diff --git a/frontend-vue/tests/download-url.test.ts b/frontend-vue/tests/download-url.test.ts
new file mode 100644
index 00000000..6ec2cf1d
--- /dev/null
+++ b/frontend-vue/tests/download-url.test.ts
@@ -0,0 +1,78 @@
+import { test } from 'node:test'
+import assert from 'node:assert/strict'
+import { getJavaDownloadUrl } from '../src/shared/api/download-url.ts'
+
+/** task-215：下载 URL 格式契约（公开直链、绝对 schema、origin 补齐、user_id 附加、query 拼接）。 */
+
+function setup(uid = '42', origin = 'http://localhost:5173') {
+  ;(globalThis as Record<string, unknown>).window = {
+    localStorage: { getItem: (k: string) => (k === 'uid' ? uid : null) },
+    location: { origin },
+  }
+}
+
+test('绝对 https 直链被保留并追加 user_id', () => {
+  setup()
+  const url = getJavaDownloadUrl('https://api.example.com/result/a.xlsx')
+  assert.ok(url.startsWith('https://api.example.com/result/a.xlsx'), url)
+  assert.ok(url.includes('?user_id=42'), url)
+})
+
+test('相对路径在 window 环境补齐 origin（schema 完整）', () => {
+  setup()
+  const url = getJavaDownloadUrl('/newApi/download/x')
+  assert.ok(url.startsWith('http://localhost:5173'), url)
+  assert.ok(url.includes('user_id=42'), url)
+})
+
+test('绝对 http 直链不被 origin 包裹', () => {
+  setup()
+  const url = getJavaDownloadUrl('http://cdn.example.com/result/b.xlsx')
+  assert.ok(url.startsWith('http://cdn.example.com/result/b.xlsx'), url)
+  assert.ok(!url.startsWith('http://localhost:5173'), url)
+})
+
+test('已带 query 的 URL 用 & 拼接 user_id', () => {
+  setup()
+  const url = getJavaDownloadUrl('https://api.example.com/result/c.xlsx?k=1')
+  assert.ok(url.includes('k=1&user_id=42'), url)
+  assert.ok(!/\?user_id=42/.test(url), '不应出现第二个 ?')
+})
+
+test('user_id 为当前 uid 且 URL 编码可解析', () => {
+  setup('42')
+  const url = getJavaDownloadUrl('https://api.example.com/result/d.xlsx')
+  const params = new URL(url).searchParams
+  assert.equal(params.get('user_id'), '42')
+})
+
+test('相对产物 query 仅含 user_id（无签名/多余参数）', () => {
+  setup('42')
+  const url = getJavaDownloadUrl('/api/result/e.xlsx')
+  const params = new URL(url).searchParams
+  const keys = [...params.keys()]
+  assert.deepEqual(keys, ['user_id'], url)
+  assert.ok(!url.includes('X-Amz-Signature'), '不应出现签名参数')
+})
+
+test('不含重复问号', () => {
+  setup()
+  const url = getJavaDownloadUrl('https://api.example.com/result/e.xlsx')
+  const questionMarks = (url.match(/\?/g) ?? []).length
+  assert.equal(questionMarks, 1, url)
+})
+
+test('返回 URL 始终带 schema（save_file 兼容）', () => {
+  setup()
+  for (const p of ['/a', 'relative', '/newApi/result/f.xlsx']) {
+    const url = getJavaDownloadUrl(p)
+    assert.ok(url.startsWith('http://') || url.startsWith('https://'), `${p} -> ${url}`)
+  }
+})
+
+test('结果稳定可复现', () => {
+  setup()
+  const a = getJavaDownloadUrl('https://api.example.com/result/g.xlsx')
+  const b = getJavaDownloadUrl('https://api.example.com/result/g.xlsx')
+  assert.equal(a, b)
+})