diff --git a/apps/ai-game-creator-shell/scripts/build-release.mjs b/apps/ai-game-creator-shell/scripts/build-release.mjs
index 2bfce8d02..579220319 100644
--- a/apps/ai-game-creator-shell/scripts/build-release.mjs
+++ b/apps/ai-game-creator-shell/scripts/build-release.mjs
@@ -143,27 +143,57 @@ export function resolveManifestPlatformKeys(target = releaseTarget) {
   throw new Error(`不支持的发布目标：${target}`);
 }
 
-async function readRemoteVersion(channel = resolveReleaseChannel()) {
-  const manifestUrl = updateManifestUrl(channel);
+/** 旧协议迁移指针：只在迁移窗口内存在，是历史版本高水位的来源。 */
+function legacyBridgeManifestUrl() {
+  return `${ossBaseUrl()}/latest.json`;
+}
+
+async function readManifestVersion(manifestUrl, label) {
   let response;
   try {
     response = await fetch(manifestUrl, {
       headers: { Accept: 'application/json' },
     });
   } catch (error) {
-    throw new Error(`读取 OSS 渠道清单失败：${error.message}`);
+    throw new Error(`读取 ${label} 失败：${error.message}`);
   }
   if (response.status === 404) return null;
   if (!response.ok) {
-    throw new Error(`读取 OSS 渠道清单失败：HTTP ${response.status}`);
+    throw new Error(`读取 ${label} 失败：HTTP ${response.status}`);
   }
   let manifest;
   try {
     manifest = await response.json();
   } catch (error) {
-    throw new Error(`OSS 渠道清单不是有效 JSON：${error.message}`);
+    throw new Error(`${label} 不是有效 JSON：${error.message}`);
   }
-  return parseVersion(manifest?.version, 'OSS渠道清单 version');
+  return parseVersion(manifest?.version, `${label} version`);
+}
+
+/**
+ * 版本高水位：渠道清单与旧协议迁移指针取较大值。
+ *
+ * 只看渠道清单会在「渠道刚启用、旧指针还停在更高版本」时把版本链改小 ——
+ * 2026-09-17 首次渠道发布就是这样把 0.1.57 退回 0.1.48 的。旧指针只服务
+ * Windows 渠道，其它渠道不参与比较；旧指针 404（迁移窗口结束）后自动只剩渠道清单。
+ */
+export async function resolveRemoteHighWaterVersion(
+  channel = resolveReleaseChannel(),
+) {
+  const channelVersion = await readManifestVersion(
+    updateManifestUrl(channel),
+    'OSS 渠道清单',
+  );
+  if (channel !== 'dev-win') return channelVersion;
+  const legacyVersion = await readManifestVersion(
+    legacyBridgeManifestUrl(),
+    'OSS 迁移指针',
+  );
+  if (channelVersion == null) return legacyVersion;
+  if (legacyVersion == null) return channelVersion;
+  return compareVersions(channelVersion, legacyVersion) >= 0
+    ? channelVersion
+    : legacyVersion;
 }
 
 function replaceVersionLine(source, version, pattern, label) {
@@ -174,7 +204,7 @@ function replaceVersionLine(source, version, pattern, label) {
 export async function prepareReleaseVersion() {
   const channel = resolveReleaseChannel();
   const localVersion = parseVersion(readPackageJson().version, '本地版本');
-  const remoteVersion = await readRemoteVersion(channel);
+  const remoteVersion = await resolveRemoteHighWaterVersion(channel);
   const requestedVersion = process.env.AGC_RELEASE_VERSION?.trim();
   const nextVersion = requestedVersion
     ? parseVersion(requestedVersion, '指定版本')
diff --git a/apps/ai-game-creator-shell/scripts/build-release.test.mjs b/apps/ai-game-creator-shell/scripts/build-release.test.mjs
index 904bb079f..f085a10d0 100644
--- a/apps/ai-game-creator-shell/scripts/build-release.test.mjs
+++ b/apps/ai-game-creator-shell/scripts/build-release.test.mjs
@@ -13,6 +13,7 @@ import {
   nextPatchVersion,
   resolveManifestPlatformKeys,
   resolveReleaseChannel,
+  resolveRemoteHighWaterVersion,
   selectReleaseArtifact,
   updateManifestUrl,
 } from './build-release.mjs';
@@ -49,6 +50,22 @@ function withSignedArtifact(fileName, run) {
   }
 }
 
+function jsonResponse(body, status = 200) {
+  return {
+    status,
+    ok: status >= 200 && status < 300,
+    json: async () => body,
+  };
+}
+
+function withStubbedFetch(handler, run) {
+  const originalFetch = globalThis.fetch;
+  globalThis.fetch = async (url) => handler(String(url));
+  return Promise.resolve(run()).finally(() => {
+    globalThis.fetch = originalFetch;
+  });
+}
+
 test('selects an explicit release artifact when configured', () => {
   const artifactPath = fileURLToPath(
     new URL('../package.json', import.meta.url),
@@ -173,6 +190,47 @@ test('next release version follows the higher local or channel version', () => {
   assert.equal(nextPatchVersion('0.1.12', null), '0.1.13');
 });
 
+test('version high water keeps the legacy pointer during the migration window', async () => {
+  await withStubbedFetch(
+    (url) =>
+      url.endsWith('/agc/dev-win/latest.json')
+        ? jsonResponse({}, 404)
+        : jsonResponse({ version: '0.1.57' }),
+    async () => {
+      assert.equal(await resolveRemoteHighWaterVersion('dev-win'), '0.1.57');
+      // 旧指针 0.1.57 已是高水位，下一次发布必须是 0.1.58，不能退回渠道本地版本。
+      assert.equal(nextPatchVersion('0.1.47', '0.1.57'), '0.1.58');
+    },
+  );
+});
+
+test('version high water takes the higher of channel and legacy pointer', async () => {
+  await withStubbedFetch(
+    (url) =>
+      url.endsWith('/agc/dev-win/latest.json')
+        ? jsonResponse({ version: '0.1.60' })
+        : jsonResponse({ version: '0.1.57' }),
+    async () => {
+      assert.equal(await resolveRemoteHighWaterVersion('dev-win'), '0.1.60');
+    },
+  );
+});
+
+test('version high water ignores the windows migration pointer for other channels', async () => {
+  await withStubbedFetch(
+    (url) => {
+      assert.ok(
+        !url.endsWith('/agc/latest.json'),
+        'non-windows channel must not read the windows migration pointer',
+      );
+      return jsonResponse({ version: '0.1.12' });
+    },
+    async () => {
+      assert.equal(await resolveRemoteHighWaterVersion('dev-mac'), '0.1.12');
+    },
+  );
+});
+
 test('release upload forces overwrite for artifact, signature and channel pointers', () => {
   const source = readFileSync(
     new URL('./release-upload.mjs', import.meta.url),
diff --git a/docs/technical/【技术方案】AGC客户端更新检查与下载-2026-08-31.md b/docs/technical/【技术方案】AGC客户端更新检查与下载-2026-08-31.md
index 61a738e77..314b98419 100644
--- a/docs/technical/【技术方案】AGC客户端更新检查与下载-2026-08-31.md
+++ b/docs/technical/【技术方案】AGC客户端更新检查与下载-2026-08-31.md
@@ -82,6 +82,7 @@
 - 上一条的两个键不能合成单一 `darwin-universal` 键：更新插件按运行时实际架构解析清单键（Apple Silicon 命中 `darwin-aarch64`，Intel 命中 `darwin-x86_64`），不存在自动命中 `darwin-universal` 的情形。将来真要单独发该键，必须在客户端同时设置自定义 target，否则清单里这一项永远不会被读取。
 - 构建期要求：打开 `bundle.createUpdaterArtifacts` 以生成 `.sig`；构建环境提供签名私钥与密码（私钥内容不得入库）；公钥写入客户端配置。公钥在首个带更新能力的版本发布后不可更换，更换等于放弃自动更新（只能手动重装）。
 - 版本递增按渠道独立进行：发布脚本读取该渠道远端 `latest.json` 的 `version`，与本地版本取较高者递增 patch；两个渠道的版本号互不影响。
+- 版本高水位：发布脚本取「渠道清单版本」与「旧协议迁移指针版本」（迁移窗口内）中的较大值再递增。只看渠道清单会在渠道启用初期把版本链改小 —— 2026-09-17 首次渠道发布即把旧指针的 0.1.57 退回 0.1.48，随后以显式 0.1.60 纠偏；迁移窗口结束（旧指针 404）后自动只剩渠道清单，`dev-mac` 不参与旧指针比较。
 - 迁移（旧协议 → 渠道清单）：
   - 迁移起点：已发布客户端（含当前线上版本）内置自研清单地址 `agc/latest.json`（sha256 格式），下载与安装由自研 Rust 命令完成。
   - 迁移策略见「未决问题与决策」。迁移完成后，自研清单解析、下载命令、下载进度事件以及为此放行的 CSP / HTTP 白名单条目按「四不写」整条删除，不留兼容分支与墓碑说明。