullOrWhiteSpace(item.UnsubscribeToken))
+                    {
+                        continue;
+                    }
+
+                    result[item.SubscriberId] = item.UnsubscribeToken;
+                }
+            }
+            catch (Exception ex)
+            {
+                _logger.LogWarning(ex, "One-click token batch request threw exception.");
+            }
+        }
+
+        return result;
+    }
+
+    private bool HasOneClickTokenEndpointConfigured()
+    {
+        return !string.IsNullOrWhiteSpace(ResolveMemberCenterUrl(
+            _configuration,
+            null,
+            "MemberCenter:BaseUrl",
+            "MemberCenter:OneClickUnsubscribeTokensPath",
+            "/newsletter/one-click-unsubscribe-tokens"));
+    }
+
+    private static Dictionary<string, string> BuildPlaceholderValues(
+        SendJob job,
+        Campaign campaign,
+        Subscription subscription,
+        string? unsubscribeToken)
+    {
+        var values = new Dictionary<string, string>(StringComparer.OrdinalIgnoreCase)
+        {
+            ["email"] = subscription.Email,
+            ["tenant_id"] = job.TenantId.ToString("D"),
+            ["list_id"] = job.ListId.ToString("D"),
+            ["campaign_id"] = campaign.Id.ToString("D"),
+            ["send_job_id"] = job.Id.ToString("D"),
+            ["unsubscribe_token"] = unsubscribeToken ?? string.Empty
+        };
+
+        var unsubscribeTemplate = ExtractTemplateString(campaign.Template, "unsubscribe_url");
+        var unsubscribeUrl = Personalize(unsubscribeTemplate, values);
+        values["unsubscribe_url"] = unsubscribeUrl;
+
+        return values;
+    }
+
+    private static async Task<string?> ResolveMemberCenterAccessTokenAsync(
+        IConfiguration configuration,
+        HttpClient client,
+        ILogger logger,
+        CancellationToken cancellationToken)
+    {
+        var tokenUrl = ResolveMemberCenterUrl(
+            configuration,
+            null,
+            "MemberCenter:BaseUrl",
+            "MemberCenter:TokenPath",
+            "/oauth/token");
+        var clientId = configuration["MemberCenter:ClientId"];
+        var clientSecret = configuration["MemberCenter:ClientSecret"];
+        var scope = configuration["MemberCenter:Scope"];
+
+        if (!string.IsNullOrWhiteSpace(tokenUrl) &&
+            !string.IsNullOrWhiteSpace(clientId) &&
+            !string.IsNullOrWhiteSpace(clientSecret))
+        {
+            var form = new Dictionary<string, string>
+            {
+                ["grant_type"] = "client_credentials",
+                ["client_id"] = clientId,
+                ["client_secret"] = clientSecret
+            };
+            if (!string.IsNullOrWhiteSpace(scope))
+            {
+                form["scope"] = scope;
+            }
+
+            try
+            {
+                using var response = await client.PostAsync(tokenUrl, new FormUrlEncodedContent(form), cancellationToken);
+                if (response.IsSuccessStatusCode)
+                {
+                    await using var stream = await response.Content.ReadAsStreamAsync(cancellationToken);
+                    using var json = await JsonDocument.ParseAsync(stream, cancellationToken: cancellationToken);
+                    if (json.RootElement.TryGetProperty("access_token", out var tokenElement))
+                    {
+                        var accessToken = tokenElement.GetString();
+                        if (!string.IsNullOrWhiteSpace(accessToken))
+                        {
+                            return accessToken;
+                        }
+                    }
+                }
+                else
+                {
+                    var body = await response.Content.ReadAsStringAsync(cancellationToken);
+                    logger.LogWarning("MemberCenter token request failed. status={StatusCode} body={Body}", (int)response.StatusCode, Truncate(body, 1000));
+                }
+            }
+            catch (Exception ex)
+            {
+                logger.LogWarning(ex, "MemberCenter token request failed.");
+            }
+        }
+
+        return configuration["MemberCenter:ApiToken"];
+    }
+
+    private static string? ResolveMemberCenterUrl(
+        IConfiguration configuration,
+        string? fullUrlKey,
+        string baseUrlKey,
+        string pathKey,
+        string defaultPath)
+    {
+        if (!string.IsNullOrWhiteSpace(fullUrlKey))
+        {
+            var fullUrl = configuration[fullUrlKey];
+            if (!string.IsNullOrWhiteSpace(fullUrl))
+            {
+                return fullUrl;
+            }
+        }
+
+        var baseUrl = configuration[baseUrlKey];
+        if (string.IsNullOrWhiteSpace(baseUrl))
+        {
+            return null;
+        }
+
+        var path = configuration[pathKey];
+        if (string.IsNullOrWhiteSpace(path))
+        {
+            path = defaultPath;
+        }
+
+        return $"{baseUrl.TrimEnd('/')}/{path.TrimStart('/')}";
+    }
+
+    private static string Truncate(string? value, int maxLength)
+    {
+        if (string.IsNullOrEmpty(value))
+        {
+            return string.Empty;
+        }
+
+        return value.Length <= maxLength ? value : $"{value[..maxLength]}...(truncated)";
+    }
+
+    private static string? ExtractTemplateString(string? templateJson, string key)
+    {
+        if (string.IsNullOrWhiteSpace(templateJson))
+        {
+            return null;
+        }
+
+        try
+        {
+            using var doc = JsonDocument.Parse(templateJson);
+            if (doc.RootElement.TryGetProperty(key, out var value) && value.ValueKind == JsonValueKind.String)
+            {
+                return value.GetString();
+            }
+        }
+        catch
+        {
+            // keep empty when template payload is not a valid object JSON
+        }
+
+        return null;
+    }
+
+    private static string Personalize(string? template, IReadOnlyDictionary<string, string> values)
+    {
+        if (string.IsNullOrWhiteSpace(template))
+        {
+            return string.Empty;
+        }
+
+        var content = template;
+        foreach (var pair in values)
+        {
+            content = content.Replace($"{{{{{pair.Key}}}}}", pair.Value, StringComparison.OrdinalIgnoreCase);
+        }
+
+        return content;
+    }
+
+    private sealed record RecipientPreview(
+        string Email,
+        Dictionary<string, string> Placeholders,
+        string Subject,
+        string BodyHtml,
+        string BodyText);
+
+    private sealed class OneClickTokensResponse
+    {
+        [JsonPropertyName("items")]
+        public List<OneClickTokenItem>? Items { get; set; }
+    }
+
+    private sealed class OneClickTokenItem
+    {
+        [JsonPropertyName("subscriber_id")]
+        public Guid SubscriberId { get; set; }
+        [JsonPropertyName("unsubscribe_token")]
+        public string? UnsubscribeToken { get; set; }
+        [JsonPropertyName("status")]
+        public string? Status { get; set; }
+    }
+}