diff --git a/frontend/src/views/admin/ops/components/OpsErrorDetailModal.vue b/frontend/src/views/admin/ops/components/OpsErrorDetailModal.vue
index 81fe982c..a7edff96 100644
--- a/frontend/src/views/admin/ops/components/OpsErrorDetailModal.vue
+++ b/frontend/src/views/admin/ops/components/OpsErrorDetailModal.vue
@@ -167,6 +167,7 @@ import Icon from '@/components/icons/Icon.vue'
 import { useAppStore } from '@/stores'
 import { opsAPI, type OpsErrorDetail } from '@/api/admin/ops'
 import { formatDateTime } from '@/utils/format'
+import { resolvePrimaryResponseBody, resolveUpstreamPayload } from '../utils/errorDetailResponse'
 
 interface Props {
   show: boolean
@@ -192,11 +193,7 @@ const showUpstreamList = computed(() => props.errorType === 'request')
 const requestId = computed(() => detail.value?.request_id || detail.value?.client_request_id || '')
 
 const primaryResponseBody = computed(() => {
-  if (!detail.value) return ''
-  if (props.errorType === 'upstream') {
-    return detail.value.upstream_error_detail || detail.value.upstream_errors || detail.value.upstream_error_message || detail.value.error_body || ''
-  }
-  return detail.value.error_body || ''
+  return resolvePrimaryResponseBody(detail.value, props.errorType)
 })
 
 
@@ -224,7 +221,9 @@ const correlatedUpstreamErrors = computed<OpsErrorDetail[]>(() => correlatedUpst
 const expandedUpstreamDetailIds = ref(new Set<number>())
 
 function getUpstreamResponsePreview(ev: OpsErrorDetail): string {
-  return String(ev.upstream_error_detail || ev.error_body || ev.upstream_error_message || '').trim()
+  const upstreamPayload = resolveUpstreamPayload(ev)
+  if (upstreamPayload) return upstreamPayload
+  return String(ev.error_body || '').trim()
 }
 
 function toggleUpstreamDetail(id: number) {
diff --git a/frontend/src/views/admin/ops/utils/__tests__/errorDetailResponse.spec.ts b/frontend/src/views/admin/ops/utils/__tests__/errorDetailResponse.spec.ts
new file mode 100644
index 00000000..7d294e0c
--- /dev/null
+++ b/frontend/src/views/admin/ops/utils/__tests__/errorDetailResponse.spec.ts
@@ -0,0 +1,138 @@
+import { describe, expect, it } from 'vitest'
+import type { OpsErrorDetail } from '@/api/admin/ops'
+import { resolvePrimaryResponseBody, resolveUpstreamPayload } from '../errorDetailResponse'
+
+function makeDetail(overrides: Partial<OpsErrorDetail>): OpsErrorDetail {
+  return {
+    id: 1,
+    created_at: '2026-01-01T00:00:00Z',
+    phase: 'request',
+    type: 'api_error',
+    error_owner: 'platform',
+    error_source: 'gateway',
+    severity: 'P2',
+    status_code: 502,
+    platform: 'openai',
+    model: 'gpt-4o-mini',
+    is_retryable: true,
+    retry_count: 0,
+    resolved: false,
+    client_request_id: 'crid-1',
+    request_id: 'rid-1',
+    message: 'Upstream request failed',
+    user_email: 'user@example.com',
+    account_name: 'acc',
+    group_name: 'group',
+    error_body: '',
+    user_agent: '',
+    request_body: '',
+    request_body_truncated: false,
+    is_business_limited: false,
+    ...overrides
+  }
+}
+
+describe('errorDetailResponse', () => {
+  it('prefers upstream payload for request modal when error_body is generic gateway wrapper', () => {
+    const detail = makeDetail({
+      error_body: JSON.stringify({
+        type: 'error',
+        error: {
+          type: 'upstream_error',
+          message: 'Upstream request failed'
+        }
+      }),
+      upstream_error_detail: '{"provider_message":"real upstream detail"}'
+    })
+
+    expect(resolvePrimaryResponseBody(detail, 'request')).toBe('{"provider_message":"real upstream detail"}')
+  })
+
+  it('keeps error_body for request modal when body is not generic wrapper', () => {
+    const detail = makeDetail({
+      error_body: JSON.stringify({
+        type: 'error',
+        error: {
+          type: 'upstream_error',
+          message: 'Upstream authentication failed, please contact administrator'
+        }
+      }),
+      upstream_error_detail: '{"provider_message":"real upstream detail"}'
+    })
+
+    expect(resolvePrimaryResponseBody(detail, 'request')).toBe(detail.error_body)
+  })
+
+  it('uses upstream payload first in upstream modal', () => {
+    const detail = makeDetail({
+      phase: 'upstream',
+      upstream_error_message: 'provider 503 overloaded',
+      error_body: '{"type":"error","error":{"type":"upstream_error","message":"Upstream request failed"}}'
+    })
+
+    expect(resolvePrimaryResponseBody(detail, 'upstream')).toBe('provider 503 overloaded')
+  })
+
+  it('falls back to upstream payload when request error_body is empty', () => {
+    const detail = makeDetail({
+      error_body: '',
+      upstream_error_message: 'dial tcp timeout'
+    })
+
+    expect(resolvePrimaryResponseBody(detail, 'request')).toBe('dial tcp timeout')
+  })
+
+  it('resolves upstream payload by detail -> events -> message priority', () => {
+    expect(resolveUpstreamPayload(makeDetail({
+      upstream_error_detail: 'detail payload',
+      upstream_errors: '[{"message":"event payload"}]',
+      upstream_error_message: 'message payload'
+    }))).toBe('detail payload')
+
+    expect(resolveUpstreamPayload(makeDetail({
+      upstream_error_detail: '',
+      upstream_errors: '[{"message":"event payload"}]',
+      upstream_error_message: 'message payload'
+    }))).toBe('[{"message":"event payload"}]')
+
+    expect(resolveUpstreamPayload(makeDetail({
+      upstream_error_detail: '',
+      upstream_errors: '',
+      upstream_error_message: 'message payload'
+    }))).toBe('message payload')
+  })
+
+  it('treats empty JSON placeholders in upstream payload as empty', () => {
+    expect(resolveUpstreamPayload(makeDetail({
+      upstream_error_detail: '',
+      upstream_errors: '[]',
+      upstream_error_message: ''
+    }))).toBe('')
+
+    expect(resolveUpstreamPayload(makeDetail({
+      upstream_error_detail: '',
+      upstream_errors: '{}',
+      upstream_error_message: ''
+    }))).toBe('')
+
+    expect(resolveUpstreamPayload(makeDetail({
+      upstream_error_detail: '',
+      upstream_errors: 'null',
+      upstream_error_message: ''
+    }))).toBe('')
+  })
+
+  it('skips placeholder candidates and falls back to the next upstream field', () => {
+    expect(resolveUpstreamPayload(makeDetail({
+      upstream_error_detail: '',
+      upstream_errors: '[]',
+      upstream_error_message: 'fallback message'
+    }))).toBe('fallback message')
+
+    expect(resolveUpstreamPayload(makeDetail({
+      upstream_error_detail: 'null',
+      upstream_errors: '',
+      upstream_error_message: 'fallback message'
+    }))).toBe('fallback message')
+  })
+})
diff --git a/frontend/src/views/admin/ops/utils/errorDetailResponse.ts b/frontend/src/views/admin/ops/utils/errorDetailResponse.ts
new file mode 100644
index 00000000..8fd9aed9
--- /dev/null
+++ b/frontend/src/views/admin/ops/utils/errorDetailResponse.ts
@@ -0,0 +1,91 @@
+import type { OpsErrorDetail } from '@/api/admin/ops'
+
+const GENERIC_UPSTREAM_MESSAGES = new Set([
+  'upstream request failed',
+  'upstream request failed after retries',
+  'upstream gateway error',
+  'upstream service temporarily unavailable'
+])
+
+type ParsedGatewayError = {
+  type: string
+  message: string
+}
+
+function parseGatewayErrorBody(raw: string): ParsedGatewayError | null {
+  const text = String(raw || '').trim()
+  if (!text) return null
+
+  try {
+    const parsed = JSON.parse(text) as Record<string, any>
+    const err = parsed?.error as Record<string, any> | undefined
+    if (!err || typeof err !== 'object') return null
+
+    const type = typeof err.type === 'string' ? err.type.trim() : ''
+    const message = typeof err.message === 'string' ? err.message.trim() : ''
+    if (!type && !message) return null
+
+    return { type, message }
+  } catch {
+    return null
+  }
+}
+
+function isGenericGatewayUpstreamError(raw: string): boolean {
+  const parsed = parseGatewayErrorBody(raw)
+  if (!parsed) return false
+  if (parsed.type !== 'upstream_error') return false
+  return GENERIC_UPSTREAM_MESSAGES.has(parsed.message.toLowerCase())
+}
+
+export function resolveUpstreamPayload(
+  detail: Pick<OpsErrorDetail, 'upstream_error_detail' | 'upstream_errors' | 'upstream_error_message'> | null | undefined
+): string {
+  if (!detail) return ''
+
+  const candidates = [
+    detail.upstream_error_detail,
+    detail.upstream_errors,
+    detail.upstream_error_message
+  ]
+
+  for (const candidate of candidates) {
+    const payload = String(candidate || '').trim()
+    if (!payload) continue
+
+    // Normalize common "empty but present" JSON placeholders.
+    if (payload === '[]' || payload === '{}' || payload.toLowerCase() === 'null') {
+      continue
+    }
+
+    return payload
+  }
+
+  return ''
+}
+
+export function resolvePrimaryResponseBody(
+  detail: OpsErrorDetail | null,
+  errorType?: 'request' | 'upstream'
+): string {
+  if (!detail) return ''
+
+  const upstreamPayload = resolveUpstreamPayload(detail)
+  const errorBody = String(detail.error_body || '').trim()
+
+  if (errorType === 'upstream') {
+    return upstreamPayload || errorBody
+  }
+
+  if (!errorBody) {
+    return upstreamPayload
+  }
+
+  // For request detail modal, keep client-visible body by default.
+  // But if that body is a generic gateway wrapper, show upstream payload first.
+  if (upstreamPayload && isGenericGatewayUpstreamError(errorBody)) {
+    return upstreamPayload
+  }
+
+  return errorBody
+}