diff --git a/backend/src/main.ts b/backend/src/main.ts
index b2076a0..12e8691 100644
--- a/backend/src/main.ts
+++ b/backend/src/main.ts
@@ -1,9 +1,18 @@
 import { NestFactory } from '@nestjs/core';
 import { ValidationPipe } from '@nestjs/common';
+import { NestExpressApplication } from '@nestjs/platform-express';
+import { join } from 'path';
+import { existsSync, mkdirSync } from 'fs';
 import { AppModule } from './app.module';
 
 async function bootstrap() {
-  const app = await NestFactory.create(AppModule);
+  const app = await NestFactory.create<NestExpressApplication>(AppModule);
+
+  // 自托管媒体(超分图/动图)静态服务：/media/**  ->  /app/media/**
+  // 容器内 /app/media 通过卷挂载服务器目录，MEDIA_BASE_URL 指向本服务 /media
+  const mediaRoot = join(__dirname, '..', 'media');
+  if (!existsSync(mediaRoot)) mkdirSync(mediaRoot, { recursive: true });
+  app.useStaticAssets(mediaRoot, { prefix: '/media' });
 
   if (process.env.CORS_ENABLED !== 'false') {
     app.enableCors();
diff --git a/miniprogram/pages/detail/detail.js b/miniprogram/pages/detail/detail.js
index 99c650f..d998ddd 100644
--- a/miniprogram/pages/detail/detail.js
+++ b/miniprogram/pages/detail/detail.js
@@ -37,8 +37,8 @@ Page({
   load() {
     this.setData({ loading: true });
     svc.getExercise(this.data.id).then((ex) => {
-      // 详情页用 GIF 演示动作；记录当前图源以便失败时降级到 JPG / 占位
-      const heroSrc = ex && (ex.gifUrl || ex.image) ? (ex.gifUrl || ex.image) : '';
+      // 详情大图优先用超分 JPG(720px 清晰)；失败再降级到 GIF / 占位
+      const heroSrc = ex && (ex.image || ex.gifUrl) ? (ex.image || ex.gifUrl) : '';
       this.setData({ exercise: ex, heroSrc, heroError: false, loading: false });
       if (ex && ex.target) {
         svc.listExercises({ target: ex.target, pageSize: 6 }).then((res) => {
@@ -110,11 +110,13 @@ Page({
     }
   },
 
-  // 详情大图加载失败：GIF→JPG→emoji 占位，三级降级保证不空白
+  // 详情大图加载失败：JPG↔GIF 互为降级，最后 emoji 占位，保证不空白
   onHeroError() {
     const ex = this.data.exercise || {};
-    const showingGif = this.data.heroSrc && ex.gifUrl && this.data.heroSrc === ex.gifUrl;
-    if (showingGif && ex.image) {
+    const cur = this.data.heroSrc;
+    if (cur === ex.image && ex.gifUrl) {
+      this.setData({ heroSrc: ex.gifUrl });
+    } else if (cur === ex.gifUrl && ex.image) {
       this.setData({ heroSrc: ex.image });
     } else {
       this.setData({ heroError: true });