diff --git a/backend-java/src/test/java/com/nanri/aiimage/modules/file/service/oss/DownloadUrlNonExpiringTest.java b/backend-java/src/test/java/com/nanri/aiimage/modules/file/service/oss/DownloadUrlNonExpiringTest.java
new file mode 100644
index 00000000..8f27725a
--- /dev/null
+++ b/backend-java/src/test/java/com/nanri/aiimage/modules/file/service/oss/DownloadUrlNonExpiringTest.java
@@ -0,0 +1,97 @@
+package com.nanri.aiimage.modules.file.service.oss;
+
+import com.nanri.aiimage.config.OssProperties;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertNotNull;
+import static org.junit.jupiter.api.Assertions.assertNull;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+/**
+ * task-147：downloadUrl 永不过期验证（plan 08）。
+ * generateFreshDownloadUrl：result/ 前缀走下载域名、非 result/ 走公开端点、
+ * URL 无签名（不含 X-Amz 系列 / Expires / Signature 等过期参数）、bucket 前缀正确、
+ * null/空白安全、同输入同输出稳定。
+ */
+class DownloadUrlNonExpiringTest {
+
+    private OssProperties properties;
+    private OssStorageService storageService;
+
+    @BeforeEach
+    void setUp() {
+        properties = new OssProperties();
+        properties.setEndpoint("https://oss.aishufu.top");
+        properties.setPublicEndpoint("https://oss.aishufu.top");
+        properties.setDownloadEndpoint("https://download.aishufu.top");
+        properties.setBucket("nanri-ai-images");
+        properties.setImageVideoBucket("shufu-video");
+        properties.setDigitalHumanBucket("nanri-ai-digital-human");
+        properties.setTemplateBucket("aiimage-templates");
+        properties.setAccessKeyId("test-access-key");
+        properties.setAccessKeySecret("test-secret-key");
+        storageService = new OssStorageService(properties);
+    }
+
+    @Test
+    void resultPrefixUsesDownloadEndpoint() {
+        assertEquals(
+                "https://download.aishufu.top/nanri-ai-images/result/publish/1/result.xlsx",
+                storageService.generateFreshDownloadUrl("result/publish/1/result.xlsx"));
+    }
+
+    @Test
+    void nonResultPrefixUsesPublicEndpoint() {
+        assertEquals(
+                "https://oss.aishufu.top/nanri-ai-images/supply_images/main.jpg",
+                storageService.generateFreshDownloadUrl("supply_images/main.jpg"));
+    }
+
+    @Test
+    void urlHasNoExpiringSignatureParameters() {
+        String url = storageService.generateFreshDownloadUrl("result/publish/1/result.xlsx");
+        assertFalse(url.contains("X-Amz-"), "不得包含 AWS 签名参数: " + url);
+        assertFalse(url.contains("Signature"), "不得包含签名: " + url);
+        assertFalse(url.contains("Expires"), "不得包含过期时间: " + url);
+        assertFalse(url.contains("?") || url.contains("&"), "不得携带任何查询参数: " + url);
+    }
+
+    @Test
+    void bucketPrefixIsCorrect() {
+        String url = storageService.generateFreshDownloadUrl("result/collect_data/2/data.xlsx");
+        assertTrue(url.contains("/nanri-ai-images/result/collect_data/2/data.xlsx"),
+                "主 bucket 前缀正确: " + url);
+        String imageUrl = storageService.generateFreshDownloadUrl("shufu-video/result/image_video/demo.mp4");
+        assertTrue(imageUrl.contains("/shufu-video/result/image_video/demo.mp4"),
+                "image-video bucket 前缀正确: " + imageUrl);
+    }
+
+    @Test
+    void nullUrlIsSafe() {
+        assertNull(storageService.generateFreshDownloadUrl(null), "null 输入返回 null 不抛错");
+    }
+
+    @Test
+    void blankUrlIsSafe() {
+        assertNull(storageService.generateFreshDownloadUrl("   "), "空白输入返回 null 不抛错");
+        assertNull(storageService.generateFreshDownloadUrl(""), "空串返回 null 不抛错");
+    }
+
+    @Test
+    void generatedUrlIsStable() {
+        String first = storageService.generateFreshDownloadUrl("result/similar_asin/3/re.xlsx");
+        String second = storageService.generateFreshDownloadUrl("result/similar_asin/3/re.xlsx");
+        assertEquals(first, second, "同输入同输出（无随机签名）");
+    }
+
+    @Test
+    void contractFrozen() {
+        String url = storageService.generateFreshDownloadUrl("result/similar_asin/3/re.xlsx");
+        assertNotNull(url);
+        // 快照：https://{download-endpoint}/{bucket}/{objectKey}，纯路径无签名
+        assertEquals("https://download.aishufu.top/nanri-ai-images/result/similar_asin/3/re.xlsx", url);
+    }
+}