diff --git a/apps/backend/src/db/migrations/127_repair_affiliate_dash_task_context.sql b/apps/backend/src/db/migrations/127_repair_affiliate_dash_task_context.sql
new file mode 100644
index 00000000..06266ee9
--- /dev/null
+++ b/apps/backend/src/db/migrations/127_repair_affiliate_dash_task_context.sql
@@ -0,0 +1,40 @@
+-- 127_repair_affiliate_dash_task_context.sql
+--
+-- 修复电子凭证绑定并发覆盖任务上下文的问题：
+-- affiliate_dash 建单事件已经记录了 orderNo/clientOrderNo，但任务 context_json
+-- 随后被旧 TaskRow 整段覆盖为空。回调按这两个键查任务时会 404。
+-- 只补缺失键，不覆盖现有 affiliateDash 其它字段。
+
+WITH latest_created AS (
+  SELECT DISTINCT ON (te.task_id)
+    te.task_id,
+    NULLIF(BTRIM(te.payload_json->>'orderNo'), '') AS order_no,
+    NULLIF(BTRIM(te.payload_json->>'clientOrderNo'), '') AS client_order_no
+  FROM task_events te
+  WHERE te.event_type = 'affiliate_dash_order_created'
+  ORDER BY te.task_id, te.created_at DESC, te.id DESC
+)
+UPDATE fulfillment_tasks ft
+SET
+  context_json = COALESCE(ft.context_json, '{}'::jsonb) || jsonb_build_object(
+    'affiliateDash',
+    COALESCE(ft.context_json->'affiliateDash', '{}'::jsonb) || jsonb_build_object(
+      'orderNo',
+      latest_created.order_no,
+      'clientOrderNo',
+      COALESCE(
+        latest_created.client_order_no,
+        NULLIF(ft.context_json #>> '{affiliateDash,clientOrderNo}', ''),
+        ft.platform_order_id
+      )
+    )
+  ),
+  updated_at = NOW()
+FROM latest_created
+WHERE ft.id = latest_created.task_id
+  AND ft.executor_key = 'affiliate_dash'
+  AND latest_created.order_no IS NOT NULL
+  AND (
+    COALESCE(ft.context_json #>> '{affiliateDash,orderNo}', '') = ''
+    OR COALESCE(ft.context_json #>> '{affiliateDash,clientOrderNo}', '') = ''
+  );
diff --git a/apps/backend/src/repositories/task-repo.ts b/apps/backend/src/repositories/task-repo.ts
index 2fece3cc..66bd067c 100644
--- a/apps/backend/src/repositories/task-repo.ts
+++ b/apps/backend/src/repositories/task-repo.ts
@@ -10,6 +10,7 @@ import type {
   TaskUpdatePatch,
 } from '../types/repository/inputs.js'
 import type { TaskListQueryResult, TaskRow } from '../types/repository/rows.js'
+import type { JsonObject } from '../types/json.js'
 
 type TaskQueryExecutor = (text: string, params?: unknown[]) => Promise<{ rows: unknown[] }>
 const AFFILIATE_DASH_EXECUTOR_KEY = 'affiliate_dash'
@@ -255,6 +256,31 @@ export async function updateTask(
   })
 }
 
+/**
+ * 原子合并任务上下文，避免调用方拿旧 TaskRow 整段覆盖并发写入的其它字段。
+ * 只合并顶层 key；调用方应传入完整的子对象 patch。
+ */
+export async function mergeTaskContext(
+  taskId: number | string,
+  patch: JsonObject,
+  updatedAt?: string | undefined,
+): Promise<TaskRow | null> {
+  return withTransaction(async (client) => {
+    const result = await client.query<{ id: number }>(
+      `
+        UPDATE fulfillment_tasks
+        SET context_json = COALESCE(context_json, '{}'::jsonb) || $2::jsonb,
+            updated_at = COALESCE($3, updated_at)
+        WHERE id = $1
+        RETURNING id
+      `,
+      [Number(taskId), JSON.stringify(patch), updatedAt || null],
+    )
+    if (!result.rows[0]) return null
+    return getTaskByIdWithExecutor(client.query.bind(client) as TaskQueryExecutor, taskId)
+  })
+}
+
 export async function updateTaskStatusIfCurrent(
   taskId: number | string,
   currentStatus: string,
diff --git a/apps/backend/src/services/platforms/kuaishou-industry/voucher-binding-service.test.ts b/apps/backend/src/services/platforms/kuaishou-industry/voucher-binding-service.test.ts
new file mode 100644
index 00000000..0a1432b1
--- /dev/null
+++ b/apps/backend/src/services/platforms/kuaishou-industry/voucher-binding-service.test.ts
@@ -0,0 +1,54 @@
+import assert from 'node:assert/strict'
+import test from 'node:test'
+
+import type { JsonObject } from '../../../types/json.js'
+import type { KuaishouIndustryVoucherRow, TaskRow } from '../../../types/repository/rows.js'
+import { attachKuaishouIndustryVoucherToTask } from './voucher-binding-service.js'
+
+test('电子凭证绑定只原子合并自己的 context key，不覆盖 affiliateDash', async () => {
+  const task = {
+    id: 120509,
+    context_json: {
+      affiliateDash: {
+        orderNo: 'FO2026110313080188725b91e99',
+        clientOrderNo: '2630702009068141',
+      },
+    },
+  } as unknown as TaskRow
+  const voucher = {
+    oid: '2630702009068141',
+    voucher_code: 'KSV4YQWP6SBEQFRBCBD',
+    token: 'token',
+    status: 'CONSUMED',
+    unit_index: 1,
+    send_callback_status: 'success',
+    send_callback_attempt_count: 1,
+  } as unknown as KuaishouIndustryVoucherRow
+  let capturedTaskId = 0
+  let capturedPatch: JsonObject | null = null
+  let capturedUpdatedAt = ''
+
+  const merged = await attachKuaishouIndustryVoucherToTask(
+    task,
+    voucher,
+    { now: '2026-11-03T13:08:01.383Z' },
+    {
+      mergeTaskContext: async (taskId, patch, updatedAt) => {
+        capturedTaskId = Number(taskId)
+        capturedPatch = patch
+        capturedUpdatedAt = String(updatedAt || '')
+        return task
+      },
+    },
+  )
+
+  assert.equal(merged, task)
+  assert.equal(capturedTaskId, 120509)
+  assert.equal(capturedUpdatedAt, '2026-11-03T13:08:01.383Z')
+  assert.deepEqual(Object.keys(capturedPatch || {}), ['kuaishouIndustryVoucher'])
+  assert.equal(
+    (capturedPatch?.kuaishouIndustryVoucher as Record<string, unknown> | undefined)?.oid,
+    '2630702009068141',
+  )
+  assert.equal('affiliateDash' in (capturedPatch || {}), false)
+})
diff --git a/apps/backend/src/services/platforms/kuaishou-industry/voucher-binding-service.ts b/apps/backend/src/services/platforms/kuaishou-industry/voucher-binding-service.ts
index 83c91e22..80c9c60e 100644
--- a/apps/backend/src/services/platforms/kuaishou-industry/voucher-binding-service.ts
+++ b/apps/backend/src/services/platforms/kuaishou-industry/voucher-binding-service.ts
@@ -1,11 +1,10 @@
-import { updateTask } from '../../../repositories/task-repo.js'
+import { mergeTaskContext } from '../../../repositories/task-repo.js'
 import type { JsonObject } from '../../../types/json.js'
 import {
   listKuaishouIndustryVouchersByOid,
   updateKuaishouIndustryVoucherByCode,
 } from '../../../repositories/kuaishou-industry-voucher-repo.js'
 import { normalizeTimestampIso } from '../../../utils/time.js'
-import { parseTaskContext } from '../../../utils/task-json.js'
 import {
   isKuaishouIndustryVoucherSendCallbackSuccess,
   normalizeKuaishouIndustrySendCallbackStatus,
@@ -17,6 +16,10 @@ import type {
   TaskRow,
 } from '../../../types/repository/rows.js'
 
+type VoucherBindingDeps = {
+  mergeTaskContext?: typeof mergeTaskContext
+}
+
 export async function bindKuaishouIndustryVouchersToOrderTasks(
   order: OrderRow | null | undefined,
   tasks: TaskRow[] = [],
@@ -62,27 +65,17 @@ export async function attachKuaishouIndustryVoucherToTask(
     source?: string
     now?: string
   } = {},
+  deps: VoucherBindingDeps = {},
 ) {
   const now = normalizeTimestampIso(options.now || new Date().toISOString())
-  const context = parseTaskContext(task)
-  const nextVoucherContext = buildKuaishouIndustryVoucherContext(
-    voucher,
-    context.kuaishouIndustryVoucher,
+  const nextVoucherContext = buildKuaishouIndustryVoucherContext(voucher, null, now)
+  const mergeContext = deps.mergeTaskContext || mergeTaskContext
+  // 只原子替换本模块负责的顶层 key，禁止用旧 TaskRow 整段覆盖 affiliateDash。
+  return mergeContext(
+    task.id,
+    { kuaishouIndustryVoucher: nextVoucherContext } satisfies JsonObject,
     now,
   )
-  const nextContext: JsonObject = {
-    ...context,
-    kuaishouIndustryVoucher: nextVoucherContext,
-  }
-
-  if (JSON.stringify(context) === JSON.stringify(nextContext)) {
-    return task
-  }
-
-  return updateTask(task.id, {
-    context_json: JSON.stringify(nextContext),
-    updated_at: now,
-  })
 }
 
 function resolveTaskForVoucher(voucher: KuaishouIndustryVoucherRow, tasks: TaskRow[]) {