diff --git a/apps/backend/src/services/platforms/affiliate-dash/http-client.ts b/apps/backend/src/services/platforms/affiliate-dash/http-client.ts
index 8a5854b1..c54a240a 100644
--- a/apps/backend/src/services/platforms/affiliate-dash/http-client.ts
+++ b/apps/backend/src/services/platforms/affiliate-dash/http-client.ts
@@ -95,18 +95,20 @@ export async function affiliateDashRequest(input: {
       logExternalHttpPacket('[affiliate-dash/http]', 'HTTP 响应失败', responsePacket, {
         level: 'warn',
       })
-      throw createHttpError(
-        summarizeAffiliateDashMessage(json) || `affiliate-dash 请求失败: HTTP ${response.status}`,
-        {
-          statusCode: 502,
-          errorCode: 'affiliate_dash_http_failed',
-          context: {
-            status: response.status,
-            message: summarizeAffiliateDashMessage(json),
-            body: text,
-          },
+      const upstreamMessage =
+        summarizeAffiliateDashMessage(json) || `affiliate-dash 请求失败: HTTP ${response.status}`
+      // 上游 4xx 透传状态码，便于领取页展示真实原因；5xx 仍归一为 502。
+      const statusCode =
+        response.status >= 400 && response.status < 500 ? response.status : 502
+      throw createHttpError(upstreamMessage, {
+        statusCode,
+        errorCode: 'affiliate_dash_http_failed',
+        context: {
+          status: response.status,
+          message: summarizeAffiliateDashMessage(json),
+          body: text,
         },
-      )
+      })
     }
 
     if (!isAffiliateDashSuccessResponse(json)) {
diff --git a/apps/backend/src/utils/http.test.ts b/apps/backend/src/utils/http.test.ts
index fe0fa410..af0e43ae 100644
--- a/apps/backend/src/utils/http.test.ts
+++ b/apps/backend/src/utils/http.test.ts
@@ -1,7 +1,7 @@
 import assert from 'node:assert/strict'
 import test from 'node:test'
 
-import { resolveRouteErrorLogLevel } from './http.js'
+import { buildErrorPayload, createHttpError, resolveRouteErrorLogLevel } from './http.js'
 
 test('expected worker session expiry is debug-level', () => {
   assert.equal(
@@ -14,3 +14,22 @@ test('expected worker session expiry is debug-level', () => {
   )
   assert.equal(resolveRouteErrorLogLevel({ statusCode: 500, errorCode: 'internal_error' }), 'error')
 })
+
+test('affiliate_dash errors surface upstream message even when mapped to 502', () => {
+  const error = createHttpError('乐玩开放平台 AccessKey 或 SecretKey 未配置', {
+    statusCode: 502,
+    errorCode: 'affiliate_dash_http_failed',
+  })
+  const payload = buildErrorPayload(error, '提交 UID 失败')
+  assert.equal(payload.msg, '乐玩开放平台 AccessKey 或 SecretKey 未配置')
+  assert.equal(payload.errorCode, 'affiliate_dash_http_failed')
+})
+
+test('generic 5xx still uses fallback message', () => {
+  const error = createHttpError('secret internal boom', {
+    statusCode: 500,
+    errorCode: 'internal_error',
+  })
+  const payload = buildErrorPayload(error, '服务内部错误')
+  assert.equal(payload.msg, '服务内部错误')
+})
diff --git a/apps/backend/src/utils/http.ts b/apps/backend/src/utils/http.ts
index c087a3ef..aed97fdb 100644
--- a/apps/backend/src/utils/http.ts
+++ b/apps/backend/src/utils/http.ts
@@ -29,12 +29,16 @@ export function buildSuccessPayload(data: unknown, msg: string = 'ok') {
 
 export function buildErrorPayload(error: unknown, fallbackMessage: string) {
   const classification = classifyRouteError(error)
-  const message =
-    classification.statusCode >= 500
+  const errorMessage = error instanceof Error ? String(error.message || '').trim() : ''
+  // 依赖方错误（如 affiliate_dash）即使映射为 5xx，也优先透出上游可读原因。
+  const preferUpstreamMessage =
+    errorMessage &&
+    (classification.statusCode < 500 || classification.errorCode.startsWith('affiliate_dash'))
+  const message = preferUpstreamMessage
+    ? errorMessage
+    : classification.statusCode >= 500
       ? fallbackMessage || '服务内部错误'
-      : error instanceof Error
-        ? error.message
-        : fallbackMessage
+      : errorMessage || fallbackMessage
 
   return {
     code: 1,