diff --git a/frontend-vue/src/shared/merge-live-progress.ts b/frontend-vue/src/shared/merge-live-progress.ts
index de26559e..530dcd07 100644
--- a/frontend-vue/src/shared/merge-live-progress.ts
+++ b/frontend-vue/src/shared/merge-live-progress.ts
@@ -17,13 +17,20 @@ export const FILE_PROGRESS_KEYS = [
 export interface DownloadableItem {
   resultId?: number | null
   fileReady?: boolean | null
+  fileStatus?: string | null
   downloadUrl?: string | null
 }
 
-/** 可下载判定：有结果记录且文件已就绪（fileReady 或 downloadUrl 非空）。 */
+/**
+ * 可下载判定（Task 145）：有结果记录，且满足其一——
+ * fileReady=true、downloadUrl 非空、fileStatus 为终态（SUCCESS 可下载结果文件，
+ * FAILED 可下载错误文件或用于展示错误）。
+ */
 export function canDownloadItem(item: DownloadableItem | null | undefined): boolean {
   if (!item) return false
-  return Boolean(item.resultId && (item.fileReady || item.downloadUrl))
+  const ready = item.fileReady || Boolean(item.downloadUrl)
+  const terminalStatus = item.fileStatus === 'SUCCESS' || item.fileStatus === 'FAILED'
+  return Boolean(item.resultId && (ready || terminalStatus))
 }
 
 /** 有效进度值：仅 fileProgressPercent 需要严格 >0，其余字段非空即可（0 是合法计数）。 */
diff --git a/frontend-vue/tests/downloadability.test.ts b/frontend-vue/tests/downloadability.test.ts
new file mode 100644
index 00000000..e09c055b
--- /dev/null
+++ b/frontend-vue/tests/downloadability.test.ts
@@ -0,0 +1,60 @@
+import { test } from 'node:test'
+import assert from 'node:assert/strict'
+
+import { canDownloadItem } from '../src/shared/merge-live-progress.ts'
+
+interface Item {
+  taskId?: number
+  resultId?: number
+  fileReady?: boolean
+  fileStatus?: string
+  downloadUrl?: string
+}
+
+test('downloadable when fileReady is true', () => {
+  assert.equal(canDownloadItem({ resultId: 1, fileReady: true }), true)
+})
+
+test('downloadable when fileStatus is SUCCESS', () => {
+  assert.equal(canDownloadItem({ resultId: 1, fileStatus: 'SUCCESS' }), true)
+})
+
+test('downloadable when fileStatus is FAILED (error file or display)', () => {
+  assert.equal(canDownloadItem({ resultId: 1, fileStatus: 'FAILED' }), true)
+})
+
+test('not downloadable when not ready', () => {
+  assert.equal(canDownloadItem({ resultId: 1, fileReady: false, fileStatus: 'RUNNING' }), false)
+  assert.equal(canDownloadItem({ resultId: 1 }), false)
+})
+
+test('downloadable when downloadUrl present', () => {
+  assert.equal(canDownloadItem({ resultId: 1, downloadUrl: 'https://dl.example/a.xlsx' }), true)
+})
+
+test('not downloadable without resultId', () => {
+  assert.equal(canDownloadItem({ fileReady: true }), false)
+  assert.equal(canDownloadItem({ fileStatus: 'SUCCESS' }), false)
+})
+
+test('not downloadable while pending or running', () => {
+  assert.equal(canDownloadItem({ resultId: 1, fileStatus: 'PENDING' }), false)
+  assert.equal(canDownloadItem({ resultId: 1, fileStatus: 'RUNNING' }), false)
+  assert.equal(canDownloadItem({ resultId: 1, fileStatus: null }), false)
+})
+
+test('downloadability contract frozen', () => {
+  assert.equal(canDownloadItem(undefined), false)
+  assert.equal(canDownloadItem(null), false)
+  assert.equal(canDownloadItem({}), false)
+  // 终态与就绪任一满足即可下载；RUNNING/PENDING/空态均不可
+  const terminalCases = ['SUCCESS', 'FAILED']
+  const runningCases = ['PENDING', 'RUNNING', undefined, null]
+  for (const status of terminalCases) {
+    assert.equal(canDownloadItem({ resultId: 1, fileStatus: status as string }), true, `终态 ${status} 可下载`)
+  }
+  for (const status of runningCases) {
+    assert.equal(canDownloadItem({ resultId: 1, fileStatus: status as string | undefined }), false,
+      `非终态 ${String(status)} 不可下载`)
+  }
+})