diff --git a/src/main/java/com/yunhai/cms/utils/PortalUrlHelper.java b/src/main/java/com/yunhai/cms/utils/PortalUrlHelper.java
index 6cb088a..d34f0ee 100644
--- a/src/main/java/com/yunhai/cms/utils/PortalUrlHelper.java
+++ b/src/main/java/com/yunhai/cms/utils/PortalUrlHelper.java
@@ -57,8 +57,12 @@ public class PortalUrlHelper {
      */
     public static PortalUrlHelper forPreview(HttpServletRequest request, String siteCode, String theme) {
         PortalUrlHelper base = fromRequest(request, siteCode, theme);
-        // 显式走 5 参构造：第 4 参是 base-origin，代理前缀必须落第 5 参（避免误绑 4 参重载）
-        return new PortalUrlHelper(base.baseUrl, siteCode, theme, null, "/api/theme/" + theme + "/asset/");
+        // 显式走 5 参构造：第 4 参是 base-origin，代理前缀必须落第 5 参（避免误绑 4 参重载）。
+        // W3（方案 §7.4）：前缀拼 request.getContextPath()——base/prod 上下文 /yschcms 下
+        // 不拼会导致 iframe 内 CSS/JS 链接打到网关根 404（预览裸 HTML）；
+        // 空上下文（dev）退化为根相对 /api/theme/…，dev 形态不回归（T-W3-02）。
+        return new PortalUrlHelper(base.baseUrl, siteCode, theme, null,
+                request.getContextPath() + "/api/theme/" + theme + "/asset/");
     }
 
     /**
diff --git a/src/test/java/com/yunhai/cms/theme/PreviewApiIT.java b/src/test/java/com/yunhai/cms/theme/PreviewApiIT.java
index c24184d..b5816a8 100644
--- a/src/test/java/com/yunhai/cms/theme/PreviewApiIT.java
+++ b/src/test/java/com/yunhai/cms/theme/PreviewApiIT.java
@@ -137,6 +137,17 @@ class PreviewApiIT extends CmsIntegrationTestBase {
         assertThat(body(result)).contains("/api/theme/t-demo-red/asset/css/main.css");
     }
 
+    @Test
+    @DisplayName("T-W3-04: 端到端回归：contextPath=/yschcms 时预览资产 href 带上下文前缀")
+    void previewAssetHrefCarriesContextPathEndToEnd() throws Exception {
+        MvcResult result = standalone.perform(get("/yschcms/api/theme/preview")
+                        .contextPath("/yschcms")
+                        .param("siteCode", "demo").param("theme", "t-demo-red"))
+                .andExpect(status().isOk()).andReturn();
+        assertThat(body(result))
+                .contains("href=\"/yschcms/api/theme/t-demo-red/asset/css/main.css\"");
+    }
+
     @Test
     @DisplayName("T26: 预览响应 no-store（不进缓存/CDN）")
     void previewNoStore() throws Exception {
diff --git a/src/test/java/com/yunhai/cms/utils/PortalUrlHelperTest.java b/src/test/java/com/yunhai/cms/utils/PortalUrlHelperTest.java
index 0c3e9c3..30f1e25 100644
--- a/src/test/java/com/yunhai/cms/utils/PortalUrlHelperTest.java
+++ b/src/test/java/com/yunhai/cms/utils/PortalUrlHelperTest.java
@@ -149,6 +149,37 @@ class PortalUrlHelperTest {
         assertThat(url.rewriteUploadUrls(null)).isNull();
     }
 
+    // ===== forPreview 预览资产前缀（W3：context-path 修复，方案 §7.3）=====
+
+    @Test
+    @DisplayName("T-W3-01: forPreview 带上下文：资产前缀含 contextPath")
+    void forPreview_assetPrefixCarriesContextPath() {
+        PortalUrlHelper url = PortalUrlHelper.forPreview(
+                request("http", "base.yunhaixingtong.com", 80, "/yschcms"), "demo", "scholar-blue");
+        assertThat(url.asset("css/main.css"))
+                .isEqualTo("/yschcms/api/theme/scholar-blue/asset/css/main.css");
+    }
+
+    @Test
+    @DisplayName("T-W3-02: forPreview 空上下文退化：前缀 /api/theme/…（dev 形态不回归）")
+    void forPreview_emptyContextFallsBackToRootPrefix() {
+        PortalUrlHelper url = PortalUrlHelper.forPreview(
+                request("http", "localhost", 8072, ""), "demo", "t-demo-red");
+        assertThat(url.asset("css/main.css"))
+                .isEqualTo("/api/theme/t-demo-red/asset/css/main.css");
+    }
+
+    @Test
+    @DisplayName("T-W3-03: forPreview 站内链接不受资产前缀串味（home/category 仍指真实门户）")
+    void forPreview_homeStaysRealPortal() {
+        PortalUrlHelper url = PortalUrlHelper.forPreview(
+                request("http", "base.yunhaixingtong.com", 80, "/yschcms"), "demo", "scholar-blue");
+        assertThat(url.home()).isEqualTo("http://base.yunhaixingtong.com/yschcms/portal/demo/");
+        assertThat(url.category(3)).isEqualTo("http://base.yunhaixingtong.com/yschcms/portal/demo/c/3");
+        assertThat(url.search("x", null))
+                .isEqualTo("http://base.yunhaixingtong.com/yschcms/portal/demo/search?q=x");
+    }
+
     // ===== siteHome 分支（B-4：学校域形态下未配域子站不再退化为 "/"）=====
 
     @Test