From a069be4538a1b67252dfa41d3769171b9e9aa328 Mon Sep 17 00:00:00 2001
From: kanomahoro1224 <3497593286@qq.com>
Date: Sat, 3 Oct 2026 15:43:19 +0800
Subject: [PATCH] =?UTF-8?q?=E9=9F=B3=E9=A2=91=E6=94=B9=E8=B5=B0=E6=97=A0?=
 =?UTF-8?q?=E6=89=A9=E5=B1=95=E5=90=8D=E7=9A=84=20/media=20=E8=B7=AF?=
 =?UTF-8?q?=E7=94=B1=EF=BC=9AIDM=20/=20=E8=BF=85=E9=9B=B7=20=E8=BF=99?=
 =?UTF-8?q?=E7=B1=BB=E4=B8=8B=E8=BD=BD=E7=AE=A1=E7=90=86=E5=99=A8=E4=B8=8D?=
 =?UTF-8?q?=E5=86=8D=E5=BC=B9=E3=80=8C=E4=B8=8B=E8=BD=BD=E6=96=87=E4=BB=B6?=
 =?UTF-8?q?=E4=BF=A1=E6=81=AF=E3=80=8D?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

玩家那边遇到的是：游戏放着 BGM，突然弹出下载管理器的「下载文件信息」框，有时还会把整条
音轨抢去下载。原因是这些工具会嗅探以媒体扩展名结尾的 XHR/fetch。改成客户端统一请求不带
扩展名的 `/media/<原路径去掉 .mp3>`，服务端再解析回 `public/assets/audio/…`。

- `public/js/media.js`：`mediaUrl()` 把 `/assets/audio/**.mp3` 换算成 `/media/**`，只处理同源、
  且扩展名在名单内的地址；跨域、目录、`..`、点开头、不认识的扩展名一律原样返回。
- `server/index.js`：新增 `/media/` 路由。按 `AUDIO_EXTS` 顺序找 `.mp3/.m4a/.aac/.ogg/.oga/.opus/.wav`，
  显式写了扩展名的以它为准；Range/ETag/Content-Type/缓存策略都复用 `serveFile`，所以和直接请求
  `/assets/audio/…` 行为一致（一天缓存、支持 Range）。
- 直接请求 `/assets/audio/…` 仍然可用 —— 这是给不支持 `/media/` 的纯静态托管留的退路，客户端
  在 `/media/` 404 时才回退到原地址。

安全：`/media/` 的路径只接受正常片段，`..`/`.` 直接 403，点开头或点结尾的片段 404，解析出的
绝对路径必须落在 `public/assets/audio` 之内，且只允许上面那几个音频扩展名 —— 不会变成任意文件读取。

测试：
- `test/media-url.test.js`：`mediaUrl()` 的换算与各种「别动它」的边界。
- `test/lobby.test.js`：真实服务器上的 `/media` 路由（正常解析、显式扩展名优先、Range、HEAD、
  目录与穿越请求被拒、客户端回退用到的 `/media/bgm.mp3` 仍 200）。
- `test/ui/audio.test.js`：音频管理器现在先请求无扩展名地址，404 才回退原地址；断言跟着
  `mediaUrl()` 换算后再比对（原先拿 manifest 原地址比对，等于断言一个客户端永不请求的 URL）。
---
 public/js/audio.js     |  6 ++-
 public/js/media.js     | 60 ++++++++++++++++++++++++++++++
 server/index.js        | 52 ++++++++++++++++++++++++++
 test/lobby.test.js     | 38 +++++++++++++++++++
 test/media-url.test.js | 56 ++++++++++++++++++++++++++++
 test/ui/audio.test.js  | 83 +++++++++++++++++++++++++++++++++++-------
 6 files changed, 281 insertions(+), 14 deletions(-)
 create mode 100644 public/js/media.js
 create mode 100644 test/media-url.test.js

diff --git a/public/js/audio.js b/public/js/audio.js
index 9550511b..a8948dd8 100644
--- a/public/js/audio.js
+++ b/public/js/audio.js
@@ -31,6 +31,7 @@
 // which follows the store).
 
 import { PHASE } from '../../shared/constants.js';
+import { mediaUrl } from './media.js';
 
 const MAX_VOICES = 8;
 const UNIT_COOLDOWN_MS = 160;
@@ -383,7 +384,10 @@ export class AudioManager {
     }
     const p = (async () => {
       try {
-        const res = await fetch(url);
+        // Extension-less URL first so download managers leave the BGM alone; a host without /media/ still works.
+        const media = mediaUrl(url);
+        let res = await fetch(media);
+        if (!res.ok && media !== url) res = await fetch(url);
         if (!res.ok) throw new Error(`HTTP ${res.status}`);
         const ab = await res.arrayBuffer();
         return await new Promise((resolve) => {
diff --git a/public/js/media.js b/public/js/media.js
new file mode 100644
index 00000000..6b7fade5
--- /dev/null
+++ b/public/js/media.js
@@ -0,0 +1,60 @@
+// Audio URLs for download managers (IDM / 迅雷 / FDM …) — and why they have no extension.
+//
+// The game plays audio with fetch() + Web Audio (`audio.js`): it never uses <audio src>, <a download> or a
+// navigation. Download managers do not care — their browser integration hooks XHR/fetch whose URL ends in a
+// media extension and (usually above ~1 MB) pops up "下载文件信息" for every BGM track. That dialog has nothing
+// to do with the game, but players see it and blame the game.
+//
+// So audio is fetched through a same-origin, extension-less path instead:
+//
+//     /assets/audio/bgm/act1.mp3   →   /media/bgm/act1
+//
+// `server/index.js` resolves /media/… back to the real file under public/assets/audio and still answers with
+// `Content-Type: audio/mpeg` + range support; Web Audio sniffs the container, so the URL is all the same to it.
+// A host that does not implement /media/ keeps working: `audio.js` falls back to the original URL on 404.
+
+/** Prefix of the extension-less audio route served by `server/index.js`. */
+export const MEDIA_PREFIX = '/media/';
+
+/** Extensions `/media/…` may resolve to, in the order the server tries them. */
+export const AUDIO_EXTS = Object.freeze(['.mp3', '.m4a', '.aac', '.ogg', '.oga', '.opus', '.wav']);
+
+const AUDIO_PATH = /^\/assets\/audio\/(.+)$/i;
+
+/**
+ * Rewrite an audio URL to its extension-less `/media/…` form.
+ *
+ * Returns the input unchanged when the URL is not one of our audio assets, points at another origin (a CDN
+ * serves media itself, so the download-manager problem is not ours to solve there), or would produce a path the
+ * server refuses (empty / dot segments).
+ * @param {string} url
+ * @param {string} [origin] origin of the page; defaults to `location.origin`
+ * @returns {string} a URL safe to pass to fetch()
+ */
+export function mediaUrl(url, origin = globalThis.location?.origin) {
+  if (typeof url !== 'string' || !url) return url;
+  let u;
+  // No origin known (Node / tests): parse relative URLs against a placeholder, absolute ones are rejected below.
+  try { u = new URL(url, origin || 'http://localhost'); } catch { return url; }
+  // Cross-origin (or absolute while the page origin is unknown) stays untouched: that host serves its own media.
+  const absolute = /^[a-z][a-z0-9+.-]*:/i.test(url) || url.startsWith('//');
+  if (origin ? u.origin !== origin : absolute) return url;
+  const m = AUDIO_PATH.exec(u.pathname);
+  if (!m) return url;
+  let rest = m[1];
+  const ext = AUDIO_EXTS.find((e) => rest.toLowerCase().endsWith(e));
+  if (!ext) return url;             // not a file we serve as audio (e.g. "x.mp3.bak") — leave it alone
+  rest = rest.slice(0, -ext.length);
+  const segments = rest.split('/');
+  if (!rest || segments.some((s) => !s || s === '.' || s === '..' || s.startsWith('.'))) return url;
+  return `${MEDIA_PREFIX}${rest}${u.search}`;
+}
+
+/**
+ * Is this URL already one of the extension-less media paths?
+ * @param {string} url
+ * @param {string} [origin]
+ */
+export function isMediaUrl(url, origin = globalThis.location?.origin) {
+  return mediaUrl(url, origin) !== url;
+}
diff --git a/server/index.js b/server/index.js
index f1aa6525..6c6f632d 100644
--- a/server/index.js
+++ b/server/index.js
@@ -311,6 +311,11 @@ export function createStaticHandler({ publicDir, dataDir, sharedDir, simDir = pa
       res.end(req.method === 'HEAD' ? undefined : shimBody);
       return;
     }
+    // Extension-less audio (download-manager avoidance): /media/bgm/act1 → /assets/audio/bgm/act1.mp3
+    if (decoded.startsWith(MEDIA_PREFIX)) {
+      await serveMedia(req, res, decoded.slice(MEDIA_PREFIX.length), query, publicDir, gzipCache, log);
+      return;
+    }
     // Bare mount paths (e.g. "/data") → treat as the mount directory.
     const mount = mounts.find((m) => decoded.startsWith(m.prefix) || decoded === m.prefix.slice(0, -1)) || mounts[mounts.length - 1];
     const rest = decoded.length > mount.prefix.length ? decoded.slice(mount.prefix.length) : '';
@@ -372,6 +377,53 @@ export function createStaticHandler({ publicDir, dataDir, sharedDir, simDir = pa
   };
 }
 
+/**
+ * Extension-less audio route: `/media/bgm/act1` → `public/assets/audio/bgm/act1.mp3`.
+ *
+ * Clients ask for audio through this path because download managers (IDM, 迅雷, FDM …) hijack XHR/fetch whose
+ * URL ends in a media extension and pop a "下载文件信息" dialog for every BGM track — see `public/js/media.js`.
+ * Requests for the direct `/assets/audio/…` URLs keep working (they are the fallback for plain static hosts).
+ */
+const MEDIA_PREFIX = '/media/';
+/** Extensions a `/media/…` request may resolve to, in order. */
+export const AUDIO_EXTS = Object.freeze(['.mp3', '.m4a', '.aac', '.ogg', '.oga', '.opus', '.wav']);
+
+async function serveMedia(req, res, rest, query, publicDir, gzipCache, log) {
+  const root = path.join(path.resolve(publicDir), 'assets', 'audio');
+  const segments = String(rest || '').split('/').filter((s) => s.length > 0);
+  if (!segments.length || rest.endsWith('/')) { sendError(req, res, 404, '页面不存在 · Not found'); return; }
+  if (segments.some((s) => s === '..' || s === '.')) { sendError(req, res, 403, '禁止访问 · Forbidden'); return; }
+  // A leading or trailing dot would address something else (dotfiles, "x..mp3") — and the client never asks for it.
+  if (segments.some((s) => s.startsWith('.') || s.endsWith('.'))) { sendError(req, res, 404, '页面不存在 · Not found'); return; }
+
+  const last = segments[segments.length - 1];
+  const given = path.extname(last).toLowerCase();
+  const wanted = AUDIO_EXTS.includes(given) ? given : '';
+  const stem = wanted ? last.slice(0, -wanted.length) : last;
+  if (!stem || stem.startsWith('.')) { sendError(req, res, 404, '页面不存在 · Not found'); return; }
+  const dir = path.join(root, ...segments.slice(0, -1));
+  if (dir !== root && !dir.startsWith(root + path.sep)) { sendError(req, res, 403, '禁止访问 · Forbidden'); return; }
+
+  // An explicit extension wins (`/media/bgm.ogg` → bgm.ogg), otherwise the usual order decides.
+  const order = wanted ? [wanted, ...AUDIO_EXTS.filter((e) => e !== wanted)] : AUDIO_EXTS;
+  for (const ext of order) {
+    const absPath = path.join(dir, stem + ext);
+    if (!absPath.startsWith(root + path.sep)) continue;
+    let stat;
+    try {
+      // eslint-disable-next-line no-await-in-loop
+      stat = await fsp.stat(absPath);
+    } catch { continue; }
+    if (!stat.isFile()) continue;
+    // serveFile decides Content-Type from the resolved name (`.mp3` → audio/mpeg) — Range/ETag handling is shared.
+    // Cache policy is that of the public path the client would otherwise have asked for (`/assets/audio/…`, 1 day).
+    // eslint-disable-next-line no-await-in-loop
+    await serveFile(req, res, absPath, stat, 'public', ['assets', 'audio', ...segments], query, gzipCache, log);
+    return;
+  }
+  sendError(req, res, 404, '页面不存在 · Not found');
+}
+
 async function serveFile(req, res, absPath, stat, mountName, segments, query, gzipCache, log) {
   const ext = path.extname(absPath).toLowerCase();
   const type = MIME[ext] || 'application/octet-stream';
diff --git a/test/lobby.test.js b/test/lobby.test.js
index ee2ac6bf..b69d6a22 100644
--- a/test/lobby.test.js
+++ b/test/lobby.test.js
@@ -281,6 +281,44 @@ describe('static http server', () => {
     assert.equal(textRange.body.toString(), js.slice(0, 2));
   });
 
+  test('extension-less /media audio route (download managers sniff .mp3 URLs)', async () => {
+    const direct = await httpReq(srv.port, '/assets/audio/bgm.mp3');
+    const media = await httpReq(srv.port, '/media/bgm');
+    assert.equal(media.status, 200);
+    assert.equal(media.headers['content-type'], 'audio/mpeg', 'resolved from the real .mp3 on disk');
+    assert.equal(media.headers['accept-ranges'], 'bytes');
+    assert.deepEqual(media.body, mp3, 'same bytes as the direct URL');
+    assert.equal(media.headers['cache-control'], direct.headers['cache-control'], 'same 1-day policy as /assets/…');
+    assert.equal(media.headers.etag, direct.headers.etag, 'ETag is the file validator, not the URL');
+
+    const range = await httpReq(srv.port, '/media/bgm', { headers: { range: 'bytes=0-9' } });
+    assert.equal(range.status, 206);
+    assert.equal(range.headers['content-range'], `bytes 0-9/${mp3.length}`);
+    assert.deepEqual(range.body, mp3.subarray(0, 10));
+    const head = await httpReq(srv.port, '/media/bgm', { method: 'HEAD' });
+    assert.equal(head.status, 200);
+    assert.equal(head.body.length, 0);
+
+    // The extension may still be given, and the other audio extension resolves too.
+    assert.equal((await httpReq(srv.port, '/media/bgm.mp3')).status, 200);
+    const ogg = await httpReq(srv.port, '/media/bgm.ogg');
+    assert.equal(ogg.status, 200);
+    assert.equal(ogg.headers['content-type'], 'audio/ogg');
+    assert.equal(ogg.body.length, 64);
+
+    // …and it only ever reaches public/assets/audio.
+    for (const p of ['/media/nope', '/media/bgm/', '/media/', '/media/.hidden', '/media/bgm.mp3/nope', '/media/js/app']) {
+      const r = await httpReq(srv.port, p);
+      assert.equal(r.status, 404, `${p} → 404`);
+      assert.doesNotMatch(r.body.toString(), /TOP-SECRET-CONTENT/, `${p} must not leak files outside public/assets/audio`);
+    }
+    for (const p of ['/media/..%2f..%2fsecret.txt', '/media/bgm/../..%2f..%2fsecret.txt']) {
+      const r = await httpReq(srv.port, p);
+      assert.equal(r.status, 403, `${p} → 403 (same as the rest of the server)`);
+      assert.doesNotMatch(r.body.toString(), /TOP-SECRET-CONTENT/);
+    }
+  });
+
   test('path traversal and dotfiles are blocked', async () => {
     const attempts = [
       '/../secret.txt', '/%2e%2e/secret.txt', '/..%2fsecret.txt', '/%2e%2e%2fsecret.txt', '/data/../../secret.txt',
diff --git a/test/media-url.test.js b/test/media-url.test.js
new file mode 100644
index 00000000..3d65cbd9
--- /dev/null
+++ b/test/media-url.test.js
@@ -0,0 +1,56 @@
+// mediaUrl(): audio is fetched through an extension-less /media/… path so download managers (IDM / 迅雷 / FDM)
+// stop hijacking BGM playback with a "下载文件信息" dialog. See public/js/media.js for the full rationale.
+import { test, describe } from 'node:test';
+import assert from 'node:assert/strict';
+import { mediaUrl, isMediaUrl, MEDIA_PREFIX, AUDIO_EXTS } from '../public/js/media.js';
+
+const ORIGIN = 'http://127.0.0.1:3000';
+
+describe('mediaUrl: 音频地址去掉扩展名（躲开下载器嗅探）', () => {
+  test('把 /assets/audio/**.mp3 改写成 /media/**', () => {
+    assert.equal(mediaUrl('/assets/audio/bgm/m_sys_act1autochess_loop.mp3', ORIGIN), '/media/bgm/m_sys_act1autochess_loop');
+    assert.equal(mediaUrl('/assets/audio/sfx/player/p_imp/hit.mp3', ORIGIN), '/media/sfx/player/p_imp/hit');
+    // 绝对同源地址同样改写
+    assert.equal(mediaUrl(`${ORIGIN}/assets/audio/bgm/a.mp3`, ORIGIN), '/media/bgm/a');
+    // 查询串保留（?v=… 会拿到 immutable 缓存）
+    assert.equal(mediaUrl('/assets/audio/bgm/a.mp3?v=2', ORIGIN), '/media/bgm/a?v=2');
+    // 各音频扩展名
+    for (const ext of AUDIO_EXTS) {
+      assert.equal(mediaUrl(`/assets/audio/x/a${ext}`, ORIGIN), '/media/x/a', ext);
+    }
+    assert.equal(mediaUrl('/assets/audio/x/A.MP3', ORIGIN), '/media/x/A', '大小写不敏感');
+  });
+
+  test('改写后的地址里不再有任何媒体扩展名（下载器就是按这个嗅探的）', () => {
+    const out = mediaUrl('/assets/audio/bgm/m_bat_vtlionk_loop.mp3', ORIGIN);
+    assert.equal(out.startsWith(MEDIA_PREFIX), true);
+    assert.doesNotMatch(out, /\.(mp3|m4a|aac|ogg|oga|opus|wav)(\?|$)/i);
+  });
+
+  test('不是我们的音频、或不是同源时不改写', () => {
+    assert.equal(mediaUrl('/assets/img/a.png', ORIGIN), '/assets/img/a.png');
+    assert.equal(mediaUrl('/assets/audio/bgm.m4a.bak', ORIGIN), '/assets/audio/bgm.m4a.bak', '扩展名不认识就原样返回');
+    assert.equal(mediaUrl('https://cdn.example.com/assets/audio/a.mp3', ORIGIN), 'https://cdn.example.com/assets/audio/a.mp3', '别的源自己负责');
+    assert.equal(mediaUrl('/data/assets.json', ORIGIN), '/data/assets.json');
+    assert.equal(mediaUrl('', ORIGIN), '');
+    assert.equal(mediaUrl(null, ORIGIN), null);
+    assert.equal(mediaUrl(undefined, ORIGIN), undefined);
+    assert.equal(mediaUrl('/assets/audio/', ORIGIN), '/assets/audio/', '空路径不改写（服务端只会 404）');
+  });
+
+  test('会产生非法路径的输入不碰（点目录 / 空段）', () => {
+    assert.equal(mediaUrl('/assets/audio/.hidden.mp3', ORIGIN), '/assets/audio/.hidden.mp3');
+    // URL 解析本来就会把 .. 归一化，改写跟着归一化后的路径走（服务端仍是同一道校验）
+    assert.equal(mediaUrl('/assets/audio/bgm/../x.mp3', ORIGIN), '/media/x');
+  });
+
+  test('isMediaUrl 只对真正会改写的地址为真', () => {
+    assert.equal(isMediaUrl('/assets/audio/bgm/a.mp3', ORIGIN), true);
+    assert.equal(isMediaUrl('/assets/img/a.png', ORIGIN), false);
+  });
+
+  test('没有 location 时（测试环境）用传入的 origin 判断同源', () => {
+    assert.equal(mediaUrl('/assets/audio/bgm/a.mp3'), '/media/bgm/a', '相对地址本来就同源');
+    assert.equal(mediaUrl('https://other.example/assets/audio/a.mp3'), 'https://other.example/assets/audio/a.mp3');
+  });
+});
diff --git a/test/ui/audio.test.js b/test/ui/audio.test.js
index 8af88ea9..837bec0c 100644
--- a/test/ui/audio.test.js
+++ b/test/ui/audio.test.js
@@ -7,11 +7,20 @@ import { readFileSync } from 'node:fs';
 import path from 'node:path';
 import { fileURLToPath } from 'node:url';
 import { bgmKeyFor, resolveBgm, SfxLimiter, AudioManager, normalAttackSfx } from '../../public/js/audio.js';
+import { mediaUrl } from '../../public/js/media.js';
 import { PHASE } from '../../shared/constants.js';
 
 const ROOT = path.resolve(path.dirname(fileURLToPath(import.meta.url)), '../..');
 const manifest = JSON.parse(readFileSync(path.join(ROOT, 'data', 'assets.json'), 'utf8'));
 
+// audio.js 取音频时**先请求无扩展名的 /media/…**（正是为了躲开下载管理器对 .mp3 后缀的嗅探），
+// 只有那样 404 了才回退到 manifest 里的原始地址。所以「某个音效响了没有」不能拿原始地址去比对——
+// 那样断言的是一个客户端永远不会请求的 URL。下面两个助手把比对放到同一条换算上。
+/** 这个 manifest 地址被请求过吗（/media/ 形式或 404 后的原始形式）。 */
+const asked = (urls, raw) => urls.includes(mediaUrl(raw)) || urls.includes(raw);
+/** 这个 manifest 地址被请求了几次。 */
+const askedCount = (urls, raw) => urls.filter((u) => u === mediaUrl(raw) || u === raw).length;
+
 describe('bgm selection', () => {
   test('route and phase → key', () => {
     assert.equal(bgmKeyFor('title', null), 'lobby');
@@ -129,11 +138,11 @@ describe('AudioManager', () => {
       fw.fire('pointerdown');
       assert.equal(a.unlocked, true);
       await new Promise((r) => setTimeout(r, 10));
-      assert.ok(urls.includes(manifest.audio.bgm.prep.loop), 'BGM fetched after unlock');
+      assert.ok(asked(urls, manifest.audio.bgm.prep.loop), 'BGM fetched after unlock');
       a.sfx('buy');
       a.sfx('nonexistent');
       await new Promise((r) => setTimeout(r, 10));
-      assert.ok(urls.includes(manifest.audio.sfx.ui.buy));
+      assert.ok(asked(urls, manifest.audio.sfx.ui.buy));
       // same loop URL ⇒ no restart
       const before = fw.made.started;
       a.playBgm('combat');
@@ -144,8 +153,8 @@ describe('AudioManager', () => {
       a.setFieldUnits([{ id: 1, side: 'ally', spine: charId }, { id: 2, side: 'enemy', spine: 'enemy_nope' }]);
       a.handleBattleEvents([['atk', 1, 2, 'arrow'], ['dmg', 2, 100, 'phys'], ['die', 2], ['spawn', { id: 3, side: 'enemy', spine: 'x' }], ['bounty', 'p', 1]]);
       await new Promise((r) => setTimeout(r, 10));
-      assert.ok(urls.includes(manifest.audio.sfx.units[charId].attack));
-      assert.ok(urls.includes(manifest.audio.sfx.battle.enemyDie), 'fallback death sound');
+      assert.ok(asked(urls, manifest.audio.sfx.units[charId].attack));
+      assert.ok(asked(urls, manifest.audio.sfx.battle.enemyDie), 'fallback death sound');
       assert.ok(a.limiter.active <= a.limiter.maxVoices);
       a.setVolumes({ muted: true });
       const n = urls.length;
@@ -176,6 +185,51 @@ describe('AudioManager', () => {
       console.warn = origWarn;
     }
   });
+  test('音频先走无扩展名的 /media/ 路由；只有它 404 才回退到带扩展名的原地址', async () => {
+    const raw = manifest.audio.bgm.prep.loop;
+    const media = mediaUrl(raw);
+    assert.notEqual(media, raw, '前提：manifest 地址确实会被换算成 /media/ 路径');
+
+    // 第一发 404：必须看到 /media/ 在前、原地址在后，两者都请求过
+    {
+      const fw = fakeWindow();
+      const urls = [];
+      const origFetch = globalThis.fetch;
+      globalThis.fetch = async (u) => {
+        urls.push(u);
+        return u === media ? { ok: false, status: 404 } : { ok: true, arrayBuffer: async () => new ArrayBuffer(8) };
+      };
+      try {
+        const a = new AudioManager({ win: fw.win, getManifest: () => manifest });
+        a.install();
+        fw.fire('pointerdown');
+        a.playBgm('prep');
+        await new Promise((r) => setTimeout(r, 25));
+        const first = urls.indexOf(media);
+        const fallback = urls.indexOf(raw);
+        assert.ok(first !== -1, '先试无扩展名路径');
+        assert.ok(fallback !== -1, '404 后回退到原地址');
+        assert.ok(first < fallback, '顺序必须是先 /media/ 再原地址');
+      } finally { globalThis.fetch = origFetch; }
+    }
+
+    // 第一发 200：不该再去碰带扩展名的地址（否则白白多一次请求，也正是 IDM 会拦的那个 URL）
+    {
+      const fw = fakeWindow();
+      const urls = [];
+      const origFetch = globalThis.fetch;
+      globalThis.fetch = async (u) => { urls.push(u); return { ok: true, arrayBuffer: async () => new ArrayBuffer(8) }; };
+      try {
+        const a = new AudioManager({ win: fw.win, getManifest: () => manifest });
+        a.install();
+        fw.fire('pointerdown');
+        a.playBgm('prep');
+        await new Promise((r) => setTimeout(r, 25));
+        assert.ok(urls.includes(media), '走了 /media/');
+        assert.ok(!urls.includes(raw), '/media/ 成功就不该再请求 .mp3 地址');
+      } finally { globalThis.fetch = origFetch; }
+    }
+  });
 });
 
 // user playtest #4 item 6: 纯烬艾雅法拉's skill sound rang outside her skill — her manifest `hit` is her S3 impact
@@ -218,23 +272,26 @@ describe('impact sounds (user playtest #4 item 6)', () => {
       { id: 3, side: 'enemy', kind: 'enemy', spine: enemyId },
     ]);
     try {
-      const own = new Set(Object.values(manifest.audio.sfx.units[AGOAT2]).filter((x) => typeof x === 'string'));
+      // 她的技能形态（_s）文件：这条断言要盯住它们一个都没响，所以先确认音效表里真的有 _s ——
+      // 否则集合为空，断言会永远成立、形同虚设。
+      const ownSkill = Object.values(manifest.audio.sfx.units[AGOAT2]).filter((x) => typeof x === 'string' && /_s\.mp3$/.test(x));
+      assert.ok(ownSkill.length > 0, '前提：她的音效表里确实有 _s（技能形态）文件');
       a.handleBattleEvents([['atk', 1, 2, 'orb'], ['heal', 2, 300], ['dmg', 2, 120, 'phys'], ['dmg', 2, 80, 'arts']]);
       await settle();
-      assert.ok(urls.includes(manifest.audio.sfx.units[AGOAT2].attack), 'her cast sound');
-      assert.ok(!urls.some((x) => x === manifest.audio.sfx.units[AGOAT2].hit), 'no impact sound of hers on the ally');
-      assert.ok(!urls.some((x) => own.has(x) && /_s\.mp3$/.test(x)), 'nothing of her S3');
+      assert.ok(asked(urls, manifest.audio.sfx.units[AGOAT2].attack), 'her cast sound');
+      assert.ok(!asked(urls, manifest.audio.sfx.units[AGOAT2].hit), 'no impact sound of hers on the ally');
+      assert.ok(!ownSkill.some((p) => asked(urls, p)), 'nothing of her S3');
       // a hostile attack still authors its impact — once, and only for a real hit (not an element gauge fill)
       a.handleBattleEvents([['atk', 3, 2, 'none'], ['dmg', 2, 900, 'burn']]);
       await settle();
-      assert.ok(!urls.includes(manifest.audio.sfx.units[enemyId].hit), 'a gauge fill is no impact');
+      assert.ok(!asked(urls, manifest.audio.sfx.units[enemyId].hit), 'a gauge fill is no impact');
       a.handleBattleEvents([['dmg', 2, 200, 'phys']]);
       await settle();
-      assert.equal(urls.filter((x) => x === manifest.audio.sfx.units[enemyId].hit).length, 1, 'the impact');
+      assert.equal(askedCount(urls, manifest.audio.sfx.units[enemyId].hit), 1, 'the impact');
       a.limiter.lastByUnit.clear(); a.limiter.lastByUrl.clear();
       a.handleBattleEvents([['dmg', 2, 50, 'phys']]);
       await settle();
-      assert.equal(urls.filter((x) => x === manifest.audio.sfx.units[enemyId].hit).length, 1, 'a later tick is not the same attack\'s impact');
+      assert.equal(askedCount(urls, manifest.audio.sfx.units[enemyId].hit), 1, 'a later tick is not the same attack\'s impact');
     } finally { restore(); }
   });
 
@@ -251,12 +308,12 @@ describe('impact sounds (user playtest #4 item 6)', () => {
     try {
       a.handleBattleEvents([['atk', 5, 6, 'chain']]);
       await settle();
-      assert.ok(!urls.includes(manifest.audio.sfx.units[enemyId].attack), 'the bounce is not an enemy attack');
+      assert.ok(!asked(urls, manifest.audio.sfx.units[enemyId].attack), 'the bounce is not an enemy attack');
       a.handleBattleEvents([['atk', 1, 5, 'arrow']]);
       fakeNow += 4000;
       a.handleBattleEvents([['dmg', 5, 100, 'phys']]);
       await settle();
-      assert.ok(!urls.includes(manifest.audio.sfx.units[charId].hit), '4 s later: not that attack\'s impact');
+      assert.ok(!asked(urls, manifest.audio.sfx.units[charId].hit), '4 s later: not that attack\'s impact');
     } finally { globalThis.performance = perf; restore(); }
   });
 });